Chapter 18539P18.40The air in the auditory canal, about 3 cm long, can vibrate with a node at the closed end andantinode at the open end,withdN to Acm==34λso=012. mandfv≈3433msmkHz.A small-amplitude external excitation at this frequency can, over time, feed energyinto a larger-amplitude resonance vibration of the air in the canal, making it audible.P18.41For a closed box, the resonant frequencies will have nodes at both sides, so the permittedwavelengths will be Ln=12, n=123,,,…bg.i.e., Lnnvf22and fnvL=2.Therefore, with L=0860±m.and ′=L210.m, the resonant frequencies arefnn=206 Hzaffor L=0860.m for each nfrom 1 to 9and n84 5. Hzaffor L.m for each nfrom 2 to 23.P18.42The wavelength of sound is=vfThe distance between water levels at resonance isdvf=2∴==Rtr drvfπ222andtRf=22.P18.43For both open and closed pipes, resonant frequencies are equally spaced as numbers. The set of
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