EP0227389A2
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EP
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Apparatus and method for calibrating recording and transmission systems
Assignee: Dolby Laboratories Licensing Corp
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Filing: 1986-12-11
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Granted: —
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Expires: 2006-12-11
Abstract
Abstract An audibly distinctive test signal provided by a generator (6) is a pink noise signal at a standard level with periodic but brief interruptions (optimized for the ear's memory for level and spectral differences) acting as an identifier. The test signal is applied to a recording medium or transmission channel (14), preferably via an equalizer (16) and gain setting means (181. The test signal recovered from the recording medium or transmission channel by playback or receiving means (22) is compared and matched to a reference uninterrupted pink noise signal provided at a standard level by a generator (24). The interruptions are used to switch between the test and reference signals and to provide via equalizer (34) and speaker (28) an audible cue as to the identity of the signal heard at any moment so that a rapid confirmation and adjustment, if necessary, of recording/reproduction or transmis- sion/reception calibration can be achieved primarily by ear and, if desired, also by applying the signals to measuring instruments, such as a meter (30) and spectrum analyser (32).
Inventors
- 👤 Ray Milton Dolby
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-03 16:11
CPC Classifications
G; G11; G11B; G11B20/00; G11B27/00; G11B27/36; G11B20/10; G11B20/18; G11B20/1816; G11B20/182
Claims Analysis
Total Claims: 57
Claim 1
Independent Claim
57 words
Apparatus for use in calibrating an audio recording medium or an audio transmission channel, comprising, means for generating a test signal, said test signal comprising a wide frequency range signal including frequency components throughout the audio spectrum and including a repetitive identifier, and means for applying said test signal to said recording medium or said transmission channel.
Claim 2
Dependent Claim
57 words
Apparatus for use in calibrating an audio recording medium or an audio transmission channel, comprising, means for generating a test signal, said test signal comprising a wide frequency range signal including frequency components throughout the audio spectrum and including a repetitive identifier, and means for applying said test signal to said recording medium or said transmission channel.
Claim 3
Dependent Claim
20 words
The combination of claim 1 wherein said repetitive identifier constitutes brief interruptions of the wide frequency range signal occurring periodically.
Claim 4
Dependent Claim
23 words
The combination of claim 2 wherein the interruptions are in the order of 20 milliseconds in length and repeat substantially every two seconds.
Claim 5
Dependent Claim
20 words
The combination of any of claims 1 through 3 wherein said wide frequency range signal is a pink noise signal.
Claim 6
Dependent Claim
143 words
5 . Apparatus for use in calibrating the playback from an audio recording medium or the reproduction from an audio transmission channel, the recording medium having a test signal recorded thereon or the transmission channel having a test signal applied thereto, the test signal having the characteristics substantially of a wide frequency range signal including frequency components throughout the audio spectrum and the test signal having a repetitive identifier, the apparatus comprising means for recovering said test signal from the recording medium or transmission channel, means for generating a reference signal having the characteristics substantially of said wide frequency range signal, said means receiving said recovered test signal also receiving said reference signal, said means including switching means responsive to said repetitive identifier in the recovered test signal for alternately selecting as an output signal said recovered test signal and said reference signal.
Claim 7
Dependent Claim
143 words
5 . Apparatus for use in calibrating the playback from an audio recording medium or the reproduction from an audio transmission channel, the recording medium having a test signal recorded thereon or the transmission channel having a test signal applied thereto, the test signal having the characteristics substantially of a wide frequency range signal including frequency components throughout the audio spectrum and the test signal having a repetitive identifier, the apparatus comprising means for recovering said test signal from the recording medium or transmission channel, means for generating a reference signal having the characteristics substantially of said wide frequency range signal, said means receiving said recovered test signal also receiving said reference signal, said means including switching means responsive to said repetitive identifier in the recovered test signal for alternately selecting as an output signal said recovered test signal and said reference signal.
Claim 8
Dependent Claim
22 words
The combination of claim 5 wherein said switching means provides an indication as to which signal is selected as the output signal.
Claim 9
Dependent Claim
20 words
The combination of claim 5 wherein said repetitive identifier constitutes brief interruptions of the wide frequency range signal occurring periodically.
Claim 10
Dependent Claim
98 words
8 . The combination of claim 7 wherein said reference signal is uninterrupted and wherein said switching means selects said test signal so as to begin and end selections of the test signal as the output signal with an interruption and to have at least one interruption between the interruptions beginning and ending such selections of the test signal, and said switching means alternately selects said reference signal as the output signal for time periods substantially equal to the time periods of selection of the test signal, whereby the interruptions distinguish the test signal from the reference signal.
Claim 11
Dependent Claim
63 words
The combination of claim 8 wherein the interruptions are in the order of 20 milliseconds in length and repeat substantially every two seconds, said switching means provides for one interruption between the interruptions beginning and ending selections of the test signal, and the time periods during which the test signal and the reference signal are alternately the output signal are about four seconds.
Claim 12
Dependent Claim
47 words
The combination of claim 9 further comprising a meter and signal processing means in the signal path to said meter receiving said output signal, said signal processing means generating signals to compensate for interruptions in said test signal, whereby the meter is less affected by said interruptions.
Claim 13
Dependent Claim
60 words
11 . The combination of claim 9 further comprising a meter and signal processing means receiving said output signal for limiting the bandwidth of said output signal and applying the bandwidth limited signal to said meter, whereby the effect on the meter reading of frequency response errors in the system is reduced and the stability of the reading is increased.
Claim 14
Dependent Claim
23 words
The combination of claim 11 wherein the bandwidth is limited so as to extend from about 200 H z to about 4 kHz.
Claim 15
Dependent Claim
58 words
The combination of claim 8 further comprising a meter and signal processing means receiving said output signal for limiting the bandwidth of said output signal and applying the bandwidth limited signal to said meter, whereby the effect on the meter reading of frequency response errors in the system is reduced and the stability of the reading is increased.
Claim 16
Dependent Claim
23 words
The combination of claim 13 wherein the bandwidth is limited to so as to extend from about 200 Hz to about 4 kHz.
Claim 17
Dependent Claim
47 words
The combination of claim 8 further comprising a meter and signal processing means in the signal path to said meter receiving said output signal, said signal processing means generating signals to compensate for interruptions in said test signal, whereby the meter is less affected by said interruptions.
Claim 18
Dependent Claim
20 words
The combination of any of claims 5 through 15 wherein said wide frequency range signal is a pink noise signal.
Claim 19
Dependent Claim
156 words
Apparatus for use in calibrating a system for recording signals on and playing back signals from an audio recording medium or for applying signals to and reproducing signals from an audio transmission channel, comprising means for generating a reference signal and a test signal, said reference signal having the characteristics of a wide frequency range signal including frequency components throughout the audio spectrum, said test signal having the same characteristics as said reference signal with the additional characteristic of a repetititive identifier, means for recording said test signal on said recording medium or applying said test signal to said transmission channel, means for recovering said test signal from said recording medium or from said transmission channel, and means receiving said reference signal and said recovered test signal, said means including switching means responsive to the repetitive identifier in said test signal for providing an output signal alternating between said reference signal and said recovered test signal.
Claim 20
Dependent Claim
156 words
Apparatus for use in calibrating a system for recording signals on and playing back signals from an audio recording medium or for applying signals to and reproducing signals from an audio transmission channel, comprising means for generating a reference signal and a test signal, said reference signal having the characteristics of a wide frequency range signal including frequency components throughout the audio spectrum, said test signal having the same characteristics as said reference signal with the additional characteristic of a repetititive identifier, means for recording said test signal on said recording medium or applying said test signal to said transmission channel, means for recovering said test signal from said recording medium or from said transmission channel, and means receiving said reference signal and said recovered test signal, said means including switching means responsive to the repetitive identifier in said test signal for providing an output signal alternating between said reference signal and said recovered test signal.
Claim 21
Dependent Claim
22 words
The combination of claim 17 wherein said switching means provides an indication as to which signal is selected as the output signal.
Claim 22
Dependent Claim
20 words
The combination of claim 17 wherein said repetitive identifier constitutes brief interruptions of the wide frequency range signal occurring periodically.
Claim 23
Dependent Claim
104 words
2 0 . The combination of claim 19 wherein said reference signal is uninterrupted and wherein said switching means selects said recovered test signal so as to begin and end selections of the recovered test signal as the output signal with an interruption and to have at least one interruption between the interruptions beginning and ending such selections of the recovered test signal, and said switching means alternately selects said reference signal as the output signal for time periods substantially equal to the time periods of selection of the recovered test signal, whereby the interruptions distinguish the recovered test signal from the reference signal.
Claim 24
Dependent Claim
71 words
The combination of claim 20 wherein the interruptions are in the order of 20 milliseconds in length and repeat substantially every two seconds, said switching means provides for one interruption between the interruptions beginning and ending selections of the played back or reproduced test signal, and the time periods during which the played back or reproduced test signal and the reference signal are alternately the output signal are about four seconds.
Claim 25
Dependent Claim
47 words
The combination of claim 21 further comprising a meter and signal processing means in the signal path to said meter receiving said output signal, said signal processing means generating signals to compensate for interruptions in said test signal, whereby the meter is less affected by said interruptions.
Claim 26
Dependent Claim
58 words
The combination of claim 21 further comprising a meter and signal processing means receiving said output signal for limiting the bandwidth of said output signal and applying the bandwidth limited signal to said meter, whereby the effect on the meter reading of frequency response errors in the system is reduced and the stability of the reading is increased.
Claim 27
Dependent Claim
23 words
The combination of claim 23 wherein the bandwidth is limited to so as to extend from about 200 Hz to about 4 kHz.
Claim 28
Dependent Claim
58 words
The combination of claim 20 further comprising a meter and signal processing means receiving said output signal for limiting the bandwidth of said output signal and applying the bandwidth limited signal to said meter, whereby the effect on the meter reading of frequency response errors in the system is reduced and the stability of the reading is increased.
Claim 29
Dependent Claim
23 words
The combination of claim 25 wherein the bandwidth is limited to so as to extend from about 200 Hz to about 4 kHz.
Claim 30
Dependent Claim
47 words
The combination of claim 20 further comprising a meter and signal processing means in the signal path to said meter receiving said output signal, said signal processing means generating signals to compensate for interruptions in said test signal, whereby the meter is less affected by said interruptions.
Claim 31
Dependent Claim
20 words
The combination of any of claims 17 through 27 wherein said wide frequency range signal is a pink noise signal.
Claim 32
Dependent Claim
38 words
A recorded medium having a test signal recorded thereon, said test signal having the characteristics substantially of a wide frequency range signal having frequency components throughout the audio spectrum and including brief interruptions of the signal occurring periodically.
Claim 33
Dependent Claim
38 words
A recorded medium having a test signal recorded thereon, said test signal having the characteristics substantially of a wide frequency range signal having frequency components throughout the audio spectrum and including brief interruptions of the signal occurring periodically.
Claim 34
Dependent Claim
25 words
The recorded medium according to claim 29 wherein the interruptions are in the order of 20 milliseconds in length and repeat substantially every two seconds.
Claim 35
Independent Claim
151 words
A method of calibrating the playback from an audio recording medium or the reproduction from an audio transmission channel, the recording medium having a test signal recorded thereon or the transmission channel having a test signal applied thereto, the test signal having the characteristics substantially of a wide frequency range signal including frequency components throughout the audio spectrum and including a repetitive identifier, comprising generating a reference signal having the characteristics substantially of said wide frequency range signal, playing back or reproducing said test signal from the recording medium or transmission channel, alternately selecting as an output signal said played back or reproduced test signal and said reference signal, comparing the alternating test signal to said reference signal, and adjusting the level and spectral balance of the playing back or reproducing of said test signal in response to the comparing so as to reduce differences between it and said reference signal.
Claim 36
Independent Claim
151 words
A method of calibrating the playback from an audio recording medium or the reproduction from an audio transmission channel, the recording medium having a test signal recorded thereon or the transmission channel having a test signal applied thereto, the test signal having the characteristics substantially of a wide frequency range signal including frequency components throughout the audio spectrum and including a repetitive identifier, comprising generating a reference signal having the characteristics substantially of said wide frequency range signal, playing back or reproducing said test signal from the recording medium or transmission channel, alternately selecting as an output signal said played back or reproduced test signal and said reference signal, comparing the alternating test signal to said reference signal, and adjusting the level and spectral balance of the playing back or reproducing of said test signal in response to the comparing so as to reduce differences between it and said reference signal.
Claim 37
Dependent Claim
20 words
The method of claim 31 wherein said repetitive identifier constitutes brief interruptions of the wide frequency range signal occurring periodically.
Claim 38
Dependent Claim
17 words
The method of claim 31 wherein the alternately selecting is done in response to said repetitive identifier.
Claim 39
Dependent Claim
20 words
The method of any of claim 31 through 33 wherein said wide frequency range signal is a pink noise signal.
Claim 40
Independent Claim
150 words
A method of calibrating an audio recording apparatus and recording medium or an audio transmitting apparatus and transmission channel, comprising applying a test signal to the audio recording apparatus or audio transmitting apparatus, the test signal comprising a wide frequency range signal including frequency components throughout the audio spectrum and including a repetitive identifier, generating a reference signal having the characteristics substantially of said wide frequency range signal, recovering, using calibrated play back or reproduction apparatus, said test signal from the recording medium or transmission channel, alternately selecting as an output signal said recovered test signal and said reference signal, comparing the alternating recovered test signal to said reference signal, and adjusting the level and spectral balance of the recording apparatus and recording medium or the transmitting apparatus and transmission channel in response to the comparing so as to reduce differences between said recovered test signal and said reference signal.
Claim 41
Independent Claim
150 words
A method of calibrating an audio recording apparatus and recording medium or an audio transmitting apparatus and transmission channel, comprising applying a test signal to the audio recording apparatus or audio transmitting apparatus, the test signal comprising a wide frequency range signal including frequency components throughout the audio spectrum and including a repetitive identifier, generating a reference signal having the characteristics substantially of said wide frequency range signal, recovering, using calibrated play back or reproduction apparatus, said test signal from the recording medium or transmission channel, alternately selecting as an output signal said recovered test signal and said reference signal, comparing the alternating recovered test signal to said reference signal, and adjusting the level and spectral balance of the recording apparatus and recording medium or the transmitting apparatus and transmission channel in response to the comparing so as to reduce differences between said recovered test signal and said reference signal.
Claim 42
Dependent Claim
20 words
The method of claim 35 wherein said repetitive identifier constitutes brief interruptions of the wide frequency range signal occurring periodically.
Claim 43
Dependent Claim
17 words
The method of claim 35 wherein the alternately selecting is done in response to said repetitive identifier.
Claim 44
Dependent Claim
21 words
The method of any of claim 35 through 3 7 wherein said wide frequency range signal is a pink noise signal.
Claim 45
Independent Claim
172 words
A method of calibrating the spectral response of a system for recording signals on and for playing back signals from a recording medium or for applying signals to and reproducing signals from a transmission channel, comprising generating a reference signal and a test signal, said reference signal having the characteristics of a wide frequency range signal, said test signal having the same characteristics as said reference signal with the additional characteristic of a repetititive identifier, recording said test signal on said recording medium or applying said test signal to said transmission channel, playing back said test signal from said recording medium or reproducing said test signal from said transmission channel, alternately selecting as an output signal said played back or reproduced test signal and said reference signal, comparing the alternating played back or reproduced test signal to said reference signal, and adjusting the level and spectral balance in the system in response to the comparing so as to reduce differences between the played back or reproduced test signal and said reference signal.
Claim 46
Independent Claim
172 words
A method of calibrating the spectral response of a system for recording signals on and for playing back signals from a recording medium or for applying signals to and reproducing signals from a transmission channel, comprising generating a reference signal and a test signal, said reference signal having the characteristics of a wide frequency range signal, said test signal having the same characteristics as said reference signal with the additional characteristic of a repetititive identifier, recording said test signal on said recording medium or applying said test signal to said transmission channel, playing back said test signal from said recording medium or reproducing said test signal from said transmission channel, alternately selecting as an output signal said played back or reproduced test signal and said reference signal, comparing the alternating played back or reproduced test signal to said reference signal, and adjusting the level and spectral balance in the system in response to the comparing so as to reduce differences between the played back or reproduced test signal and said reference signal.
Claim 47
Dependent Claim
19 words
The method of claim 39 wherein said repetitive identifier constitutes brief interruptions of the wideband noise signal occurring periodically.
Claim 48
Dependent Claim
17 words
The method of claim 40 wherein the alternately selecting is done in response to said repetitive identifier.
Claim 49
Independent Claim
19 words
The method of any of claims 39 through 41 wherein said wideband noise signal is a pink noise signal.
Claim 50
Dependent Claim
118 words
The combination of claim 8 wherein said switching means includes divider means responsive to the beginning of said interruptions for generating a square wave having a transition at the beginning of each second interruption and means for delaying one transition of said square wave by the time length of an interruption to derive an asymmetrical square wave, said asymmetrical square wave defining the time periods during which the reference signal and test signal are selected as the output signal, the longer portion of the asymmetrical square wave including said delay defining the test signal time period, whereby the test signal time period begins and ends with an interruption and includes an interruption between the beginning and ending interruptions.
Claim 51
Dependent Claim
25 words
The combination of claim 43 wherein said divider means includes means responsive to the cessation of said recovered test signal for resetting said divider means.
Claim 52
Dependent Claim
118 words
The combination of claim 20 wherein said switching means includes divider means responsive to the beginning of said interruptions for generating a square wave having a transition at the beginning of each second interruption and means for delaying one transition of said square wave by the time length of an interruption to derive an asymmetrical square wave, said asymmetrical square wave defining the time periods during which the reference signal and test signal are selected as the output signal, the longer portion of the asymmetrical square wave including said delay defining the test signal time period, whereby the test signal time period begins and ends with an interruption and includes an interruption between the beginning and ending interruptions.
Claim 53
Dependent Claim
27 words
The combination of claim 45 wherein said divider means includes means responsive to the cessation of said recorded or recovered test signal for resetting said divider means.
Claim 54
Dependent Claim
16 words
The combination of claim 29 wherein the wide frequency range signal is a pink noise signal.
Claim 55
Dependent Claim
80 words
The apparatus of claim 1 wherein the apparatus is for use in calibrating a multi-track audio tape recorder/reproducer, wherein said means for generating a test signal synchronizes itself to the timing of the repetitive identifier of the test signal played back by a record head functioning as a playback head in at least one track, and said means for applying said test signal to said recording medium applies the synchronized test signal to one or more of the other tracks.
Claim 56
Independent Claim
82 words
The apparatus of claims 2 or 3 wherein the apparatus is for use in calibrating a multi-track audio tape recorder/reproducer, wherein said means for generating a test signal synchronizes itself to the timing of the brief interruptions of the test signal played back by a record head functioning as a playback head in at least one track, and said means for applying said test signal to said recording medium applies the synchronized test signal to one or more of the other tracks.
Claim 57
Dependent Claim
83 words
The apparatus of claim 4 wherein the apparatus is for use in calibrating a multi-track audio tape recorder/reproducer, wherein said means for generating a test signal synchronizes itself to the timing of the repetitive identifier or brief interruptions of the test signal played back by a record head functioning as a playback head in at least one track, and said means for applying said test signal to said recording medium applies the synchronized test signal to one or more of the other tracks.
References Cited (Backward Citations)
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