Noise Sources for Duct Acoustics Simulations: Broadband Noise and Tones

Abstract

Although simulating acoustic tones propagating in ducts or waveguides is relatively well established, broadband noise is composed of a wide range of frequencies, and at each frequency, the acoustic energy is generally distributed over all the cut-on modes of the duct. Simulating the propagation and absorption of broadband noise is further complicated by the random nature of the sound field. This paper presents a computational method to generate truly broadband, multimode noise in a time-domain simulation. This method is equally applicable to the generation of deterministic tones. For broadband noise, we devise a stochastic source that is tailored to radiate a sound field characterized by the cross-correlation between mode amplitudes. This stochastic source allows to compute in a single time-domain simulation the complete spectrum of the broadband multimode sound field. Unlike other methods proposed for predicting broadband noise, there is no need to perform several simulations for different realizations. Results are presented for broadband noise alone as well as for a combination of tones and broadband noise.