| 摘要 |
A digital signal processor 302 is configured to receive a digital audio input signal 401and modulates 404 an ultra-sonic signal 408 with the input audio signal to produce a modulated ultrasound signal. A combiner 403 combines the input signal with the modulated ultrasound signal to produce an output signal. The signal processor includes means 406 for calculating absolute values and inverting means 407 for inverting the absolute values to produce the modulating signal (see fig 5). This is said to reduce harmonic and zero-crossing distortion introduced by a loudspeaker. |
