![Page 1: Eliminating Acoustical Barriers to Learning in Classrooms poster.pdf · vs. NCB (Balanced Noise Criterion) Curves (ANSI S12.2-1995) Shepard Hill Elementary School Gymnasium HVAC off](https://reader031.vdocument.in/reader031/viewer/2022022610/5b949ce209d3f2e5688d3ab4/html5/thumbnails/1.jpg)
Eliminating Acoustical Barriers to Learning in Classrooms
Case Study
Reverberation Reduction in Elementary School Gymnasiums
Bennett M. Brooks, PE
Brooks Acoustics Corporation 27 Hartford Turnpike, Vernon, CT 06066
1-800-817-5831 www.brooks-acoustics.com
Paper 3pAA3 - Presented at the
139th Meeting of the Acoustical Society of America
Atlanta, Georgia -- 1 June 2000
![Page 2: Eliminating Acoustical Barriers to Learning in Classrooms poster.pdf · vs. NCB (Balanced Noise Criterion) Curves (ANSI S12.2-1995) Shepard Hill Elementary School Gymnasium HVAC off](https://reader031.vdocument.in/reader031/viewer/2022022610/5b949ce209d3f2e5688d3ab4/html5/thumbnails/2.jpg)
Paper 3pAA3 -- Abstract Eliminating Acoustical Barriers to Learning in Classrooms Case Study - Reverberation reduction in elementary school gyms A gymnasium can be a highly reverberant space. This is a consequence of the large room volume coupled with an abundance of hard surfaces. School designers frequently overlook the need for reverberation control in gymnasiums, cafeterias, and other large school rooms. The high level of reverberation promotes a high noise level and interferes with speech intelligibility, degrading the primary functions of those spaces. Moreover, those rooms are often used for additional functions, such as student assemblies, community meetings and school performances, which will also suffer from excess reverberation. A case study is presented for two elementary school gymnasiums, each with mid-frequency reverberation times of about 5 seconds. Renovation treatments to control reverberation were developed using simple computer models. Significant reductions in reverberation and noise level were achieved. As a result, student manageability was improved, and teacher sanity was restored. B.M. Brooks - Eliminating acoustical barriers to learning in classrooms - Case study of reverberation reduction in elementary school gymnasiums
![Page 3: Eliminating Acoustical Barriers to Learning in Classrooms poster.pdf · vs. NCB (Balanced Noise Criterion) Curves (ANSI S12.2-1995) Shepard Hill Elementary School Gymnasium HVAC off](https://reader031.vdocument.in/reader031/viewer/2022022610/5b949ce209d3f2e5688d3ab4/html5/thumbnails/3.jpg)
EXCESS ROOM REVERBERATION
Major cause of gymnasium acoustical problems What causes excess reverberation? How does room reverberation interact with noise and speech? How does it affect the learning environment?
B.M. Brooks - Eliminating acoustical barriers to learning in classrooms - Case study of reverberation reduction in elementary school gymnasiums
![Page 4: Eliminating Acoustical Barriers to Learning in Classrooms poster.pdf · vs. NCB (Balanced Noise Criterion) Curves (ANSI S12.2-1995) Shepard Hill Elementary School Gymnasium HVAC off](https://reader031.vdocument.in/reader031/viewer/2022022610/5b949ce209d3f2e5688d3ab4/html5/thumbnails/4.jpg)
EXCESS REVERBERATION:
- Due to a combination of hard surfaces and large room volume
- Typical features of a gymnasium. - In highly reverberant environments: - Sound of speech lingers, with one word
blending into the next -- making understanding difficult, i.e. reduced intelligibility
- Noise from HVAC & children not absorbed
B.M. Brooks - Eliminating acoustical barriers to learning in classrooms - Case study of reverberation reduction in elementary school gymnasiums
![Page 5: Eliminating Acoustical Barriers to Learning in Classrooms poster.pdf · vs. NCB (Balanced Noise Criterion) Curves (ANSI S12.2-1995) Shepard Hill Elementary School Gymnasium HVAC off](https://reader031.vdocument.in/reader031/viewer/2022022610/5b949ce209d3f2e5688d3ab4/html5/thumbnails/5.jpg)
EXCESS REVERBERATION:
- High noise and low intelligibility environment - Seriously impedes learning Students cannot hear teachers Teachers cannot hear students - Safety hazard since children cannot hear warnings and instructions - High levels may cause pain in some children B.M. Brooks - Eliminating acoustical barriers to learning in classrooms - Case study of reverberation reduction in elementary school gymnasiums
![Page 6: Eliminating Acoustical Barriers to Learning in Classrooms poster.pdf · vs. NCB (Balanced Noise Criterion) Curves (ANSI S12.2-1995) Shepard Hill Elementary School Gymnasium HVAC off](https://reader031.vdocument.in/reader031/viewer/2022022610/5b949ce209d3f2e5688d3ab4/html5/thumbnails/6.jpg)
Specific Affects of Noise on Learning:
- Cause of distraction, loss of attention - Garbling of perceived speech
- Cause of listener fatigue
- Cause of vocal strain
B.M. Brooks - Eliminating acoustical barriers to learning in classrooms - Case study of reverberation reduction in elementary school gymnasiums
![Page 7: Eliminating Acoustical Barriers to Learning in Classrooms poster.pdf · vs. NCB (Balanced Noise Criterion) Curves (ANSI S12.2-1995) Shepard Hill Elementary School Gymnasium HVAC off](https://reader031.vdocument.in/reader031/viewer/2022022610/5b949ce209d3f2e5688d3ab4/html5/thumbnails/7.jpg)
CASE STUDY - TWO ELEMENTARY SCHOOLS
- Newly constructed gymnasiums (Plainfield, CT) - Moosup Elementary School - Shepard Hill Elementary School
- Complaints by teachers about noise - School Superintendent directed that problem be
analyzed and corrected.
B.M. Brooks - Eliminating acoustical barriers to learning in classrooms - Case study of reverberation reduction in elementary school gymnasiums
![Page 8: Eliminating Acoustical Barriers to Learning in Classrooms poster.pdf · vs. NCB (Balanced Noise Criterion) Curves (ANSI S12.2-1995) Shepard Hill Elementary School Gymnasium HVAC off](https://reader031.vdocument.in/reader031/viewer/2022022610/5b949ce209d3f2e5688d3ab4/html5/thumbnails/8.jpg)
BAC asked to conduct a study
- Measured noise levels - Measured reverberation times (RT60) - Metrics studied: Reverberation time (RT60) A-weighted level (dBA) Speech interference level (SIL) Balanced noise criteria rating (NCB) B.M. Brooks - Eliminating acoustical barriers to learning in classrooms - Case study of reverberation reduction in elementary school gymnasiums
![Page 9: Eliminating Acoustical Barriers to Learning in Classrooms poster.pdf · vs. NCB (Balanced Noise Criterion) Curves (ANSI S12.2-1995) Shepard Hill Elementary School Gymnasium HVAC off](https://reader031.vdocument.in/reader031/viewer/2022022610/5b949ce209d3f2e5688d3ab4/html5/thumbnails/9.jpg)
Reverberation Time study results
- Moosup worse than Shepard Hill -- both bad
- Mid-frequency RT60 very high ~ 5 seconds!! - High background noise levels - NCB 66 at Moosup - HVAC on
- NCB 53 at Shepard Hill - HVAC on
B.M. Brooks - Eliminating acoustical barriers to learning in classrooms - Case study of reverberation reduction in elementary school gymnasiums
![Page 10: Eliminating Acoustical Barriers to Learning in Classrooms poster.pdf · vs. NCB (Balanced Noise Criterion) Curves (ANSI S12.2-1995) Shepard Hill Elementary School Gymnasium HVAC off](https://reader031.vdocument.in/reader031/viewer/2022022610/5b949ce209d3f2e5688d3ab4/html5/thumbnails/10.jpg)
Design study results
- Simple computer models of gyms (RT calc)
- Based on computer analysis, recommended that 2700 to 3300 sq ft of absorbent material (NRC 0.75 or better) be installed in each gym - Material needs to be durable (basketball tough) - Calculated RT (mid freq) reduced to 1 - 1.5 secs
- Calculated noise levels reduced up to 5 dB
B.M. Brooks - Eliminating acoustical barriers to learning in classrooms - Case study of reverberation reduction in elementary school gymnasiums
![Page 11: Eliminating Acoustical Barriers to Learning in Classrooms poster.pdf · vs. NCB (Balanced Noise Criterion) Curves (ANSI S12.2-1995) Shepard Hill Elementary School Gymnasium HVAC off](https://reader031.vdocument.in/reader031/viewer/2022022610/5b949ce209d3f2e5688d3ab4/html5/thumbnails/11.jpg)
Conclusions
- Construction proceeded according to specifications
- Completed gyms in service - Teachers report much improved environment - better communication - better control of class activities - less potential for injury - Timely action by school system improves education !!
B.M. Brooks - Eliminating acoustical barriers to learning in classrooms - Case study of reverberation reduction in elementary school gymnasiums
![Page 12: Eliminating Acoustical Barriers to Learning in Classrooms poster.pdf · vs. NCB (Balanced Noise Criterion) Curves (ANSI S12.2-1995) Shepard Hill Elementary School Gymnasium HVAC off](https://reader031.vdocument.in/reader031/viewer/2022022610/5b949ce209d3f2e5688d3ab4/html5/thumbnails/12.jpg)
NCBRating
6560555045403530252015
0
10
20
30
40
50
60
70
80
90
100
31.5 63 125 250 500 1000 2000 4000 8000 Octave Band Center Frequency (Hz)
Oct
ave
Ban
d SP
L (r
e: 2
0 µP
a)
Measured Room Noise vs. NCB (Balanced Noise Criterion) Curves (ANSI S12.2-1995)
Moosup Elementary SchoolGymnasium
HVAC offBackground Test
NCB 3641 dBASIL 35
![Page 13: Eliminating Acoustical Barriers to Learning in Classrooms poster.pdf · vs. NCB (Balanced Noise Criterion) Curves (ANSI S12.2-1995) Shepard Hill Elementary School Gymnasium HVAC off](https://reader031.vdocument.in/reader031/viewer/2022022610/5b949ce209d3f2e5688d3ab4/html5/thumbnails/13.jpg)
NCBRating
6560555045403530252015
0
10
20
30
40
50
60
70
80
90
100
31.5 63 125 250 500 1000 2000 4000 8000 Octave Band Center Frequency (Hz)
Oct
ave
Ban
d SP
L (r
e: 2
0 µP
a)
Measured Room Noise vs. NCB (Balanced Noise Criterion) Curves (ANSI S12.2-1995)
Moosup Elementary SchoolGymnasium
HVAC onBackground Test
NCB 6669 dBASIL 61
![Page 14: Eliminating Acoustical Barriers to Learning in Classrooms poster.pdf · vs. NCB (Balanced Noise Criterion) Curves (ANSI S12.2-1995) Shepard Hill Elementary School Gymnasium HVAC off](https://reader031.vdocument.in/reader031/viewer/2022022610/5b949ce209d3f2e5688d3ab4/html5/thumbnails/14.jpg)
NCBRating
6560555045403530252015
0
10
20
30
40
50
60
70
80
90
100
31.5 63 125 250 500 1000 2000 4000 8000 Octave Band Center Frequency (Hz)
Oct
ave
Ban
d SP
L (r
e: 2
0 µP
a)
Measured Room Noise vs. NCB (Balanced Noise Criterion) Curves (ANSI S12.2-1995)
Shepard Hill Elementary SchoolGymnasium
HVAC offBackground Test
NCB 3337 dBASIL 29
![Page 15: Eliminating Acoustical Barriers to Learning in Classrooms poster.pdf · vs. NCB (Balanced Noise Criterion) Curves (ANSI S12.2-1995) Shepard Hill Elementary School Gymnasium HVAC off](https://reader031.vdocument.in/reader031/viewer/2022022610/5b949ce209d3f2e5688d3ab4/html5/thumbnails/15.jpg)
NCBRating
6560555045403530252015
0
10
20
30
40
50
60
70
80
90
100
31.5 63 125 250 500 1000 2000 4000 8000 Octave Band Center Frequency (Hz)
Oct
ave
Ban
d SP
L (r
e: 2
0 µP
a)
Measured Room Noise vs. NCB (Balanced Noise Criterion) Curves (ANSI S12.2-1995)
Shepard Hill Elementary SchoolGymnasium
HVAC onBackground Test
NCB 5358 dBASIL 49