Finite-amplitude standing waves in rigid-walled tubes

Abstract

Finite-amplitude standing wave effects in air at ambient conditions contained in rigid-walled cylindrical tubes with large length to diameter ratios were experimentally investigated. These results were compared to a perturbation solution of the one-dimensional non-linear acoustic wave equation which incorporates the dissipative effects due to viscous and thermal energy losses at the walls. The lowest resonance frequencies of the tubes ranged from 62.5 Hz to 1 kHz, and sound pressure levels (based on the fundamental) ranged up to 160 dB. The finite-amplitude distortion was in excellent agreement almost up to the onset of shock. A detailed investigation of small amplitude attenuation in standing wave tubes was conducted and compared with the Kirchhoff equations. Agreement within one percent was obtained when consideration was given to the numerical analysis correction and end-effect losses.