Wall treatments for aeroacoustic measurements in closed wind tunnel test sections

Aeroacoustic tests in closed wind tunnels are affected by reflections in the tunnel circuit and background noise. Reflections can be mitigated by lining the tunnel circuit. The present study investigates if lining exclusively the most accessible segment of a closed wind tunnel circuit, in particular the test section, is an approach which...

Beamforming in an annular duct with swirling flow

The fan-stator stage of turbofan engines is one of the main regions of broadband noise generation. The trend of increasing bypass ratios will make fan-stator broadband noise even more significant, as jet noise will decrease and nacelles will become shorter, thus leaving less space for liners. Within the fan-stator stage there are several...

Deterministic Model of AcousticWave Propagation in a Cavity

A mathematical model is proposed that evaluates acoustic propagation of turbulent boundary layer waves on top of a cavity enclosing a microphone. The goal is to optimize these cavity geometries to improve the signal-to-noise ratio of acoustic measurements. This model predicts the attenuation of the turbulent boundary layer fluctuations...

Improving source discrimination performance by using an optimized acoustic array and adaptive high-resolution CLEAN-SC beamforming

Beamforming performance can be improved in two ways: optimizing the location of microphones on the acoustic array and applying advanced beamforming algorithms. In this study, the effects of the two approaches are studied. An optimization method is developed to optimize the location of microphones for an acoustic array used in an open-jet...

inverse integration method for distributed sound sources

Most acoustic imaging methods assume the presence of point sound sources and, hence, fail to correctly estimate the sound emissions of distributed sound sources (such as trailing– edge noise). In this contribution, three integration techniques are suggested to overcome this issue based on models considering a single point source, a line source...

A Microphone Array Method Benchmarking Exercise using Synthesized Input Data

High-Resolution CLEAN-SC: Theory and Experimental Validation

Improving beamforming by optimization of acoustic array microphone positions

Assigning proper positions to microphones within arrays is essential in order to reduce or eliminate side- and grating lobes in 2D beamform images. In this paper an objective function is derived providing a measure for the presence of artificial sources. Using the global optimization method Differential Evolution an optimized microphone...

High-resolution clean-sc

In this paper a high-resolution extension of CLEAN-SC is proposed: HR-CLEAN-SC. Where CLEAN-SC uses peak sources in “dirty maps” to define so-called source components, HR-CLEAN-SC takes advantage of the fact that source components can likewise be derived from points at some distance from the peak, as long as these “source markers” are on the...

Using Global Optimization Methods for Acoustic Source Localization

Conventional beamforming is a common method to localize sound sources with a microphone array. The method, which is based on the delay-and-sum beamforming, provides an estimate value for the source strength at a given spatial position. It suffers from low spatial resolution at low frequencies, high side lobe levels and requires the user to...