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 ? What is the sound intensity at the threshold of pain (120 dB) ?

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.

Thresholds for hearing and pain

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

Weakest sound heardWeakest sound heard 0dB0dB Normal conversation (3-5')Normal conversation (3-5') 60-70dB60-70dB Telephone dial toneTelephone dial tone 80dB80dB City Traffic (inside car)City Traffic (inside car) 85dB85dB Train whistle at 500'Train whistle at 500' 90dB90dB Subway train at 200'Subway train at 200' 95dB95dB Level at which sustained exposure may result in hearing lossLevel at which sustained exposure may result in hearing loss dB dB Power mowerPower mower 107dB107dB Power sawPower saw 110dB110dB Pain beginsPain begins 125dB125dB Pneumatic riveter at 4'Pneumatic riveter at 4' 125dB125dB Jet engine at 100'Jet engine at 100' 140dB140dB Death of hearing tissueDeath of hearing tissue 180dB180dB Loudest sound possibleLoudest sound possible 194dB194dB 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 dB Power mower 107dB Symphonic music peak dB Pain begins 125dB Jet engine at 100‘ 140dB Rock concert peak 150dB Death of hearing tissue 180dB