Source effects on attenuation in lined ducts. Part I: A statistically based computational approach

The influence of the source on acoustic attenuation in uniform and non-uniform ducts with mean flow is investigated. It is found that realizable attenuation is sensitive to details of the source that in applications such as broadband noise may be unavailable. In this investigation a statistical source model is proposed. A finite element simulation for propagation in non-uniform ducts with compressible mean flow with a random source description is developed. Probability density functions for transmitted acoustic power and attenuation are determined based on as many as 100,000 trials with random distributions of input modal power and phase. For cases with a moderate to large number of input modes, transmitted power and attenuation appear to follow simple statistical distributions. A comparison is made with limited experimental data, and in all cases considered measured attenuation is within or close to the predicted distribution.