Enhancing audio using a mobile device

• US 9,565,497 B2
• Filed: 08/01/2014
• Issued: 02/07/2017
• Est. Priority Date: 08/01/2013
• Status: Active Grant

• Current Assignee: Caavo Inc
• Original Assignee: Caavo Inc
• Inventors: Aggarwal, Ashish Dharmpal, Satheesh, Sharath Hariharpur
• Primary Examiner(s): Nguyen, Khai N
• Application Number:
  US14/449,159
• Publication Number:
  US 20160035337A1
• Time in Patent Office: 921 Days
• Field of Search: 381/94.1, 381/94.2, 381/95, 381/96, 381/99, 381/103
• US Class Current: 1/1
• CPC Class Codes: G06F 3/165 Management of the audio stream, e.g. setting of volume, audio stream path
• CPC Class Codes: G10L 21/0232 Processing in the frequency domain
• CPC Class Codes: G10L 25/51 for comparison or discrimination
• CPC Class Codes: H03G 3/20 Automatic control H03G3/005 takes precedence; combined with volume compression or expansion H03G7/00
• CPC Class Codes: H03G 3/3005 in amplifiers suitable for low-frequencies, e.g. audio amplifiers H03G3/32, H03G3/34 take precedence
• CPC Class Codes: H03G 3/32 the control being dependent upon ambient noise level or sound level
• CPC Class Codes: H03G 5/005 of digital signals
• CPC Class Codes: H03G 5/165 Equalizers; Volume or gain control in limited frequency bands
• CPC Class Codes: H03G 7/002 in untuned or low-frequency amplifiers, e.g. audio amplifiers H03G7/007, H03G7/001, H03G7/008, H03G7/02, H03G7/06 take precedence
• CPC Class Codes: H03H 17/04 Recursive filters
• CPC Class Codes: H03H 2017/0472 based on allpass structures
• CPC Class Codes: H04R 1/08 Mouthpieces; Microphones; Attachments therefor
• CPC Class Codes: H04R 2430/01 Aspects of volume control, not necessarily automatic, in sound systems
• CPC Class Codes: H04R 2499/11 Transducers incorporated or for use in hand-held devices, e.g. mobile phones, PDA's, camera's
• CPC Class Codes: H04R 25/50 Customised settings for obtaining desired overall acoustical characteristics
• CPC Class Codes: H04R 25/505 using digital signal processing
• CPC Class Codes: H04R 29/00 Monitoring arrangements; Testing arrangements for hearing aids H04R25/30; detection of loudspeaker connection H04R5/04; sound-field adaptation dependent on speaker detection H04S7/308
• CPC Class Codes: H04R 29/001 for loudspeakers H04R29/007 takes precedence
• CPC Class Codes: H04R 29/004 for microphones H04R29/007 takes precedence
• CPC Class Codes: H04R 3/00 Circuits for transducers , loudspeakers or microphones
• CPC Class Codes: H04R 3/04 : for correcting frequency response

Abstract

Embodiment disclosed herein enable detection and improvement of the quality of the audio signal using a mobile device by determining the loss in the audio signal and enhancing audio by streaming the remainder portion of audio. Embodiments disclosed herein enable an improvement in the sound quality rendered by rendering devices by emitting an test audio signal from the source device, measuring the test audio signal using microphones, detecting variation in the frequency response, loudness and timing characteristics using impulse responses and correcting for them. Embodiments disclosed herein also compensate for the noise in the acoustic space by determining the reverberation and ambient noise levels and their frequency characteristics and changing the digital filters and volumes of the source signal to compensate for the varying noise levels.

Claims

1. A method performed by a mobile device for improving audio quality of an audio system comprising of a source device and at least one rendering device by calibrating the at least one rendering device, the method comprising:

determining by a processing unit of the mobile device, one or more frequency characteristics of at least one microphone of the mobile device;

sending, by the mobile device, a calibration signal to the source device for playback by the at least one rendering device;

capturing, by the at least one microphone of the mobile device, the calibration signal played back by the at least one rendering device;

calculating, by the mobile device, an impulse response for the calibration signal played back by the at least one rendering device based at least on the determined one or more frequency characteristics of the at least one microphone;

determining calibration settings based at least on the impulse response; and

providing the determined calibration settings to the source device for application thereby.

2. The method, as claimed in claim 1, further comprising:

determining a relative distance of the at least one rendering device by the mobile device, said determining the relative distance comprising;

capturing a reference signal by the mobile device, wherein the reference signal is played by the at least one rendering device; and

determining the relative distance of the at least one rendering device by the mobile device by calculating a delay in the captured reference signal.

3. The method, as claimed in claim 1, further comprising:

calculating a crossover filter using the impulse response by the mobile device, wherein cut-off of the crossover filter is based on a frequency response of the impulse response.

4. The method, as claimed in claim 1, further comprising:

determining loudness of the at least one rendering device using the impulse response by calculating energy of the impulse response.

5. The method, as claimed in claim 1, further comprising:

correcting a response of the at least one rendering device by the mobile device, said correcting comprising;

mimicking a non-linear frequency scale of a human auditory system by passing the impulse response through a set of all-pass filters by the mobile device;

computing a finite impulse response (FIR) filter by the mobile device, wherein the FIR filter is a minimum phase filter having a magnitude response that is an inverse of the mimicked non-linear frequency scale; and

inverting the non-linear frequency scale to yield a final equalization filter by passing the FIR filter through a set of all-pass filters by the mobile device.

6. The method, as claimed in claim 1, further comprising:

correcting a response of the at least one rendering device by the mobile device, said correcting comprising;

mimicking a non-linear frequency scale of a human auditory system by passing the impulse response through a set of all-pass filters by the mobile device;

computing a infinite impulse response (IIR) filter by the mobile device, wherein the IIR filter is a minimum phase filter having a magnitude response that is an inverse of the mimicked non-linear frequency scale; and

inverting the non-linear frequency scale to yield a final equalization filter by passing the IIR filter through a set of all-pass filters by the mobile device.

7. The method, as claimed in claim 1, further comprising:

correcting a response of the at least one rendering device by the mobile device, said correcting comprising;

mimicking a non-linear frequency scale of a human auditory system by passing the impulse response through a set of all-pass filters by the mobile device;

computing a combination filter by the mobile device, wherein the combination filter is a minimum phase filter having a magnitude response that is an inverse of the mimicked non-linear frequency scale and the combination filter is a combination of FIR and IIR filters; and

inverting the non-linear frequency scale to yield a final equalization filter by passing the combination filter through a set of all-pass filters by the mobile device.

8. The method, as claimed in claim 1, wherein the at least one rendering device comprises a plurality of rendering devices, the method further comprising:

synchronizing the plurality of rendering devices in time by;

calculating a delay between broadcast of the calibration signal from each of the plurality of rendering devices and receipt of the calibration signal at a microphone of the mobile device; and

determining a delay compensation filter by subtracting the calculated delays from a pre-determined maximum delay by the mobile device.

9. The method of claim 1, further comprising:

obtaining one or more angles of a location of the at least one rendering device with respect to a reference position by the mobile device.

10. A computer program product comprising computer executable program code recorded on a computer readable non-transitory storage medium, said computer executable program code when executed, causing a method performed by a mobile device for improving audio quality of an audio system comprising of a source device and at least one rendering device by calibrating the at least one rendering device, the method comprising:

determining by a processing unit of the mobile device, one or more frequency characteristics of at least one microphone of the mobile device;

sending, by the mobile device, a calibration signal to the source device for playback by the at least one rendering device;

capturing, by the at least one microphone of the mobile device, the calibration signal played back by the at least one rendering device;

calculating, by the mobile device, an impulse response for the calibration signal played back by the at least one rendering device based at least on the determined one or more frequency characteristics of the at least one microphone;

determining calibration settings based at least on the impulse response; and

providing the determined calibration settings to the source device for application thereby.

11. The computer program product, as claimed in claim 10, further comprising:

determining a relative distance of the at least one rendering device, said determining the relative distance comprising;

capturing a reference signal, wherein the reference signal is played by the at least one rendering device; and

determining the relative distance of the at least one rendering device by calculating a delay in the captured reference signal.

12. The computer program product, as claimed in claim 10, further comprising:

calculating a crossover filter using the impulse response, wherein cut-off of the crossover filter is based on a frequency response of the impulse response.

13. The computer program product, as claimed in claim 10, further comprising:

determining loudness of the at least one rendering device using the impulse response by calculating energy of the impulse response.

14. The computer program product, as claimed in claim 10, further comprising:

correcting a response of the at least one rendering device, said correcting comprising;

mimicking a non-linear frequency scale of a human auditory system by passing the impulse response through a set of all-pass filters;

computing a finite impulse response (FIR) filter, wherein the FIR filter is a minimum phase filter having a magnitude response that is an inverse of the mimicked non-linear frequency scale; and

inverting the non-linear frequency scale to yield a final equalization filter by passing the FIR filter through a set of all-pass filters.

15. The computer program product, as claimed in claim 10, further comprising:

correcting a response of the at least one rendering device, said correcting comprising;

mimicking a non-linear frequency scale of a human auditory system by passing the impulse response through a set of all-pass filters;

computing a infinite impulse response (IIR) filter, wherein the IIR filter is a minimum phase filter having a magnitude response that is an inverse of the mimicked non-linear frequency scale; and

inverting the non-linear frequency scale to yield a final equalization filter by passing the IIR filter through a set of all-pass filters.

16. The computer program product, as claimed in claim 10, further comprising:

correcting a response of the at least one rendering device, said correcting comprising;

mimicking a non-linear frequency scale of a human auditory system by passing the impulse response through a set of all-pass filters;

computing a combination filter, wherein the combination filter is a minimum phase filter having a magnitude response that is an inverse of the mimicked non-linear frequency scale and the combination filter is a combination of FIR and IIR filters; and

inverting the non-linear frequency scale to yield a final equalization filter by passing the combination filter through a set of all-pass filters.

17. The computer program product, as claimed in claim 10, wherein the at least one rendering device comprising a plurality of rendering devices, the method further comprising:

synchronizing the plurality of rendering devices in time by;

calculating a delay between broadcast of the calibration signal from each of the plurality of rendering devices and receipt of the calibration signal at a microphone of the mobile device; and

determining a delay compensation filter by subtracting the calculated delays from a pre-determined maximum delay.

18. The computer program product of claim 10, the method further comprising:

obtaining one or more angles of a location of the at least one rendering device with respect to a reference position by the mobile device.

19. A mobile device configured to improve audio quality of an audio system comprising of a source device and at least one rendering device by calibrating the at least one rendering device, the mobile device comprising:

a microphone; and

a processing unit configured to;

determine one or more frequency characteristics of the microphone;

send a calibration signal to the source device for playback by the at least one rendering device;

capture, by the microphone, the calibration signal played back by the at least one rendering device;

calculate an impulse response for a calibration signal played back by the at least one rendering device based at least on the determined one or more frequency characteristics of the microphone;

determine calibration settings based at least on the impulse response; and

provide the determined calibration settings to the source device for application thereby.

20. The mobile device of claim 19, wherein the processing unit is further configured to determine a relative distance of the at least one rendering device by:

determining the relative distance of the at least one rendering device by calculating a delay in a reference signal captured by the microphone, wherein the reference signal is played by the at least one rendering device.

21. The mobile device of claim 19, wherein the processing unit is further configured to:

obtain one or more angles of a location of the at least one rendering device with respect to a reference position.