| 摘要 |
At least one first signal with a high signal frequency is sent from the noise source (8) and this signal is modulated so that a low frequency signal is generated as a result of the non-linear properties of the medium (air) through which the signal is travelling. At least one second signal, also with a high signal frequency, is sent from the noise source and modulated so that a counter-signal is generated in the frequency region of a phase position in relation to the audible signal as a result of the non-linear properties of the medium. The audible signal is diminished in the room beyond a given distance from the noise source. Independent claims are also included for the following: (1) Device for generating low frequency noise with a restricted spread, comprising a first and second signal source and a modulating unit (12); and (2) Device for generating low frequency noise with a restricted spread, comprising a source for at least two first signals and at least two signals. |
