Apparatus and methods for upshifting the frequency of acoustic energy

摘要

Method and apparatus for converting acoustic energy in an unshifted acoustic signal into an upshifted acoustic signal, and emitting the upshifted acoustic signal. Using a frequency converter, acoustic energy in a first frequency range in the unshifted acoustic signal is converted into acoustic energy in the upshifted acoustic signal in a second frequency range. The upshifted acoustic signal is emitted into an ambient acoustic environment. The second frequency range is higher than the first; the unshifted acoustic signal comprises an unwanted acoustic noise signal. The effect of the acoustic noise signal can be reduced by: enhanced attenuation of upshifted signal during atmospheric propagation; enhanced attenuation of upshifted signal by a non-gaseous attenuating medium; or decreased coupling of upshifted signal into resonances of a human body or mechanical structure.

主权项

1. A method comprising:
using a frequency converter, converting at least a portion of acoustic energy in an unshifted acoustic signal emitted by an acoustic source in a first frequency range into acoustic energy in an upshifted acoustic signal in a second frequency range; and emitting at least a portion of the upshifted acoustic signal into an ambient acoustic environment, wherein: the second frequency range is higher than the first frequency range, and the unshifted acoustic signal comprises one or more unwanted acoustic noise signals; the frequency converter comprises two or more resonant members connected to the acoustic source and a coupling member connecting the resonant members together; each resonant member exhibits at least one corresponding acoustic resonance frequency in the first frequency range; each resonant member is connected to the acoustic source so that the unshifted acoustic signal drives each resonant member at its acoustic resonance frequency; the coupling member exhibits a nonlinear acoustic response so as to generate in the second frequency range sum-frequency acoustic signals from the resonant frequencies of the driven resonant members; and the upshifted acoustic signal includes the sum-frequency acoustic signals.