Impulse response delay estimation

1 . A calibration device for delay estimation of audio signals using an impulse response signal, the calibration device comprising processing circuitry configured to:

determine an energy envelope for the impulse response signal based on a moving average function of the impulse response signal;

determine an estimated delay of the impulse response signal based on at least one characteristic of the determined energy envelope, wherein the at least one characteristic includes at least one of:

a peak value of the energy envelope; and

a peak time at which the energy envelope first reaches the peak value; and

adjust at least one audio signal phase for at least one audio driver based on the estimated delay, wherein the processing circuitry is further configured to determine the estimated delay time by:

determining a noise floor of the impulse response signal;

determining a first time at which an amplitude of the impulse response signal rises to a threshold value above the noise floor, the threshold value being a predetermined fraction of the peak value of the energy envelope; and

detecting a first inflection point of a derivative of the impulse response signal in a time period from the first time to the peak time, the estimated delay time being an amount of time from a start time to the detected first inflection point.

2 . The calibration device of claim 1 , wherein the predetermined fraction is one-tenth.

3 . The calibration device of claim 1 , wherein the processing circuitry is further configured to:

generate a reference audio signal for playback on a loudspeaker; and

measure the playback of the loudspeaker to determine the impulse response, the start time being associated with the generating of the reference audio signal.

4 . A calibration device for delay estimation of audio signals using an impulse response signal, the calibration device comprising processing circuitry configured to:

determine an energy envelope for the impulse response signal based on a moving average function of the impulse response signal;

determine an estimated delay of the impulse response signal based on at least one characteristic of the determined energy envelope; and

adjust at least one audio signal phase for at least one audio driver based on the estimated delay;

wherein the moving average function is based on a root mean squared function.

5 . The calibration device of claim 4 , wherein the moving average function is further based on a raised cosine window.

6 . A system for delay estimation of audio signals, the system comprising a calibration device, a receiver, a loudspeaker, and an audio driver, wherein:

the calibration device comprises processing circuitry configured to:

generate a reference audio signal; and

cause transmission of the reference audio signal to the receiver;

the receiver comprising processing circuitry configured to:

receive the reference audio signal; and

cause transmission of the reference audio signal to the audio driver for playback on the loudspeaker;

the processing circuitry of the calibration device being further configured to:

measure the playback of the reference audio signal on the loudspeaker to determine an impulse response;

determine an energy envelope for the impulse response signal based on a moving average function of the impulse response signal;

determine an estimated delay of the impulse response signal based on at least one characteristic of the determined energy envelope;

determine an adjusted audio signal phase based on the estimated delay; and

cause transmission of the adjusted audio signal phase to the receiver; and

the processing circuitry of the receiver being further configured to:

receive the adjusted audio signal phase from the calibration device; and

adjust at least one additional audio signal for the audio driver based on the adjusted audio signal phase;

wherein the processing circuitry of the calibration device is configured to determine the estimated delay time by:

determining a noise floor of the impulse response signal;

determining a first time at which an amplitude of the impulse response signal rises to a threshold value above the noise floor, the threshold value being a predetermined fraction of the peak value of the energy envelope; and

detecting a first inflection point of a derivative of the impulse response signal in a time period from the first time to the peak time, the estimated delay time being an amount of time from a start time to the detected first inflection point.

7 . The system of claim 6 wherein the predetermined fraction is one-tenth.

8 . The system of claim 6 , wherein the start time is associated with the generating of the reference audio signal.

9 . A system for delay estimation of audio signals, the system comprising a calibration device, a receiver, a loudspeaker, and an audio driver, wherein:

the calibration device comprises processing circuitry configured to:

generate a reference audio signal; and

cause transmission of the reference audio signal to the receiver;

the receiver comprising processing circuitry configured to:

receive the reference audio signal; and

cause transmission of the reference audio signal to the audio driver for playback on the loudspeaker;

the processing circuitry of the calibration device being further configured to:

measure the playback of the reference audio signal on the loudspeaker to determine an impulse response;

determine an energy envelope for the impulse response signal based on a moving average function of the impulse response signal;

determine an estimated delay of the impulse response signal based on at least one characteristic of the determined energy envelope;

determine an adjusted audio signal phase based on the estimated delay; and

cause transmission of the adjusted audio signal phase to the receiver; and

the processing circuitry of the receiver being further configured to:

receive the adjusted audio signal phase from the calibration device; and

adjust at least one additional audio signal for the audio driver based on the adjusted audio signal phase;

wherein the moving average function is based on a root mean squared function.