Panasonic WX-LA20 Reference manual

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
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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.
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…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.
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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:
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