Distance-based audio processing for parametric speaker system
View Patent ↗A hybrid ultrasonic audio system includes one or more ultrasonic speakers and one or more conventional speakers. An optical imaging system may be used to automatically determine the distance of a listener relative to the audio system. Channel processors apply distance-related transfer function filters to one or more of the audio channels based on the determined distances to equalize the amplitude of the audio played by the ultrasonic speakers relative to the conventional speakers. Channel processors may further apply a phase or time delay to the audio channels to match the phase and time delay of the ultrasonic speaker audio to the conventional speaker audio.
1. A method of producing parametric audio in an audio system comprising an ultrasonic speaker and a conventional speaker, the method comprising:
determining a distance of a listener relative to either or both of the ultrasonic speaker and the conventional speaker;
receiving first and second input audio channel signals at a parametric audio processor;
processing the first input audio channel signal for playback by the ultrasonic speaker, and processing the second input audio channel signal for playback by the conventional speaker; and
playing the processed first input audio channel signal using the ultrasonic speaker, and playing the processed second input audio channel signal using the conventional speaker;
wherein processing the first input audio channel signal for playback by the ultrasonic speaker comprises mixing or combining the first input audio channel signal with an ultrasonic carrier signal generated by an oscillator to generate an audio-modulated ultrasonic signal for playback by the ultrasonic speaker; and
wherein the processing comprises applying a distance-related transfer function to either or both of the first and second input audio channel signals based on the determined distance to adjust the amplitude of either or both of the first and second input audio channel signals such that the volume of the audio signal played by the conventional speaker and the volume of the audio signal played by the ultrasonic speaker are equalized for the listener at the determined distance.
2. The method of claim 1 , wherein the processing further comprises applying at least one of a phase or time delay to at least one of the first and second input audio channel signals.
3. The method of claim 2 , wherein the distance-related transfer function is based on the free space propagation loss that a sound pressure wave experiences as it propagates through the determined distance.
4. The method of claim 3 , wherein the distance-related transfer function attenuates the amplitude of the first input audio channel signal.
5. The method of claim 4 , wherein the distance-related transfer function changes the frequency of the first input audio channel signal.
6. The method of claim 2 , wherein the processing comprises applying at least one of amplitude adjustment, a phase delay and a time delay to the first input audio channel signal to more closely match at least one of the amplitude, phase delay and time delay of the audio signal played by the conventional speaker relative to the audio signal played by the ultrasonic speaker.
7. The method of claim 2 , wherein the distance is determined by an optical imaging system configured to recognize the listener.
8. The method of claim 7 , wherein the optical imaging system comprises a digital camera and a depth sensor.
9. The method of claim 8 wherein the distance is based on the distance from the ultrasonic speaker to the listener's head.
10. A parametric audio system, comprising:
an ultrasonic speaker;
a conventional speaker;
means for determining a distance of a listener relative to the parametric audio system; and
a parametric audio processor comprising:
circuitry for receiving first and second input audio channel signals;
a channel processor configured to apply a distance-related transfer function to at least one of the first and second input audio channel signals based on the determined distance to adjust the amplitude of either or both of the first and second input audio channel signals such that the volume of audio played by the ultrasonic speaker and the volume of audio played by the conventional speaker are equalized for the listener at the determined distance; and
a modulator configured to modulate the first input audio channel signal onto an ultrasonic carrier to generate an audio-modulated ultrasonic signal for playback by the ultrasonic speaker, wherein the modulator generates the audio-modulated ultrasonic signal by mixing or combining the first audio channel signal with an ultrasonic carrier signal generated by an oscillator.
11. The system of claim 10 , wherein the channel processor is further configured to apply at least one of a phase or time delay to at least one of the first and second input audio channel signals.
12. The system of claim 11 , wherein the distance-related transfer function is based on the free space propagation loss that a sound wave experiences as it propagates through the distance.
13. The system of claim 12 , wherein the distance-related transfer function attenuates the amplitude of the first input audio channel signal.
14. The system of claim 13 , wherein the distance-related transfer function changes the frequency of the first input audio channel signal.
15. The system of claim 12 , wherein the distance-related transfer function increases the amplitude of the second input audio channel signal.
16. The system of claim 11 , wherein the first channel processor applies at least one of a phase or time delay to the first input audio channel signal to further match the phase and time delay of the audio played by the conventional speaker relative to the audio played by the ultrasonic speaker.
17. The system of claim 11 , further comprising an optical imaging system configured to automatically recognize the listener and determine the distance.
18. The system of claim 17 , wherein the optical imaging system comprises a digital camera and a depth sensor.
19. The system of claim 17 , wherein the distance is based on the distance from the ultrasonic speaker to the listener's head.
20. The system of claim 11 , wherein the determined distance is a distance from the listener to at least one of the conventional speaker and the ultrasonic speaker.