Having grown tired of hearing loud music from passing cars at 3 am and the boist

Question

Having grown tired of hearing loud music from passing cars at 3 am and the boisterous yelling of bar patrons at closing, a professor buys a new home in a quiet neighborhood. She is, however, concerned about noise from freeway traffic. Using a sound intensity level meter,she stands at an overpass 13 above the passing cars and measures a maximum intensity level of 90 . If her new home is 2.4 from the freeway, what's the intensity level there? Assume no decrease due to absorption by air, trees, or other objects. Compare your result with a quiet whisper, 20 .

Explanation / Answer

example a) for open pipe, fundamental frequency f = V / 2L = 340 / 2x 1.2 = 141.67 Hz. first overtone f1 = 2 f = 283.33Hz, second overtone f2 = 3 f = 425 Hz, third overtone f3 = 4 f = 566.68 Hz. b) for closed pipe, the fundamental frequency f = V / 4L = 340 / 4 x1.2 = 70.833 Hz similarly, the frequencies of the overtones are f1 = 3 f = 212.5 Hz, f2 = 5 f = 354.165Hz, f3 = 7 f = 495.83 Hz. 2) for the open pine second harmonic f2 = 3 f = 3 x 330 = 990 Hz then as per your question, freqeuncy of second harmonic of open pipe = frequency of third harmonic of closed pipe ie., (f2) open = (f3) closed 990 = 3V / 4 Lc, where Lc is the length of closed pipe ie., Lc = 3 V / 4 x 990 = 3 x330 / 4 x 990 = 0.25 m similarly for open pipe f2 = V / Lo, where Lo is the length of the open pipe so that, Lo = V / 990 = 330 / 990 = 0.33 m.

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