Panasonic WX-LA20 Manuale di riferimento

The Impact of Sound-Field Amplification

(Summary)

Dillon, Harvey and Robyn Massie

Australian J of Education, 50(1):62-77 2006

Introduction

The goal of classroom instruction is comprehension. In order for speech to be

comprehended, the individual must be able to hear well enough to discriminate

the word-sound distinctions of individual phonemes. Poor comprehension in the

classroom is not, however, limited to those with hearing loss. Young listeners

perform more poorly in noisy situations than do adults and the ability to listen in

noise is not fully developed until adolescence. A child’s auditory brain is not like

an adult’s until about the age of 15; therefore, children cannot rely on years of

language and learning experiences to fill in the gaps of missed information.

National Acoustic Standards in the United States require classrooms to meet the

following acoustical standards:

Noise Level: 35 dBA

Reverberation Time: < 0.6 seconds (medium-size rooms) < 0.7 seconds (large-

size rooms)

Signal to Noise Ratio: +15 dB. Studies have shown that actual classroom

conditions range from 41 to 69 dBA which lead to unfavorable Signal to Noise

ratios and reverberation times.

Communication in Cross-Cultural Classrooms

Individuals for whom English is a second language (ESL) experience greater

speech perception difficulties. ESL students performance has shown to be poorer

across most classroom listening conditions. Understanding spoken English in

noise is related to the individual’s proficiency with the English language.

Sound-field Amplification

Sound-field amplification is an exciting educational tool that allows control of the

acoustic environment in a classroom allowing acoustic accessibility to teacher

instruction for all children in the room. Originally designed as an assistive

Continued…

…cont’d

technology for children with mild hearing loss, research over the

past twenty years has shown that the benefits of sound-field amplification include

improved academic achievement, speech recognition, attending skills, and

learning behaviors.

Recent studies have shown that sound-field amplification technology enhances

classroom learning. Students in amplified classrooms demonstrated

improvement in listening and learning behaviors and progressed at a faster rate

than tier grade-alike peers in unamplified rooms. Other findings include reduction

in special education referrals, greater literacy gains, improved reading test scores

and greater development of phonemic awareness skills. Benefits were also

shown for teachers including reduced vocal strain and fatigue, increased ease of

teaching, increased versatility of instructional techniques and increased teacher

mobility.

Of the few studies done on cross-cultural classrooms, it was found that non-

native English children with normal hearing sensitivity was significantly improved

at speaker-listener distances of 12 and 24 feet and significant improvements

were shown in speech intelligibility.

The benefit of the dual-channel transmission system is that two teachers can use

the system at the same time, or the second microphone can be handed around

among the children during interactive class sessions. Microphone techniques

need to be demonstrated to teachers so they can learn strategies to utilize both

single and dual channel transmission options more effectively. The passaround

microphone for students can “enhance teacher effectiveness”. Teachers may

need to use different teaching strategies to best take advantage of sound-field

amplification technology.

Study

The purpose of this study is to examine how sound-field amplification effects

reading, writing and numeracy on children in mainstream cross-cultural

classroom. The majority of the participants were ESL students. A major

component of the study was to identify the patterns of use and range of

additional benefits.

Continued…

…cont’d

Participants

12 2nd Grade Classes

128 male

114 female

Mean age: 6 years 8 months

43% were from an ethnic background (Vietnamese, Samoan, Spanish,

Aboriginal and Torres Strait Islander)

Equipment

NAL Twin FM Sound-field Amplification Systems (Type 3032) featuring:

2 Lapel Microphone/Transmitters

Volume controls set to the highest level

4 - 8 Ohm Speakers mounted on the wall

Teachers were given an information booklet outlining the project and rationale of

using sound-field amplification. Teachers also received in-service training

addressing classroom acoustics, speech perception difficulties, suggestions for

management and practical demonstration of the sound-field amplification

systems.

Audiological Assessment

Hearing screenings were performed on all the subjects at the beginning of the

school year. The same screenings were performed on 25% of the children mid-

year and at the end of the year.

Classroom Acoustic Measurements

Classroom acoustic measurements were carried out in each of the twelve

classrooms. The following calculations were made:

a) ambient noise levels

b) classroom RT measurements,

c) S/N ratios in unamplified classrooms

d) S/N ratios in amplified classrooms.

Occupied classroom noise measurements and S/N ratio calculations were

obtained during class time when the teachers and children were in their usual

positions during instructional teaching.

Continued….

…cont’d

Design

Each of the twelve classrooms acted as its own control. The two experimental

conditions were unamplified “OFF” and amplified “ON”. Classrooms 1-4 began

the school year in the “ON” condition (two classrooms had one microphone;

two classrooms had two microphones). Classrooms 5-8 began the school year in

the “OFF” condition. At the mid-point of the school year the classrooms switched

listening conditions.

Classrooms 9-12 alternated between single-channel and dual-channel

transmission options. Ninety-two percent of teachers used the amplification

systems every day. Forty-two percent of teachers used amplification for more

than one hour but less than two hours each time. Twenty-five percent of

teachers reported using the systems for more than two hours each time.

Results

To reduce inflated results from outlying sources, the mean skill increases were

calculated to get a true indication of how many skills were gained through

amplification. Once the means were established, it the final results are a direct

result of increases due to amplification and not other sources. The following

graphs indicate the actual gain in skills from the use of classroom amplification:

classroomaudio@us.panasonic.com

877.268.7215

ENGLISH

Reading Writing Number

-2

Skill increase

ENGLISH +

Reading Writing Number

NO ENGLISH

Reading Writing Number

System On

System Off

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