8.9 Localizing the height or distance of a source

Problem

Read this section if you wish to determine

The height of a sound source, as well as its direction on a horizontal surface
The distance to a sound source as well as the direction it is coming from.

Solution

The current LocalizeMUSIC module estimates only the direction of sound on a horizontal surface. To also estimate the height of a sound source and its distance from a microphone array, the program of the module must be remodeled. Since the MUSIC algorithm itself does not assume angles on a horizontal surface, it may be expanded. However, transfer functions for each datum to be localized will be required. For example, to estimate the height of a sound source, a transfer function from the sound source is required when changing the horizontal direction and height. Moreover, the microphone array must be positioned to capture the required information. For example, for direction localization on a horizontal surface, the microphones should be positioned on a horizontal surface; for also estimating height, the microphones should be positioned on the surface of a sphere.

Discussion

Since the MUSIC algorithm estimates source locations based on prior transfer functions, this algorithm can be used to estimate height by measuring a transfer function according to the information required. However, since the implementation in HARK is limited to determining the direction of a sound source on horizontal surfaces, appropriate modifications are required.