Sound & Acoustics In Technology Classrooms

Transcription

1 Sound & Acoustics In Technology Classrooms David P. Stadler CTS, DMC-E, MS Senior Manager Media Technology Services Carnegie Mellon University

2 Carnegie Mellon University Fast Facts Established 1900 Private research university 1,368 Faculty 6,000 Undergraduates & 5,420 Graduate & Doctoral students Main campus: Pittsburgh, Pennsylvania Undergraduate branch campus: Doha, Qatar 13 graduate branch campuses in 11 countries Athletics: 17 Division III athletic teams - Tartans

3 Media Technology Services Classroom Technologies Media Production Videoconferencing AV & Media Consultation Facility Design

4 Qualifications and Biases David P. Stadler CTS,MS Senior Manager Media Technology Services Carnegie Mellon University

5 50:50 How many total campuses are in the SUNY system?? $1 Million $500,000 $250,000 $125,000 $64,000 $32,000 $16,000 $8,000 $4,000 $2,000 $1,000 $500 $300 $200 $100 A: 10 B: 64 C: 100 D: 18

6 Has your college or university ever conducted an acoustical evaluation of your learning spaces? A. Yes B. No

7 What priority do you give sound in designing an integrated media learning space? A. Sound then display B. Display and sound equal C. Display then sound

8 What was the percentage of acoustical exhibitors who were on the Infocomm 2010 show floor? A. 2% B. 5% C. 20% D. 30%

9 InfoComm exhibitors 21 acoustical exhibitors representing 2% of exhibitors

10 a/v Manufacturers Historically focused on maximizing visual displays Digital revolution Auditory content- second string

11 How do we see classroom sound?

12 How do we see classroom sound?

13 Learning Space Acoustical Standards

14 Acoustic Basics Sound Isolation Sound Ratings Signal to Noise ratio (S/N) Reverberation Reflected Sound Room Modes

15 Sound Isolation Keep out exterior room sound Preserve generated sound inside a room Reduce unwanted interior room sound Implement during construction Architectural components Walls, Doors Floors, Ceilings, HVAC

16 Sound Isolation Rating Systems STC- Sound Transmission Class Based on ASTM E (1994) Hz Typically used for speech and media OITC-Outdoor Indoor Trans. Class Based on ASTM E1332 (1990) Hz Typically used for exterior sound

17 Sound Isolation STC for walls - higher STC values more efficient in reducing sound transmission STCratings.com

18 Sound Isolation Changes in STC rating Changes in apparent loudness +/- 1 Almost imperceptible +/- 3 Just perceptible +/- 5 Clearly noticeable +/- 10 Twice as loud +/- 20 Four times as loud STCratings.com

19 Demonstration

20 Learning Space Sound Isolation Recommendations Wall ceiling and floor if adjacent to: STC-45: corridor, staircase, office or conference room STC-50: core learning space, speech clinic, health care room or outdoors STC-53: restroom STC-60: music room, mechanical equipment room, cafeteria, gymnasium or indoor swimming pool Door ratings: STC -30: classroom doors STC-40: music room doors STC-45-60: ancillary space separation Acoustics.com

21 STC Use as a reference for targeting new construction and architecture Calculation Best left to the professionals Do it yourself Small room acoustic forum

22 Sound Isolation Isolation will be improved by extending walls to structural deck, not just the ceiling. A. True B. False STCratings.com

23 Sound Isolation Sound will travel through speaker and electrical outlet penetrations. A. True B. False STCratings.com

24 Demonstration

25 Sound Isolation Installing insulation within a wall or floor/ceiling cavity will improve the STC by 4-6 points. A. True B. False STCratings.com

26 Sound Isolation Changes in STC rating Changes in apparent loudness +/- 1 Almost imperceptible +/- 3 Just perceptible +/- 5 Clearly noticeable +/- 10 Twice as loud +/- 20 Four times as loud STCratings.com

27 Sound Isolation Metal studs perform better than wood studs. A. True B. False STCratings.com

28 Learning Space Background Noise Level < 20,000 cubic feet < 35 dba for spaces > 20,000 cubic feet < 40 dba for spaces Need a sound-to-noise level of 15 db. Nelson,Soli & Seltz (2002) Acoustical Barriers to Learning- Acoustical Society of America

29 Reverberation Definition: Prolongation of the sound in a space caused by continued multiple reflections. Acoustics.com

30 Reverberation Acoustics.com

31 Learning Space Reverberation Standards Space volumes... < 10,000 cu. ft. are not relevant > 10,000 cu. ft. should be < 0.6 seconds between 10,000 and 20,000 cu. ft. should be < 0.7 seconds > 20,000 cu. ft. (see ANSI.ASA S12.60 guidelines ) Acoustics.com

32 Learning Space - Speech Intelligibility Combination of reverberation time (RT) and signal-to-noise ratio (S/N) 0.5 second RT and +10 db S/N - 90 % speech intelligibility 0.5 second RT and 0 S/N - 55 % speech intelligibility 1.5 second RT and +10 S/N 75 % speech intelligibility 1.5 second RT and 0 S/N 30 % speech intelligibility Seep,Glosemeyer, Hulce, Linn& Aytar (2000) Classroom Acoustics- Acoustical Society of America

33 Reflected Sound Sound strikes a surface or several surfaces before reaching the receiver Reverberation is continuous multiple reflections Controlling the reverberation time in a space does not alleviate reflection problems Acoustics.com

34 Reverberation & Reflected Sound Remediation Fiberglass/Foam non-parallel walls Bass Traps DIY Owens Corning 703 & 705 panels 48"x 24"x Fabric covered Flexible mounting

35 Reverberation & Reflected Sound Remediation Mid and high frequency traps

36 Reverberation & Reflected Sound Remediation Bass traps 4 thick 705-FRK and spaced 16 inches away from the wall can be quite effective for frequencies below 125 Hz

37 Room Mode Definition Sound having the same pitch as a natural resonance of the room will sound louder and have a longer decay time than other notes. Ballou, Glen, Ed., Handbook for Sound Engineers, 2nd ed, Howard Sams, Carmel, Indiana, 1991

38 Optimize Room Modes Use standard modal approach Create as many different resonances as possible spread evenly across the frequency spectrum Proper space design Create space with length, width, and height ratios that are as unrelated as possible Ballou, Glen, Ed., Handbook for Sound Engineers, 2nd ed, Howard Sams, Carmel, Indiana, 1991

39 Room Mode Optimum room dimensions Dimension Design #1 Design #2 Design #3 Width 1.14 x Height 1.28 x Height 1.60 x Height Length 1.39 x Height 1.54 x Height 2.33 x Height According to the modal design theory, the worst possible room shape is a cube. Ballou, Glen, Ed., Handbook for Sound Engineers, 2nd ed, Howard Sams, Carmel, Indiana, 1991

40 Realtraps.com

41 Realtraps.com

42 Room Modes - Remediation Bass traps can improve room modes Moving walls and ceilings are the only true solution

43 Acoustic Focus for Learning Spaces Background noise All learning spaces Reverberation Large learning spaces Reflection All learning spaces Dead spots Room Modes Specialized or media integrated learning spaces

44 How do we see classroom sound?

45 CMU Learning Space - Acoustic Evaluation Existing classrooms Background sound level Isolation Reverberation Reflection Dead spots

46 CMU Equipment Operating Noise Evaluation Equipment selection Integrated room design

47 High volume, low velocity

48 Integrated room design component selection 2 dba increase in baseline room noise 0 dba Cost Savings

49 Integrated room design component selection 2 dba increase in baseline room noise 0 dba Cost Premium

50 Crossing the Chasm Marketing and selling high-tech products to the mainstream customers Geoffrey A. Moore

51 Sound & Acoustics In Technology Classrooms David P. Stadler CTS, DMC-E, MS Senior Manager Media Technology Services Carnegie Mellon University