Showing papers on "Microphone array published in 1980"
TL;DR: In this article, a square microphone array with 256 elements was constructed along with interfacing electronics to study low-frequency (1-5 kHz) sound sources in air using the principles of acoustical holography.
Abstract: A square microphone array with 256 elements has been constructed along with interfacing electronics to study low‐frequency (1–5 kHz) sound sources in air using the principles of acoustical holography. The array is used in the nearfield of a radiating object and the sound source structure of that object is reconstructed with an on‐line minicomputer. Reconstruction of the source structure of a point source and an unbaffled, free rectangular plate point excited below its coincidence frequency are presented. The latter shows clear evidence of ’’corner’’ and ’’edge’’ modes in which the respective areas of the plate are the dominant radiating sources. A new imaging process which is not limited in resolution by the wavelength of the radiated sound is introduced.
241 citations
TL;DR: In this article, a super-resolution passive imaging system was constructed to obtain the fine structures of a wave field on a noise emitting object. But the wave field was detected by a hemispherically arranged microphone array, which corresponds directly to the wave fields on the object by exploiting a priori information about the object's physical structures.
Abstract: To obtain the fine structures of a wave field on a noise emitting object, a new super‐resolution passive imaging system is constructed The wave field detected by a hemispherically arranged microphone array corresponds directly to the wave field on the object by exploiting a priori information about the object’s physical structures Thus resolution of one‐tenth of a wavelength is realized The principle, concrete construction, proposal of proper sound source models, and discussions on the effects of the measuring and additive noises are given, as well as several observed results
10 citations
TL;DR: In this paper, a new microphone array system is constructed to study the radiation from noise sources and nonsteady state sources using the principles of nonwavelength limited acoustical holography, which provides an acoustic snapshot of the pressure in a plane containing an array of up to 1024 microphones with a total data acquisition time of less than 160 μs.
Abstract: A new microphone array system is being constructed to study the radiation from noise sources and nonsteady state sources using the principles of nonwavelength limited acoustical holography The system can provide an “acoustic snapshot” of the pressure in a plane containing an array of up to 1024 microphones with a total data acquisition time of less than 160 μs Up to 1024 snapshots can be recorded in a time series to provide an “acoustic filmstrip” Using digital holographic techniques, a corresponding filmstrip of the vector intensity (the energy flux) of the sound field can be reconstructed in the region above the source This intensity filmstrip can be used to visualize the time evolution of the energy flow from the sources to the farfield This new system will be described and some preliminary results will be shown
2 citations
TL;DR: The results of this study indicate that a passive acoustic bearing estimation system for ground sources should be able to achieve an accuracy of a few degrees under most conditions.
Abstract: The maximum likelihood bearing estimator has been simulated on a computer and has been used to examine the effects on performance of both environmentally imposed conditions and system parameters. The imposed conditions include source spectra, ambient noise spatial character, wind, temperature, and array tilt due to terrain. The system parameters include microphone position error, channel amplitude match, channel phase match, operating frequency band, number of microphones, size of array, number of azimuth bins, and number of delay line taps. The results of this study indicate that a passive acoustic bearing estimation system for ground sources should be able to achieve an accuracy of a few degrees under most conditions.
1 citations