In-situ calibration of a multichannel loudspeaker system for 3D sound realization

Several studies have attempted to control or manipulate sound fields in space and time using multiple sound sources. For example, we can reconstruct a sound field in a finite region using wave field synthesis (WFS) and Ambisonics, and we can focus sound energy in the desired zone using acoustic bright and contrast control. In these 3D sound control methods, transfer functions of a multichannel loudspeaker system are used to obtain the input signals of each channel so as to generate the desired sound field. A transfer function refers to the relationship between an input signal and the pressure field at the region of interest. Transfer functions can be obtained by measuring the input signal and pressure field or by modeling mathematically using a monopole or dipole model. Measured transfer functions include the characteristics of the system, for example, the frequency response of the system, the loudspeaker's radiation pattern, or the amount of reflection in the room. However, a long measurement time is necessary in these cases, as are many measuring instruments for a proper measurement of transfer functions. Modeled transfer functions can be obtained without measurement, but performance degradation can arise due to the degree of difference between the model and the actual system. This is known as modeling error. Therefore, the aim is to calibrate modeling error by modeling transfer functions which include the system characteristics. We applied this calibration method to a 32-channel loudspeaker system which was implemented for the realization of various sound field control methods. Copyright © (2011) by the Institute of Noise Control Engineering.