Subject: Blue Horseshoe Island Clay Township, Michigan ...

Soundscape Engineering LLC 3711 N. Ravenswood Ave., Ste. 104 • Chicago, IL 60613 • (312) 436-0032

729 W. Ann Arbor Trl., Ste. 150 • Plymouth, MI 48170 • (734) 418-8663 www.SoundscapeEngineering.com

June 3, 2019 Joe Henninger 7317 Dyke Rd. Clay Township, MI Subject: Blue Horseshoe Island Clay Township, Michigan Site Sound Study Report Dear Mr. Henninger: Soundscape Engineering has completed our investigation of the site sound study regarding sound propagation from the future restaurant and outdoor deck area. This report contains our findings. Project Background Your company would like to hire a qualified acoustics consultant to construct a predictive sound propagation model for the future restaurant on Blue Horseshoe Island and neighboring properties. The address of the future restaurant is 7317 Dyke Road, Clay Township, Michigan. Dyke Road/MI-29, which is located approximately 500 feet to the east from the future restaurant site, is a two-lane state highway with 20,890 AADT traffic volume (Average Annual Daily Traffic per MDOT). The area is also exposed to recreational boat noise on days with favorable weather. The local noise ordinance for Clay Township states the following in Article IV. Noise, Section 12-83 Anti-noise regulations.

(a) Unreasonable / improper noise prohibited. No person shall cause or create any unreasonable or improper noise or disturbance, injurious to the health, peace or quiet of the residents and property owners of the township. (b) Prohibited noises enumerated. The following noises and disturbances are hereby declared to be a violation of this article; provided, however, that the specifications of the same are not thereby to be construed to exclude other violations of the article not specifically enumerated:

(2) Electronic equipment, musical instrument. The playing of any electronic equipment or any musical instrument in such a manner or with such volume as to annoy or disturb the quiet, comfort or repose of other persons.

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Additionally, Section 3.12 Performance Standards of the Zoning Ordinance #126 states:

No commercial or industrial use otherwise allowed shall be permitted within any district which does not conform to the following standards of use, occupancy and operation. These standards are hereby established as the minimum requirements to be maintained for said uses. Generally accepted methods of collection and standard methods of chemical analysis shall be used in the application of these requirements:

(5) Noise. Noise shall not be emitted which exceeds seventy (70) decibels as measured at the property boundary line, except that where normal street traffic noises exceed seventy (70) decibels during such periods, the measurable noise emanating from subject premises may be equal to, but shall not exceed such traffic noises.

Typically noise ordinances use A-weighted sound level, but since the Clay Township ordinance does not directly address weighting standards in this section, we are providing sound level guidance in both unweighted (Clay Township metric cited in ordinance) and A-weighted levels (typical of other ordinances). Acoustics Terminology We have provided a brief description of the acoustics terminology used in this report in Appendix A. It may be useful to refer to the appendix while reading this report. Analysis and Results The restaurant sits at the south western edge of Blue Horseshoe Island with a series of garage doors opening from the dining room toward Lake St. Clair and the pool area. The major sound concern is loud music coming from a live DJ. It is our understanding that the DJ will set up either inside the restaurant, typically with all the garage doors open, or outside on the patio, see Figure 1. We are told that in winter and inclement weather, the garage doors will be closed with the DJ located indoors. In this analysis, we used a time averaged level (Leq) for the music source level since it is a consistent metric that is widely available on sound level meters. The style of music in the model contains high levels of bass, which is typical of DJ style music.




Figure 1: Restaurant Layout

SoundPlan, which is a commercially available software package, was used to construct a three-dimensional acoustics model to predict the sound level at the property lines. See Figures 2 and 3 for a mapping of the predicted levels using dBA as the requirement (dBA level is the software output). Based on the model, it was determined the maximum sound levels in the patio area can be no greater than the values presented in Table 1 to meet either 70 dB or 70 dBA at the property line. Typically, noise ordinances provide sound level limits in dBA. Occasionally, when the A-weighting designation is not indicated, as in “dB”, it may be inadvertently or intentionally omitted. The Clay Township ordinance cites 70 dB in this section but requires dBA in an unrelated section (Section 20.17 Composting Facilities). As there is no apparent reason for the two different metrics to be used in the same jurisdiction, we have assumed that 70 dBA may have been intended. To be complete, we have provided guidance for the levels for both cases. Please confer with you lawyer about which metric to abide by, A-weighted (dBA) or unweighted (dB). Regardless, the guideline level on the patio will be the same numeric value as long as the sound level meter settings (dB vs. dBA, fast vs. slow time weighting) are set to exactly what the Township uses.

Table 1: Patio Sound Level Limit Guidelines

Ordinance Limit Interpretation

Corresponding Patio Sound Level

70 dB 93 dB

70 dBA 93 dBA




Figure 2: SoundPlan Results – A-weighted Sound Level Prediction




Figure 3: SoundPlan Results – Sound Propagation Pattern

Note that the model predicted little impact from road noise to the overall receiver levels, which was in the 50-60 dBA range as seen along the road in Figure 3. Site sound level measurements would be needed to refine the road noise prediction.




Conclusions Our predictions indicate that the maximum allowable ordinance level of 70 dB can be achieved by limiting the sound level on the deck area to 93 dB. The loudest point along the property line is to the south, with lower levels along the east and north property lines. This concludes our assessment and results. Thank you for the opportunity to assist you with this project. Please contact us if you have any questions. Sincerely,

Soundscape Engineering LLC Per:

Anna Catton, MSAE Mandy Kachur, PE, INCE.Bd.Cert. Consultant Principal Consultant [email protected] [email protected]



Appendix A: Acoustics Terminology Sound level is measured in units called decibels (abbreviated dB). Decibels are logarithmic rather than linear quantities and thus a doubling of the sound level does not translate to a doubling of decibels. Also, the human ear does not interpret a doubling of sound energy as a doubling of loudness. The logarithmic nature of dB and the human subjective perception of relative sound levels result in the following approximate rules for judging increases in sound.

• 3 dB sound level increase or decrease - barely perceptible • 5 dB sound level increase or decrease - perceptible and is often considered significant • 10 dB sound level increase or decrease - perceived as twice as loud/half as loud

These perceived changes in the sound level are mostly independent of the absolute sound level. That is, a 35 dB sound will be perceived as twice as loud as a 25 dB sound, and a 60 dB sound will be perceived as twice as loud as a 50 dB sound. A table of common sound levels is provided on the following page. Audible sound occurs over a wide frequency range, from low pitched sounds at approximately 20 hertz (Hz) to high pitched sounds at 20,000 Hz. These frequencies are commonly grouped into octave bands or 1/3 octave bands. Building mechanical systems generally produce sound in the 63 Hz to 1000 Hz octave bands, with the lower frequency sound generated by large fans. Human speech is predominantly contained in the 250 Hz to 2000 Hz octave bands. A-weighted sound level - Humans do not hear equally well at all frequencies. We are especially poor at hearing low frequency sound and are best at hearing sound in the frequency range of human speech. A microphone does not have these same characteristics. Therefore, when sound is being measured to determine how well people will be able to hear it, a "weighting" or microphone-to-human correction factor is applied to the sound level measured using a microphone. The most common weighting is the "A-weighting" and the resulting sound level is expressed in A-weighted decibels (dBA). This weighting reduces the low frequency sound, slightly increases the sound at the dominant frequencies of human speech, and slightly lowers the sound level at high frequencies. Equivalent Sound Level (Leq) is essentially the average sound level in an environment. However, the Leq is not a simple arithmetic average of the sound level over time, but is a logarithmic average. It is the average sound energy level over a period of time. Leq can be measured for any time period, but is typically measured for some increment or fraction of an hour such as 15 minutes, 1 hour or 24 hours. Maximum sound level (Lmax) is the highest sound level that occurs during a measurement period. Slow Response or Slow Time Weighting is a measurement setting that uses a time constant of 1 second. This setting is most appropriate when the sound level being measured does not fluctuate much. Fan and condensing unit noise are examples of sounds that do not fluctuate much. Some regulations, ordinances, and standards call for a slow response setting regardless of the type of sound source. Fast Response or Fast Time Weighting is a measurement setting that uses a time constant of 125 milliseconds. This setting is most appropriate when the sound level being measured fluctuates quickly, but is also often used as a default setting. Music and speech are examples of sounds that fluctuate quite a

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bit. Some regulations, ordinances, and standards call for a slow response setting regardless of the type of sound source.

Various sound sources and their approximate levels

Sound Pressure Level (dBA) Sound Source

130 Threshold of pain

120 Loud rock band near loudspeaker

110 Train siren at 50 ft

100 Loud automotive horn at 10 ft

90 Subway train at 20 ft

80 Lawn mower at 10 ft

70 Boeing 757 aircraft cabin during flight

60 Conversational speech at 3 ft

50 A quiet dishwasher at 3 ft

40 Soft background music or Wind in trees (10 mph)

30 Average residential interior with closed windows – no activity

20 Whisper

10 Human breathing

0 Threshold of audibility

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