Question

8. -4 points SerPSE10 16.9 P041 My Notes Ask Your Teache A block with a speaker bolted to it is connected to a spring having spring constant k 19.0 N/m and oscillates as showrn in the figure below. The total mass of the block and speaker is 6.00 kg, and the amplitude of this unit's motion is 0.500 m. The speaker emits sound waves of frequency 120 Hz. (a) Detemine the highest frequencles heard by the person to the right of the speaker. (Glve your answer correct to 1 Hz.) (b) Detemine the lowest frequencies heard by the persun to the right of the speaker. (Give your arnswer correct to 1 Hz.) (c) If the maximum sound level heard by the person is 55.0 dB when the speaker is at its closest distance d 1.00 m from him, what is the minimum sound level heard by the observer? dD Need Help? Readt

Answer 1

Solution,

Angular frequency, w = sqrt(19/6) = 1.78 rad/sec

Maximum velocity, v = 0.5 x 1.78 = 0.89 m/s

A)

Highest frequency, f = 420 x 343/(343 - 0.88) = 421.09 Hz

B)

Lowest frequency, f = 420 x 343/(343 + 0.89) = 418.91 Hz

C)

55 = 10 log (P/4 pi x 1^2) x 10^12

P = 3.97 x 10^-6 W

Intensity = (3.97 x 10^-6)/(4 pi x 4) = 7.91 x 10^-8 W/m^2

Max sound level = 10 log(7.91 x 10^-8)/10^-12 = 48.98 dB

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