Quiet Zone at Duval Road In Effect February 2nd

From the city’s quiet zone information page:

Update: 01/13/2011
The City of Austin submitted the Notice of Establishment (NOE) to the Federal Railroad Administration (FRA) for the railroad crossing of the Union Pacific Railroad at Duval Road on January 12, 2011. This Quiet Zone will be officially in effect on February 2, 2011 (21 days from January 12, 2011).

A quiet zone for this location means that trains will no longer sound their horns as they approach the crossing.  This will reduce the noise exposure of homes near the tracks substantially.

Railroad Quiet Zone Information Page Now Up

The city has created a webpage with information on current quiet zone applications.


From Jody Zemel in the Planning and Development Review Department:

In response to those who have asked about the “Quiet Zones” being
established around some of Austin’s railroad tracks, I have created a
web page in the Neighborhood Assistance Center for updates on this

This page has all the latest information we have at the city currently
and I will be updating the page when the information changes.

The COA will inform the Citizens of the final designation of the quiet
zone, when it occurs.

Thanks for your patience and please share this information with your
neighborhood listserves.


Jody Zemel | Neighborhood Advisor | Neighborhood Assistance Center

Decibel Flavors Part 1 – L Values

Over the next few articles I will explain some of the different meanings of the word “decibel” as it relates to sound.  “Decibel,” by itself, is not a unit of measurement of loudness.  Decibels are a way of counting large numbers, very similar to the Richter scale.  For people to be talking apples to apples about noise, they need to be clear about what flavor of decibels they’re using.

In this article I will talk about the different kinds of L Values.  In the next article I will talk about weighted values and sound spectra.  You need both of these pieces to determine what “decibel” means.

Sound level measurements are taken over time.  If you have an inexpensive sound level meter, it probably just has a screen with a single number that bounces up and down on the screen depending on what it’s measuring right at that moment.  While this is useful for getting a general idea of what sound levels you’re measuring, it’s not very useful for making numerical comparisons.  The type of sound level meter used by acoustical engineers makes a complete measurement with a beginning and an end; basically a short recording.

This chart shows a basic sound level measurement.  The curve is the Sound Pressure Level (SPL), which is the sound level at a specific moment.  SPL fluctuates with time.  If you were making this measurement with an inexpensive meter, you would see the value on the meter move up and down in time in a way that resembled the curve below.

The problem is a sound that lasts over time never has a single SPL value.  Since it fluctuates over time you have to find a way of describing the entire curve with a single number.  It turns out there are several ways of doing just that.

Very frequently, the metrics Leq, Lmax, and Lmin are used.  These refer to the Equivalent Level, the Maximum Level, and the Minimum Level.  Lmax and Lmin are the easiest to understand, they’re simply the highest and lowest values the sound level meter saw during the measurement:

Leq is trickier to understand.  Technically the following charts aren’t a correct representation, because Leq depends on the actual numerical value for sound pressure level, not the decibel value.  But understanding that is not necessary for understanding the idea behind Leq.

Leq is the Time Weighted Equivalent Level. That’s kind of a mouthful but it’s not too complicated.  Weighting is a way of averaging.  Here’s how it works out:

The below chart shows everything below the curve highlighted in red.  The size of the red area is, essentially, the SPL multiplied by the amount of time of the measurement.  In order to multiply something by a curvy line, you have to use calculus, which is actually what an “integrating sound level meter” is doing.

If you take the entire red area and rearrange it so that it makes a nice square shape, you’ll have something like this:

This red square has the same area as the red area under the curve in the previous figure.

The Equivalent Level, Leq, is the sound level that would result in a square with the same area as the curve.

Leq and Lmax are used quite frequently.  Lmin is not used as often, but is usually recorded alongside Leq and Lmax anyway.

Another method of deriving a single number from a sound level measurement is with a Statistical Analysis, or “Ln values.”  “Ln” by itself describes the methodology and isn’t an actual level.  The actual levels are written with a number in place of the letter n.  Typical Ln metrics are L10, L50, and L90.  You can have any Ln value you want, L37.5, for example.

What the number refers to is the “percentile” of the value.  Specifically, the amount of time the sound level was above the Ln value.  L10 is the level, in decibels, that the sound level exceeded for 10% of the time.  L50 is the value that the sound level was above for 50% of the time and can be considered the median value.  L90 is the value that the sound level was above 90% of the time.

Graphically speaking, Ln values are calculated by adjusting a line up and down until exactly the correct percentage of the line is below the curve.  The L10 line is adjusted until 10% of it is below the curve, the L50 line is adjusted until exactly half of it is below the curve, and the L90 line is adjusted until 90% of it is below the curve. Once those lines are adjusted to the proper height, you read the value from the left axis of the graph to determine your Ln values.

So on the following chart, if our Lmax was 80 dB and our Lmin was 40 dB, L10 would be about 78 dB, L50 would be about 65 dB, and L90 would be about 45 dB.

The chart below shows the lines without showing the SPL curve.  The sections in red are what would appear below the curve.  For L10, the section below the curve (red) is 10% of the total length of the line.  For L50, the red portions make up half of the length of the line.  For L90, the red portions make up 90% of the length of the line. The length of the lines left to right is equal to the amount of time of the measurement.

Ln values are very useful for long term noise measurements, such as what you would use for an environmental noise study.  Such studies often have measurements that last for several days.  L90 is commonly used to determine the ambient, background level.  If your L90 value is 45 dB,  that is the same as saying “the sound level was 45 dB or higher 90% of the time.”

In the next article I will write about the different ways of combing all the different frequencies of a given sound into a single number.  This includes A-weighted decibels, or dBA, which are the most commonly used single-number flavor of decibels, and what the great majority of noise ordinances refer to.

Is something still unclear?  Did I make a mistake?  If so, please ask any questions or share any comments in the comments section of this article.  I will attempt to clarify anything I didn’t explain well or correct any mistakes I may have made.

Latest Change to Noise Ordinance is Not Equitable

The City Council voted last Thursday, November 5, to change the Austin Noise Ordinance once again.  This time they’ve added a distance limit for audibility from “sound equipment” on boats.

Section 9-2-3 (6):  A person may not operate sound equipment in a watercraft audible or causing vibration 100 feet from the equipment.

It takes effect November 16.

This is one more example of why our source-oriented ordinance is not tenable.  When the ordinance is source-oriented, you end up with a patchwork of restrictions that is stitched together over many years and terms of city council members.  The result is an inconsistent set of rules, each of which panders to whoever had a complaint at the time it was implemented.

The new watercraft noise rule is designed specifically to protect people who live on one of our lakes from hearing music from boats.  While this goal is not, in and of itself, a negative thing (people on lakes have just as much right to quiet as people not on lakes), it is hard to argue that it is equitable for a specific set of homeowners to get their own special protection.

Technically speaking, the new rule is all but impossible to satisfy.  There is no shielding and practically no ground absorption over water, so sound travels very efficiently.  In order to be inaudible, a sound needs to have levels somewhat below ambient levels.  In an area somewhat isolated from freeways and other typical city noise sources, you can expect ambient levels of around 35-40 dBA Leq.  In order to achieve 35 dBA from a distance of 100 feet, the noise source must be no louder than 61 dBA at a distance of 5 feet.

A typical conversation with someone a few feet from you is around 65 dBA Leq.  So in order to satisfy the new ordinance, someone on a boat may not turn up their stereo any louder than 4 dB below what a normal conversation would be (assuming they’re about 5 feet away from the stereo).  You can choose to talk to someone on your boat or you can choose to listen to music, but you cannot do both simultaneously.

And where do motors fall into this?  What boat motors are inaudible at 100 feet?

Even further, these simple estimates are based on generic A-weighted decibels.  In reality, music will have substantial low-frequency content that is not well represented in A-weighting but is still quite audible, especially against the backdrop of a quiet afternoon on the lake.

The arbitrary limit of 100 feet is also inequitable.  Boats that are 300 feet from any receiver are held to the same standards as boats that are near the shore.  I understand that the spirit of the law is not to punish people who are considerate enough to move further from the shore before turning up their stereos and that such people will probably never be ticketed.  However, there is no reason that the letter of the law should not truly capture the spirit of the law if it is possible.

It is time for us to rewrite our noise ordinance from scratch.  A fair, objective, uniform set of receiver-oriented standards should be established that applies to everyone equally.  The law should define illegal behavior based on its impact on other people.  A single rule defining a limit to how much noise one can subject a residence to will protect all residences equally, whether they are on Lake Austin or East of I-35.

The Nutty Brown Cafe: Noise Measurements and Comparison to Acoustical Criteria


On the evening of November 6, 2009, I visited several residences in the area around the Nutty Brown Cafe to make an objective determination of noise impacts.  Using a professional, scientific sound level meter, I measured sound levels at a residence approximately 1200 feet from the stage.

I compared the measured levels to 3 criteria for noise disturbance:  The Austin Noise Ordinance;  The Word Health Organizations Guidelines for Community Noise; and the German DIN 45680 standard for low-frequency noise exposure assessment.  In all 3 comparisons, sound from the Nutty Brown was found to exceed criteria by substantial margins.


In 2006 a new stage was added to the Nutty Brown Cafe near Dripping Springs, turning it into an important concert venue.  Since then, people in the community have complained about the sound levels of music from the Nutty Brown, and it has become a very contentious issue. Many complaints have been made by upset neighbors, including a number of complaints filed with the TABC.

As the Nutty Brown and its neighbors are in an unincorporated area, there are no applicable noise ordinances; counties in Texas are simply not permitted to have them.  The TABC, however, does have a provision for noise, as follows:

Sec. 101.62. OFFENSIVE NOISE ON PREMISES. No licensee or permittee, on premises under his control, may maintain or permit a radio, television, amplifier, piano, phonograph, music machine, orchestra, band, singer, speaker, entertainer, or other device or person that produces, amplifies, or projects music or other sound that is loud, vociferous, vulgar, indecent, lewd, or otherwise offensive to persons on or near the licensed premises.

In internet conversations on the issue, it is commonly held that residents of the new Belterra development are to blame for the complaints against The Nutty Brown.  This is only partially true.  In reality, residents from all of the communities surrounding the Nutty Brown have filed complaints. Contrary to popular belief, most complainants are not from California, do not live in Belterra, and have lived in the area since before 2006. In some cases, long before 2006.

Conversation on this topic is frequently emotionally charged and lacking in independent facts.  It is the goal of Austin Noise to encourage objective conversation on community noise by providing scientifically based opinions and analysis and, when possible, to provide objective data.  Therefore I determined that it would be in keeping with the mission of Austin Noise to perform my own measurements during a concert at the Nutty Brown and share the results publicly. I contacted some homeowners near The Nutty Brown and conducted a set of measurements the evening of Friday, November 6.

During conversations with various homeowners during the evening, they all indicated that the sound levels from the Nutty Brown were below typical that evening.  This agrees with my own assessment, as I visited some of these residences to perform measurements last year and I remember the music having been louder.  Nevertheless, the data collected this night shows significant noise impacts at the measurement location.

Measurement Procedure

I conducted sound level measurements using a Larson Davis model 824 ANSI Type I sound level meter.  This is a very accurate, scientific instrument that I am quite familiar with.  My measurements will be more reliable than those conducted by someone untrained in acoustics wielding a Type II or Type III meter, such as what you might buy from Radio Shack.  My employer was kind enough to lend me the meter over the weekend for this project.

The measurement location was 1180 feet from the Nutty Brown Cafe’s stage, and significantly off-axis.  By off-axis, I mean the stage was not pointing at my location.  In other words, measurements taken on-axis would likely yield higher sound levels.  Following the path between the stage and the measurement location, the property line of the Nutty Brown is 320 feet from the stage.

The measurement location was relatively shielded by topography from traffic noise emitted by Highway 290. This was very beneficial, as it allowed a more definite determination of noise levels caused by music from the Nutty Brown.  During the measurement, it was clear by observation that music from the Nutty Brown was the dominant sound source at the measurement location.

The sound level meter ran continuously through the show (except during a 20-minute period due to a depleted battery), collecting data in 5-minute intervals.  Sound data was recorded in octave band, third-octave band, Leq, Lmax, Lmin, and statistical levels L1, L5, L10, L50, L90, and L99.  This is a very complete set of data that Type II and Type III meters are usually not even capable of producing.

Keep in mind that this is a single set of data, collected on a single night, in a single location.  A comprehensive study would include data collected on multiple nights and in multiple locations.  Even so, the single set of data should be sufficient to give a good idea of the types of sound levels the Nutty Brown exposes its neighbors to.


The applicable standard is the TABC restriction on offensive noise.  In particular, sound that is “loud… or otherwise offensive to persons on or near the licensed premises.” While “loud” is a somewhat subjective term, it is still possible to make an objective determination of whether a sound can be considered “loud.”

There are many studies and standards that relate measurable sound levels to human annoyance, sleep disturbance, and hearing damage.  I compare my measured levels against 3 criteria, each of which presents a different, testable version of “loud.”  The selected criteria are:

  1. Austin Noise Ordinance – This criteria is familiar to people in the area.  Also, the owner of the Nutty Brown claims to follow the Austin ordinance voluntarily. The Nutty Brown is not in city limits and therefore not required to abide by the Austin ordinance.
  2. World Health Organization Guidelines for Community Noise – The WHO compiled a large collection of research papers and texts on acoustics and community noise, then determined a representative set of recommended criteria for community noise regulation.
  3. DIN 45680 – This is a German standard for the measurement and evaluation of low-frequency noise emissions in neighborhoods.  I selected this standard based on a 2005 study by P. McCullough and J. O. Hetherington that compared the relative performances of various objective noise criteria for assessing disturbance due to entertainment music.  The study determined that DIN 45680 performed best at predicting subjective assessment of nuisance.

While valid arguments can be made for the appropriateness of all of these criteria (and dozens of other available criteria), the determination of what is acceptable ultimately falls under the responsibility of the TABC.  I don’t know what methodology they use, or if they even have one. I would like to think that their decision process is objective, rather than political.

A secondary criterion at play comes from the Texas Penal Code, which states that once a person has been warned about creating noise, they may not produce sound in excess of “85 decibels.”  The Penal Code does not define decibels, leaving its interpretation open.  In acoustics, “decibels” can mean a number of things.  Although it presents a numeric criterion, it will likely not come into play in the decision process of the TABC.

Nutty Brown vs Austin Noise Ordinance

To be clear, The Nutty Brown is not in the Austin city limits and not required to abide by the Austin Noise Ordinance.  I make this comparison because people in the Austin area might be familiar with the ordinance, and because the owner of The Nutty Brown has stated that he voluntarily follows the ordinance in an effort to be a good neighbor.

If The Nutty Brown were within city limits, it would presumably be considered either a restaurant or a permitted outdoor music venue.  You may recall that establishments such as Freddie’s and Shady Grove have struggled with the “restaurant” classification, which is held to a lower sound level limit due to a zoning restriction.  We will examine both criteria.

A restaurant with live entertainment must not exceed “70 decibels,” as measured at any point along its property line. A permitted music venue must not exceed “85 decibels,” as measured at any point along its property line.  The Austin ordinance defines “decibels” as sound pressure level using A-weighting and the “slow” impulse response.  This translates to the Lmax value of a measurement using the slow response in dBA.

I did not measure directly at the property line.  However, knowing the absolute distances between the measurement point, the property line, and the stage, it is possible to calculate sound pressure levels at the property line due to music from the stage.  This has the benefit of removing the impact of traffic noise from the measured values, thereby making this method potentially more accurate than measurements taken at the actual property line.

To calculate property line noise levels, I used the method for outdoor sound propagation specified by Hoover & Keith in Noise Control for Buildings and Manufacturing Plants. This method takes frequency, atmospheric conditions (temperature and humidity), and anomalous excess attenuation into account.  It is considered to be quite accurate.

Since my data was recorded in 5-minute intervals, each 5-minute period yielded a unique value for Lmax.  Below are the calculated values for Lmax at the Nutty Brown property line shown against the 70 dBA and 85 dBA standards.

Nutty Brown vs Austin Ordinance

The lower levels between 8:55 and 9:25 represent the time between the opening act and the headlining band, while recorded music was being played over the PA.  All Lmax values recorded while performers were on stage indicate exceedance of the Austin Noise Ordinance at both the 70 dBA and 85 dBA threshholds.

Nutty Brown vs The World Health Organization

The WHO publishes a set of guidelines for community noise regulation.  It is based on a study of hundreds of scientific papers, texts, and standards dealing with community noise and human noise response.  The set of guidelines most applicable to the Nutty Brown situation is Dwellings, which is derived from studies on sleep disturbance and human annoyance responses.

From Section 4.2.3 Sleep Disturbance Effects, of Guidelines For Community Noise:

Measurable effects on sleep start at background noise
levels of about 30 dB LAeq. Physiological effects include changes in the pattern of sleep stages,
especially a reduction in the proportion of REM sleep. Subjective effects have also been
identified, such as difficulty in falling asleep, perceived sleep quality, and adverse after-effects
such as headache and tiredness. Sensitive groups mainly include elderly persons, shift workers
and persons with physical or mental disorders.
Where noise is continuous, the equivalent sound pressure level should not exceed 30 dBA
indoors, if negative effects on sleep are to be avoided. When the noise is composed of a large
proportion of low-frequency sounds a still lower guideline value is recommended, because lowfrequency
noise (e.g. from ventilation systems) can disturb rest and sleep even at low sound
pressure levels.

Measurable effects on sleep start at background noise levels of about 30 dB LAeq. Physiological effects include changes in the pattern of sleep stages, especially a reduction in the proportion of REM sleep. Subjective effects have also been identified, such as difficulty in falling asleep, perceived sleep quality, and adverse after-effects such as headache and tiredness. Sensitive groups mainly include elderly persons, shift workers and persons with physical or mental disorders. Where noise is continuous, the equivalent sound pressure level should not exceed 30 dBA indoors, if negative effects on sleep are to be avoided. When the noise is composed of a large proportion of low-frequency sounds a still lower guideline value is recommended, because low frequency noise (e.g. from ventilation systems) can disturb rest and sleep even at low sound pressure levels…

If the noise is not continuous, LAmax or SEL are used to indicate the probability of noise induced awakenings. Effects have been observed at individual LAmax exposures of 45 dB or less. Consequently, it is important to limit the number of noise events with a LAmax exceeding 45 dB. Therefore, the guidelines should be based on a combination of values of 30 dB LAeq,8h and 45 dB LAmax. To protect sensitive persons, a still lower guideline value would be preferred when the background level is low. Sleep disturbance from intermittent noise events increases with the maximum noise level. Even if the total equivalent noise level is fairly low, a small number of noise events with a high maximum sound pressure level will affect sleep.

Therefore, to avoid sleep disturbance, guidelines for community noise should be expressed in terms of equivalent sound pressure levels, as well as LAmax/SEL and the number of noise events. Measures reducing disturbance during the first part of the night are believed to be the most effective for reducing problems in falling asleep.

From Section 4.2.7 Annoyance Responses

During the daytime, few people are seriously annoyed by activities with LAeq levels below 55 dB; or moderately annoyed with LAeq levels below 50 dB. Sound pressure levels during the evening and night should be 5–10 dB lower than during the day. Noise with low frequency components require even lower levels. It is emphasized that for intermittent noise it is necessary to take into account the maximum sound pressure level as well as the number of noise events.

These observations are combined into a set of guidelines in section 4.3.1 Dwellings

In dwellings, the critical effects of noise are on sleep, annoyance and speech interference. To avoid sleep disturbance, indoor guideline values for bedrooms are 30 dB LAeq for continuous noise and 45 dB LAmax for single sound events. Lower levels may be annoying, depending on the nature of the noise source. The maximum sound pressure level should be measured with the instrument set at “Fast”.

At night, sound pressure levels at the outside façades of the living spaces should not exceed 45 dB LAeq and 60 dB LAmax, so that people may sleep with bedroom windows open. These values have been obtained by assuming that the noise reduction from outside to inside with the window partly open is 15 dB.

To protect the majority of people from being seriously annoyed during the daytime, the sound pressure level on balconies, terraces and outdoor living areas should not exceed 55 dB LAeq for a steady, continuous noise. To protect the majority of people from being moderately annoyed during the daytime, the outdoor sound pressure level should not exceed 50 dB LAeq…

My measurements were taken near a residence, and are representative of other nearby residences.  Therefore, the raw measured values can be compared directly to the criteria.  Since the intruding sound is music with significant low-frequency content, the limits should be lowered.  However, even without adjusting for low frequency content, the measured limits exceed these guidelines significantly, and it is not necessary to account for the nature of the sound to see that the criteria are not being exceeded.

Sleep disturbance is the more important criterion.  One complaint I heard often from residents was that music from the Nutty Brown made sleep difficult, especially for children.  Measured levels are compared to the WHO sleep disturbance criteria in the following chart.  The dark blue line is Leq, or the time-weighted average, and should be compared to the dotted light blue line at 45 dBA.  The dark green line is Lmax with the meter set to fast response, and should be compared to the dotted light green line at 60 dBA.

Nutty Brown vs WHO Sleep

Both criteria for sleep disturbance were exceeded for every measured interval, sometimes by as much as 20 dB.  This is based on the assumption of a partially open window.  A closed window would allow for an additional 5 to 10 dB.  It is not surprising, then, that residents in the area frequently complain of sleep disturbance.

Nutty Brown vs DIN 45680

The German criterion DIN 45680 (Deutsches Institut für Norman, 1997) is frequently used to assess human annoyance due to low-frequency noise.  Rather than a single A-weighted value, the criterion uses 1/3-octave values between 10 Hz and 80 Hz.  The values in the curve represent the 50% auditory threshold.  Measured values that exceed the criterion curve can be considered annoying or disturbing by a significant fraction of the population.

For comparison to the DIN curve, measured 1/3-octave Leq values for all intervals recorded when a performer was on the stage were combined into time-weighted averages.  Those values were then reduced by 15 dB to simulate outdoor to indoor reduction through a building shell with a partially-open window (borrowed from WHO).  This is a very conservative method, since residential building shells are usually more transparent to sound at such low frequencies.

Nutty Brown vs DIN 45680

The bump at 50Hz and 63Hz is very typical for live music.  These are the frequencies that are responsible for the majority of complaints from people who live near music venues.  Even with a conservative outdoor to indoor noise reduction estimate, the 63Hz band still exceeds the criterion by more than 20 dB.

People who live further from the Nutty Brown, such as those in Belterra, complain about low frequency noise, which permeates their houses.  Reportedly, this effect occurs even several miles away.  This is not unusual for outdoor venues in quiet areas and the data seems to support such claims.


In every test, criteria was exceeded by significant amounts.  Even the Austin Noise Ordinance, which is heavily skewed to favor the noise source, was exceeded by at least 5 dB at a point over 300 feet from the stage.  For all tests, conservative assumptions and methods for estimation and calculation were used.  A more comprehensive analysis would likely determine greater impacts.

Comparing the measured levels to all 3 criteria suggests that noise from the Nutty Brown is not just loud, but very loud. In my professional experience, I don’t recall ever seeing this level of noise impact at a residence from a music venue over 1000 feet away.

With or without my personal interpretations, the data is clear and presented here for use in the discussion by anyone who would like to use it. Also, I will be happy to share any portion of my data or perform comparisons to additional criteria at anyone’ s request.

New Railroad Quiet Zones Possibly Coming Next Summer

Austin, along with 32 other municipalities in Texas, has submitted an application to the FRA for additional quiet zones.  The new quiet zones would be at 6 at-grade crossings:

  • In the South
    • Mary St.
    • Oltorf St.
    • Banister Ln.
    • W Stassney Ln.
  • Duval Rd. Up North
  • Matthews Ln in Sunset Valley

Except in quiet zones, a train operator must sound his horn about 20 seconds before reaching an at-grade railroad crossing.  This usually happens when the train passes a “whistle post,” which are located 1/4 mile in each direction from the crossing.  This is mandated by Federal law and supersedes any local or state laws.

For a quiet zone to be established, the community must apply to the FRA and install sufficient safety equipment at the crossing to warrant a lack of warning sounds from a train.  Usually this means quad crossing guards that prevent vehicles from driving across the tracks, plus whatever measures are needed to prevent pedestrians from crossing tracks while a train is approaching.  Sometimes this means miniature crossing guards for sidewalks.

Upon receiving the application, the FRA will review and determine the risk factor associated with ceasing to sound horns at each crossing.  This includes a 60 day comment period.  After the quiet zone is approved, there is a notification period of 20 days after which the quiet zone will be in effect.

Austin currently has quiet zones established for rail operated by Cap Metro.  They are from US 183 to Downtown and between McNeil/Merriltown Road and Gracy Farms Road.  Although the Cap Metro trains aren’t carrying any passengers, they are running and (generally) observing the quiet zones.  There are also Cap Metro quiet zones in Leander and Cedar Park, with more in the works.

Train noise is unbelievably disturbing and is the subject of many environmental noise studies.  Any proposed HUD or (as of recently) FHA projects within 3000′ of active rail must undergo a noise study and, if necessary, show adequate noise mitigation plans before receiving approval.

Train noise is difficult to mitigate because it is very loud and has significant low frequency content.  Low frequency sound has longer wavelengths, making it more difficult to control with noise barriers.  Also, railroad tracks tend to be elevated, and horns are mounted near the tops of locomotives.  It’s common for a horn to be 20′ off of the ground.  A high source height makes building an effective barrier even more difficult, since the required wall heights go up substantially.

Quiet zones are an excellent compromise between safety and community livability.  The cost of installing sufficient safety equipment is typically small, in city budget terms.  Communities that are organized enough to submit applications and who have the money to make the necessary improvements see substantial increases in the quality of lives of people who live within half a mile of a crossing.

FRA Crossing and Quiet Zone Page

Story at KXAN

New Quiet Zone Locations Across Nation

The Comprehensive City Plan Should Have a Noise Element

Yesterday, October 12th, the development of Austin’s new Comprehensive City Plan got underway with an excellent open house kickoff event.  Representatives from the city were on-hand with large displays to educate visitors about the process of developing a city plan and, more importantly, to collect information and opinions from the community.

To an acoustical engineer who has worked with the noise elements of many city plans, the lack of a planned noise element in Austin’s comprehensive plan seems like a glaring omission.  While speaking to city representatives, it occurred to me that the very idea of a noise element was a foreign concept.  When I mentioned noise, people immediately thought of community noise complaints, particularly concerning live music venues.  I also detected frequent misunderstandings about noise and acoustics in general.

The purpose of this article is two-fold.  The first goal is to make the case for including a noise element in the Austin comprehensive city plan.  The second, parallel goal will be to inform the reader about noise elements; what they are, and how they can be written.  To accomplish both of these goals simultaneously, this article steps through the sections of a typical noise element, explaining them and showing how they would relate to Austin.

Other than it simply being useful, there are some good reasons that Austin should have a noise element in its comprehensive plan.

  • First and most compelling, most of the content of a complete noise element already exists in the Austin Tomorrow Comprehensive Plan, 2008 Interim Update.  There are noise-related sections of ATCP listed throughout this article.
  • In addition to ATCP, more noise element content can be found in the Austin Code of Ordinances and in other sources, such as the Live Music Task Force recommendation report.
  • Austin is a leader in Texas.  While we lead Texas and, in some cases, the country, in environmental issues, we are lagging far behind most of the nation in noise issues.  Austin should be the conduit for good ideas into the state and a center for developing better ones.
  • CAMPO recommends that all cities develop noise elements for their general plans.

The Austin Tomorrow Interim Update includes a goal devoted strictly to noise.  Goal 350 and its subsections, listed below, can be found starting on page 59.


  • Objective 351.0 Reduce transportation related noise.
    • Policy 351.1 Minimize road vehicle noise.
    • Policy 351.2 Improve the design of residential areas relative to major arterials, and promote the use of buffers along major traffic routes.
    • Policy 351.3 Restrict non-compatible land uses near Austin-Bergstrom International Airport.
  • Objective 352.0 Regulate noise from stationary sources.
    • Policy 352.1 Limit construction and repair work to particular daylight hours.
    • Policy 352.2 Set specific noise performance standards for industry.
    • Policy 352.3 Control the location of noisy commercial establishments relative to residential areas.
  • Objective 353.0 Encourage acoustic considerations in residential construction.
    • Policy 353.1 Improve noise insulation and noise reduction features in the building codes.
    • Policy 353.2 Improve noise control features in multi-unit housing.
There are more sections found in the Austin Tomorrow Update dealing with noise listed in the following sections of this article.  All of these sections should be combined into a single document:  The noise element.

Purpose of a Noise Element

The goal of a noise element is simple, but important:  Protect people who live and work in Austin from excessive noise.  The negative effects of excessive noise are researched and well documented.  Sleep deprivation, distraction, and annoyance from intrusive sounds can lower quality of life and productivity in very real ways. Mindful planning can go a long ways towards avoiding unnecessary noise exposure.

A noise element is often divided into sections dealing with different aspects of community noise.  Each section gives information about a type of noise and what relevant measures the city proposes to take to protect its citizens.

Often city plans begin with an assessment of the current noise environment of the city.  This includes statements and general information about the most important noise sources in the city.  Some cities go so far as to commission noise studies by acoustical consultants to develop city-wide noise contours to aid in planning development.

The noise element will state the city’s general goals as they relate to noise.  This can include statements about what noise levels are considered acceptable or unacceptable or what general methodologies might be followed in protecting the city’s population from excessive noise.

Land Use Compatibility

A very important aspect of a noise element is its contribution to defining compatible land uses.  Land use compatibility guidelines assist planners and developers in deciding whether proposed developments meet the city’s vision as it pertains to noise.  Frequently, numerical guidelines are developed to define compatible, conditionally compatible, and incompatible land uses based on ambient noise at a location of interest.

Below is a simplified example of a table of compatible land uses similar to what you might find in a noise element.

Exterior Noise Exposure (dBA DNL)
Land Use Category Compatible Conditionally Compatible Incompatible
Open Space and Parks < 65 65 to 75 75+
Commercial < 70 70 to 75 75+
Residential <65 65 to 70 70+
Educational <65 65 to 70 70+

Austin already has compatible land uses defined by airport noise contours in the code of ordinances.  You can find them in Section 25-13-41.  It is not a large leap to expand that philosophy to include other sources of noise.

The Austin Tomorrow Plan includes the following sections relating to noise and land use compatibility planning:

  • Objective 123.0 Reduce the negative effects of automobile traffic in neighborhood environments.
    • Policy 123.1 Protect residential areas from excessive levels of noise pollution and physical danger from traffic.
  • Objective 322.0 Create and continue to support strong environmental standards for new development within the City limits and in the City’s ETJ.
    • Policy 322.8 Create development standards based on noise impact and air quality.

Transportation Noise

Often divided into traffic and rail, sections dealing with transportation noise present guidelines or standards for avoiding preventable exposure to noise from busy roadways and freight and commuter rail.  This may include minimum setbacks, triggers for noise studies based on traffic density, road design guidelines, or guidelines for establishing rail “quiet zones.”

Highway noise in particular is of increasing concern in Austin.  New and expanding roadways like MoPac and 183 bring with them new noise issues for nearby residents and businesses.

The Austin Tomorrow Plan has the following sections relating to transportation noise:

  • Objective 721.0 Maintain acceptable noise standards.
    • Policy 721.1 Develop appropriate noise standards for each classification of transportation and include noise considerations in the design, operation and maintenance of transportation facilities.
    • Policy 721.2 Within the city, limit the operation of motor freight vehicles to designated truck routes.
    • Policy 721.3 Use various means of buffering sound to reduce noise impacts on areas adjacent to transportation facilities.
    • Policy 721.4 Control the location and design of land uses so that noise-producing transportation facilities are not located near land uses which require a quiet setting.
    • Policy 721.5 Vigorously enforce noise regulations.

Aircraft Noise

The aircraft noise section of the element would include statements about the present aircraft noise environment in the city.  Most likely this would include graphics of present airport noise contours.  If there are military airfields in the city, noise contours developed in an AICUZ study may be included in the noise element, or at least referenced.

Objectives and policies relating to aircraft noise would be presented.  This could include guidelines for land use compatibility based on airport noise contours.  There may also be future projections of airport contours or AICUZ contours.

As previously mentioned, the existing code of ordinances addresses aircraft noise by defining compatible land uses based on noise contours (referred to as Airport Overlay Zones in Austin’s code).  This can be found in section 25-13-4.


(A) Within the controlled compatible land use area, the following airport overlay zones are created:

(1) Airport overlay zone one (AO-1) consists of the portions of the controlled compatible land use area that have a yearly day-night average sound level of at least 70 decibels and not more than 75 decibels.

(2) Airport overlay zone two (AO-2) consists of the portions of the controlled compatible land use area that have a yearly day-night average sound level of at least 65 decibels and not more than 70 decibels.

(3) Airport overlay zone one (AO-3) consists of the portions of the controlled compatible land use area that have a yearly day-night average sound level of less than 65 decibels and are located within approximately one-half mile of the 65 decibel contour line.

(B) The controlled compatible land use area and the airport overlay zones are depicted on the Austin-Bergstrom International Airport Land Use Map on file with the City Department of Aviation. The director of the Department of Aviation shall determine the location or meaning of a boundary or other feature on the map.

Events and Live Music

This is of special interest to Austin.  The issue of neighborhoods dealing with live music permeating the night air is a frequent topic of discussion and news stories.  Austin’s identity as The Live Music Capital puts a unique spin on this subject.

Considerable thought has been put into this topic in Austin, and some of this shows in the Live Music Task Force’s recommendation report.  The sum of this work can be collected into the noise element to help define Austin’s vision as a community for supporting live music as a premier feature of the city while simultaneously protecting its citizens from unfair intrusive sound.

Probably the  most relevant recommendation from the Live Music Task Force to the comprehensive plan is the following:


a. Recommend appropriate City departments and Austin Energy jointly explore and develop construction methods that reduce and improve sound attenuation at outdoor venues.

b. Recommend the City require all future Central Business District (CBD) commercial venues to adhere to enhanced construction methods that include improving acoustical insulation and soundproofing.

Noise Mitigation

Noise elements frequently provide guidelines for noise mitigation methodology.  This can include recommendations for erecting noise barriers, suggested building shell design, and land use or property arrangement techniques.  To those not trained in acoustics, the benefits or pitfalls of certain noise mitigation techniques may not be obvious and such a section provides a good starting place for any noise mitigation effort.

Other Sections

Additional sections addressing other noise sources such as industrial noise or commercial noise are common.

Also, sections dealing with types of noise sensitive areas, such as parks, religious places, or solemn areas such as cemeteries are possible.  Austin is a very outdoor oriented city that features a number of important outdoor public spaces.  Parks, trails, gardens, and outdoor museums all benefit from protection from noise.

In Conclusion

The impetus for a noise element in the comprehensive city plan already exists, as evidenced by ATCP 2008 and other official city documents.  The reason for the exclusion of a noise element from the initial 10 planned elements of the Comprehensive Plan is probably a simple lack of knowledge of such a document type.  When reviewing Austin’s already existing goals for protecting its residents and workers from unwanted noise, developing a noise element should seem like an obvious choice.  Consolidating all noise goals into a single location will provide uniformity and avoid redundancy.

Here are a few examples of noise elements from other city plans.

San Diego



Comprehensive Plan Open House, October 12

The open house for the in-development Austin Comprehensive Plan is this Columbus day, October 12th.  Between 3:00 to 8:00 at the Austin Convention Center, Ballroom B.

This will be an opportunity for the public to start to get involved in the development of the new plan.  After this, there will be a series of workshops and meetings and other forms of communication between city representatives and the general public, but this will probably be the best opportunity to just show up and talk to people for just as long as you’d like.  Children are welcome.

Comprehensive Plan Website

I will try to author a succinct explanation of why Austin should have a noise element in our city plan before the open house.  I intend to keep delivering that message throughout the plan development process, or until a good reason to the contrary is presented to me.

Certifying Outdoor Live Music Venues

This is the result of an idea I had while thinking about the concept of certifying sound engineers to work live music venues in an effort to help control community noise.  This idea was presented by the Live Music Task Force last November in their Overview and Recommendations Report.

My intention with this article is to generate discussion.  I feel like I might have a good idea here, but I could be missing something very important.  So please, share any thoughts you have.

I do, actually, like the idea of training sound engineers in acoustics.  I think giving them a better understanding of acoustics on a scientific level will help them understand how music from their venue travels to their neighbors, and things that can be done to mitigate it.  I don’t know that a training or certification program is necessary, however, to accomplish the goal of increasing harmony between music venues and their neighbors.  I think money and time might be better spent analyzing and certifying the venues themselves.

Address the Noise Issue Before the First Band Takes the Stage

In some places, when a new outdoor venue is built, or when an existing outdoor venue is modified, an acoustical analysis is performed to determine whether the new or remodeled venue will exceed noise levels specified in ordinances or agreements between the venue’s owners and the city or county or neighborhood.  When I worked in California, I performed several of these analyses, including one for the proposed (but never built, as far as I know) new State Fairground amphitheater in Sacramento.

It makes a lot of sense to do this type of analysis before spending a lot of money on a new venue.  A venue that undergoes an analysis by an acoustical engineer (either by contract or through the city) can provide a sort of guarantee to the surrounding community that, during normal operation, they will not exceed specified noise levels.

It is almost always easier and cheaper to avoid noise issues up front than to fix them after they occur.  There’s a very real and relevant psycho-acoustical concept: once someone is aware of a noise, it is almost impossible to quiet the noise enough that the person won’t hear it any more.  Likewise, once a venue plays music that is too loud and annoys the neighbors, it becomes difficult or impossible for the venue to operate in a way that does not generate more ill will from the surrounding community.

Special Live Music Venue Noise Limits

The A-weighted levels that appear in virtually every noise ordinance are meant to act as a catch-all, and aren’t well suited to music in particular.  dBA are much better suited to broadband noise sources, such as machinery and highway traffic. Using the same A-weighted limits for all types of noise is sort of like hammering a nail with a wrench: it works, but there’s a better tool for the job. Since a live music venue produces a very specific type of sound, a separate set of noise level limits could be developed that apply only to permitted venues.

The Hollywood Bowl has a special set of rules for property line noise that was developed in an agreement between Los Angeles County and the surrounding neighborhood.  Recogizing that music is dynamic and tonal, the crafters of this agreement created a very fair and well thought out system.  Rather than a single do-not-exceed level, there are 4 different levels that trigger depending not just on whether they are exceeded, but for how long they are exceeded.  The highest level is not to be exceeded, the second highest level can only be exceeded a few minutes every hour, the third highest level can be exceeded for around 10 minutes per hour, and the lowest level can be exceeded for up to around 20 minutes per hour.  This keeps the majority of noise below the lowest limit but offers some leeway for the dynamics that are inherent to music.

A system exactly like the Hollywood Bowl’s might be too complicated to apply to every outdoor music venue in Austin, but the idea is still sound.  When a permit is issued to a venue, that venue becomes exempt from general limits in the noise ordinance, and instead becomes bound by a set of limits designed around live music. This is fair to both the venue and the neighbors around it.

Every Venue is Different

Each venue has its own characteristics.  Different equipment, different stage location, different natural features, different paths and distances to neighbors. Instead of a blanket policy that applies blindly to all venues, each venue should be set to operate to a set of limits that are specific to its situation. An analysis by an acoustical engineer could determine the maximum sound pressure level (SPL) generated by the venue, as measured at the mixer, that would not impact the neighbors. Any sound engineer working at that venue would be made aware of the maximum level and, using a sound level meter at the mixer, could set his PA volume confidently, knowing levels at the neighbor’s house will always be acceptable.

Perhaps some venues are in neighborhoods that are more amenable to the sounds of live music in the air at night.  Through negotiations between the neighborhood and the venue, higher levels could be agreed upon.  Maybe these agreements could be attached to the properties involved in the negotiation, like a sort of “sound easement.” There are a lot of ways this could go, and as far as I can tell, it will always result in a more equitable arrangement than the blanket 85 dBA at the property line system that’s in place now.

Make it Part of The Permitting Process

To get an outdoor music venue permit, the owner would need to demonstrate that, during normal operations, music from their venue will not exceed the applicable limits, as measured at the nearest residences. This could be accomplished through an actual physical demonstration, or it could be accomplished through analysis by an acoustical engineer.  The acoustical engineer could be a third party, hired by the venue, or perhaps there will be an acoustical engineer on staff at the city.

After the city reviews the analysis or demonstration, a permit could be issued that is particular to that venue, including specifications for noise limits at the nearest neighbors and sound level limits at the mixer.  If a venue makes a significant change to their equipment or orientation, they would need to have a new analysis performed a provide a new demonstration to renew their permit.

If a venue is found to be in violation of the limits specified in their permit, the permit could be threatened, suspended, or revoked.  The potential for loss of a music permit is likely a much stronger deterrent than periodic warnings from police officers.

What About the Cost?

Hiring an acoustical engineer is not inexpensive. Neither is the process of acquiring all of the other permits and licenses needed to operate a venue.  At first glance this seems unfair to the venue owners.

If the analyses could, optionally, be performed by an acoustical engineer on the city staff, this work could be done on a non-profit cost basis.  A permitting fee of, say, $500, could go a long way towards covering this. We often hear that live music is a $1-billion dollar industry in Austin.  In comparison to that figure, the cost of keeping a single acoustical engineer on staff at the city seems pretty small.

Some of these costs would also be offset through the reduction of the indirect costs.  Equipping and training a police force with dozens of sound level meters and deploying officers for every noise complaint is not cheap.  Also, owners would save money by avoiding noise issues through intelligent venue design, rather than expensive fixes later in the process.

Comprehensive Plan Draft Participation Plan available

The Comprehensive Plan Committee will be meeting next Monday, September 14th at 6:00 PM.  Up for discussion is the just-released Draft Participation Plan (see below for download link).

The goal of the Participation Plan is to create a framework to solicit public input to create a new Comprehensive Plan for Austin. This new plan should give clear direction for future policies, be rooted in Austin’s broad common ground, and incorporate, where possible, novel reconciliations of diverse interests.

The process of developing the City Plan is still in its early stages.  The plan itself isn’t yet being crafted, but the methodology that will be used to do so is.  I intend to pay close attention to the process because I believe very strongly that the new City Plan should have a Noise Element.

Although there is currently no noise element planned for the City Plan, there are a number of  noise-related items scattered throughout the 2008 Austin Tomorrow Comprehensive Plan Interim Update, which will provide the basic framework for the beginning of the Comprehensive Plan (I counted 15 policy goals dealing with noise when I skimmed through it last).  It makes sense to consolidate these policies into a single body for consistency and clarity.

The idea of a noise element isn’t new.  In 2001, CAMPO recommended that cities in the CAMPO area, including Austin, develop noise elements for their city plans.  In California, all cities are required to incorporate noise elements in their city plans.  There are plenty of examples to work with.

Relevant Documents:

Draft Participation Plan

Recommendations for Action by CAMPO, City of Austin, Capital Metro and Others

Austin Tomorrow Comprehensive Plan Interim Update