System and method for providing a quiet zone
A system and method for quieting unwanted sound. As a non-limiting example, various aspects of this disclosure provide a system and method, for example implemented in a premises-based or home audio system, for quieting unwanted sound at a particular location.
1. A system comprising:
a microphone configured to receive an unwanted audio signal;
a processor configured to generate a cancellation signal; and
a speaker configured to output the cancellation signal to counteract, at least in part, the unwanted sound, wherein:
the unwanted audio signal corresponds to a predetermined frequency band,
the source of the unwanted audio signal is at a distance away from the microphone,
a length of the distance is at least one fourth of a wavelength of a lowest frequency of the predetermined frequency band, and
to generate the cancellation signal, the processor is configured to:
filter the unwanted audio signal to pass the predetermined frequency band,
determine a relationship between a local audio signal and the filtered unwanted audio signal, and
generate the cancellation signal according to the local audio signal and the relationship.
2. The system of claim 1 , wherein to determine the relationship, the processor is configured to:
generate a test stimulus signal to cause the speaker to output a test sound; and
analyze the test stimulus signal and a test sound, received by the microphone, to determine a functional relationship between the test stimulus signal and the received test sound.
3. The system of claim 2 , wherein the test stimulus signal comprises a pseudo-random noise signal comprising a pink noise signal.
4. The system of claim 2 , wherein the test stimulus signal comprises a swept frequency signal comprising frequencies in a range up to at least twice a quieting passband of the system.
5. The system of claim 1 , wherein a magnitude of the cancellation signal is set 6-10 dB lower than a level determined for an ideal cancellation.
6. The system of claim 1 , wherein the processor is operable to determine the relationship between the local audio signal and the filtered unwanted audio signal according to sound received by a plurality of microphones where each of the plurality of microphones is positioned at a respective fixed geographical location.
7. The system of claim 6 , wherein each of the respective fixed geographical locations is within a same room of a premises.
8. A system comprising:
a plurality of microphones configured to receive a plurality of unwanted audio signals;
a processor configured to generate a cancellation signal; and
a speaker configured to output the cancellation signal to counteract, at least in part, the unwanted sound, wherein:
the plurality of unwanted audio signals corresponds to a predetermined frequency band,
the source of the plurality of unwanted audio signals is at a distance away from the microphone,
a length of the distance is at least one fourth of a wavelength of a lowest frequency of the predetermined frequency band, and
to generate the cancellation signal, the processor is configured to:
filter the plurality of unwanted audio signals to pass the predetermined frequency band,
determine a relationship between a local audio signal and the filtered plurality of unwanted audio signals, and
generate the cancellation signal according to the local audio signal and the relationship.
9. The system of claim 8 , wherein each of the plurality of microphone is positioned within a same room of a premises.
10. The system of claim 8 , wherein the processor is operable to determine the relationship by, at least in part, operating to:
generate a test stimulus signal to cause the speaker to output a test sound; and
analyze the test stimulus signal and a plurality of test sounds, received by the plurality of microphones, to determine a functional relationship between the test stimulus signal and the received plurality of test sounds.
11. The system of claim 10 , wherein the test stimulus signal comprises a pseudo-random noise signal comprising a pink noise signal.
12. The system of claim 10 , wherein the test stimulus signal comprises a swept frequency signal comprising frequencies in a range up to at least twice a quieting passband of the system.
13. The system of claim 8 , wherein a magnitude of the cancellation signal is set 6-10 dB lower than a level determined for an ideal cancellation.
14. A system comprising:
a microphone;
a speaker; and
processor operable to:
receive, via the microphone, a unwanted sound, wherein the microphone is positioned at least one fourth of a particular wavelength away from a particular location;
filter the unwanted sound to pass a frequency band to be counteracted, wherein a lower frequency of the frequency band is determined by the particular wavelength;
determine a relationship between a local audio signal, at the particular location, and the filtered unwanted sound; and
generate, according to the local audio signal and the determined relationship, a cancellation signal that, when output by the speaker, will counteract, at least in part, the unwanted sound.
15. The system of claim 14 , wherein the processor is operable to determine the relationship by, at least in part, operating to:
generate a test stimulus signal to cause the speaker to output a test sound;
receive the test sound at the location; and
analyze the test stimulus signal and the received test sound to determine a functional relationship between the test stimulus signal and the received test sound.
16. The system of claim 15 , wherein the test stimulus signal comprises a pseudo-random noise signal comprising a pink noise signal.
17. The system of claim 15 , wherein the test stimulus signal comprises a swept frequency signal comprising frequencies in a range up to at least twice a quieting passband of the audio system.
18. The system of claim 14 , wherein a magnitude of the cancellation signal is set 6-10 dB lower than a level determined for an ideal cancellation.
19. The system of claim 14 , wherein the processor is operable to determine the relationship according to sound received by a microphone that is outside a target zone of sound cancellation.
20. The system of claim 14 , wherein the processor is operable to determine the relationship according to sound received by a plurality of microphones positioned at fixed geographical locations.