Cylindrical expansions of sound radiation from resilient and rigid infinite strips with reduced error.

This paper derives expressions for the sound pressure due to free-space resilient and rigid strips in cylindrical coordinates. A method is derived for improving the convergence and reducing the error of the expansions for radii less than the one-sided strip width. Low-frequency approximations are also derived, which simplify calculation at low frequencies, and expansions for the far-field responses are derived.

Spherical expansions of sound radiation from resilient and rigid disks with reduced error.

This paper derives expressions for the sound pressure due to free-space resilient and rigid disks using a spherical harmonic expansion. A method is derived for improving the convergence and reducing the error of the expansions for radii less than the disk radius. Low-frequency approximations are also derived which simplify calculation at low frequencies.

Two dimensional sound field reproduction using higher order sources to exploit room reflections.

In this paper, sound field reproduction is performed in a reverberant room using higher order sources (HOSs) and a calibrating microphone array. Previously a sound field was reproduced with fixed directivity sources and the reverberation compensated for using digital filters. However by virtue of their directive properties, HOSs may be driven to not only avoid the creation of excess reverberation but also to use room reflection to contribute constructively to the desired sound field.

Comparison of sound reproduction using higher order loudspeakers and equivalent line arrays in free-field conditions.

Higher order sound sources of Nth order can radiate sound with 2N + 1 orthogonal radiation patterns, which can be represented as phase modes or, equivalently, amplitude modes. This paper shows that each phase mode response produces a spiral wave front with a different spiral rate, and therefore a different direction of arrival of sound. Hence, for a given receiver position a higher order source is equivalent to a linear array of 2N + 1 monopole sources.

Adaptive phase calibration of a microphone array for acoustic holography.

Previous work has indicated that a limitation on the performance of a circular microphone array for holographic sound field recording at low frequencies is phase mismatch between the microphones in the array. At low frequencies these variations become more significant than at mid-range and high frequencies because the high order phase mode responses at low frequencies are lower in amplitude. This paper demonstrates the feasibility of a "self-calibration" method.

Beamforming synthesis of binaural responses from computer simulations of acoustic spaces.

Auditorium designs can be evaluated prior to construction by numerical modeling of the design. High-accuracy numerical modeling produces the sound pressure on a rectangular grid, and subjective assessment of the design requires auralization of the sampled sound field at a desired listener position. This paper investigates the production of binaural outputs from the sound pressure at a selected number of grid points by using a least squares beam forming approach.