sound

19 flashcards · Physics · by inquisitive learner

1. wave speed in solid?

   v=Yρv = \sqrt{Y \over \rho}v=ρY​ ​ v=v =v= speed of sound Y=Y =Y= Young's modulus, tensile stress/strain ρ=\rho =ρ= density of solid

2. wave speed in a liquid

   v=Bρv = \sqrt{ B \over \rho}v=ρB​ ​ v=v =v= speed of a longitudinal wave B=B =B= Bulk modulus of the liquid ρ\rhoρ == = density of liquid

3. wave speed in a gas

   v=γRTMv = \sqrt{\gamma R T \over M}v=MγRT​ ​ v=v =v= speed of sound in an ideal gas γ\gammaγ === ratio of heat capacities R=R =R= molar gas constant T=T =T= absolute temperature M=M = M= molar mass

4. sound intensity, β\betaβ ​

   β\beta β === (10dB)(10 dB)(10dB) log⁡\loglog II0I \over I_0I0​I​

5. Standing wave, stopped pipe formula

   fn=nv4Lf_n = \frac{nv}{4L}fn​=4Lnv​

6. Which harmonics are possible with a stopped pipe?

   Only odd harmonics are possible with a stopped pipe

7. With an open pipe, even and odd harmonics are possible.

8. sound wave intensity (in terms of displacement)

   III === 121 \over 221​ ρB\sqrt{\rho B}ρB ​ ω2\omega^2ω2 A2A^2A2

9. sound wave intensity (in terms of pressure amplitudes)

   II I === pmax22ρv\frac{p^2_{max}}{2 \rho v} 2ρvpmax2​​ === pmax22ρB\frac{p_{max}^2}{2 \sqrt{\rho B}}2ρB ​pmax2​​

10. frequency of a beat

    fbeatf_{beat}fbeat​ === faf_a fa​ −-− fbf_bfb​

11. What causes a beat?

    sounding two sounds of slightly different frequency

12. Doppler effect for a moving source and a moving listener

    fLf_LfL​ === v+vLv+vS\frac{v + v_L}{v+v_S}v+vS​v+vL​​ fSf_SfS​

13. What causes a shock wave?

    A shock wave is created by a sound source moving with a speed v_s grater than the speed of sound

14. Doppler effect

    the frequency shift that occurs when there is motion of a source of sound, a listener, or both, relative to the medium

15. interference

    the superposition of two waves in the same region of space

16. A closed end is a displacement node and a pressure antinode.

17. An open end is a displacement antinode and a pressure node

18. intensity of a sound wave [definition]

    the time average rate at which energy is transported by the wave, per unit area

19. speed of a transverse wave on a string

    vv v === Fμ\sqrt{\frac{F}{\mu}}μF​ ​ v=v =v= F=F =F= restoring force μ=\mu =μ= mass per unit length (inertia)