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Logarithms

Logarithms. Powers of 10. log ab = log a + log b log 1/a = -log a. How to measure loudness. Intensity (I) ~ (pressure difference) 2. W/m 2 = J/m 2 s. minimum audible sound. Examples: What if we double the sound intensity ? How much more intense is a sound 10 db louder ?

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Logarithms

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  1. Logarithms Powers of 10

  2. log ab = log a + log b log 1/a = -log a

  3. How to measure loudness Intensity (I) ~ (pressure difference)2 W/m2 = J/m2s minimum audible sound

  4. Examples: What if we double the sound intensity ? How much more intense is a sound 10 db louder ? What is the sound intensity at the threshold of pain (120 dB) ?

  5. The point of using the decibel scale is the Weber-Fletcher “Law” A doubling of volume feels like the same increase, regardless of how much increase in intensity actually occurred.

  6. Thresholds for hearing and pain

  7. Decibel scale measures the intensity of the sound Phons scale measures the intensity compared to the minimum at each frequency Sone scale measure the subjetive loudness

  8. Environmental Noise Weakest sound heard 0dB Normal conversation (3-5') 60-70dB Normal piano 60-70dB Telephone dial tone 80dB City Traffic (inside car) 85dB Walkman on 5/10 94dB Subway train at 200‘ 95dB Level at which sustained exposure may result in hearing loss 90 - 95dB Power mower 107dB Symphonic music peak 120-137dB Pain begins 125dB Jet engine at 100‘ 140dB Rock concert peak 150dB Death of hearing tissue 180dB

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