Audio testing system and method

• US 20030235311A1
• Filed: 06/21/2002
• Published: 12/25/2003
• Est. Priority Date: 06/21/2002
• Status: Active Grant

• Current Assignee: Dolby Laboratories Licensing Corporation (Dolby Laboratories Incorporated)
• Original Assignee: Lake Technology Ltd. (Dolby Laboratories Incorporated)
• Inventors: Penfold, Stephen John, Grancea, Alexandru
• Granted Patent: US 7,120,256 B2
• Time in Patent Office: Days
• US Class Current: 381/58
• CPC Class Codes: H04R 2499/13 Acoustic transducers and sound field adaptation in vehicles
• CPC Class Codes: H04R 29/002 Loudspeaker arrays
• CPC Class Codes: H04R 5/02 Spatial or constructional arrangements of loudspeakers

Abstract

A method is provided for increasing the quality of audio reproduction of a binaural rendering in a passenger environment having a number of seats, each seat having an audio system including a headphone jack for interconnection with a headphone device. The method comprising the steps of: playing predetermined audio tones over the audio system, and interconnecting a testing system to the headphone jack of the seats to monitor the signal received by the headphone jack to determine the audio quality of reproduction of the seat. The invention extends to an audio monitoring device, an audio monitoring system, and a storage medium carrying said audio tones.

Claims

1. A method of increasing the quality of audio reproduction of a stereo rendering in a multi-listener environment having an audio system with a plurality of multi-channel listener stations, each listener station having an audio transducer interface for interconnection with an audio transducer device, the method comprising the steps of:

(a) playing predetermined first and second audio test signals over respective first (L) and second (R) channels of the audio system;

(b) interconnecting a testing apparatus in turn to the audio transducer interface of at least some of said listener stations and monitoring the audio test signals received by said audio transducer interface to identify a fault condition, on the basis of the received audio test signals.

2. A method as claimed in claim 1 wherein said monitoring of said signal includes at least two of the following:

(i) monitoring for the presence of both a left and right channel signal in said audio transducer device;

(ii) monitoring for a level imbalance between the first and second signals of said audio transducer device;

(iii) monitoring for a phase imbalance between the first and second signals of said audio transducer device;

(iv) determining whether a reversal of polarity exists between the left and right signals of said audio transducer device;

(v) determining if the first and second signals are reversed;

(vi) determining if the first and second signals include a distortion exceeding a predetermined threshold; and

(vii) determining if a DC bias exceeding a predetermined threshold exists in the first or second signals;

(viii) monitoring if a noise cancelling voltage exists in the first or second signals; and

(ix) determining if the first or second signals are earthed.

3. A method as claimed in claim 2 which includes monitoring at least three of (i) to (ix).

4. A method as claimed in claim 2 which includes monitoring at least four of (i) to (ix).

5. A method as claimed in claim 1 wherein the first and second audio test signals are distinguishable on the basis of at least one variation to assist in analysis by the testing apparatus of the fault condition.

6. A method as claimed in claim 5 wherein the variation involves a predetermined phase shift between the first and second audio test signals.

7. A method as claimed in claim 1 wherein the stereo rendering is a binaural rendering, and the audio transducer interface is a speaker interface.

8. A method as claimed in claim 7 wherein the speaker interface is a headphone interface.

9. A method as claimed in claim 7 wherein the listener stations are seat-based and the multi-listener environment is a passenger environment.

10. A method as claimed in claim 9 wherein said passenger environment is chosen from a group including a passenger airline, a passenger vessel, a passenger train or a passenger vehicle.

11. A method as claimed in claim 6 wherein the first test signal includes a first periodic tone played on the first channel and the second test signal includes a second periodic tone played on the second channel, said second periodic tone having substantially the same period as that of the first periodic tone but having a predetermined phase delay relative to the first periodic tone.

12. A method as claimed in claim 11 which further comprises the step of using the testing apparatus to analyze the phase difference between the outputted tones played on the first and second channels to determine the fault condition.

13. A method as claimed in claim 12 which further comprises the step of delaying the phase of the tone played on one of the channels and analyzing the phase difference between the delayed tone and the tone played on the other channel to determine the fault condition.

14. A method as claimed in claim 13 which comprises the step of delaying the phase of the tone played on the other channel and analyzing the phase difference between the delayed tone played on the other channel and the tone played on the one channel to determine the fault condition.

15. A testing system for increasing the quality of audio reproduction of a stereo rendering in a multi-listener environment, said environment having a plurality of multi-channel listener stations, each listener station having an audio system including an audio transducer interface for interconnection with an audio transducer device, the testing system comprising:

audio storage means for interconnection with the audio system of each listener station for the storage and playback of predetermined audio test signals over the audio system; and

at least one audio testing apparatus adapted to be interconnected in turn with the audio transducer interface of each listener station to monitor the audio reproduction quality of the predetermined audio test signals and to assist in the analysis of a fault condition.

16. A system as claimed in claim 15 wherein said audio storage means includes said predetermined audio signals stored in a machine readable format on a detachable storage medium inserted into a machine player which outputs first and second audio test signals to the audio system of each audio station in said multi-listener environment.

17. A system as claimed in claim 15 wherein said testing apparatus is arranged to compare first (L) and second (R) audio test signals so as to determine at least two of:

the presence of both a left and right channel signal;

the presence of a level imbalance between the left and right signals;

the presence of a phase imbalance between the left and right signals of said headphones;

the presence of a reversal of polarity between the left and right signals;

the presence of a reversal of the left and right signals;

the presence of distortion exceeding a predetermined threshold in the left or right signals;

the presence of a DC bias exceeding a predetermined threshold;

the presence of a noise cancelling voltage or the determination of the left or right signals being earthed.

18. A system as claimed in claim 15 wherein said predetermined audio test signals include a first periodic tone played on a first channel and a second periodic tone played on a second channel, said second periodic tone having substantially the same period as the period of the first periodic tone but having a predetermined phase shift relative to the first periodic tone, and said testing apparatus includes a first phase detector for detecting the phase difference between said first and second tones received on said first and second channels.

19. A system as claimed in claim 18 wherein said testing apparatus includes a second phase detector for comparing the phase difference between a phase delayed first channel and a second channel.

20. A testing apparatus for monitoring the quality of audio reproduction of stereo signals at a listener station, the device comprising:

first and second channel inputs for receiving first (L) and second (R) stereo test signals from the listener station;

phase detection means for detecting the phase differences between the left and right stereo test signals;

level detection means for detecting the relative levels of the first and second stereo test signals; and

analyzing means for analyzing outputs of the phase and level detection means and for generating a fault type on the basis of the analysis.

21. A testing apparatus according to claim 20 which includes first and second phase shifters for shifting the phases of the left and right signals to yield left and right phase shifted signals, the phase detection means comprising a first phase detector for detecting the phase differences between the left and phase shifted right signals, and a second phase detector for detecting the phase differences between the right and phase shifted left signals.

22. A testing apparatus according to claim 21 which includes gain control means for controlling the levels of the left and right input signals whilst preserving their amplitude ratios.

23. A testing apparatus according to claim 21 in which the analyzing means includes at least one look-up table for receiving and analyzing phase-related measurements constituting the outputs from the phase detection means.

24. A testing apparatus according to claim 23 in which the analyzing means includes at least one look-up table for receiving and analyzing amplitude-related measurements constituting the outputs from the level detection means.

25. A testing apparatus according to claim 24 which includes display means for displaying the fault types derived from the at least one look-up table, the fault types being chosen from a group including at least two of the following:

phase imbalance between the left and right test signals, level imbalance between the left and right test signals, absence of a left or right test signal, reversal, polarity reversal, distortion or DC bias above a predetermined threshold, absence of noise cancelling voltage, and earthing of the left or right test signal.

26. A testing apparatus according to claim 20 which includes a connector for enabling the left and right inputs to be selectively and in turn connected to a plurality of headphone interfaces at a series of audio stations in a multi-listener environment.

27. A testing apparatus for monitoring the quality of audio reproduction of a stereo rendering in a multi-listener environment having a plurality of listener stations, with each listener station having an audio system including an audio transducer interface for interconnection with an audio transducer device, the testing apparatus being adapted to be inserted in turn into the audio transducer interface of each listener station to monitor the audio reproduction quality of the audio test signals generated by audio playback means for playback over the audio system of each listener station, the testing apparatus comprising left and right inputs for receiving left and right components of the test signals from the listener station;

phase detection station;

phase detection means for detecting the phase differences between the left and right components of the test signals;

level detection means for detecting the relative levels of the left and right components of the test signals; and

analyzing means for analyzing outputs of the phase and level detection means and for generating, where present, a fault type on the basis of the analysis.

28. A testing system for testing first (L) and second (R) channels of an audio stereo system in a multi-listener environment having a plurality of listener stations, each listener station having an audio transducer interface for interconnecting with an audio transducer device, the system comprising:

audio storage playback means for interconnection with the audio system of each listener station for the storage and playback of predetermined first and second test signals over the respective first and second channels of the audio system, and

at least one testing apparatus adapted to be connected in turn with the audio transducer interface of each listener station to monitor the audio reproduction quality of the predetermined audio test signals, wherein the audio playback means are arranged to generate first and second audio test signals which are distinguishable on the basis of at least one variation, and wherein said testing apparatus is arranged to detect any further variation in the first and second audio test signals, for assisting in analysis of a fault condition.

29. A system as claimed in claim 28 wherein the variation involves a phase shift between the first and second test signals.

30. A system as claimed in claim 29 which includes at least one phase detector for detecting the relative phases of the first and second test signals, and an analyzer responsive to the phase detector for analyzing a particular identifiable fault condition on the basis of the phase related measurement.

31. A system as claimed in claim 30 wherein the identifiable fault condition is chosen from a group including reversed polarity, reversed channels, a combination of the above two and phase imbalance, and wherein each fault condition is identifiable on the basis of a characteristic phase vector set.