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Loudness

Loudness. Power, intensity, intensity level,. Power and intensity. Sound detector. 1J=1Nm. Energy: will accumulate in time. 1W=1J/s. Power: rate of energy transfer, stays the same. Dependent on detector area. 1 W/m 2 =1J/sm 2. Intensity: rate of energy transfer per area.

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Loudness

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  1. Loudness Power, intensity, intensity level,

  2. Power and intensity Sound detector 1J=1Nm Energy: will accumulate in time 1W=1J/s Power: rate of energy transfer, stays the same Dependent on detector area 1 W/m2=1J/sm2 Intensity: rate of energy transfer per area

  3. Inverse Square Law B radius B = 2 radius A A area B = 4 area A intensity B = 1/4 intensity A

  4. Sound intensity level • Physiological response to loudness does not simply scale with intensity • Loudest possible sound waves: • 1 Watt / square meter • Softest perceptible sound: • 10-12 Watt / square meter • Chosen as reference intensity

  5. Sound intensity level • 1 Decibel=1/10 bel (Alexander Graham Bell) • “1 bel” for a sound means: • the ratio of its intensity to a reference is 10:1 Decibel measure the relation between two sounds, not an amount of sound.

  6. Chart of sound levels

  7. Sound level and music • More than 50 dB (eliminates background) • Above 100 dB: damage to ears • ffff (95 dB) to ppp (50 dB) • More likely 60…85 dB for symphony concert • Determined by range of instruments (typically < 40dB) • Wood-wind: only 10 dB dynamic range

  8. Sound levels and multiple sources What is the resulting sound level L? Violinist A IA=60 dB Violinist B IB=60 dB 10-6 W/m2 10-6 W/m2 (60+Log2) dB = 63 dB 2∙10-6 W/m2

  9. Sound levels and multiple sources 10-6 W/m2 10-6 W/m2 10-6 W/m2 10-6 W/m2 10-6 W/m2 10-6 W/m2 10-6 W/m2 10-6 W/m2 10-6 W/m2 10-6 W/m2 What is the resulting sound level L? 10∙10-6 W/m2 10-5 W/m2 70 dB

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