HomeMy WebLinkAboutLighning Speed Karts Yarmouth sound study DRAFTJune 14, 2023
Ms. Maria Curtis
Lightning Speed Karts
228 MA Route 28
West Yarmouth, MA
mcurtis1@hotmail.com
SUBJECT: Acoustic Evaluation
Lightning Speed Karts Yarmouth Facility
West Yarmouth, MA
Dear Ms. Curtis,
Cavanaugh Tocci has evaluated environmental sound impacts associated with the proposed Lightning
Speed Karts facility in Yarmouth, MA. The objective of this evaluation is to characterize sound from the
facility, and to estimate the potential acoustic impact of the facility on the surrounding community. This
memo summarizes the results of our cursory evaluation. Appendix A of this report is a glossary of
relevant acoustic terminology.
Site and Vicinity
The proposed facility is located at 228 MA Route 28, West Yarmouth, MA. Proposed operating hours are
10 AM – 10 PM July-August, and 3 PM – dusk April-June and September-October, with no operations
November-March. The proposed facility and most abutting properties are zoned for business use (B2).
The nearest occupancy is the Sunbird Cape Cod Resort Hotel to the northwest, with nearest units
approximately 150 feet from the kart track. Residences are located south, west, and northeast of the
proposed track with at distances of 200-900 feet.
Figure 1 shows a plan view of the proposed facility and abutting properties.
State and Local Regulations
Noise is addressed in Section 104 of the Code of the Town of Yarmouth. The code does not establish
specific limits regarding sound, and does not establish any restrictions during the hours 7 AM – 11 PM,
when the facility would be operating.
Sound Measurements
Short-term handheld measurements were performed to assess existing ambient sound levels and sound
levels produced by typical karts to be used on the track. The instrument used was a Bruel & Kjaer 2250
Type 1 sound level meter calibrated on site. Sound produced by two types of karts (Rimo and Bowman)
was measured.
Ms. Maria Curtis, June 14, 2023 Page 2
Environmental Sound Evaluation
Lightning Speed Karts Yarmouth Facility
Ambient Sound
Ambient sound was measured continuously for a period of 10 minutes with no karts operating. The
location for this measurement is labeled “BKG” in Figure 1. The ambient measurement location was
aligned with the end motel unit of the Sunbird Cape Cod Resort furthest from Route 28 where ambient
sound levels are lowest.
Measured sound at this location varied between 50 and 60 dBA throughout the measurement interval,
and was dominated by MA Route 28 traffic. Ambient sound levels at other times will vary depending on
traffic volumes and speeds. We recommend a facility noise design goal of 50 dBA at the nearest Sunbird
Cape Cod Resort units. This goal would apply for typical busy operation, assumed to be four Rimo and
four Bowman karts operating simultaneously.
Sound Source Measurements
Each type of kart was operated at full throttle. Sound was measured as karts passed by the microphone
at a distance of 20 feet. The maximum measured sound pressure levels are presented in Table 1 for the
two types of karts.
Table 1. Maximum Measured Kart Sound Pressure Level (dBA)
Kart Type Measured Sound
Pressure Level (20 ft)
Rimo 75
Bowman 81
Facility Sound Analysis
The Sunbird Cape Cod Resort has installed a solid vinyl fence along the lot line between the two
properties. In addition, a four-foot masonry wall is being considered to separate the kart track from the
facility parking lot, as shown in Figure 1. A simple model of the facility estimates that the combined
barrier effects from these structures will reduce sound levels at the nearest Sunbird Cape Cod Resort
units by 8-11 dBA from measured property-line values.
Combining measured sound levels, estimated barrier effects of the vinyl fence alone, and four Rimo and
four Bowman karts operating simultaneously, we would expect sound levels at the facade of the nearest
Sunbird Cape Cod Resort units to be approximately 56 dBA with levels as low as 50 dBA for minimal
operation of two Rimo karts.
Typical glazing can be expected to reduce sound levels by 25 dB when closed or 15 dB when open,
resulting in in-room sound levels due to the kart facility of 25-30 dBA with closed windows or 35-40 dBA
with open windows. For comparison, sound for mechanical systems in hotel facilities is recommended to
be 35 dBA. This recommendation is intended for central ventilation systems, whereas the Sunbird Cape
Cod Resort units are cooled by through-wall air conditioners, which are typically noisier than central
units and most typically produce room sound levels exceeding the usual recommended design goal of
Ms. Maria Curtis, June 14, 2023 Page 3
Environmental Sound Evaluation
Lightning Speed Karts Yarmouth Facility
35 dBA. We would therefore expect kart facility sound to be somewhat below the recommended level
for room ventilation system sound with windows closed, somewhat above with windows open, but, in
either case, probably below sound levels produced by existing through the wall units currently installed.
Recommendations
Measured sound levels for the Bowman kart were 6 dB higher than for the Rimo. This means that a
single Bowman kart generates the same sound energy as four Rimo karts. Sound impacts would be
reduced by preferential use of Rimo karts, or by implementing exhaust controls and throttle restrictions
for Bowman karts to lower sound levels by 6 dBA. The facility operators intend to replace the exhaust
units on the Bowman karts, and to install exhaust baffles to further reduce sound levels. Speeds of all
karts will be limited to 19 mph (karts were unrestricted during sound measurements). These controls
would be of particular benefit to neighboring properties that would experience less shielding from the
barrier structures discussed above.
We would recommend proceeding with implementation of the proposed 4-foot tall masonry wall to
obtain the needed reduction in sound level.
If exhaust treatment of the Bowman Karts achieves a sound reduction of 6 dB, and the 4-foot masonry
wall is implemented, we would expect the facility to achieve our recommended design goal of 50 dBA at
nearest Sunbird Cape Cod Resort units.
Conclusion
A brief environmental sound study was performed for the proposed Lightning Speed Karts facility in
Yarmouth, MA. Measurements were performed to determine sound levels due to operation of facility
karts, as well as the background sound level in the area. We expect in-room sound levels at the
neighboring Sunbird Cape Cod Resort units will be acceptable if the proposed 4-foot masonry wall is
constructed at the location shown in Figure 1 and if exhaust and throttle sound controls are
implemented on Bowman karts.
Sincerely,
CAVANAUGH TOCCI
Bradley M. Dunkin, Associate Principal Consultant
23147/Lighning Speed Karts Yarmouth sound study 1d.docx
FIGURES
Figure 1
Appendix A
Sound Measurement Terminology
Appendix A – 1
SOUND MEASUREMENT TERMINOLOGY
In order to quantify the amplitude, frequency, and temporal characteristics of sound, various acoustical
descriptors are used. The following is an introduction to acoustic terminology that is used in this report.
Sound Level
Sound levels are typically quantified using a logarithmic decibel (dB) scale. The use of a
logarithmic scale helps to compress the wide range of human sensitivity to sound amplitude into
a scale that ranges from approximately 0 to 180 dB. Note however, that the use of the
logarithmic scale prevents simple arithmetic operations when combining the cumulative impact
of sources. For example, two sources of equal sound level operated simultaneously results in a
combined sound level that is only 3 dB higher than if only one source was operated alone. An
important feature of the human perception of continuous sound is that an increase or decrease
in sound pressure level by 3 dB or less is barely perceptible, and an increase or decrease by
10 dB is perceived as a doubling or halving of noise level.
A-weighting
Generally, the sensitivity of human hearing is restricted to the frequency range of 20 Hz to
20,000 Hz. However, the human ear is most sensitive to sound in the 500 Hz to 5,000 Hz
frequency range. Above and below this range, the ear becomes progressively less sensitive. To
account for this feature of human hearing, sound level meters incorporate filtering of acoustic
signals that corresponds to the varying sensitivity of the human ear to sound at different
frequencies. This filtering is called A-weighting. Sound level measurements that are obtained
using this filtering are referred to as A-weighted sound levels and are signified by the
identifier, dBA. A-weighted sound levels are widely used for evaluating human exposure to
environmental sounds. To help place A-weighted sound levels in perspective, Figure A-1
contains a scale showing typical sound levels for common interior and environmental sound
sources.
Spectral Characteristics – Octave and 1/3 Octave Band Sound Levels
To characterize a sound, it is often necessary to evaluate the frequency distribution of the sound
energy. As mentioned before, the frequencies of most interest where human exposure is
concerned range between 20 Hz and 20,000 Hz. This frequency range is commonly divided into
octave bands, where an octave band is a range of frequencies. Each octave band is referred to
by its center frequency and has a bandwidth of one octave (a doubling of frequency). To cover
the full range of human hearing, it is necessary to measure sound in 10 separate octave bands.
Typically, the lowest frequency band measured has a center frequency of 31.5 Hz. The next
frequency band has a center frequency of 63 Hz. This geometric series continues to the highest
frequency band that has a center frequency of 16,000 Hz. A set of octave band sound levels to
describe a particular sound is called an octave band spectrum. Covering the full range of
Appendix A – 2
hearing, an octave band spectrum would have 10 values, one for each band. Under certain
circumstances, more frequency resolution in acoustical data is needed to identify the presence
of tonal sounds. A 1/3 octave band spectrum uses filters that divide each octave band into 3
separate frequency bands. Note that octave band and 1/3 octave band sound levels are not
usually A-weighted, with their units being dB.
Environmental Noise Descriptors
Sound levels in the environment are continuously fluctuating and it is difficult to quantify these
time-varying levels with single number descriptors. Statistical approaches, which use percentile
sound levels and equivalent sound levels, are often used to quantify the temporal characteristics
of environmental sound.
Percentile sound levels (Ln) are the A-weighted sound levels that are exceeded for specific
percentages of time within a noise measurement interval. For example, if a measurement
interval is one hour long, the 50th percentile sound level (L50) is the A-weighted sound level that
is exceeded for 30 minutes of that interval.
L90 is the sound level in dBA exceeded 90 percent of the time during the measurement
period. The 90th percentile sound level represents the nominally lowest level reached
during the monitoring interval and is typically influenced by sound of relatively low
level, but nearly constant duration, such as distant traffic or continuously operating
industrial equipment. The L90 is often used in standards to quantify the existing
background or residual sound level.
L50 is the median sound level: the sound level in dBA exceeded 50 percent of the time
during the measurement period.
L10 is the sound level exceeded only 10 percent of the time. It is close to the maximum
level observed during the measurement period. The L10 is sometimes called the
intrusive sound level because it is caused by occasional louder noises like those from
passing motor vehicles or aircraft.
By using percentile sound levels, it is possible to characterize the sound environment in terms of
the steady-state background sound (L90) and occasional transient sound (L10).
The equivalent sound level (Leq) is the energy average of the A weighted sound level for the
measurement interval. Sounds of low level and long duration, as well as sounds of high level
and short duration influence this sound level descriptor.
Noise levels at night generally produce greater annoyance than do the same levels which occur
during the day. It is generally agreed that a given level of environmental noise during the day
would appear to be 10 dBA louder at night – at least in terms of potential for causing
community concern. The day night average sound level (Ldn) is a 24 hour average A-weighted
Appendix A – 3
sound level where a 10 dB “penalty” is applied to sound occurring between the hours of
10:00 p.m. and 7:00 a.m. The 10 dB penalty accounts for the heightened sensitivity of a
community to noise occurring at night.
When a steady continuous sound is measured, the L10, L50, L90 and Leq are all equal. For a
constant sound level, such as from a power plant operating continuously for a 24-hour period,
the Ldn is approximately 6 dBA higher than the directly measured sound level.
Figure A-1
Typical Sound Levels for Common Interior and Environmental Sources