lec15 - IT OCW. Sound and Hearing Sound vibrating medium...

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Sound and Hearing Sound ± vibrating medium ± longitudinal wave ± v = λ x f Vibrating body (sound source) Wavelength = Amplitude Frequency = f Amplitude Wavelength = Velocity of propagation v Image by MIT OCW. Image by MIT OCW.
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Sound and Hearing Sound ± pressure p in Pa ± intensity I in W/m 2 ± thresholds of audibility and pain (at 1000 Hz) General relation: I = p 2 / ( ρ v) For standard conditions: p = 20 (I±)± I o = 1 pW/m 2 (i.e. 10 -12 W/m 2 )I pain =1 ±W/m 2 p o = 20 μ Pa = 2 10 -5 Pa p pain = 20 Pa
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Sound and Hearing Sound field ± Point source ± Cylindrical source attenuation with distance ± Large source R 1 R 2 R L L >> λ
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Sound field ± Obstacles calculation of characteristic frequency f 0 f o = d v / (2 H 2 ) H d = min(d 1 ,d 2 ) d 1 d 2 source Barrier Reflected Sound Direct Sound Bright Zone Straight Path Shadow Zone Image by MIT OCW. High frequency: acoustic shadow Low frequency: diffraction Image by MIT OCW.
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lec15 - IT OCW. Sound and Hearing Sound vibrating medium...

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