1. You drop a stone down a well that is 6.65 m deep. How long is it before you hear the splash? The speed of sound in air is 343 m/s. Ans:- 1.18 s.
2. The sound level in decibels is typically expressed as β = 10 log(I/I0), but since sound is a pressure wave, the sound level can be expressed in terms of a pressure difference. Intensity depends on the amplitude squared, so the expression is β = 20 log(P/P0), where P0 is the smallest pressure difference noticeable by the ear: P0 = 2. 10-5 Pa. A loud rock concert has a sound level of 109 dB, find the amplitude of the pressure wave generated by this concert. Ans:- 5.64 Pa
3. Two sources, A and B, emit a sound of a certain wavelength. The sound emitted from both sources is detected at a point away from the sources. The sound from source A is a distance d from the observation point, whereas the sound from source B has to travel a distance of 4λ. What is the largest value of the wavelength, in terms of d, for the maximum sound intensity to be detected at the observation point? (Assume source A is farther from the observation point than source B.) If d = 12.6 m and the speed of sound is 340 m/s, what is the frequency of the emitted sound? Ans:- (d/2), 135 Hz.
4. A plane flies at Mach 1.5, and its shock wave reaches a man on the ground 21 s after the plane passes directly overhead. (a) What is the Mach angle? (b) What is the altitude of the plane? The speed of the plane is 514.5 m/s. Ans:- 41.8 degree, 9.66 km
5. A standing wave in a pipe with both ends open has a frequency of 444 Hz. The next higher harmonic has a frequency of 626 Hz. (a) Determine the fundamental frequency. (b) How long is the pipe? Ans:- 182 Hz, 0.942 m.
6. An observer stands between two sound sources. Source A is moving away from the observer, and source B is moving toward the observer. Both sources emit sound of the same frequency. If both sources are moving with a speed, vsound/9, what is the ratio of the frequencies detected by the observer? Ans:- 0.8
7. At a distance of 29 m from a sound source, the intensity of the sound is 62 dB. What is the intensity (in dB) at a point 1.9 m from the source? Assume that the sound radiates equally in all directions from the source. Ans:- 85.7 dB
8. A source traveling to the right at a speed of 10.80 m/s emits a sound wave at a frequency of 110.0 Hz. The sound wave bounces off of a reflector, which is traveling to the left at a speed of 5.15 m/s. What is the frequency of the reflected sound wave detected by a listener back at the source? (Use 343 m/s as the speed of sound.) Ans:- 121 Hz