Panasonic WX-LA20 User manual

Hearing and Listening in a Typical
Classroom (Summary)
Catherine V. Palmer
Language, Speech, and Hearing Services in Schools July, 1997
Vol. 28, pp. 213-217
Children spend 45% of the school day engaged in listening activities such as
talking, asking questions, and multimedia presentations. The failure we make is
assuming that all normal hearing students can hear what is spoken in typical
classrooms. There are six issues that arise when considering if the students can
hear the necessary information in the classroom.
1. Teacher’s Delivery: Teachers must speak 15 dB louder than background
noise; however, this is rarely achieved. Many teachers are not able to produce a
signal that can be heard over background noise and attempting to do so may
result in vocal fatigue. This causes teachers to miss multiple days per year.
2. Noise in the Classroom: Classroom noise levels should not exceed 35 dBA;
however, typical classroom noise levels range from 41 to 51 dBA. In the past few
decades research has shown little to no improvement in classroom noise levels.
The most important characteristic of relevant to effective communication is signal
to noise ratio (SNR). Because young listeners (with normal hearing) require
higher SNRs, it is recommended that classrooms have an SNR of +15 dBA
.
3. Reverberation: Classroom reverberation times should not exceed 0.4
seconds; however, the majority of classrooms have reverberation times between
0.4 and 1.25 seconds. Reverberation masks (blurs) direct sound energy. Higher
reverberation times cause poorer understanding.
4. Distance: Children should be within approximately 6 feet of the teacher in
order to receive maximum intelligibility; however, achieving this distance for all
children is impossible due to typical class sizes. Speaker to listener distance
(SLD) greatly impacts the direct sound field. Children with normal hearing who sit
in the middle or back of the classroom have difficulty receiving the speech
signal compared to students in the front row.
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… cont’d
5. The Student’s Hearing: Ideally, students would experience consistently
normal hearing; however, on any given day about 43% of primary level children
fail a pure-tone screening at 15 dB and/or immittance screening. It is incredibly
costly and impractical to monitor every child’s hearing due to students who may
experience episodes of middle ear infections.
6. The Student’s Experience: Adults can miss parts of a message and fill them
in using their life and language experience; however, the young student is
learning from the messages spoken in the classroom and has limited life
experience to use to fill in the blanks. An unnecessary amount of
energy is expended to just hear the signal. This energy could be better spent
thinking about what is taught, integrating the information and applying the
information into their lives.
Sound field equalization provides a solution to the listening issues by amplifying
the teacher’s voice through speakers strategically placed in the classroom.
Sound field equalization systems are the most cost-effective and acceptable
technology for facilitating classroom listening. Benefits of using sound field
equalization include:
• Reduced student fatigue
• Improved academic achievement
• Increased positive behavior
• Reduced teacher fatigue
• More positive, energetic teaching
Classroomaud[email protected]asonic.com
877.268.7215