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Home My WebLink AboutCDP 2016-0006; MFD-01; 2637 JEFFERSON STREET RESIDENTIAL DEVELOPMENT NOISE ASSESSMENT; 2017-09-14Ldn Consulting, rnc. 42428 Chisolm Trail, Murrieta CA 92562 www.ldnconsulting.net September 14, 2017 ohms Architects Miguel A. Reyes 536 Sears Avenue San Diego, CA 92118 phone 760-473-J253 fax 760-689-4943 Subject: 2637 Jefferson Street Residential Development Noise Assessment -Carlsbad CA The firm of Ldn Consulting, Inc. is pleased to submit the following noise analysis for the proposed 2637 Jefferson Street residential development in the City of Carlsbad. The purpose of the survey is to determine the estimated exterior noise levels at the proposed residential uses and recommend mitigation measures for compliance with the City of Carlsbad guidelines and requirements for noise. PROJECT LOCATION/DESCRIPTION The proposed site is located on 0.25 acres and includes 4 attached multifamily homes. The project site is located 0.25 miles west of Interstate 5 along Jefferson Street in the City of Carlsbad. The project site address is 2637 Jefferson Street, Carlsbad, CA. The primary noise source that affects the site is vehicular traffic from adjacent Jefferson Street and background noise from Laguna Drive located approximately 450 feet to the south of the site. The project vicinity can be seen in Figure 1 and the project site configuration is provided in Figure 2 below. 9/14/2017 1 1785-02 2637 Jefferson Street Noise Report ohms Architects Miguel A. Reyes 536 Sears Avenue San Diego, CA 92118 • ~ II I V Yaldo,a 9/14/2017 V @ @] Oceanside C Ldn eon.ult/1111, me. 42428 Chisolm Trail, Munieta CA 92562 phone 760-473-1253 Fax 760-689-4943 Figure 1: Project Site Location (!!) S.V.lt..l R[Y • " @ .. ... " Project ~Location DAD I! Carlsbad 2 ,. IVlYRlNCH RANCt!O OH ORO ,,. • I _,.... TRI-CITY I . .. "' . McCtellan-Polornar Airport 0 ,. " ,. Vista 1785-02 2637 Jefferson Street Noise Report ohms Architects Miguel A. Reyes 536 Sears Avenue San Diego, CA 92118 9/14/2017 Ldn CoMult/1111, Int:. 42428 Chisolm Trail, Munfeta CA 92562 phone 760-473-1.253 Fax 760-689-4943 Figure 2: Proposed Project Site Plan 3 1785-02 2637 Jefferson Street Noise Report ohms Architects Miguel A. Reyes 536 Sears Avenue San Diego, CA 92118 ACOUSTICAL FUNDAMENTALS Ldn eon.ult/1111, Int:. 42428 Chisolm Trail, Nunieta CA 92562 phone 760-473-.1253 Fax 760-689-4943 Noise is defined as unwanted or annoying sound which interferes with or disrupts normal activities. Exposure to high noise levels has been demonstrated to cause hearing loss. The individual human response to environmental noise is based on the sensitivity of that individual, the type of noise that occurs and when the noise occurs. Sound is measured on a logarithmic scale consisting of sound pressure levels known as a decibel (dB). The sounds heard by humans typically do not consist of a single frequency but of a broadband of frequencies having different sound pressure levels. The method for evaluating all the frequencies of the sound is to apply an A-weighting to reflect how the human ear responds to the different sound levels at different frequencies. The A-weighted sound level adequately describes the instantaneous noise whereas the equivalent sound level depicted as Leq represents a steady sound level containing the same total acoustical energy as the actual fluctuating sound level over a given time interval. The Community Noise Equivalent Level (CNEL) is the 24 hour A-weighted average for sound, with corrections for evening and nighttime hours. The corrections require an addition of 5 decibels to sound levels in the evening hours between 7 p.m. and 10 p.m. and an addition of 10 decibels to sound levels at nighttime hours between 10 p.m. and 7 a.m. These additions are made to account for the increased sensitivity during the evening and nighttime hours when sound appears louder. CNEL values do not represent the actual sound level heard at any particular time, but rather represents the total sound exposure. Additionally, Sound Transmission Class ( or STC) is an integer rating of how well airborne sound is attenuated by a building partition. STC is widely used to rate interior partitions, ceilings/floors, doors, windows and exterior wall configurations (see ASTM International Classification E413 and E90). The STC number is derived from tested sound attenuation values found at the 1/3 octave band frequencies. These transmission-loss (TL) values are then plotted and compared to a standard reference contour. Acoustical engineers fit these values to the appropriate TL Curve to 9/14/2017 4 1785-02 2637 Jefferson Street Noise Report ohms Architects Miguel A. Reyes 536 Sears Avenue San Diego, CA 92118 Ldn eon.ult/1111, Int:. 42428 01/60/m Trail, Nunfeta CA 92562 phone 760-473-1253 Fax 760-689-4943 determine a single STC value found at 500 Hertz. STC is roughly the decibel reduction in noise a partition can provide, abbreviated 'dB'. If an 85 dB sound on one side of a wall is reduced to 50 dB on the other side, that partition is said to have an STC of 35. This number does not apply across the range of frequencies because the STC value is derived from a curve-fit from the tested 1/3 octave band frequencies. Any partition will have less TL at lower frequencies. For example, a wall with an STC of 35 may provide over 40 dB of attenuation at 3000 Hz but only 15 dB of attenuation at 125 Hz. NOISE STANDARDS The City of Carlsbad's Noise Guidelines Manual (1995) requires that all exterior sensitive areas shall limit noise exposure. For noise sensitive residential land uses, the City has adopted a policy which has established a "normally acceptable" exterior noise level goal of 60 dBA CNEL for the outdoor areas and an interior noise level of less than 45 dBA CNEL. For residential properties identified as requiring a noise study, a study shall be prepared by an acoustical professional. This study shall document the projected maximum exterior noise level and mitigate the projected exterior noise level to a maximum allowable noise level as identified in Noise Guideline Manual. Interior noise levels should be mitigated to a maximum of 45 dBA CNEL in all habitual rooms when the exterior of the residence are exposed to levels of 60 dBA CNEL or more. If windows and doors are required to be closed to meet the interior noise standard, then mechanical ventilation shall be provided per City requirements. ANALYSIS PROCEDURES Exterior Noise Levels The primary source of noise impacts to the project site will be vehicular noise from adjacent Jefferson Street and background noise from Laguna Drive located approximately 450 feet south of the project site. The projected roadway noise levels from vehicular traffic were calculated using the methods in the Highway Noise Model 9/14/2017 s 1785-02 2637 Jefferson Street Noise Report ohms Architects Miguel A. Reyes 536 Sears Avenue San Diego, CA 92118 Ltln Conlllllt/1111, Int:. 42428 Chisolm Trail, Hunieta CA 92562 phone 760-473-1253 Fax 760-6/l!J-4943 published by the Federal Highway Administration (FHWA Highway Traffic Noise Prediction Model, FHWA-RD-77-108, December, 1978). The FHWA Model uses the traffic volume, vehicle mix, speed, and roadway geometry to compute the equivalent noise level. A spreadsheet calculation was used which computes equivalent noise levels for each of the time periods used in the calculation of CNEL. Weighting these equivalent noise levels and summing them gives the CNEL for the traffic projections. Mobile noise levels radiant in an almost oblique fashion from the source and drop off at a rate of 3 dBA for each doubling of distance under hard site conditions and at a rate of 4.5 dBA for soft site conditions. Hard site conditions consist of concrete, asphalt and hard pack dirt while soft site conditions exist in areas having slight grade changes, landscaped areas and vegetation. The future traffic noise model also utilizes the vehicle mix referenced in the City's Noise Guideline Manual of 97.9% Autos, 1.8% Medium Trucks and 0.3% Heavy Trucks for all roadways. The vehicle mix provides the hourly distribution percentages of automobile, medium trucks and heavy trucks for input into the FHWA Model. Future year 2035 traffic along Jefferson Street and Laguna Drive is expected to have 13,500 average daily trips (ADT) and 6,900 ADT, respectively, according to the SANDAG Series 13 Traffic Prediction Model for the year 2035. The speed limit along Jefferson Street is 35 MPH and 30 MPH on Laguna Drive. Based on the exterior noise model, the worst-case cumulative noise level from all the roadways was found to be 66. 7 dBA CNEL at the site. The modeling results are provided in Figure 4 on the following page. No noise barriers, existing structures or topography that may affect noise levels were incorporated in the calculations. 9/14/2017 6 1785-02 2637 Jefferson Street Noise Report ohms Architects Miguel A. Reyes 536 Sears Avenue San Diego, CA 92118 Ldn CoMu/111111, me. 42428 Chisolm Trail, Munieta CA 92562 phone 760-473-~253 Fax 760-689-4943 Figure 4: Future Cumulative Noise Levels Project Name: Project Number: Mix Ratio by Percent Propagation Rule Roadway Jefferson Street Laguna Drive Jefferson Street Laguna Drive Cumulative Noise Level 9/14/2017 37 Jefferson Street 17-85 Date: Location: Traffic Volumes, Mix and Speeds Autos Med. Trucks Heavy Trucks 97.9 1.8 0.3 Hard 14-Sep-17 carlsbad ADT 13,500 6,900 Speed MPH CNEL O SO Feet 60 CNEL {Feet) 35 66.6 231 30 62.2 83 Noise Reduction due to Distance Distance 50 450 Reduction 0.00 -14.31 7 Resultant Level 66.6 47.9 66.7 dBACNEL 1785-02 2637 Jefferson Street Noise Report ohms Architects Miguel A. Reyes 536 Sears Avenue San Diego, CA 92118 Interior Noise Levels Ldn eon.ult/1111, Int:. 42428 Chisolm Trail, /llunieta CA 92562 phone 760-473-1253 Fax 760-689-4943 The methodology used to determine the resultant interior noise levels is based upon the exterior noise level minus the sound transmission loss as identified in the American Society of Testing and Materials (ASTM) guidelines: E413 &E90. Standard building construction will provide a noise reduction of approximately 12-15 dBA with a windows open condition and a minimum 20 dBA noise reduction with the windows closed. The exterior noise levels at the proposed structures calculated in terms of dBA are converted to the six octave band sound pressure levels between: 125 -4000 Hertz. Acoustical modeling of the proposed project dwelling units was performed in accordance with the above guidelines and included combining the transmission loss for each of the building components that will reduce the interior noise levels. Building components typically include the windows, exterior doors, and exterior walls. The total noise reduction is dependent upon the transmission loss of each building component, their subsequent surface area, quality of the building/construction materials, a building fac;ade and angle correction. The interior noise level is also dependent on the acoustical energy absorbed within the room based upon the Noise Reduction Coefficients (NRC). NRC is a scalar representation of the amount of sound energy absorbed upon striking a particular surface and the arithmetic value average of sound absorption coefficients indicating a material's ability to absorb sound. The absorption coefficients for individual surface areas such as carpet, drywall and furnishings are used to calculate the interior room effects. The calculated building noise reduction includes both the room absorption characteristics and the transmission loss from the exterior wall assembly. The interior noise reduction calculations were performed using Ldn's interior noise model. The model converts the exterior sound level to octave band frequencies and accounts for the transmission loss, correction factors and room absorption. The floor plans used for this analysis were provided by ohms Architects dated December 2016. The following construction details were utilized for each of the building assemblies to determine the noise reduction characteristics: 9/14/2017 8 1785-02 2637 Jefferson Street Noise Report ohms Architects Miguel A. Reyes 536 Sears Avenue San Diego, CA 92118 Ldn Conllult/1111, Int:. 42428 Chisolm Trail, Nunieta CA 92562 phone 760-473-:1253 Fax 760-68!J-4943 Exterior walls must have a Sound Transmission Class (STC) rating of 36 or better. Exterior walls with this rating consist of 2"x4" studs or larger, spaced 16" o.c. with R-13 insulation minimum and an exterior surface of 1/4" lap siding or 7 /8" cement plaster (stucco). Interior wall and ceiling surfaces shall be at least 1/2" thick gypsum or plaster. Roof assemblies should have a minimum of 1/2" sheathing, R-19 insulation and sealed to prevent noise leaks. Exterior entry doors should be of solid core construction and glass assemblies should be dual-glazed and acoustical sealant applied around the exterior edges. The window and door assemblies are generally the weakest noise reducing component but are the most convenient and cost effective elements to change if additional attenuation is needed. The STC ratings for the glass assemblies and exterior entry doors were calculated in the interior noise model and provided in the findings below. Bathrooms, kitchens, closets and corridors are not required to meet the 45 dBA CNEL standard and therefore were not modeled. All living areas, this includes bedrooms, living rooms and dining rooms were modeled to determine the interior noise reductions. If the modeled interior noise levels were found to be higher than 45 dBA CNEL in the living areas with the minimum assembly requirements described above additional modeling was performed to determine the minimum STC rating for the glass assemblies to further reduce interior noise levels below the acceptable interior threshold of 45 dBA CNEL. FINDINGS The exterior noise levels were determined to be as high as 67.7 dBA CNEL for the buildings located adjacent to Jefferson Street. Basic calculations show that a windows open condition will typically reduce the interior noise levels roughly 15 dBA CNEL and not provide adequate interior noise mitigation. To meet the 45 dBA CNEL interior noise standard, an overall minimum interior noise level reduction of 22.7 dBA CNEL is needed for the proposed project. Therefore, a closed window condition is required to reduce interior noise levels to comply with CCR Title 24 and City requirements. The windows closed condition requires that mechanical ventilation is installed to move air within the structure and control temperatures. The mechanical ventilation must meet the jurisdictional requirements for these dwelling units. 9/14/2017 9 1785-02 2637 Jefferson Street Noise Report ohms Architects Miguel A. Reyes 536 Sears Avenue San Diego, CA 92118 Ldn eon.ult/1111, me. 42428 Chisolm Trail, Hunieta CA 92562 phone 760-473-1253 Fax 760-689-4943 The necessary Sound Transmission Class and transmission losses for all glass assemblies and entry doors of the residential units located adjacent to and having direct line of sight to Jefferson Street are provided in Table 1. The modeled results with an anticipated interior noise level of 45 dBA CNEL or less are provided as an Attachmentto this report. Table 1: Sound Transmission Class Ratings STC Octave Band Transmission Loss (Hz) Assembly Rating1 125 250 500 1000 2000 4000 Windows 30 20 21 26 34 38 29 Fixed Windows 30 20 20 26 35 39 37 Glass Doors 30 22 20 29 33 39 30 1 STC Ratings used in Model All glass assemblies of the units having direct line of sight to Jefferson Street should be dual-paned and acoustical sealant applied around the exterior edges having an STC 30 rating. No impacts are anticipated with the incorporation of the STC ratings provided in Table 1. If you have any questions, please do not hesitate to contact me directly at (760) 473-1253 or jlouden@ldnconsulting.net. Sincerely, Ldn Consulting, Inc. Jeremy Louden, Principal Attachments: Interior Noise Model Calculations 9/14/2017 10 1785-02 2637 Jefferson Street Noise Report INTERIOR NOISE CALCULATIONS Project Name: 2637 Jefferson Building (s) All Floor Level 1 Arch Plan: A&B Room Type: Living/Dining Exterior Noise Levels Exterior Assembly Source Area Stucco NBS W-50-71 470 Windows Champion 65 Fixed Window Champion 12 Glass Doors Thermal Tru 24 Exterior Door NBS Monograph 77 0 Room Absorption (RA) Interior Characteristics Source Carpet Army TM 5-805-4 Furnishings Army TM 5-805-4 Drywall Netwell Overall Absorption Factor (Furnished Room) Noise Reduction Noise Reduction from Absorption based upon Floor Area Noise Level Increase for Defects and Exposed Surface Area STC 36 30 30 30 28 NRC 0.28 0.45 0.07 0.8 Overall Reduction from Tranmission Loss + Room Absorption -Surfa Building Fac;ade Noise Level (dBA CNEL) Ldn Consulting, Inc. Date: 9/14/17 Project# 17-85 Transmission Loss (dB) Frequency (Hz.) 125 250 500 1000 2000 4000 15 25 33 44 so 43 20 21 26 34 38 29 20 20 26 35 39 37 22 20 29 33 39 30 16 14 23 30 36 26 Absorption Coeffidents Frequency {Hz.) 125 250 500 1000 2000 4000 0.15 0.17 0.12 0.32 0.52 0.30 0.32 0.29 0.42 0.58 0.60 0.48 0.09 0.08 0.05 0.03 0.06 0.09 0.56 0.54 0.59 0.93 1.18 0.87 125 250 500 1000 2000 4000 -24.6 -24.6 -24.6 -24.6 -24.6 -24.6 18.4 18.4 18.4 18.4 18.4 18.4 ce Exposure 22.9 67.7 Resultant Interior Noise Level (dBA CNEL) 45 * Corrections for Fa~de Level was accounted for In the modeling. INTERIOR NOISE CALCULATIONS Project Name: Building (s) Floor Level Arch Plan: Room Type: 2637 Jefferson All 2 A&B Bedroom 1 Exterior Noise Levels Exterior Assembly Source Stucco NBS W-50-71 Windows Champion Fixed Window Champion Glass Doors Thermal Tru Exterior Door NBS Monograph 77 Room Absorption (RA) Interior Characteristics Source Carpet Army TM 5-805-4 Furnishings Army TM 5-805-4 Drywall Netwell Overall Absorption Factor (Furnished Room) Noise Reduction Area 160 15 9 0 0 Noise Reduction from Absorption based upon Floor Area Noise Level Increase for Defects and Exposed Surface Area src 36 30 30 30 28 NRC 0.28 0.45 0.07 0.8 Overall Reduction from Tranmission Loss + Room Absorption -Surfa Building Fa<;ade Noise Level (dBA CNEL) 125 250 15 25 20 21 20 20 22 20 16 14 125 250 0.15 0.17 0.32 0.29 0.09 0.08 0.56 0.54 125 250 -20.8 -20.8 16.4 16.4 ce Exposure Ldn Consulting, Inc. Date: 9/14/17 Project# 17-85 Transmission Loss (dB} Frequency {Hz.} 500 1000 2000 4000 33 44 50 43 26 34 38 29 26 35 39 37 29 33 39 30 23 30 36 26 Absorption Coefficients Frequency {Hz.} 500 1000 2000 4000 0.12 0.32 0.52 0.30 0.42 0.58 0.60 0.48 0.05 0.03 0.06 0.09 0.59 0.93 1.18 0.87 500 1000 2000 4000 -20.8 -20.8 -20.8 -20.8 16.4 16.4 16.4 16.4 27.7 67.7 Resultant Interior Noise Level (dBA CNEL) 40 * Corrections for Fai;ade Level was accounted for in the modeling. INTERIOR NOISE CALCULATIONS Project Name: 2637 Jefferson Building (s) All Floor Level 2 Arch Plan: A&B Room Type: Bedroom 2 Exterior Noise Levels Exterior Assembly Source Area Stucco NBS W-50-71 260 Windows Champion 30 Fixed Window Champion 15 Glass Doors Thermal Tru 0 Exterior Door NBS Monograph 77 0 Room Absorption (RA) Interior . Characteristics Source Carpet Army TM 5-805-4 Furnishings Army TM 5-805-4 Drywall Netwell Overall Absorption Factor (Furnished Room) Noise Reduction Noise Reduction from Absorption based upon Floor Area Noise Level Increase for Defects and Exposed Surface Area src 36 30 30 30 28 NRC 0.28 0.45 0.07 0.8 Overall Reduction from Tranmission Loss + Room Absorption -Surfa Building Fac;ade Noise Level (dBA CNEL) 125 250 15 25 20 21 20 20 22 20 16 14 125 250 0.15 0.17 0.32 0.29 0.09 0.08 0.56 0.54 125 250 -21.8 -21.8 17.0 17.0 ce Exposure Ldn Consulting, Inc. Date: 9/14/17 Project# 17-85 Transmission Loss {dB} Frequency {Hz.} 500 1000 2000 4000 33 44 so 43 26 34 38 29 26 35 39 37 29 33 39 30 23 30 36 26 Absorption Coeffidents Frequency {Hz.} 500 1000 2000 4000 0.12 0.32 0.52 0.30 0.42 0.58 0.60 0.48 0.05 0.03 0.06 0.09 0.59 0.93 1.18 0.87 500 1000 2000 4000 -21.8 -21.8 -21.8 -21.8 17.0 17.0 17.0 17.0 26.3 67.7 Resultant Interior Noise Level (dBA CNEL) 41 * Corrections for Fa~de Level was accounted for in the modeling. INTERIOR NOISE CALCULATIONS Project Name: Building (s) Floor Level Arch Plan: Room Type: 2637 Jefferson All 1 C&D Bedroom 1 Exterior Noise Levels Exterior Assembly Stucco Windows Fixed Window Glass Doors Exterior Door Source NBS W-50-71 Champion Champion Thermal Tru NBS Monograph 77 Room Absorption {RA) Interior Characteristics Source Carpet Army TM 5-805-4 Furnishings Army TM 5-805-4 Drywall Netwell Overall Absorption Factor (Furnished Room) Noise Reduction AIN 130 15 0 0 0 Noise Reduction from Absorption based upon Floor Area Noise Level Increase for Defects and Exposed Surface Area STC 36 30 30 30 28 NRC 0.28 0.45 0.07 0.8 overall Reduction from Tranmission Loss + Room Absorption -Surfa Building Fac;ade Noise Level (dBA CNEL) 125 250 15 25 20 21 20 20 22 20 16 14 125 250 0.15 0.17 0.32 0.29 0.09 0.08 0.56 0.54 125 250 -21.4 -21.4 15.2 15.2 ce Exposure Ldn Consulting, Inc. Date: 9/14/17 Project# 17-85 Transmission Loss {dB} Frequency {Hz.} 500 1000 2000 4000 33 44 so 43 26 34 38 29 26 35 39 37 29 33 39 30 23 30 36 26 Absorption Coeffidents Frequency {Hz.} 500 1000 2000 4000 0.12 0.32 0.52 0.30 0.42 0.58 0.60 0.48 0.05 0.03 0.06 0.09 0.59 0.93 1.18 0.87 500 1000 2000 4000 -21.4 -21.4 -21.4 -21.4 15.2 15.2 15.2 15.2 29.5 67.7 Resultant Interior Noise Level (dBA CNEL) 38 * Corrections for Fa~de Level was accounted for in the modeling. INTERIOR NOISE CALCULATIONS Project Name: 2637 Jefferson Building (s) All Floor Level 2 Arch Plan: C&D Room Type: Bedroom 2 Exterior Noise Levels Exterior Assembly Source Area Stucco NBS W-50-71 130 Windows Champion 15 Fixed Window Champion 0 Glass Doors Thermal Tru 0 Exterior Door NBS Monograph 77 0 Room Absorption (RA) Interior Characteristics Source Carpet Army TM 5-805-4 Furnishings Army TM 5-805-4 Drywall Netwell Overall Absorption Factor (Furnished Room) Noise Reduction Noise Reduction from Absorption based upon Floor Area Noise Level Increase for Defects and Exposed Surface Area STC 36 30 30 30 28 NRC 0.28 0.45 0.07 0.8 Overall Reduction from Tranmission Loss + Room Absorption -Surfa Building Fa<;ade Noise Level (dBA CNEL) Ldn Consulting, Inc. Date: 9/14/17 Project# 17-85 Transmission Loss {dB) Frequency {Hz.) 125 250 500 1000 2000 4000 15 25 33 44 so 43 20 21 26 34 38 29 20 20 26 35 39 37 22 20 29 33 39 30 16 14 23 30 36 26 Absorption Coeffidents Frequency {Hz.) 125 250 500 1000 2000 4000 0.15 0.17 0.12 0.32 0.52 0.30 0.32 0.29 0.42 0.58 0.60 0.48 0.09 0.08 0.05 0.03 0.06 0.09 0.56 0.54 0.59 0.93 1.18 0.87 125 250 500 1000 2000 4000 -21.4 -21.4 -21.4 -21.4 -21.4 -21.4 15.2 15.2 15.2 15.2 15.2 15.2 ce Exposure 29.5 67.7 Resultant Interior Noise Level (dBA CNEL) 38 * Corrections for Fai;ade Level was accounted for in the modeling. INTERIOR NOISE CALCULATIONS Project Name: Building (s) Floor Level Arch Plan: Room Type: 2637 Jefferson All 3 C&D Living/Dining Exterior Noise Levels Exterior Assembly Stucco Windows Fixed Window Glass Doors Exterior Door Source NBS W-50-71 Champion Champion Thermal Tru NBS Monograph 77 Room Absorption (RA) Interior Characteristics Source Carpet Army TM 5-805-4 Furnishings Army TM 5-805-4 Drywall Netwell Overall Absorption Factor (Furnished Room) Noise Reduction Area 550 45 38 112 0 Noise Reduction from Absorption based upon Floor Area Noise Level Increase for Defects and Exposed Surface Area STC 36 30 30 30 28 NRC 0.28 0.45 0.07 0.8 Overall Reduction from Tranmission Loss + Room Absorption -Surfa Building Fa<;ade Noise Level (dBA CNEL) 125 250 15 25 20 21 20 20 22 20 16 14 125 250 0.15 0.17 0.32 0.29 0.09 0.08 0.56 0.54 125 250 -25.8 -25.8 19.0 19.0 ce Exposure Ldn Consulting, Inc. Date: 9/14/17 Project # 17-85 Transmission Loss {dB} Frequency {Hz.} 500 1000 2000 4000 33 44 50 43 26 34 38 29 26 35 39 37 29 33 39 30 23 30 36 26 Absorption Coefficients Frequency {Hz.} 500 1000 2000 4000 0.12 0.32 0.52 0.30 0.42 0.58 0.60 0.48 0.05 0.03 0.06 0.09 0.59 0.93 1.18 0.87 500 1000 2000 4000 -25.8 -25.8 -25.8 -25.8 19.0 19.0 19.0 19.0 22.3 66.7 Resultant Interior Noise Level (dBA CNEL) 44 * Corrections for Fai;ade Level was accounted for in the modeling.