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Optimizing Classroom Acoustics and Classroom Amplification Systems. Jeffery B. Larsen, PhD, CCC-A Utah State University. How Important is Classroom Listening?. Two-thirds of a student’s day consists of listening to and participating in spoken communication

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Optimizing Classroom Acoustics and Classroom Amplification Systems


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    1. Optimizing Classroom Acoustics and Classroom Amplification Systems Jeffery B. Larsen, PhD, CCC-A Utah State University

    2. How Important is Classroom Listening? • Two-thirds of a student’s day consists of listening to and participating in spoken communication • Listening environments need to be free of acoustic and non-acoustic barriers

    3. The Problem – Classroom Communication • Classrooms can be difficult places for good communication to take place • TEACHER TO STUDENT COMMUNICATION • STUDENT TO TEACHER COMMUNICATION • STUDENT TO STUDENT COMMUNICATION • Communication in the classroom can be difficult because of NOISE, REVERBERATION, AND DISTANCE

    4. Results of poor acoustics on kids in school • Poor performance on cognitive tasks • Cohen, Evans, Krantz, Sokols, & Kelly, 1981 • Poor reading skills • Bonzaft & McCarthy, 1975; Green, Pasternack, & Shore, 1982; Gertel, McCarty, & Schoff, 2004 • Poor math skills • Zentall & Shaw, 1980 • Poor attention and on-task behavior • Palmer, 1998; Ryan, 2009

    5. One problem is reverberation • Reverberation occurs when sound encounters a hard wall • Sound bounces around a room • The effect of reverberation is slurring of speech as you move away from the talker • Normal listeners do best when reverberation times are below .6 seconds

    6. Other Problems • As talker moves away from the listener the signal decreases 6dB every time the distance is doubled (distance is the least thought about problem) • Start at 65dB HL, 6” from mouth, at 1 foot the intensity is 59dB, at 2 feet the intensity is 53dB, at 4 feet 47dB, at 8 feet 42 dB, and at 16 feet it is 36dB • Noise is usually the biggest problem • At the back of a typical classroom with no children present, the signal-to-noise ratio (SNR) would be +1 dB • With children present, the background noise is going to be at least 45dB, resulting in a SNR of about -3dB

    7. The Overall Problem • When noise, distance, and reverberation are combined the result is speech is difficult to understand • For normal listeners a +6dB signal-to-noise ratio leads to a 9% decrement in speech recognition • When a reverberation time of .7seconds is combined with a signal-to-noise ratio of +6dB word recognition scores decrease by as much as 20% • A student at the back of the room has a huge disadvantage

    8. A study to demonstrate the overall effect • Young adult listeners (18-30 years old) were asked to write down words while seated at desks in a quiet elementary school classroom. • Acoustic measurements showed that the classroom had about 45 dB SPL of noise when empty and the reverberation time was 0.7 seconds. • Results showed that those students seated in the back row got scores between 65% and 75%

    9. So Why Don’t We Complain • It’s always been this way • We figure out strategies • We get notes from the teacher/presenter • We read the text or the references • We talk to our friends about what was discussed • We sit close to the front of the room • We would never allow children to be taught in a dark room, but we will allow them to be taught in a room in which they can not hear well

    10. WHAT SHOULD WE DO? • Change the acoustics or amplify the teacher? • I am not an audiologist who believes that amplification is always the solution • Dispensing hearing aids can sometimes lead us to think this way • Apparently the Acoustical Society of America is also not thrilled about the amplification option as they released a position statement in 2006 claiming that classroom amplification, as a general policy, was a bad idea.

    11. Concerns of the Acoustical Society • Classroom amplification… • will amplify bad acoustics • equipment can break down • will add more sound to an already loud room • does not address student to student communication and student to teacher communication • Improving the acoustic properties of the room is a permanent fix that does not need repairs and will help everyone in the room

    12. Acoustic Modifications VS Classroom Amplification • As with everything else, there are no silver bullets • The truth about what is best probably lies somewhere between the Acoustical Society and supporters of Classroom Amplification • Or maybe what is best is to do what both suggest…

    13. Tips for Improving SNR without classroom amplification • Place rubber tips on chair and desk legs • Move kids away from high noise source • Use acoustically treated furniture • Use doors with solid cores • Install double paned windows • Keep doors and windows shut • Improve classroom discipline

    14. Study – Larsen & Blair 2008 • Five different classrooms used in the study • All were similar in size – all 4th grade • 30 to 35 feet deep • 32 to 40 feet wide • All met ANSI standard for noise and reverberation • RT 60 .32 • Noise Criteria 32 dB • Four teachers used classroom amplification, one did not • A pass-around microphone was used in one classroom regularly, but either sporadically or not at all in the other three classrooms

    15. Procedures • A measuring microphone was placed on a tripod, positioned at the level of the child’s ear (placed near a child’s ear) • Measurements were made at 9 different locations in each room (back center, left back, right back, left center, middle center, right center, front right, front left, front center) • Measurements were made in 10 minute increments • The Time, Energy, Frequency (TEF) system was used to obtain measurements

    16. SNRswith infrared classroom amplification • Obtained signal-to-noise ratios were on average between +13 to +20 dBA at every position measured in the rooms • One classroom was not fit with a classroom system and all other teachers were asked to turn off their systems for 5 minutes during the data collection • The average signal-to-noise ratios were between +2 and +6 dBA without amplification

    17. Actual Conditions (unamplified) • Teacher asked children to read in a random order around the classroom. • Average sound level at the microphone based on distance away from the microphone. • 2 feet - 59dB • 3 feet - 56 dB • 6 feet - 55 dB • 12 feet - 46 dB • There are times when the sound level is 13 dB less intense than at other times.

    18. Results: Unamplified Classroom • Teacher’s measured vocal intensity; • Front of the room at nearest student’s desk was 58 dBA, with a range of 50 to 65 dB • Middle of the room at child’s desk, the level was 52 dB, again with a range of 40 to 60 dB • At the most distant point, this is measured as being 18 feet from the most common place from which the teacher presents information, was 48 dB with a range of 40 to 52 dB

    19. Implications • The results indicate that, without amplification, at the front of the room the average signal-to-noise ratio was +15 with a range between +8 and +20 • In the middle of the room the S/N ratio was 8 dB with a range between +1 and +10 • At the back of the room the S/N ratio was 0 dB with a range of -15 to +6 dB

    20. Implications (continued) • Depending on where the child is seated at any given time changes the amount and quality of input available • There are times when everything is audible and other times when information is not audible at all • The child who has any kind of hearing problem is getting at best variable auditory input (about 10% of the students) • Remember this room meets ANSI standards

    21. Amplified Classrooms • In these classrooms all speakers were in the ceiling, providing direct sound to the children. • No matter where the child was seated in the room they were getting no less than a +10 signal-to-noise advantage. • When the hand-held microphone was used the same advantage was present for the children as for the teacher, when not used it was like the results in an unamplified room.

    22. Observations without amplification • Many students did not listen well when the teacher was talking • After the teacher explained an assignment on a poem and the children started to work, the teacher noticed one child looking around as if trying to discover what to do. When the teacher asked if she had started to look at the poem, the student said, “Oh, I thought you were talking about some kind of foam and I didn’t know what you wanted us to do.” • Little differences can make for a great deal of confusion

    23. Logan City School District • Few classrooms have used systems for many years • Middle School was convinced that a system for their school was important • Opted not to repave a parking lot and used the money to purchase audio enhancement for all instructional classrooms • Legislature provided money for technology • Superintendent and Board decided to use the bulk of the money to put audio enhancement in every classroom in the district

    24. Current Findings in Logan City Schools • Three-hundred five teachers (K-12) were surveyed • One-hundred sixty-five responded (54%) • Questions and answers: • Do you have classroom amplification in your room? • 93.9% yes; 6.1% no • Do you personally use the equipment? • 89.6% yes; 10.4% no • How often do you use the equipment? • All day, every day: 48.2% • When presenting information: 28.4% • Occasionally, for special presentations: 10.6% • When I think about it: 5.7% • Other: 7.1% (don’t use it when there are groups in the class)

    25. Findings (continued) • Do students use the microphone? • Yes, 59.1% • No, 40.9% • How often and under what conditions? • Pass the microphone around during class discussions: 3.3% • Use the microphone when presenting in front of the class: 68.5% • They use the microphone whenever they are talking to the whole class: 17.4% • Do guests in the classroom use the system? • Yes: 62.3%; No: 37.7% • How often and under what conditions? • When reading a story to the children: 29.5% • When presenting information to children formally: 61.1% • Whenever a guest talks they use the system: 61.1%

    26. Findings (continued) • What is your impression of the system? • I believe students are more attentive: 80.1% • I can control classroom behavior more effectively: 65.2% • It helps children in my class perform better: 53.9% • The children like it when I use the system: 65.2% • Because I don’t need to talk loud, or yell, I am less tired at the end of the day: 66.0% • I don’t think that the system helps at all: 5.7% • How important do you think an amplification system is in a classroom? • Detrimental: 0% • Not too useful: 8.6% • Useful: 13.2% • Quite useful: 11.8% • Very useful: 35.5% • Essential: 30.9%

    27. How to make it better • Put it in the gym: 2 • Need hand-held mic: 19 • Cuts out all the time: 2 • Mic too heavy: 18 • Need smaller mic: 15 • Needs to connect to all systems: 13 • Mic Reverberates/Feedback: 6 • Too soft: 2 • Dead places in the room: 1 • Too loud: 1 • I have a loud voice, don’t need it: 2 • I wear it for hard of hearing child: 2 • We need complete technology classrooms: 2

    28. How can we make it better? (continued) • We need someone to maintain it and teach about it: 3 • I love it: 6 • It is wonderful: 3 • Amazing: 1 • Nothing: 2

    29. Some Considerations • Installation of classroom amplification follows no systematic procedure • In most states they are installed by the companies • They are fit subjectively • We are finding considerable variability across classrooms and we have had to retrofit a number

    30. Some Considerations (cont.) • Many teachers will not wear the systems • Too loud • I speak loudly already • Does not work well • Unwieldy • I rarely teach the whole class at one time • What to do when it does not work well • I forget to put it on • Microphone is too heavy and gives me a headache

    31. Unresolved issues for classroom amplification • We know that anything is better than nothing (unless it is not loud enough to make a difference) • We don’t know what is truly feasible in a classroom (research says +15) • Comfort • Feedback • Overflow • We are not sure what is usual (study in process says we are at about +8)

    32. Student’s Opinions (N=258) • It is easier to hear the teacher • It is easier to listen when the teacher is talking • “I like it when the teacher uses the system” • “I feel that what I have to say is important” • “I feel listened to when I can use the microphone.” • Where it is used, all student respondents had only positive comments to make about the use of sound enhancement

    33. Teachers’ Opinions (4 large school districts) • Students are more attentive • Teachers can project their voices more easily • Teachers feel less fatigued at the end of the day (no need to talk loud or yell) • Teachers experience less vocal strain • Teachers report that students like it when they use the system • Teachers believe that students achieve at a higher level • Of all the equipment in the schools audio enhancement is ranked as first or second as ”the piece of equipment that has the greatest direct influence on learning”

    34. Does it matter where the speakers are located? • Choices: • Speaker in the front of the room • Speakers on the walls • Speakers in a cluster • Speakers in the ceiling • Any speaker is better than none • Provided they are turned up loud enough to improve the signal-to-noise ratio • The best placement is in the ceiling so as to be over the head of the children. • This arrangement provides the most consistent sound to every child in the room. • Other arrangements provide variable intensity as the child is moved away from the speaker

    35. Loudspeaker characteristics • Two-way loudspeakers • Woofers and tweeters • Results in an increasingly directive beam of sound with increasing frequency • Flat panel loudspeaker • Multiple excitation points • Spreads high frequencies well • Not as great for amplifying low frequencies

    36. Two-way loudspeakers – 1000 Hz

    37. Two-way loudspeakers – 2000 Hz

    38. Two-way loudspeakers – 3150 Hz

    39. Two-way loudspeakers – 4000 Hz

    40. Academic Findings • Ray, Sarff, and Glassford, 1984 • Higher scores on academic achievement tests • Gertel, McCarthy, and Schoff, 2004 • District improved academic achievement test scores by as much as one grade in one year • Especially helped Title I students and ESL students • More and better research is needed to establish this link between academics and classroom amplification conclusively

    41. Other Findings • Teacher absences due to loss of voice or fatigue is reduced • Student’s interest in and attention to teacher improved • Behavior problems are reduced • Fewer questions asked that are for clarification purposes • Increased student participation in class when a pass-around microphone is used

    42. SUMMARY • We need to do better in helping kids have an acoustic environment where they can have the best chance for success • The current debate between whether its better to modify classrooms to improve classroom acoustics or put a classroom amplification system is a distraction – we need both • We need more and better research to optimize all options to help remove the classroom as a barrier to learning