Multizone 2D soundfield reproduction via spatial band stop filters

Abstract

Any attempt to create multiple independent soundfields in separate zones over an extended region of open space results in unintended interference in a given zones from other zones. In this paper, we design spatial band stop filters to suppress interzone interference in the regions of interests and pass the desired soundfields with no distortion. This is achieved by using the higher order spatial harmonics of one zone to cancel the undesirable effects of the lower order harmonics of the same zone on the other zones. We illustrate the work by designing and simulating a 2D two-zone soundfield.Index Terms-soundfield reproduction, multizone, cylindrical harmonic expansions, spatial band stop filters.

An approach to generating two zones of silence with application to personal sound systems

“…This contrasts with the spatial bandstop approach which creates local zones using lower order modes in each zone, and cancels the residual effect of these local modes in a second zone using higher order modes which have small amplitudes in the first zone 13 .…”

“…If the low-order modes of the cylindrical expansion are suppressed, a null is formed, due to the high-pass nature of the Bessel functions at low values of the argument. A second field can then be generated which will produce a desired field in the null region without interference, and avoiding the need to suppress interference terms 13 . Similarly, suppressing the low order terms of the second field will produce a null in which the first field can be heard without interference.…”

“…Control of the energy and the direction of propagation can be provided by direct pressure matching 7,12 , by modal control 5,6,13 , by the control of acoustic intensity 3 or by combining optimum contrast methods with pressure matching [14][15][16][17] .…”

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

“…The methods used can be classified into acoustic contrast control, 1-5 pressure matching, [6][7][8][9][10] and combinations of the two methods. [12][13][14][15] Acoustic contrast control was initially investigated by Choi and Kim 1,2 with the aim of generating a bright zone with high acoustic energy and a dark zone with low acoustic energy.…”

3D multizone soundfield reproduction using spherical harmonic analysis

“…However, the soundfield derived by employing an angular window functions is not a physically realizable soundfield. Considering this problem, J. Wu adopted spatial band stop filters to suppress the unintended inter-zone sound interference in [3]. But this method can only be applicable for two zones.…”