Classroom Acoustics. Classroom Acoustics Slides 2005 [G ABP Sales Training CES Presentations Classroom Acoustics 2005]

Transcription

1 Classroom Acoustics This program is registered with the AIA/CES for continuing professional education. As such, it does not include content that might be deemed or construed to be an approval or endorsement by the AIA of any material of construction or any method or manner of handling, using, distributing, or dealing in any material or product. Questions related to specific materials, methods, and services will be addressed at the conclusion of this presentation. Classroom Acoustics Slides 2005 [G ABP Sales Training CES Presentations Classroom Acoustics 2005]

2 Classroom Acoustics Seminar Review how acoustical design and sound quality impact the learning environment. Explain ANSI Standard S for classroom acoustics. Identify sound reverberation and background noise reduction techniques for classrooms. Discuss how to create a better learning environment through improved classroom design. 2

3 Is Noise A Problem? 28% of our nation s schools list noise as the #1 problem. Noise causes students to miss one-third of spoken communication in class. Noise interferes with speech intelligibility. The effort to counter noise creates vocal fatigue in teachers. Source: Coalition For Classroom Acoustics 3

4 Is Noise A Problem? Noise affects children: Visual or hearing impairments. Attention Deficit Disorder [ADD]. English as a Second Language [ESL]. Learning disorders. Middle-ear infections. Younger children learning the language. 4

5 The Effect Of A Hearing Loss Due to middle-ear infections, school-aged children commonly experience a 25 decibel loss. Place your hand over your ear to experience this level of hearing loss. 5

6 Benefit: Reduced Teacher Absenteeism Vocal Strain A Costly Concern There were 2.9 million public school teachers in the U.S. in Teachers lose an average of two days per year for vocal fatigue. Cost for substitute teachers was about $220 per day. The national cost for teacher vocal fatigue is estimated at $638 million. A large fraction of that cost could be saved each year if schools were quieter. Source: Acoustical Society of America 6

7 How Will Acoustical Standards Help? Standards can make possible: An improved learning environment for all students. Improved speech intelligibility for all students and teachers. A better teaching environment for teachers. Uniformity in classroom design for architects and designers. 7

8 The ADA s Involvement In Speech Intelligibility The ADA, along with the Access Board, is making efforts to apply specific requirements on classroom acoustics. ADA requires that communications with persons with disabilities be as effective as communications with others. [Americans with Disabilities Act, Public Law , Title III, Section Auxiliary Aids and Services] 8

9 Standard Development Process Timeline 1997 Parents petitioned Access Board to have classroom standard developed Draft of standard submitted to Access Board for review Access Board issued Request For Information [RFI] on the subject Various groups developed standard [March-June] Board received proposed standard [January] Standard completed and approved as ANSI/ASA S , Acoustical Performance Criteria, Design Requirements and Guidelines for Schools ANSI Standard for Classroom Acoustics adopted in various districts throughout the United States. 9

10 ANSI Standard Adoption An Update Currently adopted: New York City Department of School Construction. New Jersey School Construction Authority. Minneapolis Public Schools. New Hampshire Department of Education. Ohio s School Facility Commission. States with pre-existing comparable requirements: Washington State Education Department. NY State Department of Education. Other states: Minnesota Department of Education proposing own. Connecticut considering adoption. Minnesota considering adoption. California high-performing school recommendation [CHPS]. 10

11 Who Helped Develop The Standards? Acousticians Advocates for People with Disabilities Architects ASTM Standards Group Audiologists Contractors Government Agencies Manufacturers Noise Engineers Speech Language Pathologists Specification Writers Teachers 11

12 Organizations That Helped Develop The Standards AAA AFT AG BELL AIA ANSI ASA ASHA ASHRAE ASTM ATBCB CEFPI CISCA CRI CSI Department of Education EAA GA INCE Manufacturers of Construction Materials NAIMA SHHH 12

13 ANSI Standard Video Featuring: What s the ANSI Standard S all about? Dr. Kenneth Roy, PhD. Donna Ellis, architect, formerly with the Washington DC Public School District 13

14 New Standard Requirements 1. For reverberation time: Rooms less than 10,000 cubic feet: 0.6 seconds Rooms 10,000-20,000 cubic feet: 0.7 seconds Studies show: Some classrooms today have reverberation times as high as 2.8 seconds. 14

15 Sound In Rooms Black arrows are direct sound. [Direct sound is good for intelligibility.] Red arrows are reflected sound. [Reflected sound might compromise intelligibility.] 15

16 Reducing Reflected Sound When you reduce reflected sound, you lower the reverberation time. Treat the room with high NRC acoustical walls and high NRC ceilings. 16

17 Cost Benefit Ratio: Upgraded Ceiling Costs Installed Cost Guide: 1000 SF Classroom [20' x 50'] Ceiling Description Installed Cost Difference/ Classroom Annual Cost* NRC " x 48" x ⅝" no sag resistance $1250 $1500 NRC " x 48" x ⅝" cleaner visual sag resistance $1300 $1550 $50 $5 NRC " x 48" x ⅝" sag resistance higher durability $1600 $1800 $300 $30 NRC " x 48" x ¾" sag resistance superior acoustics $1750 $2000 $500 $50 *Products have a 10-year life/panel warranty. 17

18 New Standard Requirements 2. For background noise level: Core learning spaces equal to or less than 20,000 cubic feet, reduce the background noise level to a maximum 35 dba. Studies show: Some classrooms today have background noise levels as high as 66 dba. 18

19 Background Noise Background noise is the effect of all sound sources, from both outside and inside the classroom, but excluding students and teacher. High levels of background noise can mask speech sounds, thus reducing speech intelligibility. Background noise is measured in dba. 19

20 Sources Of Background Noise 20

21 Reduce Noise Traveling Through The Plenum 21

22 Reduce Noise Traveling Through The Walls 22

23 Minimize HVAC Noise Through Design Place no mechanical equipment in the classroom. Variable air volume boxes must be located away from the classroom. HVAC units should be completely isolated from the classroom. Duct attenuators should be placed upstream in the duct work. 23

24 Real-World Case Study #1 Second Grade Classroom All hard surfaces. High plaster ceiling [14'6"]. Located outside the cafeteria. Large windows facing the playground. Children had difficulty understanding the teacher and each other. 24

25 Real-World Case Study #1 Method Of Evaluation Measure the loudness of classroom while occupied [reading class]. Measure reverberation time in empty classroom after school. Install 0.65 NRC glue-up ceiling board during holiday break. Repeat above measurements after installation. 25

26 Real-World Case Study #1 Classroom Layout Closet Door Ceiling Height 14'6" Room Volume ~ 9000 cubic feet Speaker 23' Closets and Sink Teacher Desk Student Desks Microphone Computer Station windows adjacent to playground along this wall 27' 26

27 Real-World Case Study #1 Maximum Sound Levels Results Classroom SPL Before and After Treatment Levels Exceeded Only 5% of Time During Reading Class Before Treatment After Treatment Sound Pressure Level, db Before Frequency, Hz After 27

28 Real-World Case Study #1 Background Noise Levels Results Classroom SPL After Treatment Minimum Levels and Levels Exceeded 95% of Time During Reading Class Exceeded 95% of Time Minimum Sound Pressure Level, db db Before Frequency, Hz 28 After

29 Real-World Case Study #1 Reverberation Times Reverberation Times Before and After Treatment Before Treatment After Treatment Reverberation Time, sec/60 db Open markers indicate data points which don't meet ASTM C423-99a 0.6 sec Before After Frequency, Hz 29

30 Real-World Case Study #2 Classroom Acoustics Demonstration Lamberton School, Philadelphia PA The Architecture: Built in K-12 grades. Quiet residential area. Masonry construction. Ceilings are spray-applied fiberglass insulation on plaster. Floors are vinyl tile. Acoustic evaluations and ceiling installation performed January 15-24,

31 Classroom Before Change Architecture: before change Ceiling: Spray-up fiberglass insulation approximately ½" thick on plaster. Walls: CMU [concrete block] and DS [double strength] glass. Floor: Solid vinyl tile. Room Dimensions: 24' x 44' x 11. Acoustical Design Criteria For Classrooms ANSI S12.60 reverberation time, maximum acceptable 0.6 seconds [at 500, 1000, 2000 Hz] Lamberton Classroom Reverberation Time Measured performance before change 1.1 seconds [average 500 to 2000 Hz] 31

32 Reverberation Before Change Architecture: before change Ceiling: Spray-up fiberglass insulation approximately ½" thick on plaster. Walls: CMU and DS glass. Floor: Solid vinyl tile. 2.5 Lamberton School Classroom 101, before Ceiling change The highlighted frequencies represent ANSI S12.60 [at 500, 1000, 2000 Hz]. Max. 0.6 seconds Reverberation Time, seconds k Rev Time, sec The The classroom classroom fails fails to to meet meet reverberation reverberation time time per per the the ANSI ANSI standard standard at at all all three three frequencies frequencies [highlighted]. [highlighted]. Reverberation Reverberation isn t isn t uniform, uniform, and and speech speech sounds sounds boomy. boomy k Frequency, 1/3 OB 1.6k 2k 2.5k 3.15 k 4k 5k 6.3k 8k 10k

33 Classroom With New Ceiling Architecture: after change Ceiling: Suspended ceiling, high NRC/high CAC, ¾" mineral fiber panels Walls: Floor: CMU and DS glass. Solid vinyl tile. Room Dimensions: 24' x 44' x 10. Acoustical Design Criteria For Classrooms ANSI S12.60 reverberation time, maximum acceptable 0.6 seconds [at 500, 1000, 2000 Hz] Lamberton Classroom Reverberation Time Measured performance after change 0.56 seconds [average Hz] 33

34 Reverberation After New Ceiling Architecture: after change Ceiling: Walls: Floor: Suspended ceiling, high NRC/high CAC ¾" mineral fiber panels. CMU and DS glass. Solid vinyl tile. 2.5 Lamberton School Classroom 101, after Ceiling change 2 The highlighted frequencies represent ANSI S12.60 [at 500, 1000, 2000 Hz]. Max. 0.6 seconds Reverberation Time, seconds k 1.25k 1.6k 2k 2.5k 3.15k 4k 5k 6.3k 8k 10k Rev Time, sec Frequency, 1/3 OB The The classroom classroom now now meets meets reverberation reverberation time time per per the the ANSI ANSI standard standardat at all all three three frequencies frequencies [highlighted]. [highlighted]. Reverberation Reverberation is is uniform, uniform, and and speech speech sounds sounds natural. natural. 34

35 Comparison Of Reverberation Time Before After Ceiling Spray-up fiberglass insulation. Approximately ½" thick. Approximate NRC Ceiling Suspended ceiling. High NRC 0.70/high CAC 40. ¾" mineral fiber panels. Ref. ANSI S12.60, 0.6 seconds max. 500 Hz, 1.3 seconds 1000 Hz, 1.09 seconds 2000 Hz, 0.85 seconds Ref. ANSI S12.60, 0.6 seconds max. 500 Hz, 0.60 seconds 1000 Hz, 0.56 seconds 2000 Hz, 0.52 seconds The The before before classroom classroom did did not notmeet the the ANSI ANSI standard standard for for reverberation reverberation time time at at all all three three frequencies. frequencies. The The new new after after ceiling ceiling meets meets the the standard standard at at all all three three frequencies. frequencies. 35

36 Where Can I Find Out More? Classroom Acoustics Brochure from the Acoustical Society of America can be downloaded from: ANSI S can be ordered from: Go to the Standards Store at either site. Quiet in the Classroom can be downloaded from: 36

37 Summary We ve reviewed: How sound impacts the learning environment. How choosing the appropriate acoustical ceiling can reduce sound reverberation and background noise in the classroom. How ANSI Standard S12.60 affects classroom design. How to create a better learning environment through improved classroom design. 37