Acoustic imaging of sound sources - a junior year student research project

In this paper the development of an acoustic camera within the scope of an undergraduate research project is presented, with a particular consideration of the projectpsilas embedding into the curriculum. At the start of the project sixteen microphones and a data acquisition device with the capability of sampling all channels simultaneously were available. In order to build an acoustic camera out of it, the students had to develop both the hardware for a microphone array and the software for the generation of an acoustic image. The physical principle that was made use of is the phase information present in the signals picked up by spatially separated microphones. For the computation of the acoustic image two different algorithms were employed. Delay-and-sum beamforming was used for the determination of the sound intensity as a function of the direction of arrival. And multiple signal classification was implemented in order to enhance the microphone arraypsilas spatial resolution. For a flexible mounting of the microphones a portable tripod was designed, thus enabling a variety of microphone arrangements. The functionality of the acoustic camera is demonstrated by a spatially resolved noise measurement of a combustion engine in its engine compartment.