Performance degradation due to transfer function errors in acoustic brightness and contrast control: Sensitivity analysis

Acoustic brightness/contrast control is a method to generate acoustically bright zone (loud region) or acoustically bright zone and dark zone (quiet region) at the same time using several sound sources. For example, in implementing private audio system, it has been demonstrated that acoustic contrast control is one of effective means to maximize the acoustic energy density ratio between acoustically bright zone (listener region) and dark zone (elsewhere). In acoustic brightness /contrast control, measured transfer functions, which shows the relation between the input signal of a sound source and the output signal of a microphone, are normally used because there are several components in the system, i.e. microphone array, loudspeaker array, and measurement/playback devices. If there are errors in measuring transfer function due to noises, system nonlinearity, or any kinds of disturbances, the desired performance might be distorted by the errors. These errors degrade the system performance whose measure is brightness, contrast and spatial mean-squared-error of the control zone. In this paper, the errors are expressed in terms of magnitudes and phases in general, and we have formulated the performance variation of acoustic brightness/contrast control due to the errors in measuring transfer functions mathematically and evaluated its validity through the simulation results. Copyright© (2010) by the International Congress on Acoustics.