Sound Study, Seattle, Washington

Date of study:  02/12/04
Engineer:  Matthew Lee Johnston

Study Guidelines

I. Study goals:

  • To audit and measure various sources of ambient persistent noise in and surrounding the proposed Ballard Civic Center Park site.
  • Compare noise levels of sources within the park site with other common sources of ambient noise in the community.
  • Determine specific compliance of noise sources with maximum noise levels allowed as outlined by Seattle Department of Planning and Developmentπs Noise Abatement Program.

II. Selection of Study Locations

In choosing locations to perform the above study, there were criteria set forth that locations must meet.  These criteria were as follows:

  • The locations must be contained within the community of Ballard.
  • The survey locations must be adjacent to each other so each location is somewhat relative to the other.

These criteria were examined and it was determined that these sources were to be the subjects of the subsequent study:

  • Sources in and around the commercial property adjacent to the Civic Center Park site – selection: the QFC Grocery store.
  • Sources in and around the Civic Center site – selection:  The skateboarding facility.

III. Selection of Measurement Locations

Criteria were also set for the selection of measurement location.  The criteria are as follows:

  • Locations with a history of noise complaints.
  • Locations where citizens have expressed an interest in their neighborhood noise levels.
  • Locations along busy roads and at busy intersections that possess a high volume of traffic.
  • Source and survey locations are to be no more than .5 miles apart, regardless.
  • Each location must be able to satisfy the measurement process that is explained below.

IV. Measurement Taking Protocol

Measurements for this study will be taken as follows:

  • Each location will be measured for no less than 10 minutes a session, and each location will be measured three times.
  • All measurements will be taken on the same day.
  • Each measurement will be taken once, for the full 10 minutes, unless circumstances deem otherwise, such as weather. In this case, if the particular measurement is or is under 10 minutes, then the remaining time will be made up at a later date to fulfill requirement.
  • The measurements taken during each session must contain a real-time dB (decibel) readout, and a tape recording of the sounds recorded if needed, so that analysis can be made as to the frequency makeup of particular sounds.  The dB measurement shall be taken with an A weighting.  This weighting coincides with the level of volume that people associate with a noise.  Also, preferably, but not necessarily, a photographic record of the object(s) producing the sound(s) should be obtained.  If this is not obtained, then a written description of the object(s) should be done.
  • Measurements will be taken using the Bruel & Kjaer 2225 Sound Level Meter, which will be calibrated before each reading using the Bruel & Kjaer 4230 Sound Level Calibrator.
  • The equipment used in this study is known and proven to comply with the requirements outlined in the Seattle Municipal Code article 25.08.680  ≥Measurement of sound≤.

V. Processing of Data

When processing the data, the real time dB reading will be the key to this study.  These go as follows:

  • A description/photo of the object, business, etcä that seems (to the person recording) the source(s) of the loudest/most disturbing noise.
  • The Max and Min values of the dB
  • Basic Frequency Spectrum analysis from the measurement of the loudest source, most disturbing source, etc.

Study Data

All of the noise monitoring was accomplished using a B+K 2225 Sound Level Analyzer. A B+K 4230 calibrator was used to routinely calibrate the system. At all locations the microphone was adapted with a random incidence corrector and mounted on a tripod which placed the microphone at a height of at least five feet above the ground. The tripod was normally placed at the property line separating the public premise (street or sidewalk) and the monitoring site and at least ten feet from any large reflecting surface (wall, building etc.)

Environmental conditions were noted and evaluated at each site and dictated whether the noise monitoring would be conducted at any particular time and date. No monitoring was conducted if any the following conditions existed:

  • Precipitation sufficient to cause the streets to become wet.
  • Wind speed in excess of ten miles per hour even though a wind screen was always used on the microphone.
  • The presence of any temporary atypical noise source above minimal (L90) levels such as chain saws used in tree trimming operations, or nearby lawn maintenance equipment.

Field forms were used to document each site. Recorded information included the site address, premise type, zoning, date and time of daytime/nighttime monitoring, wind speed, temperature, ambient noise sources, and a diagram showing the location of the site and the location of the microphone at the site.

Primary Site – The Ballard Civic Center Park site (Seattle, WA)


Site #1: “Across the street”

Site address: 2217 NW 57th St
Time: 12:32 PM start 12:55PM end
Wind: <2mph
Temp: high 50πs
Precip: none
Noise conditions: local vehicles

General observations: This site was selected due to the lack of surrounding reflective surfaces around the equipment, and because it was directly in front of a business that has complained about the noise coming from the skate facility.  I asked the skateboarders to please skate without prejudice to my sound readings.  I observed one skateboarder clearly and deliberately making ≥slapping≤ noises with the tail of his skateboard.  Also, I observed a large cement wall on the North side of the bowl, which was clearly reflecting the sounds made in the bowl to the adjacent environment.  This wall likely amplifies the general noise form the bowl by at least 20% and the more punctuated sounds made by skateboards up to 30%.  There was a light amount of local traffic on 57th but it was not interfering with the test.  While I was taking readings of the skateboard facility, a large panel truck pulled in to the loading dock at the QFC store but did not immediately begin unloading.  After reading the skateboard facility, I waited at site #1 approximately 15 minutes before taking readings of the unloading activity at the QFC.  I also asked the skateboarders to please stop using the facility while I took the reading and they complied.

Test notes: I calibrated the sound meter, which tested accurate at +/- 0dB.  Once I verified the instrumentation, I began the reading.  I then observed the environment for 30 minutes to determine the prominent sound sources.  At 12:32pm I starting capturing data, focusing on each source for no less than 10 minutes.  Three incidental sources were also observed from this location.

Reading data from location 1:

SourceAveragePeak
Skate bowl55dB83dB
Loading dock at QFC store73dB101dB
Car with snow tires drive-byX91dB
Automatic dumpsterX101d

Site #2: “Behind the nearby store”

(image does not include truck as driver refused to be photographed)

Site address: 2237 NW 58th Street
Time: 1:05 PM start 1:17PM end
Wind: <2mph
Temp: high 50πs
Precip: none
Noise conditions: local vehicles

General observations: This site caught my attention due to the clearly audible loud and punctuated noises that seemed to be originating in the loading dock area during my test from site #1.  Again, I asked the skateboarders to please refrain from skateboarding while I took the readings and they complied.  The driver asked me what I was doing, and I explained the purpose of the test.  He then explained to me that he did not want himself or the logo on his truck to be photographed. I agreed and asked him to please go about business as usual, and try to ignore that I am there, as to not skew the readings.  There was some traffic going in and out of the parking lot, and some car door noise, but it was not interfering with the test.

Test notes: I calibrated the sound meter, which tested accurate at +/- 0dB.  Once I verified the instrumentation, I began the reading.  I then observed the environment for 30 minutes to determine the prominent sound sources.  At 1:05pm I started capturing data, focusing on the unloading activity.  No incidental sources were also observed from this location.

Reading data from location 2:

SourceAveragePeak
Loading dock at QFC store89dB117dB

Site #3: “Next to the bowl”

Site address: NW 57th Street and 22nd Ave. NW
Time: 1:25 PM start 1:38PM end
Wind: <0mph
Temp: high 50πs
Precip: none
Noise conditions: vent on side of QFC, local traffic

General observations: This site was selected because it has been cited as a disruptive source of noise by neighboring businesses.  I again asked the skateboarders to please skate without prejudice to my sound readings.  The skateboarders performed tricks directly in front of my metering equipment.  The large cement wall on the North side of the bowl did not appear to be a factor in this local reading of the source, as I did not hear a ≥slapback≤ caused by reflection.  There was less local traffic on 57th than there was during the readings from location #1, in fact I only counted two vehicles.  At this point the truck in the loading area was gone.  Finally, as I was about to move from site #3, the automatic dumpster next to the skate facility started.  I was able to get a peak reading of the dumpster, but it did not interfere in the cumulative reading of the skate facility as a source.

Test notes: I calibrated the sound meter, which tested inaccurate at + 2dB.  I made an adjustment and re-calibrated which tested accurate at +/- 0dB.  Once I verified the instrumentation, I began the reading.  The prominent sound sources in the soundscape had not changed dramatically.  At 1:25pm I started capturing data, focusing on the skate facility.  One incidental source was observed from this location.

Reading data from location 3:

SourceAveragePeak
Skate bowl68 dB91dB
Automatic dumpsterX121dB

Site #4: “Down the alley”

Site address: NW 58th Street and 22nd Ave. NW
Time: 1:45 PM start 2:01 PM end
Wind: <2mph
Temp: high 50πs
Precip: none
Noise conditions: local vehicles, vent on rear of QFC building

General observations: This site was selected in an effort to get a balanced set of data from both sides of the property.  I also wanted to get a reading from the perspective of the nearest residential zoning, which was directly behind me.  I would estimate that the distance between the measurement site and the residential property would result in approximately 30dB of attenuation.  Therefore, this reading can not technically be categorized as a reading from adjacent residential zone, but extrapolation would bring about a reasonable estimate on SPL within the residential property.   There was no local traffic on 58th during the test.  However, the vent on the rear wall of the QFC provided a substantial noise floor, which factors in to this reading.  Therefore, you will see both average and peak data for this incidental source.  Because of the large distance from all sources, the peak values are understandably low.

Test notes: I calibrated the sound meter, which tested accurate at +/- 0dB.  Once I verified the instrumentation, I began the reading.  At 1:45pm I starting capturing data, focusing on each source for no less than 10 minutes.  Two incidental sources were also observed from this location.

Reading data from location 4:

SourceAveragePeak
Skate bowl45 dB48dB
Vent on rear of QFC65dB66dB
Helicopter fly-byX70d

Seattle Noise Ordinance

This study attempts to put noise sources around the Ballard Civic Center Park location into perspective, using the Seattle Department of Planning and Developmentπs guidelines as presented in the Seattle Noise Ordinance.  The Seattle Noise Ordinance defines unlawful sound in Seattle Municipal Code subchapter 25.08.400:

SMC 25.08.400  Unlawful sounds.

It is unlawful for any person to cause sound, or for any person in possession of property to permit sound originating from such property, to intrude into the real property of another person whenever such sound exceeds the maximum permissible sound levels established by this subchapter.

Maximum permissible sound levels are defined in Seattle Municipal Code subchapter 25.08.410:

SMC 25.08.410  Maximum permissible sound levels.

For sound sources located within the City or King County, the maximum permissible sound levels are as follows:

DAYTIME (7 am-10 pm)
District of Sound Source District of Receiving Property
ResidentialCommercialIndustrial
Residential555760
Commercial576065
Industrial606570

(Ord. 106360 Section 302, 1977.)

It is unclear to the author of this study where a park site fits into this matrix, or if a city park site is even subject to the same ordinance.  Therefore, I have chosen to assess the data using the site’s current zoning classification; “Commercial.”  This being the median value on the matrix makes this acceptable to the author for the purposes of this study.

It is also important to note that intermittent punctuated noises are not themselves subject to scrutiny within the Seattle Noise Ordinance, therefore the peak values in this study are merely for reference.  The average values should be assumed as the cumulative result of noise emanating from the source cited, and therefore should be considered to be the driving data by which comparisons are made.

Study Summary

In summary, my assessment of the area surrounding the Ballard Civic Center Park site is typical of any central urban area: itπs noisy.  The driving focus of this study was to compare the major sources of noise within the Ballard Civic Center Park to each other, as well as contrast them with the noise limits set forth by the City of Seattle in the Seattle Municipal code.

If one were to look at the peak values associated with any of the subjects in this study, one would clearly see that almost all subjects exceed the limits set forth in the DPD’s Noise Ordinance.  However, the ordinance clearly states that duration and time-of-day are key to the equation.  With this in consideration, it’s clear that the majority of the incidental sources are merely good points of reference as they do not embody a constant point of presence in the local sonic environment, especially in the evenings.  However, it is important to note that when looked at in comparison, it’s clear that everyday events such as passing cars and overhead air traffic are often intrusive elements in our sonic surroundings.

The QFC Store

Average SPL:  73dB

Status of Seattle Noise Ordinance compliance:  non-compliant

The average data suggests that the QFC is non-compliant at 73dB from the nearest adjacent property.  The reading however can be somewhat misleading as the average values are largely built on a summary of 5-10 peak events over the course of the reading duration.  The primary difference however, is that the base frequency of those intermittent events is much lower and therefore travels much further.

Lower frequencies such as those observed during the tests, are omni directional and have a much lower rate of attenuation.  Therefore the sounds originating from the QFC loading dock travel much further and are more pervasive in the immediate environment.  It is not known for sure if the loading activity continues into the evening or early morning, however even by daytime standards the noise originating from then QFC greatly exceeds the legal limits defined by the Seattle Noise Ordinance.

Readings taken from site #2 show that at point blank range, the peak events occurring within the QFC loading dock are 25dB higher than the skate facility.  This is merely comparison data, as stated earlier, these readings are not useful when trying to determine Noise Ordinance compliance.  However, it does show that there is a substantial differential of volume between the loading dock and the skateboard facility.

It should also be noted that while not a direct subject of the study, the automatic compacting dumpster directly adjacent and between the skate facility and the QFC loading dock is also non-compliant.

The Skateboard Facility

Average SPL:  55dB

Status of Seattle Noise Ordinance compliance:  compliant

The average data suggests that the skateboard facility is compliant at 55dB from the nearest adjacent property.  The reading, like the reading of the QFC, can be somewhat misleading as the average values are largely built on a summary of 5-10 peak events over the course of the reading duration.  Therefore, while there may be intermittent bursts of noise emanating from the facility, it does not pose a considerable problem in terms of consistent noise pollution.

The existence of the large cement wall to the north of the facility is of great consequence to the perception of noise from surrounding perspectives. A substantial ≥echo≤ effect can be heard from site #1. This must be factored in to the study, if only as a point of consideration by the reader.  The physical construction of the cement bowl structure is typically a sound trap that serves to keep most of the persistent noise contained within the structure. This is why the sound signature of this particular subject is that of intermittent “slapping” and not a constant “wooshing” of movement heard when standing on the platform surrounding the bowl itself.

Readings from site #3 do not provide much useful information beyond what was gathered from across the street at location #1.  However, the data captured at the edge of the bowl is useful for comparison with other point-blank readings from adjacent sound sources such as the trash dumpster and the loading dock.

Readings from site #4 provide a useful point of reference for attenuation values relating to the nearest residential properties.  The data shows that the skateboarding facility does not pose a noise risk to the residential properties on 58th street, and that noise from the bowl attenuates substantially in less than a block due to the high-frequency nature of the sound produced by the skateboarders.

About Soni-Fi LLC

Soni-Fi LLC is a firm dedicated to consulting, design, and implementation of environmental audio solutions.  Soni-fi was founded by Matthew Lee Johnston, a ten year Microsoft veteran.  Soni-Fi is currently designing civic audio installations, commercial audio environments, hardware device interfaces, and specialized consumer products that all aim at creating a more harmonious and less polluted sonic environment for all people.