Analysis of Potential Community Noise Impacts

Transcription

1 "\-A Veneklasen Associates v~ Consultants in Acoustics AV/ T Environmental Noise Catch Melrose Roof Level Restaurant 8715 Melrose Ave. West Hollywood, CA Analysis of Potential Community Noise mpacts June 6, 2015 Prepared by: CT~ George Kourtis, MOA Associate Approved by: Stephen A. Martin, Ph.D, P.E. Associate Principal TEM 10. B. EXHBT C 1711 Sixteenth Street Santa Monica California tel: fa x:

2 "\?\- Veneklasen Associates 1.0 ntroduction An outdoor restaurant, known as Catch Melrose, is to be constructed on the roof level of a newly constructed building at Melrose Avenue in West Hollywood, California. The 2-story +roof building is located on the northwest corner of N San Vicente Blvd. and Melrose Ave. These are major arterials with significant vehicular traffic day and night. A site plan is shown in Figure 1. The building is to contain retail establishments on the first and second floors, Catch Restaurant on the roof as mentioned, and parking on subterranean levels. Figure 1. Site Plan ALLEY,-----,,, 17tt-11U llteuloh A\11: MELROSE AVE The aerial photograph in Figure 2 indicates the relationship of the Project to the surrounding community. t is surrounded by commercial or municipal properties on all four sides. The nearest residences are to the south on Rangely Ave. Figure 2. Project Neighborhood Context 1

3 "\r\- Veneklasen Associates Figure 3 indicates the roof plan of the restaurant, seating 278 persons, including Terrace level seating. The floor of the Catch Restaurant is located approximately 49.5 feet above Melrose Ave. The Restaurant uses most of the available roof space, and the majority of the seating areas are situated towards the south and southwest of the space Figure 3. Catch Restaurant Roof Plan m DOD DOD 0 0 [J DOD ODD Figure 4 illustrates t he configuration ofthe restaurant as it was modeled for purposes of assessing noise impact on the community. All retractable elements including and the canvas canopy are in the open positions. Note the presence of the continuous glass barrier wall at the roof edge. Figure 4. Conceptual Rendering of Catch Restaurant as viewed from above 2

4 "7\- Veneklasen Associates Figure 5 shows the relationship of the project to commercial versus residential properties to the west and south. Figure 6 illustrates that, from the southern edge of the roof, there is a direct line of sight across Melrose Ave to the northern property line of 8713 Rangely Ave and to the roofs and yards of other residences on this street. Figure 5. View to the West of the project site Residential Properties on Rangely Ave. Commercial Properties on Melrose Ave. Figure 6. Line of sight to the South towards nearest residences Property line of nearest residence to south, 8713 Rangely Ave. This report summarizes the acoustical analysis of the potential noise impact of the proposed restaurant on the residential area to the south. 3

5 '\f\- Veneklasen Associates 2.0 Executive Summary This report describes the noise conditions at and around the restaurant location and presents measures to control sounds in keeping with the West Hollywood Municipal Code. The City of West Hollywood Noise Ordinance is not quantitative, therefore this analysis is presented in keeping with the language and objectives of the ordinance. The following items summarize the analysis and conclusions contained in this report: The goal of this analysis is to determine whether sounds from the approved Catch Melrose restaurant (8715 Melrose Avenue) could be "plainly audible or not" at the rear property line of the nearest residence. "Plainly audible" can be defined as within 5 dba of the existing ambient sound level at the nearest residence. E.g. if the sound generated by Catch restaurant is equal to: Ambient sound level -1 dba =Plainly audible Ambient sound level - 2 dba =Plainly audible Ambient sound level - 3 dba = Perceptible Ambient sound level - 4 dba = Barely perceptible Ambient sound level - 5 dba = Not audible Based on our measurements and conservative calculations and assumptions about construction and operations at the restaurant, we predicted that the sound from the restaurant would be 4 dba below the ambient sound level at the nearest residence, and therefore would be "Barely perceptible".. With the goal of rendering the sounds from the restaurant "Not audible" we have identified mitigating construction and operational measures presented herein to maintain sound levels generated by Catch Restaurant at 5 dba below the ambient sound level at the nearest residence f the proposed glass sound barrier, background music level adjustment, and operational measures as described herein are exercised, any noise from the restaurant will be sufficiently controlled and the operations at Catch Restaurant are predicted to be in compliance with the West' Hollywood Noise Ordinance. 3.0 Terminology The acoustic terminology used in this report is explained in the Terminology page at the end of this report. 4.0 West Hollywood Noise Ordinance West Hollywood is a densely developed city with residential and commercial uses adjoining each other. The City's Noise Ordinance acknowledges this fact, stating "This pattern of land use development makes it almost inevitable that everyday noise will be audible to one degree or another." 1 This juxtaposition of commercial and residential land uses is true for the proposed Catch Restaurant, a commercial use. The Noise Ordinance continues, "The purpose of this chapter is to strike a balance between normal, everyday noises that are unavoidable in an urban environment and those noises that are so excessive and annoying to persons of ordinary sensitivity that they must be curtailed in order to protect the comfort and tranquility of all persons who live and work in the city." The Noise Ordinance limits noise from commercial establishments adjacent to residential property between 10:00 pm and 8:00 am. t prohibits "continuous, repeated, or sustained noise from the premises of any 1 West Hollywood Municipal Code Section

6 ~ Veneklasen Associates commercial establishment which is adjacent to one or more residential dwelling units, including any outdoor area part of or under control ofthe establishment, between the hours of 10:00 p.m. and 8:00 a.m. that is plainly audible from the residential dwelling unit's property line." 5.0 Noise mpact Criteria The West Hollywood Noise Ordinance is clear in its intent, but the criteria for evaluating potential noise violations is stated in subjective terms rather than with numerical values which would allow assessing compliance quantitatively. Therefore, we must consider the magnitude of the noise levels the roof level restaurant may produce compared to the existing ambient noise levels in the project vicinity in order to determine compliance with the Noise Ordinance's subjective criteria. Because the human ear responds to sound levels logarithmically and not linearly, we quantify sound levels on a logarithmic scale in decibels. Therefore, conventional arithmetic cannot be used when adding or comparing sound levels. For instance, adding two sound levels of SO decibels equals S3 decibels, not 100 decibels, while a sound level of 4S decibels added to an existing sound level of SO decibels raises the new sound level by only 1 decibel. See Table 1 for how decibel levels add together. The average human ear cannot distinguish an increase in a sound level of 1 decibel, and raising a sound level by 3 decibels is typically needed for an individual to notice the increase 2 However, when the frequency characteristics of a newly generated sound are different than an existing sound or the newly generated sound is intermittent and significantly louder than the ambient sound level, the new sound is more readily perceived. Difference between two sound levels to be added together Table 1. Explanation of Decibel Addition. Number of decibels to add to the higher of the two sound levels s When speech is below the existing ambient sound level by S decibels or more, it does not contribute significantly to the overall noise level and will not be "plainly audible" at a residential dwelling unit's property line. Summarizing the above paragraphs, a sound level equal to the ambient sound level would increase the overall level by 3 decibels, an increment just distinguishable by the human ear. Speech sound levels S decibels below the ambient would increase the overall level by 1 decibel, an increase the average human ear cannot distinguish. 2 J.R. Hassall and K. Zaveri, Acoustic Noise Measurements,

7 ~ Veneklasen Associates Therefore, for sound levels produced by Catch Restaurant, we would consider the sound level that reaches the nearby residential areas to have no significant adverse noise impact and to be in compliance with the intent of the West Hollywood Noise Ordinance if it is less than the existing ambient sound level by 5 decibels or more for sound levels such as continuous general conversation. For varying sounds including music, we would consider a sound level 10 decibels or more below the arnbient sound level to have no negative noise impact. 6.0 Ambient Noise Measurement Procedures Our acoustical analysis incorporated ambient noise measurements performed at 8723 Rangely Ave on the North side ofthe street. These measurements were performed over a 1/2 hour period between 12:00 am and 12:30 am on October 7, Catch restaurant is expected to be open until 2 am, but our experience of ambient noise levels measured in West Hollywood indicates that there is not a significant reduction in ambient noise between 12:30 am and 2 am. A Brue & Kja:!r Type 2270 Type 1 Precision Sound Level Meter was used for the measurements. The meter was calibrated before and after the measurements. The measurements show the Equivalent Noise Level (Leq} during the measurement period to be 48 dba. This includes auto traffic events including bus, car, and motorcycle activity. The noise level exceeded 90% of the time is designated Lgo (see terminology page and example in Figure 7), and represents a realistic minimum sound level (i.e., background noise). Figure 7. Example Measurement Profile with Exceedance Percentile Levels. db (A) Maximum Q) > Q)... Q)... :::l r.f) r.f) Q)... CL "C c :::l 0 (/} 0 - Lso - L _...-+ Minimum T Time (s) t is expected that the ambient noise level will not drop significantly below this value except for short periods of time, and thus the use of the Lgo noise level is conservative. Based on the data obtained from the sound level meter, the Lgo representing the minimum neighborhood ambient noise level at each measurement position was determined for purposes of the noise impact analysis. The Lgo measured at 8723 Rangely Ave was 43 dba. See Terminology page for explanation of the term "A-weighted". The octave band ambient noise levels were also measured for use in the analysis. 6

8 "\f\- Veneklasen Associates 7.0 Comparison of Predicted Noise Levels to Ambient Noise Levels Our analysis compared the measured ambient noise levels to the predicted noise levels from the proposed roof level Catch Restaurant. Conversations Among Customers We predicted sound levels at the rear property line of 8713 Rangely Ave. based upon published data 3 for the Sound Power Level of conversation and the attenuation due to distance traveled to the property line and shielding of the glass barrier wall at the roof edge. The barrier was modeled at its design height of 6 feet as measured from the Terrace Level finish floor, which is proposed to be at an elevation of 49.5 feet. We then compared the predicted conversational noise levels to the existing ambient sound levels using the objective criteria outlined above at the rear property line 8713 Rangely Ave. to determine whether conversation from the Catch Restaurant would be plainly audible or not. Our calculations were conservative in three ways : 1. We assumed all retractable elements including glass walls and the canvas canopy were in their open positions. 2. We assumed that one-half of the roof level restaurant's 278 customers were conversing simultaneously in a loud voice level. This assumption was made since typically only one person is speaking in a group of two persons. n groups of 2 or more persons, more persons might be speaking, but usually no more than 50%. 3. We utilized ambient noise levels that were exceeded 90% of the time at post-12 am periods when the ambient noise level is lowest. To reiterate, this noise level is termed the Lgo (see terminology page), and represents a realistic minimum sound level. t is expected that the ambient sound level will not drop significantly below this value except for short periods of time. f the sound levels from the roof level restaurant are acceptable during this time period, they will be acceptable when the ambient noise level is higher. With these assumptions in place, the predicted sound level from conversations from the roof-level Catch Restaurant at the rear property line of 8713 Rangely Ave. to the south is 39 dba. As mentioned earlier, the Lgo ambient noise level measured during the 12 am to 12:30 am measurement period was 43 dba. Therefore, the predicted noise levels from the roof level restaurant at the at the rear property line of this nearest residence will be 4 dba less than the ambient noise level, which will be audible to a receiver at the 8713 Rangely Ave property line. As a result, this noise level will not meet the criterion which stipulates that conversations. from the Catch Restaurant roof are not to be "plainly audible." Noise Mitigation measures are summarized in Section 8.0. Background Music Background music is also intended for the roof level restaurant. Background music levels are typically lower than the conversational vocal levels of patrons assumed in our previous analysis. Based upon our experience, background music levels propagating to the residential areas will also comply with the intent of the West Hollywood Noise Ordinance, since they will be lower than the predicted sound levels from conversation, as long as the mitigation measures in Section 8.0 are implemented. However, as a further precautionary measure and to aid in compliance with the West Hollywood Noise Ordinance, we recommend utilizing numerous 3 Leo L. Beranek, Acoustics,

9 "'1\- Veneklasen Associates loudspeakers directed towards the restaurant seating area. A larger number of speakers played at a lower level provides even coverage and controls sound from spilling into other areas. 8.0 Summary of Noise Mitigation Measures We recommend the following mitigation measures to aid in meeting the provisions of the West Hollywood Noise Ordinance with respect to noise levels at the property line of the nearest residence: The height of the glass barrier located along the south edge of the roof should be increased from 6 feet to 7 feet as measured from the 49.5 foot finish floor of the Terrace Level. Our modeling predicts this change to add 1 dba of sound attenuation, thereby reducing the modeled sound level at the nearest residence to 38 dba, which is 5 dba below the ambient noise level and will not be "plainly audible" above the ambient noise level. solated events such as laughs or guffaws may be noticeable, but these events will not be "continuous, repeated, or sustained." The glass used for the barrier should ideally exhibit a surface mass of at least 2 pounds per square foot, and must be solid without holes or gaps. Locate background music loudspeakers near the customers. Adjust the sound levels so that they serve the required function in the roof level restaurant and are inaudible at the property line of the nearest residence. VA recommends that any live music be restricted to amplified instruments only (i.e. No acoustic drums, brass or reed instruments, or vocal soloists) with the volume levels adjusted to levels equal to those prescribed for background music. When sound sources atypical of the normal background music system are used on the roof deck, VA recommends conscientious noise monitoring in the neighborhood via short term sound measurements or aural checks be performed to ensure that the activity is not audible. 8

10 "7\- Veneklasen Associates ACOUSTCAL TERMNOLOGY Decibel, db A measure for rating the level of a sound, which uses a logarithmic scale. The decibel unit is equivalent to 20 times the logarithm, to the base 10, of the ratio of the pressure of the sound to the reference pressure of 20 Pa. Frequency, Hz The repetition rate of a sound wave measured in cycles per second, which is usually expressed in Hertz (Hz). The audible frequency range for normal hearing individual spans from 20Hz to 20 khz. Frequency is that characteristic of a sound which is perceived by a listener as the "pitch". A-Weighted Sound Level, dba Ambient Noise Level The sound pressure level in decibels as measured in a A weighting filter network. The A-weighting de-emphasizes the very low frequency components of the sound in a manner similar to the frequency response of the human ear and correlates well with subjective reactions to noise. All sound levels in this report are in the A-weighted scale. The composite noise from all sources near and far. The normal or existing level of environmental noise at a given location. Lo (Lmax ), L10, Lgo The A-weighted sound levels that are exceeded 0 percent (maximum sound level), 10 percent, and 90 percent of the time during the measurement period. The Lo rep resents the absolute loudest sound level (Lmax or maxi mum sc:>und level) during the measurement period as it was exceeded 0% of the time. The Lio represents a realistic maximum sound level that is not expected to be significantly exceeded except for short periods of time. The Lgo represents a realistic minimum sound level which the measured value is not expected to drop significantly below except for short periods of time. 9