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THE SCIENCE AND APPLICATIONS OF ACOUSTICS - H. H. Arnold ...

THE SCIENCE AND APPLICATIONS OF ACOUSTICS - H. H. Arnold ...

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Problems for Chapter 3 69(a) the wave number(b) the wavelength(c) the root-mean-square pressure13. Convert the following rms pressures into decibels:(a) 20 μPa(b) 150 μPa(c) 1 kPa(d) 50 kPa14. Convert the following values expressed in dB into rms pressure:(a) 20 dB(b) 60 dB(c) 90 dB(d) 130 dB15. Two machines are running. One machine puts out 95 dB and the other 98 dB.What will be the combined sound pressure level in dB?16. Three machines are operating simultaneously. Their combined noise level is115 dB. One machine is shut down and noise level drops to 110 dB. Theremaining two machines have identical noise output. What is the noise outputof these two machines?17. An octave-band analysis of a machine yields the following results:Band-center frequencySPL (Hz)31.5 7263 76125 77250 72500 691000 842000 924000 838000 8016,000 78Find the total A-weighted sound level, the total B-weighted sound level, andthe total C-weighted sound level.18. The following SPL readings were taken of a noisy electric generator:Amount of time, sUnweighted SPL reading, dB15 73.422 79.420 88.912 91.9Find the equivalent sound pressure level L eq .

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