(a) You are standing 3 m from a loudspeaker and measure the sound intensity leve

Question

(a) You are standing 3 m from a loudspeaker and measure the sound intensity level to be 60 dB, Calculate the sound intensity at that point. 2 _____ (b) How much does the sound level change by if you triple your distance from the source, answer in dB 3 _____ (c) A crude model of the human vocal tract treats it as a pipe closed at one end. Calculate the effective length of the vocal tract in a person whose fundamental tone (first harmonic) is 620 Hz. 2 _____ A rope is stretched between supports 9 m apart: it's under a tension of 60 N. If one end of the rope is tweaked, the resulting disturbance reaches the other end 0.45 s later. (d) What is the longest wavelength that will form a standing wave on the rope? 1 _____ (e) Calculate the lowest standing wave frequency. 2 _____

Explanation / Answer

2.)

dB = sound level = 60 dB

I = intensity of sound

Io = 10-12

using the equation

dB = 10 log10 (I/Io)

60 = 10 log10 (I/10-12)

I = 1 x 10-6 W/m2

b)

intensity depends inversly on distance

I1/I2 = r22/r12

(1 x 10-6)/I2 = (3/1)2

I2 = 1.11 x 10-7

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