Perception of sound waves Pressure fluctuation versus time for a Loudness(pressure amplitude) clarinet with funda- mental frequency 斤=233Hz =4.29ms Pitch (high or low frequency) ·Timbre(淳厚圆润柔和 Harmonic content of the sound in (a) 清脆尖锐干涩温暖) (b) 05所10听 20听3040 Pressure fluctuation versus time for an alto recorder with fundamental frequency 万=523Hz T=1.91ms Noise(all frequencies) Harmonic content of the sound in (c) (d) 05f10所20听30听40听 Copyright2008 Pearson Education,inc.pubishing as Paarson Addison-Wesey
Perception of sound waves • Loudness (pressure amplitude) • Pitch (high or low frequency) • Timbre(淳厚 圆润 柔和 清脆 尖锐 干涩 温暖) • Noise(all frequencies)
Speed of sound △F=F(x+△x)-F(x) AreaA =A[S(x+△x)-S(x)] A force called a stress is applied to section of rod. =A△ as(x) x+△r Ox (a) a2z(x,）=A△ Original position Displaced position pA△x as(x) 0t2 Ox The stress above results in a displacement of rod or a strain. z(x) (x+△x) e==(x+Ax)-=(x) az (b) △x 8x →S=Y 0z Y= stress S Ox strain e a2S(x)_1∂2z(x,) Ox2 In solid:v= P
x S x A x A S x x S x F F x x F x [ ( ) ( )] ( ) ( ) x S x A x t z x t A x ( , ) 2 2 x z S Y e S strain stress Y x z x z x x z x e 2 2 2 2 1 ( , ) t z x t x Y S x Speed of sound ρ Y In solid : v