Acoustics & Beam Steering Technology David Stadler Media Infrastructure Architect Media Services Grove City College David Test Group Leader Technology Classrooms Penn State University
Has your college or university ever conducted an acoustical evaluation of your learning spaces? A. Yes B. No
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
How do we see classroom sound?
How do we see classroom sound?
Learning Space Acoustical Standards
Acoustic Basics Sound Isolation Sound Ratings Signal to Noise ratio (S/N) Reverberation Reflected Sound Room Modes
Speech Intelligibility Standards Scales Tools Technology solutions Beam Steering Case Studies Demonstrations Questions
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
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
Reverberation Definition: Prolongation of the sound in a space caused by continued multiple reflections. Acoustics.com
Reverberation Acoustics.com
Reflected Sound Sound strikes a surface or several surfaces before reaching the receiver Reverberation is continuous multiple reflections Control of the reverberation time in a space does not alleviate reflection problems Acoustics.com
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
Reverberation & Reflected Sound Remediation Mid and high frequency traps
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
Room Mode Definition Sound having the same pitch as the 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
Optimize Room Modes Proper space design Create space with length, width, and height ratios that are as unrelated as possible Create as many different resonances as possible, spreading evenly across the frequency spectrum Ballou, Glen, Ed., Handbook for Sound Engineers, 2nd ed, Howard Sams, Carmel, Indiana, 1991
Room Modes - Remediation Bass traps can improve room modes Moving walls and ceilings are the only true solution
Learning Space - Speech Intelligibility (non amplified) 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
Speech Intelligibility Standards STI- Speech Transmission Index Complex and long testing time using up to 98 measurements per room RASTI Room Acoustics Speech Transmission Index Older and not as accurate, but allowed portable testing STI-PA Speech Transmission Index for Public Address Bose and other manufactures created it Designed to cope with advanced sound systems Fast and portable measurement tools 15 seconds per room position Test ranges from 0-1 with 1 being perfect NTI-audio.com
Speech Intelligibility Scales NTI-audio.com
STI-PA Measurement tools Software IOS app-studio 6 Digital Approximately $200 Dedicated tools XL2 analyzer from NTI audio Approximately $900 Optional add-on tools NTI-audio.com
What if I can t improve speech intelligibility?
Technology to the Rescue!
Beam Steering
Beam Steering Digitally manipulating the magnitude and phase of individual loudspeakers Goal is to evenly direct acoustical energy onto the audience and away from the walls Typically controls only a limited number of frequencies due to digital sound processing complexity Focused primarily on Speech Intelligibility
Beam Steering - Primer Digital sound processing manipulates each loudspeaker Each loudspeaker element can have its own unique filter set
Beam Steering - Primer Creates a very narrow vertical angle with a wide horizontal dispersion
Beam Steering - Primer Highly efficient at distributing available loudspeaker power SPL (Sound Pressure Level - volume) is approximately the same regardless of the listener s distance to the speakers
Case studies
Grove City College - Ketler Auditorium Mixed theater, event and presentation space with big live sound and speech lift needs Spoken word, theatrical performances, big live sound require shorter reverb times Orchestral performances require longer reverb time
Grove City College - Ketler Auditorium Acoustical study conducted
Grove City College - Ketler Auditorium
Grove City College - Ketler Auditorium Acoustical recommendations unless major architectural acoustics issues are addressed, no level of sound reinforcement will be ideal $11 million construction for the IDEAL
Grove City College - Ketler Auditorium Lemons to Lemonade Approach Multi-purpose space requires multiple systems JBL VRX array big live sound needs JBL Intelevox - Beam steering Speech Intelligibility
Grove City College - Ketler Auditorium JBL VRX array
Grove City College - Ketler Auditorium JBL Intelevox
Grove City College - Ketler Auditorium JBL Intelevox
Penn State University 100 Thomas Building 8,800 Square Feet 31 ceiling at stage to 12 ceiling at back 101 deep 726 Seats
Penn State University 100 Thomas Building
Penn State University 100 Thomas Building
Penn State University 100 Thomas Building Primarily lecture space, with occasional live performances Largest General Purpose Classroom on campus
Penn State University 100 Thomas Building Before: System designed and built in 2001 2 large venue PA speakers for program audio Grid of 24 ceiling speakers for spoken audio
Penn State University 100 Thomas Building Before: System designed and built in 2001 2 large venue PA speakers for program audio Grid of 24 ceiling speakers for spoken audio Result: Loud but boomy program audio Spotty, hard to understand spoken audio with delay issues
Penn State University 100 Thomas Building Result: Even, intelligible program and spoken audio levels at any seat in the room Less equipment, less power, less cabling Happy customers
Penn State University 100 Thomas Building After: 2 x JBL Pro Invellivox DSX280 line arrays 14 4 speakers each 9 tall x 5 wide x 4 deep 55 lbs 2 x Crown CT475 Amps Biamp CS Nexia Mixer
Demonstration
Questions
Acoustics & Beam Steering Technology David P. Stadler Media Infrastructure Architect Media Services Grove City College David Test Group Leader Technology Classrooms Penn State University