Time-domain acoustic contrast control design with response differential constraint in personal audio systems

Abstract

The acoustic contrast control (ACC) approach is applied to reproduce the focused sound in personal audio systems utilizing an array of loudspeakers. A time-domain design of ACC is developed here for broadband input signals, where a response differential term is introduced to control the frequency response. Based on experimental results in an anechoic chamber, the proposed method demonstrates the potential capability to provide excellent acoustic contrast over the continuous frequency and maintain a flat frequency response. Furthermore, compared with the previous method, fewer parameters need to be tuned in the proposed method.

Time Domain Optimization of Filters Used in a Loudspeaker Array for Personal Audio

“…The frequency responses between loudspeakers and microphones have been calculated with point source free-field Green functions, with the two sources separated by a distance of 4 cm. For a point source at a distance from the microphone, the free-field Green function is defined as (20) where kgm is the density of air, is the wave number, with ms being the speed of sound in air. These frequency responses have then been inverse Fourier transformed to obtain the impulse responses from each source to each control point, using points at a sampling frequency kHz.…”

“…The formulation of inverse acoustical problems in the time domain has previously been considered to invert room responses [14], to reproduce virtual audio sources with a stereo dipole [15], for cross-talk cancellation systems [16], [17], and for active control applications using matrices of filtered reference signals [18]. Using the active control formulation, the acoustic contrast maximization [13] has also been formulated in the time domain [19], [20].…”

“…The time domain optimization of the acoustic contrast maximization can cause an uneven directional response at different frequencies [21]. This problem has been mitigated by the introduction of a modified cost function which takes into account the uniformity of the frequency response [20]. Furthermore, the acoustic contrast maximization method does not generally provide a uniform spatial distribution of the pressure over the bright zone [2], [8], [22], [23], which is not good in terms of the perceived audio quality.…”

Acoustic contrast control in an arc-shaped area using a linear loudspeaker array

“…Recently, Cai et al studied the time domain performance of the acoustic contrast control method and proposed some schemes to improve the frequency response consistency in the bright zone. 23 Compared with the complicated operations for the acoustic contrast control method, the proposed method is rather concise since the impulse response of the filter for each loudspeaker has a simple time delay, s ¼ [2a arctan(x/a)Àx]/c, according to the phase distribution in Eq. (8).…”

Sound Zones As An Optimal Filtering Problem

“…However, this improvement in the reconstruction quality of the desired sound field came at the expense of a much higher zone leakage, i.e., a smaller acoustic contrast between the bright and dark zone. Therefore, a number of methods [11][12][13][14][15][16] have sought to modify and/or combine ACC and PM so that a better trade-off between signal distortion and zone leakage is obtained.…”