Institut des Sciences de la Terre, Université Joseph Fourier and Centre National de la Recherche Scientifique (CNRS), Grenoble, France.
J Acoust Soc Am. 2011 Jul;130(1):13-9. doi: 10.1121/1.3593365.
People are familiar with the acoustic feedback phenomenon, which results in a loud sound that is heard when a musician plays an electric instrument directly into a speaker. Acoustic feedback occurs when a source and a receiver are connected both acoustically through the propagation medium and electrically through an amplifier, such that the amplified received signal is continuously re-emitted by the source. The acoustic feedback can be initiated from a continuous sine wave. When the emitter and the receiver are in phase, resonance is obtained, which appears to be highly sensitive to any fluctuation of the propagation medium. Another procedure consists in initiating the acoustic feedback from a continuous loop of ambient noise. It then generates an unstable self-sustained feedback oscillator (SFO) that is tested here as a method for monitoring temperature fluctuations of a shallow-water oceanic environment. The goal of the present study is to reproduce and study the SFO at the laboratory scale in an ultrasonic waveguide. The experimental results demonstrate the potential applications of the SFO for the detection of a target in the framework of the acoustic-barrier problem in shallow-water acoustics.
人们对声反馈现象很熟悉，当音乐家将电乐器直接插入扬声器时，会产生听到的大声响。当源和接收器通过传播介质在声学上以及通过放大器在电学上都连接时，就会发生声反馈，使得放大后的接收信号被源连续重新发射。声反馈可以由连续的正弦波启动。当发射器和接收器同相时，就会产生共振，这似乎对传播介质的任何波动都非常敏感。另一种方法是从环境噪声的连续循环开始启动声反馈。然后它会产生一个不稳定的自维持反馈振荡器 (SFO)，在这里它被用作监测浅海海洋环境温度波动的方法。本研究的目的是在超声导波中再现和研究实验室规模的 SFO。实验结果表明，SFO 在浅海声学中的声屏障问题框架内用于检测目标具有潜在的应用。
