Acoustic source localization

Acoustic source localization is the task of locating a sound source given measurements of the sound field. The sound field can be described using physical quantities like sound pressure and particle velocity. By measuring these properties it is (indirectly) possible to obtain a source direction.

Traditionally sound pressure is measured using microphones. Microphones have a polar pattern describing their sensitivity as a function of the direction of the incident sound. Many microphones have an omnidirectional polar pattern which means their sensitivity is independent of the direction of the incident sound. Microphones with other polar patterns exist that are more sensitive in a certain direction. This however is still no solution for the sound localization problem as one tries to determine either an exact direction, or a point of origin. Besides considering microphones that measure sound pressure, it is also possible to use a particle velocity probe to measure the acoustic particle velocity directly. The particle velocity is another quantity related to acoustic waves however, unlike sound pressure, particle velocity is a vector. By measuring particle velocity one obtains a source direction directly. Other more complicated methods using multiple sensors is also possible. Many of these methods use the time difference of arrival (TDOA) technique.

Some have termed acoustic source localization an "inverse problem" in that the measured sound field is translated to the position of the sound source.

Different methods for obtaining either source direction or source location are possible.

The simplest but still a relatively new method is to measure the acoustic particle velocity using a particle velocity probe. The particle velocity is a vector and thus also contains directional information.

The traditional method to obtain the source direction is using the time difference of arrival (TDOA) method. This method can be used with pressure microphones as well as with particle velocity probes.

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