REP N Bank St. Rooftop Patio Noise Study. N45 Architecture Inc. 852 Bank Street Project Rooftop Patio Environmental Noise Study

Transcription

1 1of Robert Matthews, B.ARCH., O.A.A., A.A.N.B., R.A.I.C. N45 ARCHITECTURE INC. 2nd floor, 43 Eccles Street Ottawa, Ontario Canada K1R 6S3 TEL x 234 FAX robertm@n45.ca Dear Robert, N45 Architecture Inc. 852 Bank Street Project Rooftop Patio Environmental Noise Study We have completed an environmental noise study for the proposed Roof Top Patio at 852 Bank. St. in Ottawa. The purpose of our study is to assess the potential noise impact from patrons on the roof top patio to the nearest residential buildings, corresponding to two apartment building located at 147 and th Ave, between Bank St. and Monk St. The two closest Points of Reception (POR) are: POR 1: The 3 rd level of the apartment building at th Ave, approximately 15.5m North of the center of the edge of the roof top patio, considering the actual diagonal sound path. POR 2: The 3 rd level of the apartment building at th Ave, approximately 15.5m North of the center of the edge of the rooftop patio, considering the actual diagonal sound path. With a patio occupancy of 150 patrons, corresponding to a Sound Power Level (SWL) of 68.4 dba/m 2, we calculated Sound Pressure Levels (SPL) of 56 dba at POR 1 and POR 2. These noise levels are in the same range as typical daytime background traffic noise in Ottawa, recently measured to be dba SPL on a side street 150m from St. Laurent Boulevard. Therefore, based on our model and assumptions about the patio conditions, described in this report, the patio noise will be noticeable at the points of reception but not significantly louder than the daytime background noise. The methodology and results of our noise study are described below. 1.0 Site Description and Methodology Based on site plans of the proposed roof top patio and aerial maps of the surrounding area, we created a 3D computer model of the 852 Bank St. commercial building and the nearest residential buildings using the environmental noise modeling software package Cadna/A, which references ISO Cadna/A predicts environmental noise through calculations based on a 3D model, taking into account building geometry, topography and the Sound Power Levels of noise sources.

2 2of7 The proposed commercial building at 852 Bank St. is divided into two sections with differing elevations: one 4m tall section with a proposed roof top patio and one 9m tall section, with two stories of commercial space and HVAC mechanical equipment on the roof. This report will only consider noise from the rooftop patio only. Figure 1 below shows a site map of the proposed commercial building at 852 Bank St. and the closest points of reception. POR 2: th Ave POR 1: th Ave 852 Bank St. Proposed Commercial Building Property Line Figure 1 Site map of 852 Bank St. and closest residential Points of Reception. Map taken from POR 1 is located on the 3 story, 13m tall residential apartment building at th Ave., approximately 15m North of the proposed 852 Bank St. commercial building. The apartment unit on the 3 rd level of th Ave. closest to the patio is the nearest point of reception and will be designated POR 1. POR 2 is located on the 3 story, 13m tall residential apartment building located at th Ave., approximately 15m North of the proposed 852 Bank St. commercial building. The apartment unit on the 3 rd level of th Ave closest to the patio is the nearest point of reception and will be designated POR 2.

3 3of7 To simulate the noise levels produced by patrons on the roof top patio, we used results from a report sent to us by Mr. Stream Shen from the City of Ottawa that reported Sound Pressure Level (SPL) measurements taken at the outdoor patio at the Canal Ritz on Queen Elizabeth Drive in Ottawa. The Canal Ritz patio has an area of approximately 138m 2, which is around 2/3 the size of the proposed 219m 2 roof top patio at 852 Bank St. There were approximately 50 diners present at the time of the measurement. The measured sound pressure level was 53.3 dba at a point of reception 20m from the centre of that patio. To calibrate our environmental noise model of the proposed rooftop patio in CadnaA, we reproduced these previous results by placing 50 identical point sources in a rectangular area of 138m 2 to represent the 50 diners on the patio. We adjusted the SWL of the diners to 69.9 dba per person to achieve the measured SPL of 53.3 dba at 20m from the center of the patio (sound pressure derives from sound power and it is the sound pressure that decreases with increasing distance). Once our model was calibrated, we defined a 219m 2 rectangular area representing the proposed rooftop patio at 852 Bank St. CadnaA only allows up to 50 point sources to be placed in a given model, so to simulate the 150 patron occupancy of the 852 Bank St. rooftop patio, we dispersed 50 point sources evenly over the rectangular area of 219m 2 and increased the SWL of each point source by 5 dba, from 69.9 dba to 74.9 dba. These point sources resulted in an SPL of 55.8 dba at a distance of 20m from the centre of the patio. We then created a 219m 2 area source and adjusted the SWL to 68.4 dba/m 2 (91.8 dba total SWL) to obtain the same SPL of 55.8 dba at 20m. Our model assumes that the noise from the roof top patio is produced by 150 patrons only, with no amplified music. 2.0 Results Using the 219m 2 roof top patio with a SWL of 68.4 dba/m 2, we calculated the noise levels on the façades of the nearest apartment buildings at 147 and th Ave. The loudest calculated SPLs on the building façades will be referred to as the Points of Reception. Table 1 below shows the calculated sound pressure level at the PORs. An image of the 3D model used for our calculations is included in the Appendix. POR # Patio Area (m 2 ) Patio # of Patrons POR distance from patio (m) POR height above patio (m) Patio SWL (dba/m 2 ) POR SPL (dba) Table 1 Maximum calculated SPL at the nearest PORs on the apartment buildings at 147 & th Ave. The maximum calculated SPL at POR 1 was 56.3 dba at a distance of 15.5m from the center of the edge of the roof top patio, considering the diagonal sound path. This corresponds to the nearest residential unit on the 3 rd level of the apartment building, 4m above the patio.

4 4of7 The maximum calculated SPL at POR 2 was 56.2 dba at a distance of 15.5m from the center of the edge of the roof top patio, considering the diagonal sound path, which corresponds to the nearest residential unit on the 3 rd level of the apartment building, 4m above the patio. We recently measured the daytime background traffic noise on a residential side street 150m from St. Laurent Boulevard, which is similar to the locations of POR 1 and POR 2 in relation to 852 Bank St., and found the noise levels to be in the range of dba SPL. The calculated noise levels at the PORs in our model are thus in the same range as the daytime background traffic noise. Using the results from our simulation, the combined patio and traffic noise levels will be around dba SPL at the nearest PORs. As such, the patio noise will be noticeable at the PORs but is not significantly louder than the background noise level. During the evening, when the background noise decreases, the patio noise will be more noticeable and will be the primary source of noise at the points of reception. If the patio is only half-full with 75 people, the noise from the patio at the PORs can be expected to decrease by 3 dba from 56 dba to 53 dba. Conversely, if the patio is at full capacity with 150 people and they are making twice as much noise as is assumed in our model, the noise at the PORs can be expected to increase by 3 dba, from 56 dba to 59 dba.

5 5of7 3.0 Conclusion Using site plans, elevations and aerial maps of the surrounding area, we have constructed a 3D model of the proposed rooftop patio at 852 Bank St. in Ottawa. Based on measurements from a previous noise study at the outdoor patio at the Canal Ritz on Queen Elizabeth Drive in Ottawa, we determined that a patio with 150 patrons with no amplified music will produce a sound pressure level of 56 dba at the two nearest points of reception (apartment buildings located at 147 and th Ave.). This noise level is in the same range as the background noise in a similar traffic area, which we recently measured to be dba SPL during the daytime. The patio noise will therefore be noticeable but in the same range as the background noise and the combined patio and background noise will add to around dba at the PORs. When the background noise decreases in the evening, the patio noise will be more noticeable at the points of reception and will be the primary source of noise. If you have any questions about the results of our calculations, please do not hesitate to contact us. Sincerely, Peter Wright, M.Sc. Acoustic Consultant

6 6of7 Appendix 3D CadnaA model of proposed roof top patio and points of reception

7 7of7 POR 2: 56.2 dba SPL at 15.5m from patio (3 rd level apartment) POR 1: 56.3 dba SPL at 15.5m from patio (3 rd level apartment) Proposed roof top patio with SWL 68.4 dba/m 2 Figure A1 3D CadnaA model of proposed rooftop patio (blue triangle) and nearest points of reception. Image will appear in colour when viewed on a computer or printed with a colour printer.