Active control of radiation from a piston set in a rigid sphere

Abstract

Active control of the sound radiated from a piston set in a rigid sphere with a set of control point sources around is considered in this paper, where the scattering sound field of the control sound from the rigid sphere has been taken into account to minimize the total radiated sound power. Analytic results of the sound power are obtained and numerical simulations show that it is possible to reduce the radiation from a small piston set in a rigid sphere similar to the size of a human head up to a certain frequency. It is found that the introduction of the scattering object makes significant differences from the active control without scattering objects. This being the case, the scattering object makes the active noise control easier. To increase the global reduction of sound-power output, the optimal number and locations of the control sources and the optimal number and locations of error sensors are discussed. Finally, experiments with one control source and one error sensor around a head simulator have been carried out to verify the simulation results.

Effects of a near-field rigid sphere scatterer on the performance of linear microphone array beamformers

“…where j ¼ (À1) 1/2 , p 0 is the amplitude of the incident wave, k is the wave number, j l (Á) is the spherical Bessel function of order l, and P l (Á) is the Legendre function of order l. The total sound field with consideration of the rigid sphere scattering can be expressed as 21,22…”

“…The superscript (*) denotes complex conjugation. The total sound field with consideration of the rigid sphere scattering can be expressed as 21,22 FIG. 1.…”

“…Considering that the microphone array is usually used to capture the voice of a speaker, a proper speaker model instead of the point source will lead to a more reasonable near-field model. In this paper, an analytical speaker model, in which the speaker's head is represented by a rigid sphere and the speaker's mouth is represented by a radially vibrating piston mounted on the surface of the rigid sphere, 21 is utilized. The basic schematic diagram of the speaker model together with the rigid sphere scatterer is shown in Fig.…”

Performance analysis of the virtual sound barrier system with a diffracting sphere

“…Since a practical VSB system has to be implemented surrounding a person, at least a human's head, the effect of such a diffracting body on the performance of the VSB system must be considered. Active control of the sound radiated from a piston set in a rigid sphere with a set of control point sources around was studied by Lin et al, where the scattering sound field of the control sound from the rigid sphere has been taken into account to minimize the total radiated sound power [4]. It has been shown that due to the scattering effect of the rigid sphere, the presence of the rigid sphere is beneficial for the active control.…”

Performance of a multichannel active sound radiation control system near a reflecting surface

“…When a rigid sphere is put near a single channel ANC system, the rigid sphere has scattering effects on both the primary and secondary fields and can increase global sound radiation control performance after optimizing the locations of secondary sources; however, no detailed mechanism was investigated [9]. It was also discovered that the presence of a human head in a three dimensional virtual sound barrier system can improve or decrease the system performance depending on the size of the quiet zone surrounded by the error sensors and the noise frequency [10].…”