Topic
Acoustic interferometer
About: Acoustic interferometer is a research topic. Over the lifetime, 1493 publications have been published within this topic receiving 19355 citations.
Papers published on a yearly basis
Papers
More filters
••
IBM1
TL;DR: In this paper, a pulse compression filter is used to convert chirp acoustic bulk wave signals into signals describing the source of the source signal, which is then converted by a focused beam.
Abstract: Electronically focused and automatically scanning acoustic bulk waves are produced by scattering chirp acoustic bulk waves at grazing incidence from an acoustic grating. The same apparatus may be used in reverse to convert diverging acoustic bulk waves produced by a focused beam into chirp acoustic bulk waves. A pulse compression filter then converts the chirp waves into signals describing the source.
17 citations
••
01 Jan 1972
17 citations
••
TL;DR: An electrically active sound wave attenuation apparatus mounted in an upright, free-standing housing for eliminating unwanted reflected waves in a room is described in this paper, which is intended to be placed in a location where undesired wave patterns, such as standing waves, are formed in order to offset or cancel such conditions.
Abstract: An electrically active sound wave attenuation apparatus mounted in an upright, free-standing housing for eliminating unwanted reflected waves in a room. The housing is intended to be placed in a location where undesired wave patterns, such as standing waves, are formed in order to offset or cancel such conditions. These conditions are offset by generating an acoustic signal which is the inverse of pressure waves at a particular location. The pressure waves are sensed by a module, including a microphone which generates a corresponding electrical signal. This signal is sent to an electrical circuit where an inverse signal is created which is then transmitted to a loudspeaker. The loudspeaker output is directed toward the location where the standing waves would be formed. The loudspeaker output nulls local acoustic waves so that no standing waves are formed. The housing may incorporate two acoustically isolated modules with resonance attenuating qualities, one at each end of the structure.
17 citations
••
TL;DR: A study of 400 Hz sound focusing and ducting effects in a packet of curved nonlinear internal waves in shallow water is presented, andputed three-dimensional propagation results compare well with field observations.
Abstract: A study of 400 Hz sound focusing and ducting effects in a packet of curved nonlinear internal waves in shallow water is presented. Sound propagation roughly along the crests of the waves is simulated with a three-dimensional parabolic equation computational code, and the results are compared to measured propagation along fixed 3 and 6 km source/receiver paths. The measurements were made on the shelf of the South China Sea northeast of Tung-Sha Island. Construction of the time-varying three-dimensional sound-speed fields used in the modeling simulations was guided by environmental data collected concurrently with the acoustic data. Computed three-dimensional propagation results compare well with field observations. The simulations allow identification of time-dependent sound forward scattering and ducting processes within the curved internal gravity waves. Strong acoustic intensity enhancement was observed during passage of high-amplitude nonlinear waves over the source/receiver paths, and is replicated in the model. The waves were typical of the region (35 m vertical displacement). Two types of ducting are found in the model, which occur asynchronously. One type is three-dimensional modal trapping in deep ducts within the wave crests (shallow thermocline zones). The second type is surface ducting within the wave troughs (deep thermocline zones).
17 citations