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HomeMy WebLinkAbout45dBReportR3_MotelInn - Revised Final45dB Acoustics, LLC www.45dB.com 805) 250 -1566 PO Box 1717 Buellton, CA 93427 This report (including any enclosures and attachments) has been prepared for the exclusive use and benefit of the addressee(s ) and solely for the purpose for which it is provided. No part of this report shall be reproduced, distributed or communicated to any third party without written permission. We do not accept any liability if this report is used for an alternative purpose from which it is intended, nor to any third party. July 27, 2022 45dB Project # 22014 Acoustical Analysis: Motel Inn 2223 Monterey St San Luis Obispo, CA 93401 Client: Covelop Attn: Bryan Hurlburd bhurlburd@covelop.net Architect: Studio Design Group Architects, Inc. 762 Higuera St, Ste 212 San Luis Obispo, CA 93401 Summary 45dB Acoustics, LLC (“45dB”) has reviewed regulatory requirements for the motel project at the above address. The potential impact of transportation noise from the principal transportation noise source— Highway 101—has been evaluated. Noise levels at the exteriors of the motel with the existing terrain (i.e., no mitigating walls) are predicted to be up to CNEL 66 dBA and outdoor activity areas as currently planned are predicted to reach CNEL 63 dBA. Interior noise levels can be maintained at or below the Noise Element criteria of CNEL 45 dBA with conventional wall, glazing, and door components, assuming properly sealed/gasketed windows and doors and mechanical ventilation is provided. However, outdoor activity areas will exceed the Noise Element criteria at the east Garden. Sufficient, appropriate mitigation for this site plan as drawn with two Garden outdoor activity) areas is provided by a solidly constructed wall, without gaps, along the northeast side of the property, as indicated in the Client’s proposed site plan. A wall height of approximately 12 feet is recommended, affording additional noise reduction for interior levels of the motel rooms and outdoor activity areas as drawn. A 16-foot-high wall was also studied, which does provide additional noise reduction as well as the potential for a slightly better guest experience, though wall heights above approximately 12 feet provide diminishing returns on mitigating effect that may not be co st-effective. A wall of any height, as studied from 8 to 16 feet, or absorptivity is not expected to perceptibly increase levels at the existing residences located to the north of Highway 101 (i.e., <1dB effect). Placement/span of the noise barrier wall was determined to be suitable; no extensions or omissions of wall sections are recommended. Because windows must be closed in order to meet the interior level criteria regardless of the presence or absence of a new noise wall, mechanical ventilation is required for the motel rooms. Noise levels will not increase more than 1 dB in 20 years assuming 1% per year traffic count growth; our recommendations are suitable for a 20-year buildout. for 45dB Acoustics, LLC Sarah Taubitz, ASA, Mem.INCE 45dB Acoustics, LLC Motel Inn page ii noise management : room acoustics : environmental impact www.45dB.com Contents Summary ....................................................................................................................................................................... i 1 Introduction ........................................................................................................................................................ 1 2 Regulatory Setting .............................................................................................................................................. 1 2.1 Federal Regulation .......................................................................................................................................... 1 2.2 State Regulation .............................................................................................................................................. 2 2.3 Local Regulation ............................................................................................................................................. 2 3 Noise Propagation Model .................................................................................................................................. 4 3.1 Local Transportation Noise ............................................................................................................................. 5 4 Modeled Noise Environment ............................................................................................................................. 5 4.1 Measured Existing Noise Levels ...................................................................................................................... 5 4.2 Modeled Noise Levels with Project (No Wall) ................................................................................................ 6 4.3 Modeled Noise Levels with Proposed Mitigation Wall ................................................................................... 6 4.4 Proposed Mitigation Wall Height Study .......................................................................................................... 8 4.5 Proposed Mitigation Wall Absorptivity Study ................................................................................................. 9 5 Mitigation and Conclusions ............................................................................................................................. 11 6 Figures ............................................................................................................................................................... 12 7 Appendix ........................................................................................................................................................... 24 7.1 Characteristics of Sound ............................................................................................................................... 24 7.2 Terminology/Glossary ................................................................................................................................... 25 7.3 SoundPLAN Acoustics Software .................................................................................................................... 27 7.4 Traffic Noise Model ....................................................................................................................................... 27 List of Figures Figure 1: Proposed Location of Motel Inn (Highlighted in Yellow) .......................................................... 12 Figure 2: Site Plan for Proposed Project (Studio Design Group) ............................................................... 13 Figure 3: Field Test Locations and Measured Levels (March 24, 2022, at 10:30 a.m.) ............................. 14 Figure 4: SoundPLAN Geometry Setup, Without Wall.............................................................................. 15 Figure 5: Sound Level Contours of Project Site, No Mitigation ................................................................. 16 Figure 6: SoundPLAN Geometry Setup, With 16-Foot Mitigating Wall ................................................... 17 Figure 7: Sound Level Contours of Project Site with Mitigation (16-ft Wall) ........................................... 18 Figure 8: Sound Level Contours of Project Site with Mitigation (12-ft Wall) ........................................... 19 Figure 9: Vertical Cross-Section View of Sound Level Contours with 16-foot Wall, Facing Eastward .... 20 Figure 10: Vertical Cross-Section View of Sound Level Contours with 12-foot Wall, Facing Eastward .. 21 45dB Acoustics, LLC Motel Inn page iii noise management : room acoustics : environmental impact www.45dB.com List of Tables Table 1: City of San Luis Obispo Noise Element - Land Use Compatibility ............................................... 3 Table 2: City of San Luis Obispo Noise Element – Maximum Noise Exposure for Noise-Sensitive Uses Due to Transportation Noise Sources ........................................................................................................... 4 Table 3: Traffic Data and 2021 Projections .................................................................................................. 5 Table 4: Measured Existing Noise Levels .................................................................................................... 6 Table 5: Noise Levels at at Selected Receiver Locations with Walls of Varying Heights ........................... 8 Table 6: Noise Levels at at Selected Receiver Locations with Absorptive Walls ...................................... 10 Table 7: Noise Levels at at Selected Receiver Locations, Three Wall Heights .......................................... 22 Table 8: Noise Levels at at Selected Receiver Locations, Three Wall Absorptivities ................................ 23 Table 9: Sound Level Change Relative Loudness/Acoustic Energy Loss .................................................. 24 45dB Acoustics, LLC Motel Inn page 1 noise management : room acoustics : environmental impact www.45dB.com 1 Introduction This sound level assessment is intended to determine the transportation noise impacts on the proposed motel and if the proposed wall is sufficient to mitigate the noise at the exterior spaces The client also desired to know what degree of noise impact would occur from the noise barrier on the residential areas located north of Highway 101. The following factors are considered: The topographical relationship of potential noise sources and the project site Identification of noise sources and their characteristics, including predicted sound levels at the exterior of the proposed project, considering present and future land usage Basis for the sound level prediction—for this project, acoustically modeled from published data—noise attenuation measures to be applied, and an analysis of the noise insulation effectiveness of the proposed construction showing that the prescribed interior noise level requirements are met Information on fundamentals of noise and vibration to aid in interpreting the report The location of the proposed Project is on the southeast corner of the intersection of Highway 101 with Monterey Street in the City of San Luis Obispo, as highlighted in yellow in Figure 1. The project consists of a motel renovation with new single-story and 2-story motel/hotel room buildings and a new kitchen/bar/restroom building near the outdoor pool area. A 16-foot high solidly constructed noise barrier wall is proposed along the eastern end of the north property line to shield the bungalows and outdoor spaces from traffic noise from the nearby highway. The site plan and proposed wall are shown in Figure 2. Elevations of the proposed noise barrier wall were also adjusted to match the topography received on April 26, 2022, which indicated that the proposed noise barrier would be placed essentially “on top of” the retaining wall along the north side of the property. 2 Regulatory Setting Noise regulations are addressed by federal, state, and local government agencies, as discussed below. Local policies are generally adaptations of federal and state guidelines, adjusted to prevailing local condition. 2.1 Federal Regulation The adverse impact of noise was officially recognized by the federal government in the Noise Control Act of 1972, which serves three purposes: a) Promulgating noise emission standards for interstate commerce. b) Assisting state and local abatement efforts. c) Promoting noise education and research. 45dB Acoustics, LLC Motel Inn page 2 noise management : room acoustics : environmental impact www.45dB.com The Department of Transportation (DOT) assumed a significant role in noise control. The Federal Aviation Administration (FAA) regulates noise of aircraft and airports. Surface transportation system noise is regulated by the Federal Transit Administration (FTA). Freeways that are part of the interstate highway system are regulated by the Federal Highway Administration (FHWA). For this project, the nearest airport (San Luis Obispo County Regional Airport) is approximately 3.25 miles to the south. The site is situated outside of the airport’s published CNEL Noise Contours1; therefore, the airport is not a significant noise factor. The nearest railroad line is approximately 3200 ft to the west and is not a concern. 2.2 State Regulation California State Code Section 653022 mandates that the legislative body of each county and city in California adopt a noise element as part of its comprehensive general plan. The local noise element must recognize the land use compatibility guidelines published by the State Department of Health Services. The guidelines rank noise land use compatibility in terms of normally acceptable, conditionally acceptable, normally unacceptable, and clearly unacceptable. 2.3 Local Regulation The City of San Luis Obispo General Plan, Noise Element3 provides regulation and guidelines regarding noise. The Noise Element provides the conclusions, recommendations, and strategies necessary to ensure an appropriately quiet and pleasurable interior environment for the residents of the proposed project. Since the regulation of transportation noise sources such as roadway and aircraft primarily fall under either State or federal jurisdiction, the local jurisdiction generally uses land use and planning decisions to limit locations or volumes of such transportation noise sources, to avoid development within noise impact zones, or to shield impacted receivers or sensitive receptors. Noise levels of up to CNEL 60 dBA for outdoor activity areas and an indoor CNEL of 45 dBA are Acceptable here for motels (see Table 1 and Table 2), and exterior noise levels of up to CNEL 75dBA are Conditionally Acceptable, i.e., with appropriate mitigation. Outdoor activity areas with a CNEL up to 60 dBA for transportation noise sources are acceptable. 1 San Luis Obispo County Regional Airport. 2021. Amended and Restated San Luis Obispo County Regional Airport SBP) Airport Land Use Plan. https://www.sloairport.com/wp-content/uploads/2021/06/Airport_Land_Use_Plan_Amended_5 -26-21.pdf 2 California State Code, Title 7, Division 1, Chapter 3, Article 5. Authority for and Scope of General Plans. https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=GOV&sectionNum=65302 3 City of San Luis Obispo, General Plan Noise Element, 1996. https://www.slocity.org/home/showpublisheddocument/6643/635670212763100000 45dB Acoustics, LLC Motel Inn page 3 noise management : room acoustics : environmental impact www.45dB.com Table 1: City of San Luis Obispo Noise Element - Land Use Compatibility 45dB Acoustics, LLC Motel Inn page 4 noise management : room acoustics : environmental impact www.45dB.com Table 2: City of San Luis Obispo Noise Element – Maximum Noise Exposure for Noise- Sensitive Uses Due to Transportation Noise Sources 3 Noise Propagation Model SoundPLAN® is a state-of-the-art sound propagation modeling software package that calculates sound levels while taking into account the air and ground attenuation factors, terrain variation and the built environment, road pavement types, and other relevant factors. This software has incorporated many noise propagation standards—for road traffic, this model utilizes the Federal Highway Administration’s Traffic Noise Model (TNM 3.0) to accurately calculate noise propagation accurately, taking into account the built environment, terrain, ground and air attenuation. The ISO 9613 calculation standard implemented into SoundPLAN® conservatively assumes downwind propagation in all directions from noise sources. Terrain is imported from Google Maps and verified against the topography provided by the Client on April 26, 2022 and contours on the City of San Luis Obispo FEMA Flood Info Map.4 Traffic counts for relevant/major roads and highways are input to the model to establish an ambient existing noise environment for comparison with the calculated noise levels due to the project’s proposed noise-generating equipment. More details about SoundPLAN®, TNM, and ISO 9613-2 can be found in Section 7.4. All sound pressure levels in this report are in units of A-weighted decibels (dBA). 4City of San Luis Obispo, FEMA Flood Info Map . https://experience.arcgis.com/experience/a51155e46d504bfab3b7a107c3eb6643/page/Flooding/ 45dB Acoustics, LLC Motel Inn page 5 noise management : room acoustics : environmental impact www.45dB.com 3.1 Local Transportation Noise Road noise has been modeled as the principal noise source for the existing environment. The nearest railroad is located approximately 3200 feet to the west of the property and is not considered to be a significant source of noise. Traffic counts in annual average daily traffic (AADT) are input directly into SoundPLAN®, which predicts exterior (outdoor) noise levels due to those noise sources. Traffic counts have been provided for Highway 101 by the California Department of Transportation5 and for Monterey Street and Buena Vista Avenue in the City of San Luis Obispo’s Traffic Data database6, as shown in Table 3. Table 3: Traffic Data and 2021 Projections Road Speed Published AADT AADT Year Years to Project 2021 ADT Projection with 1% Annual Growth Highway 101: Grand to Buena Vista 50 mph 40000 2020 2 40804 Highway 101: North of Buena Vista 50 mph 46000 2020 2 46925 Monterey Street 30 mph 8384 2018 4 8724 Buena Vista Avenue 25 mph 4211 2019 3 4339 4 Modeled Noise Environment 4.1 Measured Existing Noise Levels Short-duration (< 5-minute equivalent), A-weighted sound levels (Leq, Lmax, Lmin, etc.) were measured by 45dB on March 24, 2022, at approximately 10:30-11:00 a.m. at five locations around the project site. Figure 3 shows the hourly equivalent A-weighted Leq and Lmax for each location; each measurement was taken over approximately five minutes. Table 4, below, shows the hourly Leq for each of the measurement locations and the predicted hourly Leq from our model. The predicted levels were slightly greater (1 to 3 dB) than the measured field measurements, although generally still in very good agreement. The field measurements were taken over short periods, during a relatively low traffic period, and we suspect they do not exactly represent long-term “average” or typical conditions. Using the traffic conditions based on our prediction ensures that we are being conservative with our results. 5 CalTrans. 2020. Traffic Volumes: Annual Average Daily Traffic (AADT). https://dot.ca.gov/programs/traffic- operations/census 6 San Luis Obispo Public Works. Traffic Counts & Speed Surveys. (Accessed April 2022) https://www.slocity.org/government/department-directory/public-works/programs-and-services/transportation- planning-and-engineering/traffic-data 45dB Acoustics, LLC Motel Inn page 6 noise management : room acoustics : environmental impact www.45dB.com Table 4: Measured Existing Noise Levels Measurement Location Number Measured Hourly Leq dBA) Predicted Hourly Leq dBA) 1 62 63 2 58 59 3 58 61 4 59 60 5 59 62 4.2 Modeled Noise Levels with Project (No Wall) The geometric setups within the software are shown in Figure 4 (without mitigating wall). Resulting noise level contours, in plan view, are shown at a listener’s height of approximately 5 feet above ground level (AGL) in Figure 5 for the project site. For the bungalow exteriors nearest the highway, noise levels are predicted to reach up to CNEL 66 dBA without the wall, as shown below in Table 5. Receiver locations are indicated in Figure 5. For these exterior noise levels, typical wall, dual glazing, and doors with proper construction practices (i.e., gasketed and sealed doors and glazing, glazing specifications for tested assemblies) provides sufficient mitigation to render interior noise levels for hotels that are compliant with the Noise Element for hotels (i.e., at or below Ldn/CNEL 45 dBA). No noise barrier wall is required in order to create motel rooms that are compliant; however, since windows are required to be closed in order to be compliant, mechanical means of ventilation are required for the motel rooms under any condition. Outdoor activity areas, including the firepits, gardens, and pool areas, are expected to reach levels up to CNEL 63 dBA. These outdoor activity area levels slightly exceed the Noise Element guidelines in the Garden area near the “Garden 1” receiver point, and mitigation for outdoor activity areas is required. Results with Daytime “Leq,d” (7am-7pm), Evening “Leq,e” (7pm-10pm), and Nighttime Leq,n” (10pm-7am) levels are presented in Table 7 in Section 6. Decreases with the three wall heights studied are also shown to a tenth of a decibel for reference. Levels in the outdoor areas near the residences located to the north of Highway 101 are predicted to reach up to CNEL 69 dBA. These existing residences with receiver points labeled with the format “Res-X” in the results tables are in no way a part of this project and are shown for evaluation purposes only. 4.3 Modeled Noise Levels with Proposed Mitigation Wall The 3D model with the project and 16-foot-tall solidly constructed noise barrier wall in place is shown in Figure 6 and the resulting noise level contours are shown in Figure 7. Receiver levels at the project locations nearest the highway are expected to be reduced by up to 9 dB with the 16- 45dB Acoustics, LLC Motel Inn page 7 noise management : room acoustics : environmental impact www.45dB.com foot wall in place. Levels at some 2nd-floor receiver locations are predicted be reduced to CNEL 63 dBA, which is merely 3 dB above the 60 dBA limit specified in the Code and considered Conditionally Acceptable” for transient lodging. All ground floor receiver locations and outdoor activity areas are predicted to be 60 dBA or less. As for the previous situation with no built noise wall, for exterior levels in this range, typical exterior construction assemblies and practices will ensure the interior levels of CNEL 45 dBA can be attained—this means that lightweight framing and unrated dual glazing is anticipated to meet the Noise Element requirements for interior spaces. Because windows must be closed in order to meet the interior level criteria, mechanical ventilation is still required for the hotel rooms. PTAC units are generally not compliant, as they significantly degrade the exterior composite wall performance. With any wall of 12 feet or taller, all outdoor activity areas are predicted to be below the Code limit of CNEL 60 dBA. The current site plan concept with outdoor activity area locations— particularly the “Garden 1” area near the center of the site with no new buildings to mitigate it— drives the need for mitigation; hotel room interior noise level regulations do not require a mitigating noise barrier per se, and even without any barrier wall the motel rooms are able to be properly mitigated through wall and glazing specifications to meet the interior limits within the Code as was discussed in the previous section. Though, if a noise barrier wall is not constructed, the site layout will require rearrangement of outdoor areas. In our review the sound level contours, placement/span of the noise barrier wall was determined to be suitable; no extensions or emissions of wall sections are recommended. If the western garden location behind the parking lot were omitted, or if additional bungalows were built to act as mitigation for this outdoor activity area, then there would no longer be a requirement for the mitigating barrier wall along the highway. In any case, a barrier wall provides additional exterior, and hence interior, noise reduction for the motel rooms across the site. Levels at the residential area to the north are not expected to increase significantly (less than 0.5 dB) due to the reflection of traffic noise off the proposed wall. In order to be effective, noise barrier walls must be continuous without gaps and may be solidly constructed from concrete masonry unit blocks (CMU) or other masonry, stucco on framing, laminated glass, etc. There are many suppliers of noise barrier walls, and an STC of greater than 30 will ensure that highway noise does not transmit through the wall. Concrete block is generally STC 40 or greater. 45dB Acoustics, LLC Motel Inn page 8 noise management : room acoustics : environmental impact www.45dB.com Table 5: Noise Levels at at Selected Receiver Locations with Walls of Varying Heights Receiver Floor) Receiver Elevation Project Without Wall in Place Mitigated with 16-ft Wall Mitigated with 12-ft Wall Mitigated with 8-ft Wall ft) CNEL dB(A) CNEL dB(A) CNEL dB(A) CNEL dB(A) B12 (G) 306 64 59 59 62 B12 (F2) 316 65 62 63 65 B14 (G) 305 62 59 59 61 B14 (F2) 316 64 62 62 64 B16 (G) 308 65 56 57 60 B18 (G) 309 65 57 58 62 B19 (G) 310 65 57 58 63 B21 (G) 311 66 57 59 64 B29 (G) 311 61 60 60 61 B29 (F2) 322 65 63 65 65 Firepits 305 54 53 53 54 Garden1 305 63 58 59 61 Garden2 307 54 52 52 53 Pool 305 56 52 54 56 Res-1 328 67 67 67 67 Res-2 338 69 69 69 69 Res-3 348 68 68 68 68 Res-4 361 62 62 62 62 Res-5 341 67 67 67 67 4.4 Proposed Mitigation Wall Height Study The noise wall may also be constructed with lower heights and provide significant and reduction for the project. Table 5, above, includes the resulting sound levels for walls with 12-foot and 8- foot walls for comparison to the 16-foot wall discussed above. The 12-foot wall would provide up to 7 dB reduction, while the 8-foot wall is predicted to provide up to 4 dB reduction in traffic levels. Figure 8 shows the resulting noise level contours for the 12-foot wall. Figure 9 shows a vertical cross-section cut view, facing approximately eastward, through Building B12 with a 16-foot wall in place. Similarly, Figure 10 shows the same view with a 12- foot wall in place. These figures illustrate the mitigating effect of each wall on the exterior façade of building B12, typical of the site. The 12-foot wall provides significant increase in mitigation over the 8-foot wall, though any wall provides a mitigating effect for the outdoor activity areas and would be a benefit to the bungalows. Wall heights higher than approximately 12 feet provide diminishing returns on mitigation/benefit, particularly considering the increase in cost. 45dB Acoustics, LLC Motel Inn page 9 noise management : room acoustics : environmental impact www.45dB.com The wall presence or height does not have any significant or noticeable impact on the existing residential area to the north of Highway 101 that is not a part of this project. 4.5 Proposed Mitigation Wall Absorptivity Study The barrier wall in the previous section was assumed to have a frequency-averaged Noise Reduction Coefficient (NRC) of 0.2, which means that it is 80% reflective and 20% absorptive across the audible spectrum of frequencies. This coefficient is a good estimate for CMU or other typical/conventional walls. This level of absorptivity was calculated to reflect some traffic noise across the highway and increase levels at the residential locations by up to 0.5 dB. While this is not a perceptible change to most listeners (see Section 7.1), we also evaluated walls with increased absorptive properties and present the effect on the residential areas. Table 6 includes the resulting sound levels for a 16-foot wall having average NRC of 0.20 average for CMU), 0.84, and 0.95. These higher absorptions are only achievable with more customized/engineered and higher cost wall systems. Table 8 shows the results and effects of the three wall absorption factors down to a 0.1-dB resolution for reference. As shown, the walls with increased absorption further reduced levels at the outdoor receivers at the project site. However, levels at the existing residential locations across Highway 101 to the north showed 0-1 dB increase in comparison to the existing levels, which is imperceptible and essentially negligible. The wall’s existence, height, and absorptivity factor are not a significant factor in the total sound levels at the residence. Full results including Daytime “Leq,d” (7am-7pm), Evening “Leq,e” (7pm-10pm), and Nighttime “Leq,n” (10pm-7am) levels are also presented in Table 8 in Section 6. There are absorptive noise barrier options on the market suitable for outdoor applications. A few suppliers of noise barrier walls include: SoundSeal SoundBlox (absorptive); Aftec conventional), AIL Sound Walls (both); and Kinetics Noise Control (both). 45dB Acoustics, LLC Motel Inn page 10 noise management : room acoustics : environmental impact www.45dB.com Table 6: Noise Levels at at Selected Receiver Locations with Absorptive Walls Receiver Floor) Receiver Elevation Project Without Wall in Place Mitigated with 16-ft Wall Absorption = 20 Mitigated with 16-ft Wall Absorption = 84 Mitigated with 16-ft Wall Absorption = 95 ft) CNEL dB(A) CNEL dB(A) CNEL dB(A) CNEL dB(A) B12 (G) 305 64 59 58 58 B12 (F20 314 65 62 61 61 B14 (G) 305 63 59 59 59 B14 (F2) 314 63 62 62 62 B16 (G) 308 66 56 53 53 B18 (G) 308 66 57 54 54 B19 (G) 309 65 57 55 55 B21 (G) 310 66 57 55 54 B29 (G) 309 62 60 60 60 B29 (F2) 318 64 63 63 63 Firepits 303 55 53 53 53 Garden1 305 64 58 58 58 Garden2 307 54 52 52 52 Pool 302 55 52 51 51 Res-1 327 68 67 66 66 Res-2 337 69 69 69 69 Res-3 348 68 68 68 67 Res-4 361 62 62 62 62 Res-5 341 67 67 67 67 45dB Acoustics, LLC Motel Inn page 11 noise management : room acoustics : environmental impact www.45dB.com 5 Mitigation and Conclusions Exterior noise levels at the outdoor areas of the project closest to Highway 101 reach as high as CNEL 66 dBA without mitigation. A wall height of at least 12 feet has been determined to satisfy the Noise Element requirements for outdoor activity areas as drawn. A noise barrier wall is not needed in any case to satisfy the Noise Elements’ interior noise level limits of the motel rooms—additional wall/window mitigation of the buildings would not be required and typical construction (i.e., conventional wall types and dual glazing) do satisfy the (Title 24) State Building Code and City Noise Element interior limit of CNEL 45dBA. Because windows must be closed in order to meet the interior level criteria, mechanical ventilation is required for the hotel rooms. PTAC units are generally not permitted, as they significantly degrade the exterior composite wall performance. The 12- and 16-foot-high walls do provide further increases in noise reduction beyond what the Noise Element would require. Given the anticipated significant increase in cost for a 16-foot wall and the sufficient mitigation provided by the lower wall heights, there may not be a compelling reason for such a wall height, nor a highly-absorptive wall—CMU, stucco, etc. suffice. However, if a taller wall provides cutoff of line-of-sight for passing trucks, it may have an additional psychoacoustic7 benefit for guests, providing a better guest experience/atmosphere. A wall of any height as studied from 8 to 16 feet or absorptivity is not expected to perceptibly increase levels at the residences located to the north of Highway 101. Noise levels will not increase more than 1 dB in 20 years assuming a conservative 1% per year traffic count increase; our recommendations are suitable for a 20-year buildout. 7 Noise—both perceived and quantifiable—is one of the aspects that hotel guests cite the most often for poor experiences, particularly near roadways. An additional aspect not often discussed with noise barriers is a so -called psychoacoustic affect”, namely that, if a human listener cannot see the source emitting the noise, the perceived sound level of the source is lessened. This may be particularly accurate when the noise source moves spatially as is the case with, e.g., passing traffic, aircraft, and wind turbines 45dB Acoustics, LLC Motel Inn page 12 noise management : room acoustics : environmental impact www.45dB.com 6 Figures Figure 1: Proposed Location of Motel Inn (Highlighted in Yellow) 45dB Acoustics, LLC Motel Inn page 13 noise management : room acoustics : environmental impact www.45dB.com Figure 2: Site Plan for Proposed Project (Studio Design Group) 45dB Acoustics, LLC Motel Inn page 14 noise management : room acoustics : environmental impact www.45dB.com Figure 3: Field Test Locations and Measured Levels (March 24, 2022, at 10:30 a.m.) 45dB Acoustics, LLC Motel Inn page 15 noise management : room acoustics : environmental impact www.45dB.com Figure 4: SoundPLAN Geometry Setup, Without Wall 45dB Acoustics, LLC Motel Inn page 16 noise management : room acoustics : environmental impact www.45dB.com Figure 5: Sound Level Contours of Project Site, No Mitigation 45dB Acoustics, LLC Motel Inn page 17 noise management : room acoustics : environmental impact www.45dB.com Figure 6: SoundPLAN Geometry Setup, With 16-Foot Mitigating Wall 45dB Acoustics, LLC Motel Inn page 18 noise management : room acoustics : environmental impact www.45dB.com Figure 7: Sound Level Contours of Project Site with Mitigation (16-ft Wall) 45dB Acoustics, LLC Motel Inn page 19 noise management : room acoustics : environmental impact www.45dB.com Figure 8: Sound Level Contours of Project Site with Mitigation (12-ft Wall) 45dB Acoustics, LLC Motel Inn page 20 noise management : room acoustics : environmental impact www.45dB.com Figure 9: Vertical Cross-Section View of Sound Level Contours with 16-foot Wall, Facing Eastward 45dB Acoustics, LLC Motel Inn page 21 noise management : room acoustics : environmental impact www.45dB.com Figure 10: Vertical Cross-Section View of Sound Level Contours with 12-foot Wall, Facing Eastward 45dB Acoustics, LLC Motel Inn page 22 noise management : room acoustics : environmental impact www.45dB.com Table 7: Noise Levels at at Selected Receiver Locations, Three Wall Heights 45dB Acoustics, LLC Motel Inn page 23 noise management : room acoustics : environmental impact www.45dB.com Table 8: Noise Levels at at Selected Receiver Locations, Three Wall Absorptivities 45dB Acoustics, LLC Motel Inn page 24 noise management : room acoustics : environmental impact www.45dB.com 7 Appendix 7.1 Characteristics of Sound When an object vibrates, it radiates part of its energy as acoustical pressure in the form of a sound wave. Sound can be described in terms of amplitude (loudness), frequency (pitch), or duration (time). The human hearing system is not equally sensitive to sound at all frequencies. Therefore, to approximate this human, frequency-dependent response, the A-weighted filter system is used to adjust measured sound levels. The normal range of human hearing extends from approximately 0 to 140 dBA. Unlike linear units such as inches or pounds, decibels are measured on a logarithmic scale, representing points on a sharply rising curve. Because of the physical characteristics of noise transmission and of noise perception, the relative loudness of sound does not closely match the actual amounts of sound energy. Table 9 below presents the subjective effect of changes in sound pressure levels. Table 9: Sound Level Change Relative Loudness/Acoustic Energy Loss 0 dBA Reference 0% 3 dBA Barely Perceptible Change 50% 5 dBA Readily Perceptible Change 67% 10 dBA Half as Loud 90% 20 dBA 1/4 as Loud 99% 30 dBA 1/8 as Loud 99.9% Source: Highway Traffic Noise Analysis and Abatement Policy and Guidance, U.S. Department of Transportation, Federal Highway Administration, Office of Environment and Planning, Noise and Air Quality Branch, June 1995. Sound levels are generated from a source and their decibel level decreases as the distance from that source increases. Sound dissipates exponentially with distance from the noise source. This phenomenon is known as spreading loss. Generally, sound levels from a point source will decrease by 6 dBA for each doubling of distance. Sound levels for a highway line source vary differently with distance because sound pressure waves propagate along the line and overlap at the point of measurement. A closely spaced, continuous line of vehicles along a roadway becomes a line source and produces a 3 dBA decrease in sound level for each doubling of distance. However, experimental evidence has shown that where sound from a highway propagates close to “soft” ground (e.g., plowed farmland, grass, crops, etc.), a more suitable drop-off rate to use is not 3.0 dBA but rather 4.5 dBA per distance doubling (FHWA 2010). When sound is measured for distinct time intervals, the statistical distribution of the overall sound level during that period can be obtained. The Leq is the most common parameter associated with such measurements. The Leq metric is a single-number noise descriptor that represents the average sound level over a given period of time. For example, the L50 noise level is the level that is exceeded 50 percent of the time. This level is also the level that is exceeded 30 minutes in an hour. Similarly, the L02, L08 and L25 values are the noise levels that are exceeded 45dB Acoustics, LLC Motel Inn page 25 noise management : room acoustics : environmental impact www.45dB.com 2, 8, and 25 percent of the time or 1, 5, and 15 minutes per hour. Other values typically noted during a noise survey are the Lmin and Lmax. These values represent the minimum and maximum root-mean-square noise levels obtained over the measurement period. Because community receptors are more sensitive to unwanted noise intrusion during the evening and at night, State law requires that, for planning purposes, an artificial dB increment be added to quiet-time noise levels in a 24-hour noise descriptor called the CNEL or Ldn. This increment is incorporated in the calculation of CNEL or Ldn, described earlier. 7.2 Terminology/Glossary A-Weighted Sound Level (dBA) The sound pressure level in decibels as measured on a sound level meter using the internationally standardized A-weighting filter or as computed from sound spectral data to which A-weighting adjustments have been made. A-weighting de-emphasizes the low and very high frequency components of the sound in a manner similar to the response of the average human ear. A- weighted sound levels correlate well with subjective reactions of people to noise and are universally used for community noise evaluations. Air-borne Sound Sound that travels through the air, differentiated from structure-borne sound. Ambient Sound Level The prevailing general sound level existing at a location or in a space, which usually consists of a composite of sounds from many sources near and far. The ambient level is typically defined by the Leq level. Background Sound Level The underlying, ever-present lower level noise that remains in the absence of intrusive or intermittent sounds. Distant sources, such as Traffic, typically make up the background. The background level is generally defined by the L90 percentile noise level. Community Noise Equivalent Level (CNEL) The Leq of the A-weighted noise level over a 24-hour period with a 5-dB penalty applied to noise levels between 7 p.m. and 10 p.m. and a 10-dB penalty applied to noise levels between 10 p.m. and 7 a.m. CNEL is similar to Ldn. Day-Night Sound Level (Ldn) The Leq of the A-weighted noise level over a 24-hour period with a 10-dB penalty applied to noise levels between 10 p.m. and 7 a.m. Ldn is similar to CNEL. Decibel (dB) The decibel is a measure on a logarithmic scale of the magnitude of a particular quantity (such as sound pressure, sound power, sound intensity) with respect to a reference quantity. dBA or dB(A) A-weighted sound level. The ear does not respond equally to all frequencies, and is less sensitive at low and high frequencies than it is at medium or speech range frequencies. Thus, to obtain a single number representing the sound level of a noise containing a wide range of frequencies in a manner representative of the ear’s response, it is necessary to reduce the effects of the low and 45dB Acoustics, LLC Motel Inn page 26 noise management : room acoustics : environmental impact www.45dB.com high frequencies with respect to the medium frequencies. The resultant sound level is said to be A-weighted, and the units are dBA. The A-weighted sound level is also called the noise level. Energy Equivalent Level (Leq) Because sound levels can vary markedly in intensity over a short period of time, some method for describing either the average character of the sound or the statistical behavior of the variations must be utilized. Most commonly, one describes ambient sounds in terms of an average level that has the same acoustical energy as the summation of all the time-varying events. This energy-equivalent sound/noise descriptor is called Leq. In this report, an hourly period is used. Noise Reduction (NR) Noise reduction is the difference between outdoor sound level and indoor sound level. It is not identical to Sound Transmission Class. Outdoor-Indoor Transmission Class (OITC) A single number classification, specified by the American Society for Testing and Materials ASTM E 1332 issued 1994), that establishes the A-weighted sound level reduction provided by building facade components (walls, doors, windows, and combinations thereof), based upon a reference sound spectrum that is an average of typical air, road, and rail transportation sources. The OITC is the preferred rating when exterior façade components are exposed to a noise environment dominated by transportation sources. Once built, as much as a 5-point reduction in Apparent Outside-Inside Transmission Class (OITC) from the original, as-designed OITC may be expected. Percentile Sound Level, Ln The noise level exceeded during n percent of the measurement period, where n is a number between 0 and 100 (e.g., L10 or L90) Sound Transmission Class (STC) STC is a single number rating, specified by the American Society for Testing and Materials, which can be used to measure the sound insulation properties for comparing the sound transmission capability, in decibels, of interior building partitions for noise sources such as speech, radio, and television. It is used extensively for rating sound insulation characteristics of building materials and products. Structure-Borne Sound Sound propagating through building structure. Rapidly fluctuating elastic waves in gypsum board, joists, studs, etc. Sound Exposure Level (SEL) SEL is the sound exposure level, defined as a single number rating indicating the total energy of a discrete noise-generating event (e.g., an aircraft flyover) compressed into a 1-second time duration. This level is handy as a consistent rating method that may be combined with other SEL and Leq readings to provide a complete noise scenario for measurements and predictions. However, care must be taken in the use of these values since they may be misleading because their numeric value is higher than any sound level which existed during the measurement period. Subjective Loudness Level In addition to precision measurement of sound level changes, there is a subjective characteristic which describes how most people respond to sound: 45dB Acoustics, LLC Motel Inn page 27 noise management : room acoustics : environmental impact www.45dB.com A change in sound level of 3 dBA is barely perceptible by most listeners. A change in level of 6 dBA is clearly perceptible. A change of 10 dBA is perceived by most people as being twice (or half) as loud. 7.3 SoundPLAN Acoustics Software SoundPLAN®, the software used for this acoustic analysis, is an acoustic ray-tracing program dedicated to the prediction of noise in the environment. Noise emitted by various sources propagates and disperses over a given terrain in accordance with the laws of physics. Worldwide, governments and engineering associations have created algorithms to calculate acoustical phenomena to standardize the assessment of physical scenarios. Accuracy has been validated in published studies to be + / - 2.7 dBA with an 85% confidence level. The software calculates sound attenuation of environmental noise, even over complex terrain, uneven ground conditions, and with complex obstacles. The modeling software calculates the sound field in accordance with ISO 9613-2 “Acoustics - Attenuation of sound during propagation outdoors, Part 2: General Method of Calculation.” This standard states that “this part of ISO 9613 specifies an engineering method for calculating the attenuation of sound during propagation outdoors, in order to predict the levels of environmental noise at a distance from a variety of sources. The method predicts the equivalent continuous A-weighted sound pressure level under meteorological conditions favorable to propagation from sources of known sound emissions. These conditions are for downwind propagation under a well-developed moderate ground-based temperature inversion, such as commonly occurs at night.” 7.4 Traffic Noise Model The Federal Highway Administration Traffic Noise Model (TNM) used for the sound level analysis in this study, contains the following components: 1. Modeling of five standard vehicle types, including automobiles, medium trucks, heavy trucks, buses, and motorcycles, as well as user-defined vehicles. 2. Modeling both constant- and interrupted-flow traffic using a field-measured data base. 3. Modeling effects of different pavement types, as well as the effects of graded roadways. 4. Sound level computations based on a one-third octave-band data base and algorithms. 5. Graphically-interactive noise barrier design and optimization. 6. Attenuation over/through rows of buildings and dense vegetation. 7. Multiple diffraction analysis. 8. Parallel barrier analysis. 9. Contour analysis, including sound level contours, barrier insertion loss contours, and sound-level difference contours. These components are supported by a scientifically founded and experimentally calibrated acoustic computation methodology, as well as a flexible data base, made up of over 6000 individual pass-by events measured at forty sites across the country.