Journal of the Audio Engineering Society

2005 May - Volume 53 Number 5


The practical performance of circular microphone arrays is discussed. Such arrays are useful for the analysis of room acoustics, the recording of live sound fields for surroundsound reproduction, and in teleconferencing applications. They also produce low-cost performance relative to three-dimensional arrays when sound sources and loudspeaker reproduction systems are predominantly in the horizontal plane. The noise performance of circular arrays and their sensitivity to transducer variability are considered, and examples are given for the ideal first-order array. In addition, the analysis of arrays using a recently proposed downsampling technique is included.

A novel method of controlling reflections, using flat panel loudspeakers, in a reference listening room is described. Models and implementations are presented in the case of single-transducer monophonic reproduction as well as two-channel and five-channel stereophonic arrangements. The results of a pilot listening test showed that differences in reflection patterns were readily detected by a panel of experienced listeners.

Audible Noise Suppression with a Real-Time Broad-Band Superdirective Microphone Array

Authors: Sanchez-bote, Jose-luis; Gonzalez-rodriguez, Joaquin; Ortega-garcia, Javier

A novel audible noise suppression (ANS) multichannel processor is proposed and implemented for real-time processing of data from a 15-microphone nested linear array. The ANS processor, based on the masking properties of the human auditory system, has been used successfully in single-channel systems. An enhanced multichannel version has now been developed, taking advantage of the extra information available in the acoustic spatial samples from the microphone array. This is used to improve the clean speech signal estimates used to calculate dynamically the noise hearing thresholds for ANS filtering, which will benefit the perceived and objective quality of the processed signal. While off-line experiments with a multichannel recorded database under different noise and reverberation conditions have previously assessed the performance of the system, several on-line experiments assessing the real-time prototype are described.

[Engineering Report] A closed-box band-limited low-frequency enclosure can take advantage of the relatively higher efficiency of a moving-coil loudspeaker near system resonance. By using drivers with low voice-coil resistance the sensitivity near resonance can be increased significantly. Several possible implementations are discussed, and two experimental systems are described.

[Feature Article] It is widely accepted that listening tests are time-consuming and expensive to conduct, yet they remain the only reliable way of evaluating perceived sound quality in a number of fields. The Holy Grail of psychoacoustics research, at least in many quarters, is the ability to model the quality perception process accurately enough so that measurements of the audio signal can be converted into predictions of perceived quality. However, this is a complex issue. The judgment of sound quality depends on many perceptual and cognitive factors. In tests to judge speech quality an objective measurement has been possible for some time now, with various measures in existence designed to predict the quality of speech coded at low bit rates. More recently there have been standard models to predict the quality of full-range audio signals, and again these have tended to be driven by the introduction of perceptual audio coding at low bit rates. The accuracy of prediction varies, and researchers aim to improve this with refinements to the models they use.

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Low-DC-Resistance, Low-Frequency Loudspeaker Enclosures

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Low-DC-Resistance, Low-Frequency Loudspeaker Enclosures


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Measuring and Predicting Perceived Audio Quality


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