Classroom Acoustics and Student Learning. Gail Gegg Rosenberg, M.S., CCC-A

Transcription

1 Classroom Acoustics Gail Gegg Rosenberg, M.S., CCC-A 1

2 Registered Provider Lightspeed Technologies, Inc. is a Registered Provider with The American Institute of Architects Continuing Education Systems. Credit earned on completion of this program will be reported to CES Records for AIA members. Certificates of Completion for non-aia members available on request. This program is registered with the AIA/CES for continuing professional education. As such, it does not include content that may 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. Thank you! 2

3 Learning objectives Participants will be able to: identify the impact of classroom acoustics on student learning and speech perception recognize the societal impact of poor classroom acoustics on teacher s vocal health describe the role of educational facility planning teams to improve classroom acoustics identify key components of the acoustical standard explain strategies for improving acoustical listening environments for students and teachers 3

4 Simple concept Powerful results. Simple concept: Hearing is the primary channel for learning Immature listeners and effects of poor acoustics Critical nature of signal-to-noise ratios Hearing and Learning Powerful Results 4

5 Early Education Under Pressure More ELL students Learning environments Teacher absenteeism Larger classrooms Aging educational infrastructure Learning disabilities on the rise We share these things in common Children simply can t learn if they can t hear 5

6 21 st Century Classrooms Innovative, specialized, and interactive teaching and learning strategies Produce additional classroom noise Contributes to the acoustical complexity of many learning environments Children s auditory systems are challenged to continuously resolve the competition for speech perception and localization between a sound source and noise or reverberation (Litovsky, 2002). 6

7 Adult Basic Communication Processes (Butler, 1975) Reading 16% Writing 9% Speaking 30% Listening 45% Children and Listening 60% of the day (Butler, 1975) 75% of the school day (Dahlquist, 1998) 7

8 Student Listener Variables more adversely affected by noise and reverberation central auditory pathways, specifically interhemispheric organization and neural synchrony, do not mature until adolescence require a quieter environment and signal clarity in order to hear, listen, and comprehend 8

9 The Environment s Impact on Learning Chronic noise impairs cognitive functioning Various [classroom] noises appear to interfere with the encoding stage of memory There is strong consistent evidence for the effect of basic physical variables on learning Centre for Learning and Teaching University of Newcastle 9

10 Loudness of speech components can be masked by noise There is normally a 300 to 500:1 ratio in sound level between the strongest vowel o (ahh) and the weakest consonant sound thh. 10

11 Barriers to Hearing Clearly Ambient Noise Levels Signal to Noise Ratio Distance Directionality Reverberation We share these things in common Children lose interest when they can t hear 11

12 Synergistic Effects of Classroom Acoustics on Speech Perception Distance Directionality Listening advantage location relative to audio source Loss of high frequency consonant information Classrooms are auditoryverbal learning environments. Reverberation Smears sounds and can impair speech recognition ability Noise Masks important speech elements

13 Barriers to Hearing Clearly Ambient Noise is measured in an empty classroom External Noise Internal School Noise Classroom Noise Noise in classrooms can impair our ability to understand and comprehend speech 13

14 Signal to Noise Ratio (SNR) SNR refers to the intensity of the teacher s speech compared to any unwanted background noise. Speech Alone Click to hear +15 db Click to hear +0 db Click to hear -15 db Speech with background noise 14

15 Signal-to-Noise Ratio (S/N) Definitions S/N: relationship of the intensity of the auditory signal (e.g., teacher s voice, other audio signal) and the background noise level. Effective S/N: difference in db between the levels of the effective signal and the effective noise; goal is 15 db across a broad frequency band. (Boothroyd, 2004) Research-based S/N recommendations: Young listeners: +15 db ELL listeners: at least 10 db Hearing loss: Listeners with other learning/listening challenges: favorable S/N between levels listed above 15

16 Inverse Square Law The Inverse Square Law: Voice level is reduced by 50% each time the distance from the sound source doubles. Typical Ambient Noise: 45 db Hyper Physics C.R. Nave, 2005) 16

17 Directionality The student seated directly in front of the teacher hears the teacher s voice significantly louder than the student seated behind the teacher. For every doubling of distance from the teacher, the sound decreases by 50%. (note: 6 db = a doubling of sound) 17

18 Noise & Speech Perception Linkages Influences and interferes with verbal instructions and interactions, reading comprehension, blood pressure, and cognitive tasks Discussions deteriorate and become ineffective Psychosocial effects include inability to concentrate, lack of sustained application to learning tasks, and withdrawal from conversations 18

19 Reverberation Direct sound from the speaker will echo or reverberate as a result of bouncing off the floor, walls, ceiling, and furniture. Click to hear RT none Click to hear RT Click to hear RT 0.5 Click to hear RT

20 Definitions Direct Sound Sound arriving at listener s ear Effective Signal Combination of direct sound with early reflections reaching the listener after only a few reflections (i.e., 50 to 80 ms) Effective Noise Combination of background noise and noise created by late reflections (i.e., greater than 80 ms) and interfere with speech perception by smearing critical information such as gaps available in the effective signal. Reverberation also tends to increase noise levels. 20

21 Reverberation Time Classroom Acoustics Definition: measurement in seconds of time required for the level of a steady sound to decay by 60 db after the sound has occurred. Decay rate is dependent on: Amount and properties of sound absorption in the classroom Room size and shape Frequency of the sound Outcomes of excessive reverberation: Negative impact on speech perception Missed learning opportunities 21

22 Reverberation and Speech Perception Below age 10 there is more difficulty with speech perception in reverberation than in noise. Phoneme identification scores obtained under reverberant conditions improve as a function of age and decreased RT. Speech perception under reverberation does not reach adult like performance until age 13 or

23 Hard ceilings absent of acoustic tiles Classroom Acoustics Reverberation: Classroom Indicators Ceiling height > 10 ft. Ceiling surface > 10% non-absorptive Reference: Maryland Department of Education, 2006; U.S. Access Board,

24 Contribution of Early Reflections ms (Bradley, Sato & Picard, 2003) Early reflection energy has same effect on increasing speech perception performance as an increase in direct sound. Contributions of Early Reflections Increase direct speech level by up to 9 db in classrooms Increase as a function of expanding distance from the speaker Increase the effective S/N 24

25 Other Issues Now Linked to Classroom Environment Teacher absentee rates: Fatigue Stress Illness Job Satisfaction Teachers with voice related problems are on the rise 18% miss work each year due to voice issues 43% reduce instructional activity National estimated cost - $2.5B Source: Parker & McDade

26 Classroom Acoustics ANSI Specifications Internal Noise Improvement External Noise Improvement Teacher voice reinforcement is the key Clear, crisp audio strengthens the teacher student connection 26

27 ANSI S Acoustical Performance Criteria Allowable performance criteria specifications for background noise and reverberation, and design guidelines for attenuating noise entering learning spaces. RT60-Reverberation Time 0.6 second small rooms 0.7 second large rooms Background Sound Level 35 dba Assume 50 db teacher level: +15 SNR Partition Design Between classrooms: 50 STC Between corridor and classrooms: 45 STC Between high noise and classroom: 60 STC Source: Crandell, Samaldino, Flexer; Soundfield Amplification, Applications to Speech Perception and Classroom Acoustics 27

28 Unoccupied Classroom Noise Essentially no change over the past 28 years.

29 Reverberation in Classrooms Classroom Acoustics Investigator Classroom Type RT60 in seconds Kodaras (1960) Regular ed classrooms Nabalek & Pickett (1974) Medium size classrooms McCroskey & Devens (1975) construction Bradley (1986) 10 regular ed Crandell & Smaldino (1995) 32 mainstream for D/HH Knecht et al. (2002) 32 regular ed classrooms Mendel, Roberts & Walton (2003) 14 regular ed kindergarten & 1 st grade classrooms Beland (2003) 18 classrooms ( construction)

30 Interaction of Distance and Reverberation Listener moves away from speaker Reverberation dominates the listening environment Listener is near the speaker Direct sound level exceeds the reverberation level Critical distance for effective listening Distance from a sound source at which the direct sound and reverberant sound are at equivalent levels 30

31 Classroom Acoustics Standard Learning Space (unoccupied and furnished) Small Core Learning Space Enclosed Volume < 283 m 3 (< 10,000 f 3 ) Moderate Core Learning Space Enclosed Volume > 283 m 3 and 566 m 3 (> 10,000 ft 3 and 20,000 ft 3 ) Enclosed volumes > 566 m 3 (20,000 ft 3 ) and all ancillary learning spaces Maximum Background Noise Level in dba * Maximum Reverberation Time in seconds 35 dba dba dba Refer to ANSI S , Section C3.3 for recommendations on reverberation control. * Maximum 1-hour-average dba-weighted steady background noise level. 31

32 Applies to two types of noise Classroom Acoustics Classroom Acoustics Standard Minimum Noise Isolation 1. Intrusive noise from sources outside the school building envelope (e.g., vehicular and air traffic, industrial plants, grounds maintenance, playground activity noise) 2. noise originating within the school building that intrudes through classroom walls and partitions, floor-ceiling assemblies and ventilation systems Does not apply to some noise sources Noise generated by classroom occupants (e.g., voices, classroom activities, moving chairs) Portable or permanent built-in instructional equipment (e.g., computers, projectors, other audio-visual equipment) 32

33 Classroom Acoustics Standard Annexes - Minimum Sound Transmission Class (STC) ratings Adjacent Space Minimum STC Rating Other enclosed or open plan core learning space, speech clinic, 50 health care room and outdoors Common use and public use toilet room and bathing room 53 Corridor, staircase, office or conference room 45 Music room, mechanical equipment room, cafeteria, gymnasium, and indoor swimming 60 pool 33

34 New school budget increase to provide acoustical accessibility in all classrooms Estimated school program expenditures (20 year total): $90, Number of children benefited: 12,000 Cost per child served: $ 7.50 Classroom Acoustics Added-First-Cost for New Construction Pay-as-you-go scenario results in a 30 times greater cost per child benefitted Outcome: 12,000 students receive educational and social benefits of quiet classrooms and go on to realize increased potential in their family, public, and working lives. 34

35 Classroom Noise Noise can originate from: External noise generated from outside the school Internal noise coming from within the school building but outside the classroom Classroom noise generated within the classroom 35

36 External Noise Reduction Locate rooms away from high noise sources such as busy automobile traffic, railroads, construction sites, airports, etc. Construct walls for at least 45 to 50 db sound transmission loss (STL) Exterior walls free of cracks or openings Double pane, sealed windows Landscape strategies: Non-deciduous trees or shrubs Earthen banks Solid concrete barriers with an STL of db placed between school and noise source 36

37 Internal Noise Reduction Locate rooms away from Gymnasium, Cafeteria or Band Room Place sound absorbing materials in space above suspended ceilings and room dividers Double or thick wall construction Acoustical ceiling tile in/or carpeting in hallways Solid core, sealed doors Noise baffles in heating/cooling ducts Back whiteboards with absorptive materials 37

38 10 Fundamental Ways to Improve the Acoustical Environment in Classrooms (Siebein, 2000) 1. Carefully select and design the air-conditioning system for the school. 2. Limit room volume (ceiling height). 3. Provide sound-absorbing surfaces. 4. Install carpet on the floor. 5. Emphasize classroom furniture arrangements and teaching techniques that reduce the distance between the teacher and the students. 38

39 10 Fundamental Ways to Improve the Acoustical Environment in Classrooms (Siebein, 2000) Classroom Acoustics 6. Use FM and other sound reinforcement systems when needed. 7. Select and design the overall site plan wisely. 8. Design special-purpose rooms with special-purpose acoustics. 9. Work with audiologists, teachers, and acoustical consultants who have expertise in the design and planning of classrooms. 10. Support a vigorous national technical research effort in this area to fully explore these issues relating to speech perception and learning for all children. 39

40 Proposed Standard Audio Coverage Uniformity Proposed by INFOCOMM (June 2009) Standard for AV presentation systems within enclosed environments, including classrooms Evaluates spatial uniformity Six measurements at each measurement location Median calculation for each frequency band Compliance = +/- 3dB in each of six bands htm

41 Classroom Audio Technologies 41

42 How It Works: Full Multimedia Integration No Installation Required Installed Systems Designed for schools outfitting classrooms with the latest integrated technology 42

43 Amplifiers Use High-Quality Amplification Low feedback and distortion Wide dynamic range Equalizer for treble and bass Team teaching or student microphone capability Amplifies and controls sound of multiple A/V sources 43

44 Frequency Equalizers Alters the frequency response of the amplifier so certain frequencies are more or less pronounced than others 44

45 Speaker Loudspeakers form a key part of a sound-field system Select suitable loudspeakers to: Distribute sound evenly throughout the room Minimize acoustic feedback or howl Be easy to install in new or retrofit situations NXT FLAT-PANEL WALL SPEAKER MINI WALL SPEAKER CEILING SPEAKER MCQ Multimedia CEILING SPEAKER 45

46 Research Findings National Studies Action Research Formative Assessment Teacher voice reinforcement is the key The teacher student connection is at the heart of learning 46

47 Classroom Amplification Validated % increase on the Stanford Achievement Test over same grade level classrooms that had no audio system McCarty and Ure, BYU Research, 2003 McCarty, PJ., & Ure, A. (2003) The Effect Audio Enhanced Classrooms Have on Student Achievement and Teacher Instruction. Collaborative of High Performance Schools. Retrieved from 10% higher on the Florida Comprehensive Assessment Test than students in classrooms without classroom audio. Eucational Facility Planner, 39 (3), 2004 Gertel,S.J., McCarty, P.J., & Schoff, L. (2004) High Performance Schools Equals High Performing Students. Educational Facility Planner, 39 (3), % reduction in Teacher absenteeism in classrooms where microphone audio systems where in use. Orange County Public Schools, Florida, 2004 Gertel,S.J., McCarty, P.J., & Schoff, L. (2004) High Performance Schools Equals High Performing Students. Educational Facility Planner, 39 (3),

48 Classroom Amplification Validated ICA: STUDENT EVALUATION Ease of hearing teacher 98% Teacher s voice loud and clear 95% Helped me listen better 96% Can hear when teacher is writing on board 96% Want to use SF FM next year 95% 48

49 Classroom Amplification Validated Teacher Evaluation Teacher s voice reached all students 100% Did not have to strain voice Enjoyed using system Less emotional strain & fatigue 97% Students more attentive Decreased need to repeat information 98% Ease of use Want to use system again next year 96% Better student listening and 93% understanding System helped with classroom control & student behavior management 88% 49

50 Early Auditory Reading Success (EARS) Alachua Co. DIBELS National %ile rank in last test interval of first grade for EARS participants EARS (n=180) Control (n=143) 10 0 OLV Reading Comp OLV Oral Language Vocabulary Reading Comp Reading Comprehension Hall & Johnson, 2006

51 Literacy Project -- Escambia Co. Goal: Literacy improvement with IR classroom amplification system Grades 5 schools (N: 20) Title I schools Significantly higher reading and math scores in amplified classrooms (.05 level)

52 Summary 52

53 Summary Classrooms are noisy environments When the laws of physics are coupled with ambient noise, speech intelligibility decreases Hearing is fundamental to learning Classroom amplification must be considered The results are overwhelming 53