Environmental Noise Assessment
CCL06126 AT&T Cellular Facility
City of Santa Clara, California
BAC Job #2023-021
Prepared For:
Complete Wireless Consulting
Attn: Steve Proo
2009 V Street
Sacramento, CA 95818
Prepared By:
Bollard Acoustical Consultants, Inc.
Dario Gotchet
Principal Consultant
Elected Member, Institute of Noise Control Engineering (INCE)
September 18, 2024
Bollard Acoustical Consultants, Inc. | P.O. Box 7968, Auburn, CA. 95604 | P: (530) 537-2328 | bacnoise.com
Bollard Acoustical Consultants, Inc.
Environmental Noise Assessment
CCL06126 AT&T Cellular Facility – Santa Clara, California
Introduction
The CCL06126 AT&T Wireless Unmanned Telecommunications Facility (project) proposes the installation of cellular equipment within an existing (abandoned) telecommunications lease area located at 3111 Benton Street in Santa Clara, California (APN: 290-27-006). The outdoor equipment cabinets have been identified as the primary noise sources associated with the project.
The project overall site plan is presented in Figure 1. The studied site drawings are dated February 3, 2023.
Bollard Acoustical Consultants, Inc. has been contracted by Complete Wireless Consulting, Inc. to complete an environmental noise assess ment regarding the proposed project cellular equipment operations. Specifically, the followi ng assessment addresses daily noise production and exposure associated with operation of the project outdoor equipment cabinets. Please refer to Appendix A for definitions of acoustical terminology used in this report. Appendix B illustrates common noise levels associated with various sources.
Criteria for Acceptable Noise Exposure
City of Santa Clara Municipal Code
The City of Santa Clara Municipal Code establishes noise level performance standards for non- transportation (stationary) noise sources, such as those that would occur on the project site. The nearest (adjacent) land uses have been identified as residential to the north. Section 9.10.040 of the Municipal Code limits noise levels at residential uses to 55 dB during daytime hours (7:00 a.m. to 10:00 p.m.) and 50 dB during nighttime hours (10:00 p.m. to 7:00 a.m.).
It should be noted that the Municipal Code does not define the acoustical time descriptor such as L
eq (average noise level) or Lmax (maximum instantaneous noise level) that is associated with the established limits. For the purposes of this assessment, the City’s noise level limits were reasonably interpreted to be an average noise level (Leq).
Noise Standards Applied to the Project
Noise would be generated by this project by the ongoing operation of the cellular equipment cabinets’ cooling systems. These systems utilize fans to circulate cooling air through the electric circuitry. During warmer periods, the cooling requirements will be greater, and the fans will run continuously. During cooler periods, however, the heat transfer requirements are diminished, and the fans will run intermittently as needed. Be cause the fan operation is a normal aspect of the project, and because the fans could run continuously during warm nighttime hours (i.e., more than 30 minutes per hour), the noise standards applied to the equipment cabinets are as follows:
55 dB L
eq at residential uses during daytime hours (7:00 a.m. to 10:00 p.m.) 50 dB L eq at residential uses during nighttime hours (10:00 p.m. to 7:00 a.m.) Satisfaction with the City’s 50 dB L eq nighttime noise level standard at the nearest residential property lines would ensure compliance with the City’s less restrictive 55 dB L eq daytime noise level standard.
Legend
Figure 10 30 60
Scale (Feet)
Proposed AT&T Cellular Equipment Lease Area
CCL06126 AT&T Cellular Facility
Santa Clara, California
Project Overall Site Plan
Parcel Boundaries
290-27-006
(Project Parcel)
Residential
Bollard Acoustical Consultants, Inc.
Environmental Noise Assessment
CCL06126 AT&T Cellular Facility – Santa Clara, California
Project Noise Generation
The project proposes the installation of four (4) equipment cabinets within the lease area shown in Figure 1. Based on the project site drawings, the cabinets assumed for installation within the lease area are as follows: two (2) stacked Purcell Systems FLX12WS (GR-487 rated) cabinets, and two (2) AT&T Power/Battery cabinets. The cabinets and their respective reference noise levels are provided in Table 1. The manufacturer’s noise level data specification sheets for the proposed cabinets are provided as Appendix C.
Table 1
Reference Noise Level Data of Proposed Equipment Cabinets1 Equipment
Number of
Cabinets
Reference Noise
Level (dB)
Reference
Distance (ft)
Purcell Systems FLX12WS 2 65 5
AT&T Power/Battery 2 65 5
1 Manufacturer specification sheets provided as Appendix C.
Predicted Facility Equipment Noise at the Nearest Residential Property Lines Assuming standard spherical spreading loss (-6 dB per doubling of distance from a stationary noise source), project-equipment noise exposure at the nearest residential property lines to the north was calculated and the results of those calculations are presented in Table 2. Satisfaction of the City’s noise level criteria at the closest residential property lines would ensure compliance of the City’s noise limits at residential property lines located farther away.
The results presented in Table 2 include consideration the orientation of the proposed outdoor equipment cabinet cooling fans relative to the adjacent residential property lines. Based on the provided site plans, the cooling fans of the equipment cabinets are proposed to face south, or away from the residential property lines to the north. Reference noise level measurements conducted by BAC staff at a similarly configured facility in Livermore, California (5179 Preston Avenue) indicate that the proposed equipment cabinet cooling fans are approximately 8 dB quieter when measured from the opposite side (rear) of the cooling fans. As a result, predicted equipment cabinet noise levels were adjusted by -8 dB at the residential property lines to the north.
Finally, it should be noted that an existing 6’ CMU wall is constructed along a portion of the project equipment lease area. However, because the existing 6’ solid wall does not enclose the entire perimeter of the equipment lease area (i.e., there is a wood fence portion on the west side), the effectiveness of the CMU wall performing as a noise barrier would be significantly reduced. As a result, barrier offsets for the existing non-continuous CMU wall were not applied to predicted equipment noise levels.
Bollard Acoustical Consultants, Inc.
Environmental Noise Assessment
CCL06126 AT&T Cellular Facility – Santa Clara, California
Table 2
Predicted Equipment Noise Levels at the Nearest Residential Property Lines APN1 Land Use
Distance from Equipment
Cabinets (ft)2
Predicted Noise Level, Leq
(dB)3
290-19-012 Residential 25 49
290-19-011 Residential 30 47
1 Parcel boundaries are shown in Figure 1.
2 Distance scaled using the prov ided site plans dated 2/3/23. 3 Predicted cabinet noise levels include consideration the orientation of the cooling fans, which resulted in an -8 dB noise level reduction at the residential property lines.
Source: BAC 2024
As indicated in Table 2, project equipment cabinet noise levels are predicted to be 49 dB L eq or less at the nearest residential property lines, which would satisfy the Municipal Code 50 dB L eq nighttime noise level limit. As a result, consideration of project equipment cabinet noise mitigation measures would not be warranted for the project.
Conclusions
Project equipment noise level exposure is expected to comply with applicable City of Santa Clara Municipal Code daytime and nighttime noise level criteria at the nearest residential uses to the north. As a result, no further consideration of project equipment noise mitigation measures would be warranted for this project.
This concludes our environmental noise assessment for the proposed CCL06126 AT&T Cellular Facility in Santa Clara, California. Please contact BAC at (530) 537-2327 or [email protected] with any questions or requests for additional information.
Appendix A
Acoustical Terminology
Acoustics The science of sound.
Ambient Noise The distinctive acoustical char acteristics of a given space consisting of all noise sources audible at that location. In many cases, the term ambient is used to describe an existing or pre-project condition such as the setting in an environmental noise study.
Attenuation The reduction of an acoustic signal.
A-Weighting A frequency-response adjustment of a sound level meter that co nditions the output signal to approximate human response.
Decibel or dB Fundamental unit of sound. A Be ll is defined as the logarithm of the ratio of the sound pressure squared over the reference pressure squared. A Decibe l is one-tenth of a Bell.
CNEL Community Noise Equivalent Lev el. Defined as the 24-hour average noise level with noise occurring during evening hours (7 - 10 p.m.) weighted by a factor of three and nighttime hours weighted by a factor of 10 prior to averaging.
Frequency The measure of the rapidity of alterations of a periodic signa l, expressed in cycles per second or hertz.
IIC Impact Insulation Class (IIC): A single-number representation of a floor/ceiling partition’s impact generated noise insulation performance. The field-measured version of this number is the FIIC.
L
dn Day/Night Average Sound Level . Similar to CNEL but with no evening weighting.
Leq Equivalent or energy-averaged sound level.
Lmax The highest root-mean-square (R MS) sound level measured over a given period of time.
Loudness A subjective term for the sensation of the magnitude of sound.
Masking The amount (or the process) by which the threshold of audibility is for one sound is raised by the presence of another (masking) sound.
Noise Unwanted sound.
Peak Noise The level corresponding to the hi ghest (not RMS) sound pressure measured over a given period of time. This term is often confused with the “Maximum” level, which is the highest RMS level.
RT
60 The time it takes reverberant s ound to decay by 60 dB once the source has been removed.
STC Sound Transmission Class (STC): A single-number representation of a partition’s noise insulation performance. This number is based on laboratory-measured, 16-band (1/3- octave) transmission loss (TL) data of the subject partition. The field-measured version of this number is the FSTC.
Appendix
C
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1 Appendix
C
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2