Basic Classroom Acoustics
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Transcript of Basic Classroom Acoustics
Basic Considerations in Classroom Acoustics
Acoustic Factors to Consider
● Distance between talker and listener● Level of signal● Signal-to-noise ratio● Reverberation● Physical Barriers
Effective Signal and Effective Noise● 4 primary considerations for relating speech perception to
room acoustics
– Effective signal is both incident speech signal and its early reflections
– Effective noise is both background noise and late reflections of speech signal
– Dynamic range of speech ~30 dB in any given frequency band
– Proportion of speech signal exceeding effective noise allows for estimate of speech perception independent of patient characteristics
Effective Signal and Effective Noise● 4 primary considerations for relating speech perception to
room acoustics
– Effective signal is both incident speech signal and its early reflections
– Effective noise is both background noise and late reflections of speech signal
– Dynamic range of speech ~30 dB in any given frequency band
– Proportion of speech signal exceeding effective noise allows for estimate of speech perception independent of patient characteristics
Reverberation
● Reflections – early and late
● Early reflections ~80 ms or less
● Late reflections more than 80 ms
Reverberation and Distance● Early reflections contribute to effective signal
● Early reflections important for speech perception because they are constant in level throughout room.
● Direct signal follows inverse distance law – sound pressure is inversely proportional to the distance from the sound source
p 1/r∝
● Sound pressure decreases by 6.02 dB for every doubling of distance from the sound source
Classroom Acoustics-Effective Noise-
Classroom Acoustics-Effective Noise-
Reverberation time of room determines equivalent noise level for late reflections
Classroom Acoustics-Effective Noise-
Reverberation time of room determines equivalent noise level for late reflections
Classroom Acoustics-Effective Noise-
Classroom Acoustics-Effective Noise-