Aeroacoustic analysis of a bass-reflex loudspeaker using LES: Validation of 2D and 3D numerical model with experiment

Abstract

A bass-reflex loudspeaker has a port that amplifies low frequencies through Helmholtz resonance. However, high sound pressure levels can cause fluid flow near the port tip, leading to noise and distortion. Two-dimensional axisymmetric aeroacoustic analysis is commonly used to predict these non-linear phenomena; however, it has been reported to overestimate harmonic distortion. Presently, its accuracy has not been adequately verified through three-dimensional simulations or comparison with experimental results. This study validates the numerical model by comparing results from three- and two-dimensional analyses with experimental measurements on a straight tube port axisymmetric speaker model. In aeroacoustic analysis, large-eddy simulations are adopted, and the speaker model is acoustically driven at the Helmholtz resonance frequency. The results show that while the two-dimensional axisymmetric model overestimates the harmonic distortion and noise in the frequency response of far-field sound pressure, the three-dimensional model agrees well with the experiment up to the band where the harmonic distortion and port noise appear. This indicates that three-dimensional aeroacoustic analysis is necessary to accurately reproduce the fluid-induced distortion and noise of a bass-reflex port speaker.