Rincon Consultants, Inc.
2 5 1 1 G a r d e n R o ad , S u i te C - 2 5 0
M o n te re y , Califo rn ia 93940
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E n v i r o n m e n t a l S c i e n t i s t s P l a n n e r s E n g i n e e r s April 28, 2022
Project No. 21-11684
Bobby Latino, Associate Planner
Community Development Department
City of Salinas
Via email: [email protected]
cc: Megan Hunter, [email protected]
Subject: Interior Noise Memorandum for the John Abbott Mixed-Use Project Salinas, California
Dear Mr. Latino:
This Interior Noise Memorandum summarizes the results of our interior noise analysis for the proposed John-Abbott Mixed-Use Project (project), located on the southeast corner of John and Abbott Streets in Salinas, California. This analysis evaluates the project’s compatibility with the California Building Code’s interior noise requirement of 45 decibels (dB) Community Noise Equivalent Level (CNEL) for habitable rooms. As described below, the project’s currently planned window and wall materials are sufficient to achieve the necessary reductions to meet the 45 CNEL interior noise standard.
Project Description and Setting
The proposed multi-phase, mixed-use planned unit development (PUD) is located on the southeast corner of the John Street and Abbott Street intersection in the City of Salinas, Monterey County, California. The proposed PUD consists of seven phases and would include approximately 242 dwelling units, 149,300 square feet of retail and office use in either freestanding or mixed-use buildings. This memorandum analyzes interior noise for the first phase of development. The first phase of the PUD (the “proposed project”) includes the development of a four-story (56 feet, 8 inches), approximately 70,000- square foot hotel with 111 guest rooms, including 20 double queen studio rooms, 84 king studio rooms, and seven king one-bedroom rooms and various amenities including an indoor pool, pool lounge and BBQ patio, fitness room, outdoor lounge, and breakfast bar. Construction of the hotel, which is estimated to take 20 months, is anticipated to begin September 1, 2022, and conclude May 1, 2024.
Table 1 summarizes Phase 1 key project features. Building plans are included as Attachment 1.
Table 1 Phase 1 Project Summary
Floor Double Queen
Studio
King Studio King OneBedroom Total Area (sf)
First/Ground 5 9 1 15 19,850
Second 5 25 2 32 16,420
Third 5 25 2 32 16,420
Fourth 5 25 2 32 16,420
City of Salinas
John Abbott Mixed-Use Project
Floor Double Queen
Studio
King Studio King OneBedroom Total Area (sf)
Total 20 84 7 111 69,110
Notes: sf = square feet
Noise Overview
Sound is a vibratory disturbance created by a moving or vibrating source, which is capable of being detected by the hearing organs. Noise is defined as sound that is loud, unpleasant, unexpected, or undesired and may therefore be classified as a more specific group of sounds. The effects of noise on people can include general annoyance, interference with speech communication, sleep disturbance, and, in the extreme, hearing impairment (California Department of Transportation [Caltrans] 2013).
Noise levels are commonly measured in dB using the A-weighted sound pressure level (dBA). The Aweighting scale is an adjustment to the actual sound pressure levels so that they are consistent with the human hearing response. Decibels are measured on a logarithmic scale that quantifies sound intensity in a manner similar to the Richter scale used to measure earthquake magnitudes. A doubling of the energy of a noise source, such as doubling of traffic volume, would increase the noise level by 3 dB; dividing the energy in half would result in a 3 dB decrease (Crocker 2007).
Human perception of noise has no simple correlation with sound energy: the perception of sound is not linear in terms of dBA or in terms of sound energy. Two sources do not “sound twice as loud” as one source. It is widely accepted that the average healthy ear can barely perceive changes of 3 dBA, increase or decrease (i.e., twice the sound energy); that a change of 5 dBA is readily perceptible (8 times the sound energy); and that an increase (or decrease) of 10 dBA sounds twice (half) as loud ([10.5 times the sound energy] Crocker 2007).
Sound changes in both level and frequency spectrum as it travels from the source to the receiver. The most obvious change is the decrease in level as the distance from the source increases. The manner by which noise reduces with distance depends on factors such as the type of sources (e.g., point or line, the path the sound will travel, site conditions, and obstructions). Noise levels from a point source typically attenuate, or drop off, at a rate of 6 dBA per doubling of distance (e.g., construction, industrial machinery, ventilation units). Noise from a line source (e.g., roadway, pipeline, railroad) typically attenuates at about 3 dBA per doubling of distance (Caltrans 2013). Noise levels may also be reduced by intervening structures; the amount of attenuation provided by this “shielding” depends on the size of the object and the frequencies of the noise levels. Natural terrain features such as hills and dense woods, and man-made features such as buildings and walls, can significantly alter noise levels.
Generally, any large structure blocking the line of sight will provide at least a 5-dBA reduction in source noise levels at the receiver (Federal Highway Administration [FHWA] 2011). Structures can substantially reduce exposure to noise as well. The FHWA’s guidelines indicate that modern building construction generally provides an exterior-to-interior noise level reduction of 20 to 35 dBA with closed windows.
The impact of noise is not a function of loudness alone. The time of day when noise occurs and the duration of the noise are also important factors of project noise impact. Most noise that lasts for more than a few seconds is variable in its intensity. Consequently, a variety of noise descriptors have been developed. One of the most frequently used noise metrics is the equivalent noise level (Leq); it considers both duration and sound power level. Leq is defined as the single steady A-weighted level equivalent to the same amount of energy as that contained in the actual fluctuating levels over time. Typically, Leq is summed over a one-hour period. Lmax is the highest root mean squared (RMS) sound pressure level City of Salinas
John Abbott Mixed-Use Project
within the sampling period, and Lmin is the lowest RMS sound pressure level within the measuring period (Crocker 2007).
Noise that occurs at night tends to be more disturbing than that occurring during the day. Community noise is usually measured using Day-Night Average Level (Ldn), which is the 24-hour average noise level with a +10 dBA penalty for noise occurring during nighttime hours (10:00 p.m. to 7:00 a.m.); it is also measured using CNEL, which is the 24-hour average noise level with a +5 dBA penalty for noise occurring from 7:00 p.m. to 10:00 p.m. and a +10 dBA penalty for noise occurring from 10:00 p.m. to 7:00 a.m. (Caltrans 2013). Noise levels described by Ldn and CNEL usually differ by about 0.5 dBA.
Regulatory Framework
California Code of Regulations
Interior noise levels for habitable rooms are regulated by Title 24 of the California Code of Regulations (CCR), California Noise Insulation Standards. Title 24, Chapter 12, Section 1207.4, of the California Building Code requires that interior noise levels attributable to exterior sources not exceed 45 CNEL in any habitable room within a residential structure or 50 CNEL in commercial uses. A habitable room is a room used for living, sleeping, eating, or cooking. Bathrooms, closets, hallways, utility spaces, and similar areas are not considered habitable rooms for this regulation (24 CCR 1207 2016).
City of Salinas 2002 General Plan
The City’s General Plan contains a Noise Element which identifies and appraises existing noises in Salinas and provides guidance to avoid noise-related impacts in the future. Table 2Table 2 below shows the land use compatibility matrix from the General Plan.
Table 2 City of Salinas Noise/Land Use Compatibility Matrix Community Noise Exposure (Ldn or CNEL, dBA)
Land Use
Normally
Acceptable
Conditionally
Acceptable
Normally
Unacceptable
Clearly
Unacceptable
Residential <60 60-70 70-75 >75
Transient Lodging – Motel, Hotel <60 60-75 75-80 >80
Schools, Libraries, Churches, Hospitals, Nursing Homes <60 60-70 70-80 >80 Auditoriums, Concert Halls, Amphitheaters N/A <70 N/A >70 Playgrounds, Parks <70 N/A 70-75 >75
Golf Course, Riding Stables, Water Recreation, Cemeteries <70 N/A 70-80 >80 Office Buildings, Business Commercial, and Professional <65 60-75 >75 N/A Industrial, Manufacturing, Utilities, Agriculture <70 70-80 >80 N/A N/A = not applicable
Source: City of Salinas 2002
City of Salinas
John Abbott Mixed-Use Project
The Noise Element states that conditionally acceptable uses may require minor mitigation to meet Title 24 noise standards, which would be the 45 CNEL interior noise standard stated above for habitable rooms, which would include guest rooms at a hotel use.
Noise Environment
To determine traffic noise levels at the project site, traffic levels from the City of Salinas (City of Salinas 2018) were used in the FHWA Highway Traffic Noise Prediction Model (FHWA RD 77-108). The City’s traffic counts for the John Street and Abbott Street intersection were stated to be 12,109 to 19,380 ADT.
For a conservative analysis, it was assumed the ADT was 19,380. Traffic was assumed to be a typical breakdown of 97 percent automobiles, 2 percent medium trucks, and 1 percent heavy trucks. The posted speed limit on the streets is 35 miles per hour. The closest portion of the building to a roadway is the northern portion of the hotel, which is 330 feet to the roadway center line of John Street. The dayevening-night traffic distribution was assumed to be 80 percent day, 5 percent evening, and 15 percent nighttime. With these assumptions, noise levels at the project building would be 60 CNEL.
The project would also be exposed to rail noise from the rail line to the east. The City’s Noise Element discusses rail noise. According to the Noise Element, no change to train service or schedules is anticipated to occur in the foreseeable future; therefore, noise levels generated by the train will remain the same as under existing conditions where land uses within 250 feet of the train tracks may experience noise levels in excess of 65 dBA (City of Salinas 2002). Therefore, noise levels from rail noise are assumed to be 65 dBA at 250 feet. The closest portion of the project building to the rail line is the eastern portion of the building, which is located 500 feet from the railway centerline. Assuming a 3 dBA reduction per doubling of distance from a line source, it was assumed rail noise at the project site was 62 CNEL.
The combined exposure of 60 CNEL from roadway noise and 62 CNEL from rail noise would result in an estimated noise level of 64 CNEL at the project building.
Methodology
The project plans (Attachment 1) refer to the different unit types as King Studio, King One-Bedroom, and Double Queen Studio. For purposes of analysis, the Double Queen Studio was used due to its nearest location to the loudest noise source (the rail line). Noise levels at this unit would be similar to noise levels experienced by the King Studio and King One-Bedroom, and therefore the Double Queen Studio analysis also applies to those unit types.
The methodology used to determine the resultant interior noise levels is based upon the calculated exterior noise level minus the sound transmission loss as identified in the American Society for Testing and Materials (ASTM) Guidelines E90 and E413. The sound transmission loss values from the ASTM E90 test are used to calculate the Sound Transmission Class (STC) and Outdoor–Indoor Transmission Class ratings in accordance with ASTM E413 and ASTM E1332, respectively. To calculate interior noise levels, the exterior noise levels at the proposed structures were converted to the octave band sound pressure levels between 80 and 4,000 hertz.
Acoustical modeling of the proposed dwelling units includes combining the transmission loss for each of the building components that would reduce the interior noise levels. Building components modeled in this analysis include windows, doors, and exterior wall treatments. The noise reduction is dependent upon the transmission loss of all building components, the surface area of each component, the quality City of Salinas
John Abbott Mixed-Use Project
of the building/construction installation, the building façade composition, and the angle of the building in relation to the source.
The interior noise level is also dependent on the acoustical energy absorbed in the room based upon the Noise Reduction Coefficient of each room component, which indicates a material's ability to absorb sound. The absorption coefficients for individual surface areas such as wood flooring, drywall, and furnishings are used to calculate the interior room noise reverberation. The calculated interior noise level is determined based on both the transmission loss from the exterior assembly and the room absorption characteristics.
The composite transmission loss was calculated on an octave band basis for the building components of each habitable room. These octave band composite losses were then subtracted on an octave band basis from the source noise, adjusted for anticipated absorption, and converted to a combined interior CNEL.
Based on the proposed building plans and without consideration of windows or doors, exterior wall assemblies would have an STC rating of 57. Acoustical transmission loss data for exterior walls were obtained from Acoustical and Thermal Performance of Exterior Residential Walls, Doors and Windows (Sabine et al. 1975). The habitable rooms of the proposed buildings also incorporate horizontal sliding windows with an STC value of 32. These components are contained in the project plans in Attachment 1.
Analysis
The analysis includes analysis of the Double Queen Studio room. This would be representative of the King Studio and King One-Bedroom due to their similar architectural materials, window treatments, and size. The units on each floor are also considered approximately equivalent in noise environment.
Based on acoustic fundamentals, with windows in an open position, exterior noise levels would only be reduced by 10 CNEL (FHWA 2011) in the interior of the units and would not result in adequate interior noise reduction. To meet the 45 CNEL interior noise requirement, a minimum interior noise level reduction of 19 CNEL is required (64-19=45 CNEL). Therefore, the interior noise levels were modeled with windows in a closed position.
As shown in the calculations included in Attachment 2, with the project’s architectural materials interior noise levels would be 36 CNEL. This would be well below 45 CNEL, and therefore well within the interior noise requirement. These low noise levels are due to the high STC materials used in project design and the project’s location in the center of the project site, which is several hundred feet from rail and road noise sources. With the noise levels of the Double Queen Studio room well below standards, the noise levels of the King Studio and King One-Bedroom would also be well within standards. Other nonhabitable rooms of the project, such as the swimming pool, would also be anticipated to have similar interior noise levels. Therefore, no additional exterior-to-interior noise reduction is required beyond current project design.
Conclusions
Based on the use of STC ratings analyzed for the project that are included as part of project design, interior noise levels would comply with the California Building Code’s 45 CNEL standard.
City of Salinas
John Abbott Mixed-Use Project
Thank you for the opportunity to assist with this assignment. Please do not hesitate to contact us if you have questions about this report.
Sincerely,
RINCON CONSULTANTS, INC.
Bill Vosti, MESM Megan Jones, MPP
Senior Environmental Planner Principal
Attachments
Attachment 1 Site Plans
Attachment 2 Interior Noise Modeling
City of Salinas
John Abbott Mixed-Use Project
References
Architectural Testing. 2007. ASTM E 90 Sound Transmission Loss Test Report, Rendered to Therma-Tru Doors. Report No. 74365.01-113-11.
California Code of Regulations (CCR). 2016 California Building Code, California Code of Regulations, Title 24, Chapter 12 Interior Environment, Section 1207, Sound Transmission, accessed on February 8, 2018 and accessed at:
http://codes.iccsafe.org/app/book/toc/2016/California/Building%20Volume%201/index.html California Department of Transportation (Caltrans). 2013. Technical Noise Supplement to the Traffic Noise Analysis Protocol. (CT-HWANP-RT-13-069.25.2) September. Available at:
http://www.dot.ca.gov/hq/env/noise/pub/TeNS_Sept_2013B.pdf Federal Highway Administration (FHWA). 2011. Highway Traffic Noise: Analysis and Abatement Guidance (FHWA-HEP-10-025). Available at:
https://www.fhwa.dot.gov/environment/noise/regulations_and_guidance/analysis_and_abate ment_guidance/revguidance.pdf
Malcolm J. Crocker (Editor). 2007. Handbook of Noise and Vibration Control Book, ISBN: 978-0-471- 39599-7, Wiley-VCH, October.
Sabine, Hale J., Myron B. Lacher, Daniel R. Flynn, and Thomas L. Quindry. Acoustical and Thermal Performance of Exterior Residential Walls, Doors and Windows. NBS Building Science Series 77.
U.S. Department of Commerce, National Bureau of Standards, Washington, DC. 1975.
Salinas, City of. 2002. General Plan. September. Available at:
https://www.cityofsalinas.org/sites/default/files/departments_files/community_development_f iles/general_plan_files/generalplan.pdf
Attachment 1
Site Plans
Attachment 2
Interior Noise Modeling
John Abbott Hotel
John Abbott Mixed Use_Interior Noise.xlsx
Inches Inches Square Feet
Floor Area 144 157 157.20
Absorption Coefficient 0.25 Gypsum Walls and Wood Flooring Element Height Width Area
Floor Room Code Orientation Database Element Glazing Material STC Data Source (Inches) (Inches) (square feet) 1 to 5 Queen S12 F Wall, stuccoed, insulation, channel NA NA 57 Sabine 108 157 117.90 S6 F Horizontal sliding window, sealed single aluminum 32 Sabine 48 63 20.96 Interior CNEL 36.47 (36)
4/18/2022 4:24 PM Queen 1