The URL can be used to link to this page

Home My WebLink AboutSP202000013 Study - Sound 2020-09-21•)))1�'((* ACENTECH September 18, 2020 Nancy Sanford and Scott Kelley Hilmasco LLC 7285 Plank Rd, Afton 22920 Sanford nm(rDvahood. com skel lev(rDaetoscapita Iasi a. co m Subject Preliminary Analysis of Sound Propagation from Proposed Event Site Wavertree Hall Event Venue, 1100 Kingsway Road, Batesville, VA Acentech Project No. 633694 Dear Ms. Sanford: 2150 Wise Street #5852 Charlottesville, VA 22905 434 218 0759 acemedicom Thank you for taking the time to meet at the Wavertree Hall Estate last week to introduce me to your project. This letter report outlines our understanding of your project, our assumptions regarding sound source levels and placement, and details the associated modeling and prediction of sound levels throughout the site. A brief glossary is included at the end of this letter. EXECUTIVE SUMMARY Sound level predictions were made with a distributed house sound system around the outdoor use areas for ambience, a dance floor with typical sound levels in the upper outdoor use area, and large crowds spread throughout these areas. No review was made of indoor amplified music, but as the sources are the same, we expect significant noise reduction if event activities move indoors. Based on the results from our sound propagation model, we expect that if your site is configured to meet all of our assumptions outlined in this report, the predicted sound levels will meet the county's daytime noise ordinance and be below 60 dBA at all property lines. ALBEMARLE COUNTY NOISE ORDINANCE We understand that your team has had discussions with Albemarle County staff, and you have been given direction to conduct a noise study for inclusion with your application. Staff has also directed you to the specific portion of the Albemarle County Code they expect the noise study to review, which defines the maximum allowable sound levels 1. All of the adjacent parcels for this project are zoned rural/residential and must meet the strictest of these limits. For this type of zoning, the maximum allowable sound levels are defined as an equivalent continuous (average) sound pressure level of 60 dBA during the daytime and 55 dBA during the nighttime 2. The Albemarle County Code includes additional details outlining the necessary equipment and measurement procedure (for existing projects), applicable definitions, and source exemptions. Relevant exemptions include I Albemarle County Code, Chapter 18, Section 4.18.04, Noise. httos://Iibrary.municode.comtvalalbemwie county/codes/code of ordinances?nodele=CH18Z0 ARTIOARE S4GERE S4.18NO S4.18.04MASOLE 3 The county defines daytime as 7AM to 1OPM and nighttime as SOPM to 7AM. acoustics avriHsecurity I vibration Hilmasco LLC September 18, 2020 Page 2 of 23 transportation and a person's voice. Note that amplified music is listed as exempt, but as we understand it from county staff, that does not apply to this use. BACKGROUND Because your event site is not yet completely planned, this review allows for some future flexibility. To do this we must assume that sound will be generated at various locations around the site. The sources of this sound are expected to be transportation, voices from the gathering crowd, and amplified music. Amplified music is expected at the reception site (e.g. the dance floor) as well as being distributed around the entire outdoor use areas as depicted on the Special Use Permit Concept Plan. This review will not cover any indoor amplified music, since the sources will remain the same but benefit from significant noise reduction due to placement indoors. Based on discussions with your engineering team, we expect that the reception area will either take place inside the primary event structure (building S, indoor riding circle) or in the upper courtyard area just above it. We also understand that the cocktail reception portions of an event may leverage either of the upper or lower courtyard areas, where the stables and silos may play a part as serving stations. Below is the concept plan from the special use permit application that shows what we are calling the upper and lower courtyards. ® Outdoor Use Area for Events Crowd Noise While a person's voice is exempt from the county's noise ordinance, it is a source that will always exist during an event. This means that it is not easy, or practical, to remove a crowd's contribution from a measured sound pressure level, making it difficult to show compliance with the noise ordinance of the non-exempt sources. Therefore, to be thorough and to best reflect the constant sources of noise heard by neighbors, we have included the predicted crowd noise in our review. Crowd noise can be very difficult to predict because there are so many independent variables. In an effort to simplify the process we are relying on research 3 that characterizes the prediction of outdoor noise due to small to medium sized crowds (empirical portion of the research was limited to 100 people). Following the details outlined in this paper, the crowd's sound power level (LwAeq) can be predicted using the expected number of people at the event. The prediction shows that the sound level will increase by 4.5 dBA for each doubling of ' Prediction of Noise from Small to Medium Sized Crowds. M.J. Hayne, at al. ACOUSTICS 2011. •I010 A C E N T E C H Hilmasco LLC September 18, 2020 Page 3 of 23 crowd size ^. We understand that you are requesting two different sized events in your special use permit: a larger number of events up to 150 people and a smaller number of events of up to 350 people. Note that crowd noise predictions are generalized and actual sound levels of a given crowd will vary. Outdoor Dance Floor Amplified Music In our experience the typical sound pressure levels on the dance floor of an event with amplified music often ranges between 85 dBA and 100 dBA. For reference, 85 dBA is about the level of a loud film in a movie theater, while 100 dBA would be similar to a dance club or louder fitness class, but quieter than a rock concert. Note that these levels could fall in a wider range based on the performer/presenter's tastes and their client's wishes. However, we feel that this range is representative and offers a good starting point for our review. For our analysis, we have assumed that a two -loudspeaker configuration generates a sound pressure level of 85 dBA at a distance of 50 feet from the loudspeakers, at what might be considered the edge of the dance floor, to a sound pressure level over 100 dBA near the loudspeakers. The specific music played during a given event will dictate the frequency content of the reproduced sound. For example, some music is bass heavy, while other music is not. While we cannot predict the exact music that will be played, experience has shown us that most music has a frequency distribution similar to pink noise, where each octave band has a similar sound level. For prediction purposes, we have assumed a pink noise frequency distribution. Outdoor Cocktail Areas Amplified Music For the cocktail areas, we have assumed that each loudspeaker would be placed on or near a building and generate a sound pressure level of 70dBA at 10 feet. These sound levels would be just above conversational levels at 10 feet, near conversational levels at 20 feet, and audible but lower in sound level at more distant positions from the speaker. Again, for prediction purposes, we have assumed a pink noise frequency distribution for each of the associate cocktail area speakers. SOUND LEVEL MODELING Modeling Process We use a software package called CadnaA to build a model, predict noise levels, and present that data. CadnaA is a widely recognized and accepted noise propagation modeling software that follows ISO 9613-2 5. Your team has provided us with a detailed model of the planned site, including buildings, elevation contours, and the property boundary. Using some of this data, we have built a noise propagation model of your site for the purposes of sound level prediction. Figure 0 shows the entirety of the model area, with buildings shown as black shapes and the property boundary shown as a black line. Buildings near sound source(s) were defined to provide reflection and shielding in the sound propagation path. Elevation contours provided the necessary topographic information to aid in predicting spreading, ground absorption, shielding, and diffraction. Sound sources were added at possible locations and then given an assumed sound level, directivity, and height from the ground. Atmospheric attenuation of sound is somewhat influenced by temperature and relative humidity, but does not have a large impact on our results. This is because lower frequencies and higher frequencies do not behave the same for a given set of conditions. Because your proposed event sites are outdoors we expect they will primarily be in use during fair weather, so we have assumed a typical temperature of 80OF and a relative humidity of 70%. Foliage such as trees and bushes were not included within the project boundary to allow for a ° Crowd sound power levels are predicted to be 97 dBA for 150 people and 102 dBA for 350 people. 5 International Standards Organization 9613-2, Attenuation of Sound during Propagation Outdoors. •D;1;(l� ACENTECH Hilmasco LLC September 1B, 2020 Page 4 of 23 more conservative prediction of event sound levels up to the boundary. However, foliage was included for much of the model outside the project boundary because of the forest -like density of trees. Note that seasonal variations will occur, but the planned outdoor uses would only take place in the warmer seasons where there is little variation. We have not accounted for the effects of temperature inversions, wind speed, and wind direction the propagation model. These variables require meteorological data specific to the site and further complicate the predictions. Note that temperature inversions, where a layer of warm air covers cooler surface air, typically occur near sunrise of clear and calm nights, when events will not be taking place. A review of typical weather conditions on Weather Spark 6 shows that the warmer months, when events are expected to be held, have an hourly mean wind speed below 4 mph (roughly 1.5 m/s), which should not be high enough to perceptibly change the downwind sound level 7. Since the applicable wind correction factor would be small, imperceptible, and based on actual wind direction/speed, it has not been included in our model. This means that our model and predictions generally represent the wind conditions expected for this region. Noise Contour Maps A noise contour map is a way of graphically representing the sound level of a particular site. They allow the reviewer to quickly determine the approximate sound level at any given location in the model, and determine compliance with the noise ordinance. In our model, the sound levels on the noise contour maps are calculated on a 20-foot x 20-foot grid at a height of 5 feet, and further interpolated between points on the grid. Sound level ranges are represented with bands of color. For our purposes, most color bands represent a 5 dBA range, with individual noise contour lines (black) within each range representing 2.5 dBA steps. Noise contour maps should be used to visualize the propagation of sound only, and should not be used to determine the exact sound level at any given location, as they are drawn by interpolation. SOUND LEVEL PREDICTIONS Using the CadnaA model, we are able to predict sound levels and associated noise contour maps for individual sound sources or groups of sources. In an effort to more thoroughly review the sound level contributions for each group of sources we have run a total of 7 variants, as shown in Table 2. The noise contour maps of these variants are shown in the enclosed figures and discussed in further detail in this section. TABLE 2: CONFIGURATION OF CADNAA NOISE MODEL VARIANTS variant # Description Source Locations Noise Contours 1 Distributed Music (16 Distributed Speakers) Figure 1A Figure 1B 2 Lower Courtyard Crowd (150 people) Figure 2A Figure 2B 3 Upper Courtyard Crowd (350 people) Figure 3A Figure 3B 4 Lower Crowd (150) & Upper Crowd (350) Figure 4A Figure 4B 5 Outdoor Dance Floor (2 PA Speakers Facing South) Figure 5A Figure 5B 6 Distributed Music + Both Crowds Figure 6A Figure 6B 7 Distributed Music + Both Crowds + Outdoor Dance Floor Figure 7A Figure 7B The noise ordinance limit is 60 dBA during the day and 55 dBA during the night (starting at 10PM). Color bands in the noise contour map represent sound levels. Any bands colored a shade of white, gray, or green are predicted to be within the daytime and nighttime noise ordinance sound levels (< 55 dBA). Yellow is the first band that is predicted to be within the daytime but not nighttime sound levels (55 — 60 dBA). Red, purple and 6 httos://weathersoark.comN/20225/Average-Weather-in-Charlottesville-Virginia-United-States-Year-Round#Sections-Wind 7 ISO 9613-2 states that the correction factor for wind is typically small and around 0 —2 dBA. Any correction would. cause a reduction in the upwind sound level and an increase in the downwind sound level. •I)0o ACENTECH Hilma co LLC September 1B, 2020 Page 5 of 23 blue represent areas of higher sound levels (> 60 dBA). To determine compliance with then noise ordinance, simply verify that all bands of red (> 60 dBA) are inside the property boundary for daytime use, or all bands of yellow (> 55 dBA) are within the property boundary for nighttime use. Note that source location and noise contour maps may not show the entire boundary in an effort to focus on the areas that are the most affected by the event. Variant 1— Distributed Music This variant characterizes the impact of distributing loudspeakers around the event site to cover much of the lower and upper courtyards with music. This music is not intended to be loud, but rather to set the mood of the event. With that in mind, and as described in the background section, the sound level of each speaker was assumed to be around 70 dBA at a distance of 10 feet. A total of 16 omnidirectional loudspeakers were placed at a height of 10 feet and positioned around the event site, as shown by red symbols (+) on Figure 1A. Figure 1B shows the noise contour map for this variant. The distributed music system as modeled is predicted to produce sound levels well within the noise ordinance for day or night, with the highest predicted property line sound levels of 46 dBA at the nearest southern boundary. Variant 2 — Lower Courtyard Crowd This variant characterizes the impact of a crowd of 150 people distributed through the lower courtyard (assumes the smaller event size is fully at this location). Figure 2A shows the placement of this crowd, drawn as a red rectangle with hatch marks. Figure 2B shows the noise contour map for this variant, which is predicted to produce sound levels well within the noise ordinance, with the highest predicted property line sound levels of 46 dBA at the nearest southern boundary. Variant 3 — Upper Courtyard Crowd This variant characterizes the impact of a crowd of 350 people distributed through the upper courtyard (assumes the larger event size is fully at this location). Figure 3A shows the placement of this crowd, drawn as a red rectangle with hatch marks. Figure 3B shows the noise contour map for this variant, which is predicted to produce sound levels well within the noise ordinance, with the highest predicted property line sound levels of 42 dBA at the nearest western boundary. Variant 4 — Both Crowds This variant characterizes the impact of both courtyard spaces being occupied with people. The distribution of people during an event is unknown, so we have conservatively modeled 150 people in the lower courtyard and 350 people in the upper courtyard (Variant 2 + Variant 3), which is a larger assembly than the applicant proposes. Figure 4A shows the placement of these crowds, as presented in previous figures. Figure 4B shows the noise contour map for this variant, which is predicted to produce sound levels well within the noise ordinance, with the highest predicted property line sound levels of 47 dBA at the nearest southern boundary and 43 dBA at the nearest western boundary. Variant 5 — Outdoor Dance Floor This variant characterizes the impact of the amplified music at the outdoor dance floor. Based on the event concept plan, we have assumed that this dance floor directly abuts the horse barn on the far north side of the upper courtyard. This music is expected to be loud on the dance floor, as is typical of such events. As described in the background section, the sound level of each speaker was assumed to be around 85 dBA at a distance of 50 feet. A total of two 15" PA loudspeakers, with typical directivity for such a speaker. Each loudspeaker was placed at a height of 8 feet, turned into the dance floor by 15 degrees, and positioned as shown in Figure 5A. •D;1;(�� ACENTECH Hilma co LLC September 18, 2020 Page 6 of 23 Figure 5B shows the noise contour map for this variant. The outdoor dance floor sound system, as modeled, is predicted to produce sound levels within the daytime noise ordinance. The highest predicted property line sound levels are 54 dBA at the nearest southern boundary and 54 dBA at the nearest southwestern boundary. Variant 6 — Distributed Music + Both Crowds This variant characterizes the impact of both courtyard spaces being fully occupied with people, as well as the distributed music in use (Variant 1 together with Variant 4). Figure 6A shows the placement of these sources, as presented in previous figures. Figure 6B shows the noise contour map for this variant, which is predicted to produce sound levels within the noise ordinance for daytime and nighttime. The highest predicted property line sound levels are 50 dBA at the nearest southern boundary and 45 dBA at the nearest western boundary. Variant 7 — Distributed Music + Both Crowds + Outdoor Dance Floor This variant characterizes the impact of both courtyard spaces being fully occupied with people, as well as the distributed music and dance floors in use (Variant 1 + Variant 4 + Variant 5). Figure 7A shows the placement of these sources, as presented in previous figures. Figure 7B shows the noise contour map for this variant, which is predicted to produce sound levels near the nighttime noise ordinance and within the daytime noise ordinance. The highest predicted property line sound levels are 56 dBA at the nearest southern boundary and 54 dBA at the nearest southwestern boundary. We found that the dance floor speakers are the most prominent contributor to the sound level at the loudest property line locations. Alternate placement of loudspeakers, or distributed loudspeakers, on the dance floor may provide slightly lower predicted sound levels at the nearest property line. ADDITIONAL CONSIDERATIONS Loudspeaker Orientation Changes to the loudspeaker orientations and positions may change the noise contour map for the site. Subtle changes should not have a large impact on the contours, but you should make efforts to ensure that loudspeakers are oriented and positioned roughly as shown. If significant changes to location or orientation are made then we recommend the model be re -run with the updated details to review the noise contour maps. Community Acceptance A noise ordinance is not fully capable of characterizing a neighbor's acceptance of noise. If community members have an adverse reaction to event sound, additional considerations can be made to better address human acceptance of noise due to distant amplified music. These considerations can take the form of a lower overall sound level from the source(s), providing a visible (but not necessarily noise blocking) separation from the event, defining specific sound levels that cannot be exceeded in a given frequency band (such as for bass - frequency sound), or more extreme mitigation measures. CONCLUSION & RECOMMENDATIONS In summary, all anticipated variants, even with the conservative (louder) estimates of exempt crowd noise, have predicted sound levels that meet the daytime noise ordinance limits. We expect that the nighttime limits could be met with further administrative controls or strategic placement of the dance floor loudspeakers. However, we recommend avoiding outdoor amplified music during nighttime hours. No review was made of indoor amplified music, but as the sources are the same, we expect significantly lower property line sound levels related to indoor events. We recommend that your event space include all electronics and loudspeakers necessary for these events, essentially providing a "house sound system" This will allow you control over the sound system, including limits on sound level (volume), adjustments to frequency distribution (such as lowering the bass), and potential ability •D;ko ACENTECH Hilma co LLC September 18, 2020 Page 7 of 23 to dynamically control the volume based on sound level (though this can get expensive). We recommend you work with an AV consultant or contractor to meet these goals and are available to assist as an additional service. Additional measures not previously mentioned include locating bathrooms and valet stations far from the property line. While the people and vehicles are exempt from the noise ordinance, the noise from these activities may increase as the event nears completion and thoughtful placement can help to avoid disturbing the community. If your special use permit is approved you may be asked to provide some form of noise monitoring to verify sound levels stay within the noise ordinance. We are available to assist you with that design or process as an additional service and suggest that is best determined while the house sound system is being specified by a future AV consultant or contractor. I hope this letter provides you with the information that you need at this time. If you have any questions, please feel free to contact me at bvoder(a)acentech.com or 434.218.0759. Sincerely, Acentech Incorporated Bill Yoder Senior Staff Scientist cc: Lori Schweller (Williams Mullen) Kelsey Schlein (Shimp Engineering) •D0, ACENTECH Hilma co LLC September 18, 2020 Page 8 of 23 GLOSSARY OF ACOUSTICAL TERMS We understand that acoustic terminology may be confusing. The following is a brief glossary of some acoustical terms used in this report that you may find useful. Ambient Sound The sound due to environmental, traffic, or other nearby sources that are unrelated to the source(s) being measured or characterized. dB = decibels, dBA = decibels, A -weighted Decibels (abbreviated dB) are used to measure the relative loudness of sound, based on a logarithmic scale. For reference, normal human speech is in the range of 65 decibels, painful rock music may be more than 110 decibels, while aircraft noise may be as loud as 130 decibels. A -weighting filters the sound in a way that is similar to human hearing, and was found to be correlated to annoyance from environmental sound. Hence, dBA levels are often referenced in various acoustical standards. Note that a 10 dB increase in sound is associated with a perceived doubling in sound level. Directivity The pattern in which sound radiates from a given source. This could be spherical, hemi-spherical, or some other pattern. Directivity changes with frequency and is related to the size and shape of the source. Frequency, Hz The number of cycles or oscillations per second. Low frequency is associated with bass and are low pitch, while higher frequencies are high pitched. Leq The equivalent continuous sound level, or energy -average sound level, over a defined measurement period. Note that the sound level may be higher or lower during a given measurement period. Octave Band An octave band is a frequency band where the highest frequency is twice the lowest frequency, and characterized by its center frequency. Bands are proportional in width, being wider at higher frequency. Pink Noise Noise in which each octave band has equal energy. Propagation Loss A reduction of sound energy due to distance, absorption, and other means. Sound Power Level This is the level used to define the amount of acoustic power generated by a particular sound source. Sound Pressure Level This is the level used to characterize the loudness of a sound. In this review, sound pressure is implied unless the language specifically indicates sound power Temperature inversion A reversal of the normal behavior of temperature near the ground. This occurs when a layer of warmer air covers a layer of cool air at the surface. This can allow sound to reflect off the warmer air and travel to a greater distance. •�)0, ACENTECH Figure 0: Overall Site Model Hilmasco LLC September 18, 2020 Page 9 of 23 -5,10ACENTECH Figure 1A: Distributed Music Loudspeaker Locations Hilma co LLC September 18, 2020 Page 10 of 23 -54tk ACE NTECH Figure 1B: Distributed Music Noise Contour Map C <3 C 30 40 45 50 C 55 60 65 70 >7 Hilma co LLC September 18, 2020 Page 11 of 23 410ACE NTECH Figure 2A: Lower Courtyard Crowd Location (assumed 150 people) Hilma co LLC September 18, 2020 Page 12 of 23 -54tk ACE NTECH Figure 213: Lower Courtyard Crowd Noise Contour Map (assumed 150 people) C <3 C 30 40 45 50 C 55 60 65 70 >7 Hilma co LLC September 18, 2020 Page 13 of 23 410ACE NTECH Figure 3A: Upper Courtyard Crowd Location (assumed 350 people) Hilma co LLC September 18, 2020 Page 14 of 23 -54tk ACE NTECH Figure 313: Upper Courtyard Crowd Noise Contour Map (assumed 350 people) Adw C < 30 dBA C 30 - 40 dBA — 40 - 45 dBA \ 45 - 50 dBA 50 - 55 dBA C 55 - 60 dBA 60 - 65 dBA 65 - 70 dBA 70 - 75 dBA > 75 dBA o r - 1 Hilmasco LLC September 18, 2020 Page 15 of 23 i +O;f(�• ACENTECH Figure 4A: Lower (150 people) and Upper (350 people) Crowd Locations Hilma co LLC September 18, 2020 Page 16 of 23 410ACE NTECH Figure 413: Lower (150 people) and Upper (350 people) Noise Contour Map O� I ` _ C < 30 dBA \ C 30 40 d1 40 - 45 dBA 45 - 50 dBA� 50-55dBA C 55-60dBA 60-65dBA 65 - 70 dBA 70 - 75 dBA > 75 dBA Hilma co LLC September 18, 2020 Page 17 of 23 4.'((kACENTECH Figure 5A: Outdoor Dance Floor Speaker Locations Hilma co LLC September 18, 2020 Page 18 of 23 -5,10ACE NTECH Figure 513: Outdoor Dance Floor Noise Contour Map C < 3' C 30 40 45 50 C 55 60 65 70 M>7. Hilma co LLC September 18, 2020 Page 19 of 23 45,10ACENT ECH Figure 6A: Distributed Music + Both Crowds Source Locations Hilma co LLC September 18, 2020 Page 20 of 23 -54tk ACE NTECH Figure 6B: Distributed Music + Both Crowds Noise Contour Map C <3 C 30 40 45 50 C 55 60 65 70 >7 Hilma co LLC September 18, 2020 Page 21 of 23 410ACE NTECH Figure 7A: Distributed Music + Both Crowds + Dance Floor Source Locations Hilma co LLC September 18, 2020 Page 22 of 23 410ACE NTECH Figure 7B: Distributed Music + Both Crowds + Dance Floor Noise Contour Map to C < 30 dBA 30 - 40 dBA 40-45dBA 45-50dBA 50-55dBA EM 55-60dBA 60-65dBA 65-70dBA 70-75dBA > 75 dBA I ,l Hilma co LLC September 18, 2020 Page 23 of 23 0 -)$k, A C E N T E C H