| 摘要 |
<p>In a method and a device for generating or extinguishing low frequency sound having a high sound pressure, the wave shape is divided into air pulses with variable amplitude and with considerably higher frequency than that of the wanted tone. The air pulses thereby represent instantaneous values (sampling values) of the wanted wave shape which, thus, is formed by an imaginary curve connecting the amplitude values of the discrete air pulses. The air pulses are positive during one half-cycle and negative during the other half-cycle of the wave shape. The device comprises means to pump in high frequency pulses from a chamber (1) to the surroundings during a first period of time and during a second period of time high frequency air pulses are sucked into a said chamber (2) from the surroundings. The invention also relates to use of such a device, e.g., for actively extinguishing low frequency noise.</p> |
