Optimizing Optimizing Classroom Classroom

Acoustics and Acoustics and Classroom Classroom

Amplification Amplification SystemsSystems

Jeffery B. Larsen, PhD, Jeffery B. Larsen, PhD, CCC-ACCC-A

Utah State UniversityUtah State University

How Important is How Important is Classroom Listening?Classroom Listening?

Two-thirds of a student’s day Two-thirds of a student’s day consists of listening to and consists of listening to and participating in spoken participating in spoken communicationcommunication

Listening environments need to Listening environments need to be free of acoustic and non-be free of acoustic and non-acoustic barriersacoustic barriers

The Problem – Classroom The Problem – Classroom CommunicationCommunication

Classrooms can be difficult places for Classrooms can be difficult places for good communication to take placegood communication to take placeTEACHER TO STUDENT COMMUNICATIONTEACHER TO STUDENT COMMUNICATIONSTUDENT TO TEACHER COMMUNICATIONSTUDENT TO TEACHER COMMUNICATIONSTUDENT TO STUDENT COMMUNICATIONSTUDENT TO STUDENT COMMUNICATION

Communication in the classroom can Communication in the classroom can be difficult because of NOISE, be difficult because of NOISE, REVERBERATION, AND DISTANCEREVERBERATION, AND DISTANCE

Results of poor acoustics Results of poor acoustics on kids in school on kids in school

Poor performance on cognitive tasks Poor performance on cognitive tasks Cohen, Evans, Krantz, Sokols, & Cohen, Evans, Krantz, Sokols, &

Kelly, 1981Kelly, 1981Poor reading skillsPoor reading skills

Bonzaft & McCarthy, 1975; Green, Bonzaft & McCarthy, 1975; Green, Pasternack, & Shore, 1982; Gertel, Pasternack, & Shore, 1982; Gertel, McCarty, & Schoff, 2004McCarty, & Schoff, 2004

Poor math skillsPoor math skillsZentall & Shaw, 1980Zentall & Shaw, 1980

Poor attention and on-task behaviorPoor attention and on-task behaviorPalmer, 1998; Ryan, 2009Palmer, 1998; Ryan, 2009

One problem is One problem is reverberationreverberation

Reverberation occurs when sound Reverberation occurs when sound encounters a hard wallencounters a hard wallSound bounces around a roomSound bounces around a roomThe effect of reverberation is slurring The effect of reverberation is slurring

of speech as you move away from the of speech as you move away from the talkertalker

Normal listeners do best when Normal listeners do best when reverberation times are below .6 reverberation times are below .6 secondsseconds

Other ProblemsOther Problems

As talker moves away from the listener As talker moves away from the listener the signal decreases 6dB every time the the signal decreases 6dB every time the distance is doubled (distance is the least distance is doubled (distance is the least thought about problem)thought about problem) Start at 65dB HL, 6” from mouth, at 1 foot the Start at 65dB HL, 6” from mouth, at 1 foot the

intensity is 59dB, at 2 feet the intensity is intensity is 59dB, at 2 feet the intensity is 53dB, at 4 feet 47dB, at 8 feet 42 dB, and at 16 53dB, at 4 feet 47dB, at 8 feet 42 dB, and at 16 feet it is 36dBfeet it is 36dB

Noise is usually the biggest problemNoise is usually the biggest problemAt the back of a typical classroom with no At the back of a typical classroom with no

children present, the signal-to-noise ratio children present, the signal-to-noise ratio (SNR) would be +1 dB(SNR) would be +1 dB

With children present, the background With children present, the background noise is going to be at least 45dB, resulting noise is going to be at least 45dB, resulting in a SNR of about -3dBin a SNR of about -3dB

The Overall ProblemThe Overall Problem

When noise, distance, and reverberation When noise, distance, and reverberation are combined the result is speech is are combined the result is speech is difficult to understanddifficult to understandFor normal listeners a +6dB signal-to-noise For normal listeners a +6dB signal-to-noise

ratio leads to a 9% decrement in speech ratio leads to a 9% decrement in speech recognitionrecognition

When a reverberation time of .7seconds is When a reverberation time of .7seconds is combined with a signal-to-noise ratio of combined with a signal-to-noise ratio of +6dB word recognition scores decrease by +6dB word recognition scores decrease by as much as 20%as much as 20%

A student at the back of the room has a huge A student at the back of the room has a huge disadvantagedisadvantage

A study to demonstrate A study to demonstrate the overall effectthe overall effect

Young adult listeners (18-30 years old) Young adult listeners (18-30 years old) were asked to write down words while were asked to write down words while seated at desks in a quiet elementary seated at desks in a quiet elementary school classroom. school classroom.

Acoustic measurements showed that Acoustic measurements showed that the classroom had about 45 dB SPL of the classroom had about 45 dB SPL of noise when empty and the noise when empty and the reverberation time was 0.7 seconds. reverberation time was 0.7 seconds.

Results showed that those students Results showed that those students seated in the back row got scores seated in the back row got scores between 65% and 75%between 65% and 75%

So Why Don’t We So Why Don’t We ComplainComplain

It’s always been this wayIt’s always been this way

We figure out strategiesWe figure out strategiesWe get notes from the teacher/presenterWe get notes from the teacher/presenterWe read the text or the referencesWe read the text or the referencesWe talk to our friends about what was We talk to our friends about what was

discusseddiscussedWe sit close to the front of the roomWe sit close to the front of the room

We would never allow children to be We would never allow children to be taught in a dark room, but we will taught in a dark room, but we will allow them to be taught in a room in allow them to be taught in a room in which they can not hear wellwhich they can not hear well

WHAT SHOULD WE DO?WHAT SHOULD WE DO?

Change the acoustics or amplify the Change the acoustics or amplify the teacher? teacher?

I am not an audiologist who believes that I am not an audiologist who believes that amplification is amplification is alwaysalways the solution the solutionDispensing hearing aids can sometimes Dispensing hearing aids can sometimes

lead us to think this waylead us to think this way

Apparently the Acoustical Society of Apparently the Acoustical Society of America is also not thrilled about the America is also not thrilled about the amplification option as they released a amplification option as they released a position statement in 2006 claiming that position statement in 2006 claiming that classroom amplification, as a general classroom amplification, as a general policy, was a bad idea. policy, was a bad idea.

Concerns of the Concerns of the Acoustical SocietyAcoustical Society

Classroom amplification…Classroom amplification… will amplify bad acousticswill amplify bad acousticsequipment can break downequipment can break downwill add more sound to an already loud roomwill add more sound to an already loud roomdoes not address student to student does not address student to student

communication and student to teacher communication and student to teacher communicationcommunication

Improving the acoustic properties of the Improving the acoustic properties of the room is a permanent fix that does not room is a permanent fix that does not need repairs and will help everyone in need repairs and will help everyone in the roomthe room

Acoustic Modifications VS Acoustic Modifications VS Classroom AmplificationClassroom Amplification

As with everything else, there As with everything else, there are no silver bulletsare no silver bullets

The truth about what is best The truth about what is best probably lies somewhere probably lies somewhere between the Acoustical Society between the Acoustical Society and supporters of Classroom and supporters of Classroom AmplificationAmplificationOr maybe what is best is to do Or maybe what is best is to do

what both suggest… what both suggest…

Tips for Improving SNR Tips for Improving SNR without classroom without classroom

amplificationamplificationPlace rubber tips on chair and desk Place rubber tips on chair and desk

legslegs

Move kids away from high noise Move kids away from high noise sourcesource

Use acoustically treated furnitureUse acoustically treated furniture

Use doors with solid coresUse doors with solid cores

Install double paned windowsInstall double paned windows

Keep doors and windows shutKeep doors and windows shut

Improve classroom disciplineImprove classroom discipline

Study – Larsen & Blair Study – Larsen & Blair 20082008

Five different classrooms used in the studyFive different classrooms used in the study All were similar in size – all 4All were similar in size – all 4thth grade grade

30 to 35 feet deep30 to 35 feet deep 32 to 40 feet wide32 to 40 feet wide

All met ANSI standard for noise and All met ANSI standard for noise and reverberationreverberation RT 60 .32RT 60 .32 Noise Criteria 32 dBNoise Criteria 32 dB

Four teachers used classroom amplification, one Four teachers used classroom amplification, one did notdid not

A pass-around microphone was used in one A pass-around microphone was used in one classroom regularly, but either sporadically or classroom regularly, but either sporadically or not at all in the other three classroomsnot at all in the other three classrooms

ProceduresProcedures

A measuring microphone was placed on a A measuring microphone was placed on a tripod, positioned at the level of the tripod, positioned at the level of the child’s ear (placed near a child’s ear)child’s ear (placed near a child’s ear)

Measurements were made at 9 different Measurements were made at 9 different locations in each room (back center, left locations in each room (back center, left back, right back, left center, middle back, right back, left center, middle center, right center, front right, front left, center, right center, front right, front left, front center)front center)

Measurements were made in 10 minute Measurements were made in 10 minute incrementsincrements

The Time, Energy, Frequency (TEF) The Time, Energy, Frequency (TEF) system was used to obtain system was used to obtain measurementsmeasurements

SNRs with infrared SNRs with infrared classroom amplificationclassroom amplification

Obtained signal-to-noise ratios Obtained signal-to-noise ratios were on average between +13 to were on average between +13 to +20 dBA at every position +20 dBA at every position measured in the roomsmeasured in the rooms

One classroom was not fit with a One classroom was not fit with a classroom system and all other classroom system and all other teachers were asked to turn off teachers were asked to turn off their systems for 5 minutes during their systems for 5 minutes during the data collectionthe data collectionThe average signal-to-noise ratios were The average signal-to-noise ratios were

between +2 and +6 dBA without between +2 and +6 dBA without amplificationamplification

Actual Conditions Actual Conditions (unamplified)(unamplified)

Teacher asked children to read in a Teacher asked children to read in a random order around the classroom. random order around the classroom. Average sound level at the microphone Average sound level at the microphone

based on distance away from the based on distance away from the microphone.microphone.2 feet - 59dB2 feet - 59dB3 feet - 56 dB3 feet - 56 dB6 feet - 55 dB6 feet - 55 dB12 feet - 46 dB12 feet - 46 dB

There are times when the sound level There are times when the sound level is 13 dB less intense than at other is 13 dB less intense than at other times. times.

Results: Unamplified Results: Unamplified ClassroomClassroom

Teacher’s measured vocal intensity;Teacher’s measured vocal intensity;Front of the room at nearest student’s Front of the room at nearest student’s

desk was 58 dBA, with a range of 50 to desk was 58 dBA, with a range of 50 to 65 dB65 dB

Middle of the room at child’s desk, the Middle of the room at child’s desk, the level was 52 dB, again with a range of level was 52 dB, again with a range of 40 to 60 dB40 to 60 dB

At the most distant point, this is At the most distant point, this is measured as being 18 feet from the measured as being 18 feet from the most common place from which the most common place from which the teacher presents information, was 48 teacher presents information, was 48 dB with a range of 40 to 52 dBdB with a range of 40 to 52 dB

ImplicationsImplications

The results indicate that, without The results indicate that, without amplification, at the front of the room amplification, at the front of the room the average signal-to-noise ratio was the average signal-to-noise ratio was +15 with a range between +8 and +20+15 with a range between +8 and +20

In the middle of the room the S/N ratio In the middle of the room the S/N ratio was 8 dB with a range between +1 and was 8 dB with a range between +1 and +10+10

At the back of the room the S/N ratio At the back of the room the S/N ratio was 0 dB with a range of -15 to +6 dBwas 0 dB with a range of -15 to +6 dB

Implications Implications (continued)(continued)

Depending on where the child is seated at Depending on where the child is seated at any given time changes the amount and any given time changes the amount and quality of input availablequality of input availableThere are times when everything is audible There are times when everything is audible

and other times when information is not and other times when information is not audible at allaudible at all

The child who has any kind of hearing The child who has any kind of hearing problem is getting at best variable problem is getting at best variable auditory input (about 10% of the students)auditory input (about 10% of the students)

Remember this room meets ANSI Remember this room meets ANSI standardsstandards

Amplified ClassroomsAmplified Classrooms

In these classrooms all speakers were in In these classrooms all speakers were in the ceiling, providing direct sound to the the ceiling, providing direct sound to the children.children.

No matter where the child was seated in No matter where the child was seated in the room they were getting no less than a the room they were getting no less than a +10 signal-to-noise advantage.+10 signal-to-noise advantage.

When the hand-held microphone was When the hand-held microphone was used the same advantage was present for used the same advantage was present for the children as for the teacher, when not the children as for the teacher, when not used it was like the results in an used it was like the results in an unamplified room.unamplified room.

Observations without Observations without amplificationamplification

Many students did not listen well when Many students did not listen well when the teacher was talkingthe teacher was talking

After the teacher explained an assignment After the teacher explained an assignment on a poem and the children started to on a poem and the children started to work, the teacher noticed one child work, the teacher noticed one child looking around as if trying to discover looking around as if trying to discover what to do. When the teacher asked if what to do. When the teacher asked if she had started to look at the poem, the she had started to look at the poem, the student said, “Oh, I thought you were student said, “Oh, I thought you were talking about some kind of foam and I talking about some kind of foam and I didn’t know what you wanted us to do.”didn’t know what you wanted us to do.”

Little differences can make for a great Little differences can make for a great deal of confusiondeal of confusion

Logan City School Logan City School DistrictDistrict

Few classrooms have used systems for many Few classrooms have used systems for many yearsyears

Middle School was convinced that a system Middle School was convinced that a system for their school was importantfor their school was importantOpted not to repave a parking lot and used the Opted not to repave a parking lot and used the

money to purchase audio enhancement for all money to purchase audio enhancement for all instructional classroomsinstructional classrooms

Legislature provided money for technologyLegislature provided money for technologySuperintendent and Board decided to use Superintendent and Board decided to use

the bulk of the money to put audio the bulk of the money to put audio enhancement in every classroom in the enhancement in every classroom in the districtdistrict

Current Findings in Logan Current Findings in Logan City SchoolsCity Schools

Three-hundred five teachers (K-12) were Three-hundred five teachers (K-12) were surveyedsurveyed

One-hundred sixty-five responded (54%)One-hundred sixty-five responded (54%)

Questions and answers:Questions and answers: Do you have classroom amplification in your room?Do you have classroom amplification in your room?

93.9% yes; 6.1% no93.9% yes; 6.1% no Do you personally use the equipment?Do you personally use the equipment?

89.6% yes; 10.4% no89.6% yes; 10.4% no How often do you use the equipment?How often do you use the equipment?

All day, every day: 48.2%All day, every day: 48.2% When presenting information: 28.4%When presenting information: 28.4% Occasionally, for special presentations: 10.6%Occasionally, for special presentations: 10.6% When I think about it: 5.7%When I think about it: 5.7% Other: 7.1% (don’t use it when there are groups in the Other: 7.1% (don’t use it when there are groups in the

class)class)

Findings Findings (continued)(continued)

Do students use the microphone?Do students use the microphone? Yes, 59.1%Yes, 59.1% No, 40.9%No, 40.9%

How often and under what conditions?How often and under what conditions? Pass the microphone around during class discussions: 3.3%Pass the microphone around during class discussions: 3.3% Use the microphone when presenting in front of the class: Use the microphone when presenting in front of the class:

68.5%68.5% They use the microphone whenever they are talking to the They use the microphone whenever they are talking to the

whole class: 17.4%whole class: 17.4%

Do guests in the classroom use the system?Do guests in the classroom use the system? Yes: 62.3%; No: 37.7%Yes: 62.3%; No: 37.7%

How often and under what conditions? How often and under what conditions? When reading a story to the children: 29.5%When reading a story to the children: 29.5% When presenting information to children formally: 61.1%When presenting information to children formally: 61.1% Whenever a guest talks they use the system: 61.1%Whenever a guest talks they use the system: 61.1%

Findings Findings (continued)(continued)

What is your impression of the system?What is your impression of the system? I believe students are more attentive: 80.1%I believe students are more attentive: 80.1% I can control classroom behavior more effectively: 65.2%I can control classroom behavior more effectively: 65.2% It helps children in my class perform better: 53.9%It helps children in my class perform better: 53.9% The children like it when I use the system: 65.2%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 Because I don’t need to talk loud, or yell, I am less tired at

the end of the day: 66.0%the end of the day: 66.0% I don’t think that the system helps at all: 5.7%I don’t think that the system helps at all: 5.7%

How important do you think an amplification How important do you think an amplification system is in a classroom?system is in a classroom? Detrimental: 0%Detrimental: 0% Not too useful: 8.6%Not too useful: 8.6% Useful: 13.2%Useful: 13.2% Quite useful: 11.8%Quite useful: 11.8% Very useful: 35.5%Very useful: 35.5% Essential: 30.9%Essential: 30.9%

How to make it betterHow to make it betterPut it in the gym: 2 Put it in the gym: 2 Need hand-held Need hand-held

mic: 19mic: 19Cuts out all the Cuts out all the

time: 2time: 2Mic too heavy: 18Mic too heavy: 18Need smaller mic: Need smaller mic:

1515Needs to connect Needs to connect

to all systems: 13to all systems: 13Mic Mic

Reverberates/FeedReverberates/Feedback: 6back: 6

Too soft: 2Too soft: 2Dead places in Dead places in

the room: 1the room: 1Too loud: 1Too loud: 1I have a loud I have a loud

voice, don’t need voice, don’t need it: 2it: 2

I wear it for hard I wear it for hard of hearing child: 2of hearing child: 2

We need We need complete complete technology technology classrooms: 2classrooms: 2

How can we make it How can we make it better? (continued)better? (continued)

We need someone to maintain it We need someone to maintain it and teach about it: 3and teach about it: 3

I love it: 6I love it: 6

It is wonderful: 3It is wonderful: 3

Amazing: 1Amazing: 1

Nothing: 2Nothing: 2

Some ConsiderationsSome Considerations

Installation of classroom Installation of classroom amplification follows no systematic amplification follows no systematic procedureprocedureIn most states they are installed by In most states they are installed by

the companiesthe companiesThey are fit subjectivelyThey are fit subjectivelyWe are finding considerable We are finding considerable

variability across classrooms and variability across classrooms and we have had to retrofit a numberwe have had to retrofit a number

Some Considerations Some Considerations (cont.)(cont.)

Many teachers will not wear the Many teachers will not wear the systemssystemsToo loudToo loudI speak loudly alreadyI speak loudly alreadyDoes not work wellDoes not work wellUnwieldyUnwieldyI rarely teach the whole class at one I rarely teach the whole class at one

timetimeWhat to do when it does not work wellWhat to do when it does not work wellI forget to put it onI forget to put it onMicrophone is too heavy and gives me Microphone is too heavy and gives me

a headachea headache

Unresolved issues for Unresolved issues for classroom amplificationclassroom amplification

We know that anything is better We know that anything is better than nothing (unless it is not loud than nothing (unless it is not loud enough to make a difference)enough to make a difference)

We don’t know what is truly feasible We don’t know what is truly feasible in a classroom (research says +15)in a classroom (research says +15)ComfortComfortFeedbackFeedbackOverflowOverflow

We are not sure what is usual (study We are not sure what is usual (study in process says we are at about +8)in process says we are at about +8)

Student’s Opinions Student’s Opinions (N=258)(N=258)

It is easier to hear the teacherIt is easier to hear the teacher

It is easier to listen when the teacher is It is easier to listen when the teacher is talkingtalking

““I like it when the teacher uses the system”I like it when the teacher uses the system”

““I feel that what I have to say is important”I feel that what I have to say is important”

““I feel listened to when I can use the I feel listened to when I can use the microphone.”microphone.”

Where it is used, all student respondents had Where it is used, all student respondents had only positive comments to make about the use only positive comments to make about the use of sound enhancementof sound enhancement

Teachers’ Opinions (4 Teachers’ Opinions (4 large school districts)large school districts)

Students are more attentiveStudents are more attentive

Teachers can project their voices more easilyTeachers can project their voices more easily

Teachers feel less fatigued at the end of the day (no Teachers feel less fatigued at the end of the day (no need to talk loud or yell)need to talk loud or yell)

Teachers experience less vocal strainTeachers experience less vocal strain

Teachers report that students like it when they use the Teachers report that students like it when they use the systemsystem

Teachers believe that students achieve at a higher levelTeachers believe that students achieve at a higher level

Of all the equipment in the schools audio enhancement Of all the equipment in the schools audio enhancement is ranked as first or second as ”the piece of equipment is ranked as first or second as ”the piece of equipment that has the greatest direct influence on learning”that has the greatest direct influence on learning”

Does it matter where the Does it matter where the speakers are located?speakers are located?

Choices:Choices:Speaker in the front of the roomSpeaker in the front of the roomSpeakers on the wallsSpeakers on the wallsSpeakers in a clusterSpeakers in a clusterSpeakers in the ceilingSpeakers in the ceiling

Any speaker is better than noneAny speaker is better than noneProvided they are turned up loud enough to Provided they are turned up loud enough to

improve the signal-to-noise ratioimprove the signal-to-noise ratioThe best placement is in the ceiling so as to The best placement is in the ceiling so as to

be over the head of the children.be over the head of the children. This arrangement provides the most This arrangement provides the most

consistent sound to every child in the room.consistent sound to every child in the room. Other arrangements provide variable Other arrangements provide variable

intensity as the child is moved away from the intensity as the child is moved away from the speakerspeaker

Loudspeaker Loudspeaker characteristicscharacteristics

Two-way loudspeakersTwo-way loudspeakersWoofers and tweetersWoofers and tweetersResults in an increasingly directive beam Results in an increasingly directive beam

of sound with increasing frequencyof sound with increasing frequency

Flat panel loudspeakerFlat panel loudspeakerMultiple excitation points Multiple excitation points Spreads high frequencies wellSpreads high frequencies wellNot as great for amplifying low Not as great for amplifying low

frequenciesfrequencies

Two-way loudspeakers – Two-way loudspeakers – 1000 Hz1000 Hz

Two-way loudspeakers – Two-way loudspeakers – 2000 Hz2000 Hz

Two-way loudspeakers – Two-way loudspeakers – 3150 Hz3150 Hz

Two-way loudspeakers – Two-way loudspeakers – 4000 Hz4000 Hz

Academic FindingsAcademic Findings

Ray, Sarff, and Glassford, 1984Ray, Sarff, and Glassford, 1984Higher scores on academic achievement testsHigher scores on academic achievement tests

Gertel, McCarthy, and Schoff, 2004Gertel, McCarthy, and Schoff, 2004District improved academic achievement test District improved academic achievement test

scores by as much as one grade in one yearscores by as much as one grade in one yearEspecially helped Title I students and ESL Especially helped Title I students and ESL

studentsstudents

More and better research is needed to More and better research is needed to establish this link between academics and establish this link between academics and classroom amplification conclusivelyclassroom amplification conclusively

Other FindingsOther Findings

Teacher absences due to loss of voice Teacher absences due to loss of voice or fatigue is reduced or fatigue is reduced

Student’s interest in and attention to Student’s interest in and attention to teacher improvedteacher improved

Behavior problems are reducedBehavior problems are reduced

Fewer questions asked that are for Fewer questions asked that are for clarification purposesclarification purposes

Increased student participation in class Increased student participation in class when a pass-around microphone is when a pass-around microphone is usedused

SUMMARYSUMMARY

We need to do better in helping kids have We need to do better in helping kids have an acoustic environment where they can an acoustic environment where they can have the best chance for successhave the best chance for success

The current debate between whether its The current debate between whether its better to modify classrooms to improve better to modify classrooms to improve classroom acoustics or put a classroom classroom acoustics or put a classroom amplification system is a distraction – we amplification system is a distraction – we need bothneed both

We need more and better research to We need more and better research to optimize all options to help remove the optimize all options to help remove the classroom as a barrier to learningclassroom as a barrier to learning