Basic Classroom Acoustics

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Basic Classroom Acoustics

  1. 1. Basic Considerations in Classroom Acoustics
  2. 2. Acoustic Factors to Consider● Distance between talker and listener ● Level of signal ● Signal-to-noise ratio ● Reverberation ● Physical Barriers
  3. 3. 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
  4. 4. 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
  5. 5. Reverberation● Reflections – early and late● Early reflections ~80 ms or less● Late reflections more than 80 ms
  6. 6. 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
  7. 7. Classroom Acoustics -Effective Noise-
  8. 8. Classroom Acoustics -Effective Noise-Reverberation timeof room determinesequivalent noiselevel for latereflections
  9. 9. Classroom Acoustics -Effective Noise-Reverberation timeof room determinesequivalent noiselevel for latereflections
  10. 10. Classroom Acoustics -Effective Noise-
  11. 11. Classroom Acoustics -Effective Noise-

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