Microphone autolocalization using moving acoustic source
Provided are methods and systems for calibrating a distributed sensor (e.g., microphone) array using time-of-flight (TOF) measurements for a plurality of spatially distributed acoustic events at the sensors. The calibration includes localization and gain equalization of the sensors. Accurate measurements of TOFs are obtained from spatially distributed acoustic events using a controlled signal emitted at known intervals by a moving acoustic source. A portable user device capable of playing out audio is used to produce a plurality of acoustic events (e.g., sound clicks) at known intervals of time and at different, but arbitrary locations based on the device being moved around in space by a user while producing the acoustic events. As such, the times of the acoustic event generation are known, and are spatially diverse. The calibration signals emitted by the acoustic source are designed to provide robustness to noise and reverberation.
1. A computer-implemented method comprising:
determining registered arrival times of a set of acoustic events at a set of sensors, wherein the acoustic events are generated at time intervals known to the sensors;
calculating times of flight for the acoustic events to reach the sensors based on the registered arrival times of the acoustic events at the sensors, event generation times for the acoustic events, and estimated internal delays of the sensors; and
using the calculated times of flight to determine locations of the sensors.
2. The method of claim 1 , wherein, for each sensor, the time of flight for the acoustic event to reach the sensor is calculated by subtracting, from the registered arrival time for the sensor, the internal delay of the sensor and the event generation time for the acoustic event.
3. The method of claim 1 , wherein calculating the times of flight for the acoustic events to reach the sensors is performed iteratively to refine the times of flight.
4. The method of claim 1 , further comprising selecting the first acoustic event generated as a reference time for calculating the times of flight for the acoustic events to reach the sensors.
5. The method of claim 1 , further comprising determining a relative gain for each of the sensors using the calculated location of the sensor and the registered arrival times of the events at the sensor.
6. The method of claim 1 , wherein each of the acoustic events is a calibration signal that is a Gaussian modulated sinusoidal pulse.
7. The method of claim 1 , wherein each of the acoustic events is a calibration signal that is a time-stretched pulse.
8. The method of claim 1 , wherein each of the acoustic events is a calibration signal that is a unit impulse.
9. The method of claim 1 , wherein the set of sensors is a set of microphones.
10. The method of claim 1 , wherein the set of events is generated by a device with a loudspeaker from a plurality of different locations relative to the sensors.
11. The method of claim 1 , wherein one or more of the sensors are microphones located on mobile telephones.
12. A computer-implemented method comprising:
calculating times of flight for a set of acoustic events to reach a set of sensors based on registered arrival times of the acoustic events at the sensors, event generation times for the acoustic events, and estimated internal delays of the sensors, wherein the acoustic events are generated at time intervals known to the sensors;
calculating locations of the sensors using the times of flight for the acoustic events to reach the sensors; and
determining a relative gain for each of the sensors using the calculated location of the sensor and the registered arrival times of the events at the sensor.
13. The method of claim 12 , further comprising:
measuring arrival times of the set of acoustic events at the set of sensors; and
estimating internal delays of the sensors based on the registered arrival times of the acoustic events at the sensors.
14. The method of claim 12 , wherein calculating the times of flight for the acoustic events to reach the sensors is performed iteratively to refine the times of flight.
15. The method of claim 12 , further comprising selecting the first acoustic event generated as a reference time for calculating the times of flight for the acoustic events to reach the sensors.
16. The method of claim 12 , wherein the relative gain for each of the sensors is determined based on an estimation of the signal-to-noise (SNR) at the sensor.
17. The method of claim 12 , wherein each of the acoustic events is a calibration signal that is a Gaussian modulated sinusoidal pulse.
18. The method of claim 12 , wherein each of the acoustic events is a calibration signal that is a time-stretched pulse.
19. The method of claim 12 , wherein each of the acoustic events is a calibration signal that is a unit impulse.
20. The method of claim 1 , wherein the set of sensors is a set of microphones and the set of events is generated by a device with a loudspeaker from a plurality of different locations relative to the microphones.