Tutorial 3: Vibration and Sound

1. What is the velocity of longitudinal wave in water of bulk modulus, B= 2.0 x 10 9 Nm2

and the density 1.00 x 103 kg m-3? [v = 1414.2 m/s]

2. Calculate the length of a pipe that has a fundamental frequency of 240 Hz if the pipe is (i) closed at one end [0.36 m] (ii) open at both ends. [0.714 m]

3. The string of a violin has a fundamental frequency of 440 Hz. The length of the vibrating string is 32 cm, and has a mass of 0.35 g. What is the tension of the string?

4. One of the string on a guitar has a linear density of 5.28 x 10 -3 kg m-1 and is stretched with a tension of 226 N. The string produce the musical note E when vibrating its entire length at the fundamental frequency of 164.8 Hz.(i) What is the length of the string? [0.63 m](ii) Where must the player presses his finger so as to produce a note of

fundamental frequency 329.6 Hz? [0.313 m]

5. Sound is produced by a stretched string. The frequency of the second harmonic is 165 Hz. Calculate(a) The length of the string. [2.08 m](b) The frequency of 2nd overtone. [247.5 Hz]

[use the speed of sound = 330 m/s]

6. State what is the meaning of resonance, forced oscillation, natural frequency, intensity of sound, threshold of hearing and threshold of pain .

7. The intensity of sound at a distance of 5.0 m from the point source is 0.8 Wm -2. What will the intensity be at a distance of 10 m from the source?

8. In a rock concert, a dB meter is registering 130 dB when placed 2.8 m in front of a loudspeaker.(a) What is the power output of the speaker?(b) How far away would the sound level to be at 90 dB?