Acoustical Testing: Facts and Misconceptions. Michael L. Mackereth Architectural Testing

Transcription

1 Acoustical Testing: Facts and Misconceptions Michael L. Mackereth Architectural Testing

2 Presentation Outline Basic Acoustics Test Methods Effects on Sound Transmission Loss Codes and Regulations Acoustical Lab

3 OITC vs. STC OITC (Outdoor-Indoor Transmission Class) Calculated in accordance with ASTM E 1332 (Published in 1990) Created to provide a single number rating for façades (exterior walls) and façade elements (windows and doors) that are subjected to transportation noises The OITC is calculated over the frequency range of 80 to 4000 hertz

4 OITC vs. STC STC (Sound Transmission Class) Calculated in accordance with ASTM E 413 (Published in 1970) Created to provide a single number rating for interior building partitions that are subjected to noises from speech, television, radio and office equipment Note: ASTM E 413 specifically states that the STC calculation should not be used to evaluate partitions exposed to machinery, industrial and transportation noise such as motor vehicles, aircraft and trains. The STC is calculated over the frequency range of 125 to 4000 hertz

5 Basics of Sound Transmission Loss Source Room SPL Level = 100 db Average Noise Reduction of 45 db Receive Room SPL Level = 55 db

6 Flanking Effects on Sound Transmission Loss Average Noise Reduction of 35 db Source Room SPL Level = 100 db Receive Room SPL Level = 65 db Average Noise Reduction of 45 db Average Noise Reduction of 35 db

7 Chimney Attic Fans or Roof Vents Gable Vents Element #4 - Roof Ceiling System Roof Soffits Oven Fans Element #3 Element #1 Door Exterior Wall Element #2 Window Floor System Basement Windows Sound Transmission Paths

8 Sound Pressure Level Sound Pressure Level, Lp N/m2 (Pa) db Noise Sources 100, Saturn Rocket 10, After Burning Jet Engine 1, Jet Aircraft Engine Threshold of Pain Near Elevated Train OSHA Limit Industrial Noise Normal Speech Quiet Office Whisper Threshold of Hearing Sound Pressure Level, Lp = 20 log10 (p(t) / p ref ) Where: p(t) = instantaneous sound pressure, Pa p ref = reference sound pressure, standardized at 2 x 10-5 N/m2 (20uPa)

9 Sound Pressure Level vs. Loudness Change in Change in Decibels Perceptable Loudness 1 db Imperceptable change 3 db Just barely distinguishable 5 db 25% Change in Loudness 10 db 50% Change in Loudness 15 db 63% Change in Loudness 20 db 75% Change in Loudness

10 Estimated Window & Curtain Wall Performance Primary Glazing Only Window/Curtain Wall IG Glazing OITC STC 2.3 mm (3/32 in) annealed, 12 mm (1/2 in) air space, 2.3 mm (3/32 in) annealed mm (1/8 in) annealed, 12 mm (1/2 in) air space, 3 mm (1/8 in) annealed mm (1/8 in) annealed, 12 mm (1/2 in) air space, 4.8 mm (3/16 in) annealed 3 mm (1/8 in) annealed, 12 mm (1/2 in) air space, 4.8 mm (3/16 in) laminated mm (1/8 in) annealed, 12 mm (1/2 in) air space, 6 mm (1/4 in) annealed mm (1/8 in) annealed, 12 mm (1/2 in) air space, 6 mm (1/4 in) laminated mm (3/16 in) annealed, 12 mm (1/2 in) air space, 4.8 mm (3/16 in) annealed mm (1/4 in) annealed, 12 mm (1/2 in) air space, 6 mm (1/4 in) annealed mm (1/4 in) annealed, 12 mm (1/2 in) air space, 6 mm (1/4 in) laminated mm (1/4 in) laminated, 12 mm (1/2 in) air space, 6 mm (1/4 in) laminated

11 Estimated Window & Curtain Wall Performance Primary & Secondary Glazing Prime Window/Curtain Wall IG Glazing Prime to Secondary Air Space Secondary Window/ Curtain Wall Glazing OITC STC 3 mm (1/8 in) annealed, 12 mm (1/2 in) air space, 3 mm (1/8 in) annealed 50 mm (2 in) 3 mm (1/8 in) annealed mm (1/4 in) annealed, 12 mm (1/2 in) air space, 3 mm (1/8 in) annealed 50 mm (2 in) 6 mm (1/4 in) annealed mm (1/4 in) laminated, 12 mm (1/2 in) air space, 3 mm (1/8 in) annealed 50 mm (2 in) 6 mm (1/4 in) annealed mm (1/4 in) laminated, 12 mm (1/2 in) air space, 3 mm (1/8 in) annealed 50 mm (2 in) 6 mm (1/4 in) laminated

12 Estimated Exterior Wall Performance Wall Construction Exterior Wall Construction OITC Rating STC Rating Vinyl siding, OSB board, 2 x 4 wood studs, ½ drywall, no insulation Vinyl siding, OSB board, 2 x 4 wood studs, ½ drywall, with R-13 insulation Vinyl siding, OSB board, 2 x 6 wood studs, ½ drywall, no insulation Vinyl siding, OSB board, 2 x 6 wood studs, ½ drywall, with R-13 insulation 37-38

13 Sound Transmission Loss Variables Mass of materials Heavier materials have higher sound transmission loss. Resonant frequency of the materials or surfaces Most materials will resonate at a certain frequency when they are excited by sound waves or vibrations. The sound transmission loss will decrease at that frequency and probably at some of the surrounding frequencies. Air space between materials or surfaces Larger air spaces yield better performance. Material stiffness Limper materials provide better noise attenuation. Gypsum Board walls need to be conditioned at 40-70% R.H. for at least 72 hours. Structural coupling between materials and surfaces Decoupling surfaces from each other improves sound transmission loss. Fasteners can affect panel stiffness and coupling between surfaces. Cavity Insulation Insulating stud cavities improves the noise reduction of wall systems. Dissimilar Materials Use of dissimilar materials can reduce coincidence dip effects.

14 Acoustical Test Methods AAMA 1801, Voluntary Specification for the Acoustical Rating of Windows, Doors and Glazed Wall Sections ASTM E 1425, Standard Practice for Determining the Acoustical Performance of Exterior Windows and Doors ASTM E 90, Standard Test Method for Laboratory Measurement of Airborne Sound Transmission Loss of Building Partitions and Elements ASTM E 336, Standard Test Method for Measurement of Airborne Sound Insulation in Buildings (Field Method Interior partions or floor to floor) ASTM E 966, Standard Guide for Field Measurement of Airborne Sound Insulation of Building Facades and Facade Elements (Field Method)

15 Effects on Sound Transmission Loss Window Designs or Components Glass Thickness Air Infiltration Type of Glass (Annealed, Laminated, etc.) Type of Spacer Insulating Glass Films Air Space between Glass Lites Type of Gas Fill Edge Effects Test Conditions Temperature (For Laminated Glass)

16 Glass Thickness Effect on Transmission Loss 45 Fixed Window with 3/4" Insulating Glass Sound Transmission Loss, db /8" & 3/32", OITC = 24, STC = 28 1/4" & 1/8", OITC = 27, STC = Frequency, Hz.

17 Transmission Loss Deterioration Due to Air Leakage 60 Single Hung Window with Insulating Glass (1/4" annealed, 3/8" Air, 3/32" annealed) Sound Transmission Loss, db As Received, OITC = 24, STC = 26 Completely Sealed, OITC = 27, STC = Frequency, Hz.

18 Tempered vs. Laminated Glass 60 Sliding Glass Door with Insulating Glass Sound Transmission Loss, db /4" Temp / 1/2" Air / 1/4" Temp, OITC = 27, STC = 33 1/4" Temp / 1/2" Air / 1/4" Lami, OITC = 30, STC = 35 1/4" Lami / 1/2" Air / 1/4" Lami, OITC = 31, STC = Frequency, Hz.

19 Spacer Effect on Transmission Loss 60 Single Hung Window with Insulating Glass (1/4" annealed, 3/8" Argon, 1/8" annealed) Sound Transmission Loss, db U-Channel Spacer, OITC = 26, STC = 29 Foam Spacer, OITC = 26, STC = Frequency, Hz.

20 Transmission Loss of Insulating Glass with Suspended Films 60.0 Insulating Glass with Suspended Films Sound Transmission Loss, db IG without Film, OITC = 22, STC = 28 IG with One Film, OITC = 23, STC = 30 IG with Two Films, OITC = 24, STC = Frequency, Hz.

21 Air Space Effect on Sound Transmission Loss 60.0 Double Hung Window with 1/4" annealed and 1/4" annealed Sound Transmission Loss, db /2" Air Space, OITC = 27, STC = 33 4" Air Space, OITC = 32, STC = Frequency, Hz.

22 Argon vs. Air Filled Insulating Glass 60 Fixed Window with Insulating Glass (3/16" annealed, 9/16" space, 1/8" annealed) Sound Transmission Loss, db Argon Filled, OITC = 24, STC = 30 Air Filled, OITC = 25, STC = Frequency, Hz.

23 Codes & Regulations

24 Acoustical Requirements & Codes It is important to verify the acoustical performance of the whole assembly rather than just meeting the performance requirements of the building or glazing elements alone. The STC and OITC ratings of window and curtain wall units (tested in the laboratory) have been known to be anywhere from three to six points lower than the glass alone data that is prevalent in the fenestration industry. The difference between a laboratory tested product or assembly and a field tested product or assembly can also vary by three or more points if good construction practices are not followed.

25 Acoustical Requirements & Codes (cont d) It is evident that in order to meet the owner's performance expectations, laboratory testing of proposed building elements and field testing of installed assemblies is essential. It is only at the field testing phase of the process can the true acoustical performance of the assembly can be determined.

26 International Building Code SECTION SOUND TRANSMISSION Scope. This section shall apply to common interior walls, partitions and floor/ceiling assemblies between adjacent dwelling units or between dwelling units and adjacent public areas such as halls, corridors, stairs or service areas Air-borne sound. Walls, partitions and floor/ceiling assemblies separating dwelling units from each other or from public or service areas shall have a sound transmission class (STC) of not less than 50 (45 if field tested) for air-borne noise when tested in accordance with ASTM E 90. Penetrations or openings in construction assemblies for piping; electrical devices; recessed cabinets; bathtubs; soffits; or heating, ventilating or exhaust ducts shall be sealed, lined, insulated or otherwise treated to maintain the required ratings. This requirement shall not apply to dwelling unit entrance doors; however, such doors shall be tight fitting to the frame and sill Structure-borne sound. Floor/ceiling assemblies between dwelling units or between a dwelling unit and a public or service area within the structure shall have an impact insulation class (IIC) rating of not less than 50 (45 if field tested) when tested in accordance with ASTM E 492.

27 International Residential Code APPENDIX K - SOUND TRANSMISSION AK101.1 General.Wall and floor-ceiling assemblies separating dwelling units including those separating adjacent townhouse units shall provide air-borne sound insulation for walls, and both air-borne and impact sound insulation for floor-ceiling assemblies. SECTION AK102 - AIR-BORNE SOUND AK102.1 General. Air-borne sound insulation for wall and floor-ceiling assemblies shall meet a Sound Transmission Class (STC) rating of 45 when tested in accordance with ASTM E 90. Penetrations or openings in construction assemblies for piping; electrical devices; recessed cabinets; bathtubs; soffits; or heating, ventilating or exhaust ducts shall be sealed, lined, insulated or otherwise treated to maintain the required ratings. Dwelling unit entrance doors, which share a common space, shall be tight fitting to the frame and sill. SECTION AK103 - STRUCTURAL-BORNE SOUND AK103.1 General. Floor/ceiling assemblies between dwelling units or between a dwelling unit and a public or service area within a structure shall have an Impact Insulation Class (IIC) rating of not less than 45 when tested in accordance with ASTM E 492.

28 LEED for Classrooms Intent Provide classrooms that are quiet and in which teachers can speak to the class without straining their voices and students can effectively communicate with each other and the teacher. Requirements Design classrooms and other core learning spaces to meet the Reverberation Time (RT) requirements of ANSI Standard S , Acoustical Performance Criteria, Design Requirements and Guidelines for Schools. Also, design classrooms and other core learning spaces to meet the Sound Transmission Class (STC) requirements, excepting windows, which must meet an STC rating of at least 35. AND OPTION 1 Using the methodology described in annexes B through D of ANSI Standard S , achieve a maximum background noise level in classrooms and other primary learning spaces of 45 dba. OR OPTION 2 Design classrooms and other core learning spaces using the methodology listed in the 2003 HVAC Applications ASHRAE Handbook, Chapter 47 on Sound and Vibration Control, and achieve an RC (N) Mark II level of 37. Potential Technologies & Strategies Design considerations include reducing noise from exterior to interior spaces, between spaces within the building, and within the classroom space. External to internal noise transmission can be reduced by orienting classrooms away from external noise sources and using thick and/or massive materials in walls and roofs. Also, windows should be well sealed and have adequate air gaps between sheets of glass.

29 Housing & Urban Development Specification No. 24 CFR Part 51 U.S Department of Housing and Urban Development Site Acceptability Standards listed in table below: Day-Night Equivalent Sound Level in Decibels (Ldn) Acceptable Normally Unacceptable Unacceptable Not exceeding 65 db Above 65 db but not exceeding 75 db Above 75 db Figure 2.6 HUD site acceptability criteria In Figure 2.6, ranges of Ldn are correlated with various dispositions that classify HUD approval procedures and identify the need for noise abatement, either at the site property line or in the construction of the building exterior. These have been devised to achieve the HUD goal for interior noise levels of a day-night equivalent noise level not exceeding 45 db

30 Environmental Protection Agency U.S. Environmental Protection Agency Specification NEPA Pub. No. 550/ (November 1978) Sound Pressure Level Effect Ldn Leq (24 hrs) Area Hearing < 70 dba All areas (at the ear) Outdoor Activity < 55 db < 55 dba Outdoors in residential areas and farms and other areas where people spend widely varying amounts of time and other places in which quiet is a basis for use. Outdoor areas where people spend limited amounts of time such as school yards, playgrounds, etc. Indoor Activity < 45 db < 45 dba Indoor residential areas Other indoor areas with human activities such as schools, etc.

31 Acoustical Laboratory Control Panel

32 Large Reverberation Chamber

33 Rotating Vane in Large Reverberation Chamber

34 TL Test Frame for Single and Double Doors

35 4060 Window Installed in Test Opening

36 Questions?