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Related Concept Videos

Echo01:06

Echo

The human ear cannot distinguish between two sources of sound if they happen to reach within a specific time interval, typically 0.1 seconds apart. More than this, and they are perceived as separate sources.
Imagine the sound is reflected back to the ears. Assuming that the source is very close to the human, the difference between hearing the two sounds—the emitted sound and the reflected sound—may be more than the minimum time for perceiving distinct sounds. If this is the case, then the...
Interference: Path Lengths01:10

Interference: Path Lengths

Consider two sources of sound, that may or may not be in phase, emitting waves at a single frequency, and consider the frequencies to be the same.
Two special sources may be considered when they are in phase. This can be easily achieved by feeding the two sources from the same source. An example would be synchronizing the two speakers by feeding them with the same source, such as the sound waves produced by a tuning fork. This setup ensures that the two sources have the same frequency and are...
Sound Waves: Interference00:53

Sound Waves: Interference

Sound waves can be modeled either as longitudinal waves, wherein the molecules of the medium oscillate around an equilibrium position, or as pressure waves. When two identical waves from the same source superimpose on each other, the combination of two crests or two troughs results in amplitude reinforcement known as constructive interference. If two identical waves, that are initially in phase, become out of phase because of different path lengths, the combination of crests with troughs...

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A Stable Phantom Material for Optical and Acoustic Imaging
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Published on: June 16, 2023

Bidirectional equalization for underwater acoustic communication.

H C Song1

  • 1Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California 92093-0238, USA. hcsong@ucsd.edu

The Journal of the Acoustical Society of America
|April 17, 2012
PubMed
Summary
This summary is machine-generated.

The bidirectional decision feedback equalizer (BiDFE) enhances underwater communication performance by 0.4-1.8 dB. This advanced equalizer improves signal-to-noise ratio in challenging, time-varying shallow water environments.

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Area of Science:

  • Signal Processing
  • Underwater Acoustics
  • Communications Engineering

Background:

  • Conventional decision feedback equalizers (DFE) face performance limitations in complex communication channels.
  • Bidirectional decision feedback equalizers (BiDFE) have shown promise in simulations for improving DFE performance.
  • Multichannel time reversal communications require robust signal processing techniques.

Purpose of the Study:

  • To extend the BiDFE concept to multichannel time reversal communications.
  • To experimentally evaluate the performance enhancement of BiDFE in shallow water environments.
  • To quantify the signal-to-noise ratio (SNR) improvement offered by BiDFE.

Main Methods:

  • Implementing a BiDFE with a DFE as a post-processor in a multichannel time reversal system.
  • Collecting experimental data in shallow water acoustic channels (10-20 kHz).
  • Analyzing the output signal-to-noise ratio (SNR) to measure performance gains.

Main Results:

  • Experimental results demonstrate performance enhancement ranging from 0.4 to 1.8 dB in output SNR.
  • The BiDFE achieved a notable improvement of 1.8 dB in time-varying channel conditions.
  • Performance gains were correlated with the degree of channel diversity in opposite directions.

Conclusions:

  • The BiDFE effectively enhances the performance of DFE in multichannel time reversal systems.
  • Experimental validation confirms BiDFE's capability to improve SNR in shallow water acoustic communications.
  • BiDFE shows particular efficacy in time-varying channels, offering significant performance benefits.