Apparatus and method for calibrating recording and transmission systems
First Claim
1. 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 having simultaneous frequency components throughout the audio spectrum and having, as a repetitive identifier, brief interruptions of a substantially fixed time period of the wide frequency range signal occurring periodically, wherein the time period of the interruptions is long enough to be heard in a reverberant room yet short enough to avoid disrupting the ear'"'"'s ability to determine the level and spectral content of the wide frequency range signal, andmeans for applying said test signal to said recording medium or said transmission channel.
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Accused Products
Abstract
An audibly distinctive test signal, a pink noise signal at a standard level and periodic but brief interruptions (optimized for the ear'"'"'s memory for level and spectral differences), is applied to a recording medium or transmission channel. The test signal recovered from the recording medium or transmission channel is compared and matched to a reference uninterrupted pink noise signal at a standard level, the interruptions being used to switch between the test and reference signals and to provide 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 transmission/reception calibration can be achieved primarily by ear and, if desired, also by applying the signals to measuring instruments.
152 Citations
50 Claims
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1. 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 having simultaneous frequency components throughout the audio spectrum and having, as a repetitive identifier, brief interruptions of a substantially fixed time period of the wide frequency range signal occurring periodically, wherein the time period of the interruptions is long enough to be heard in a reverberant room yet short enough to avoid disrupting the ear'"'"'s ability to determine the level and spectral content of the wide frequency range signal, and means for applying said test signal to said recording medium or said transmission channel.
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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.
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17. 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.
- 29. A recorded medium having a test signal recorded thereon, said test signal having the characteristics substantially of a wide frequency range signal having simultaneous frequency components throughout the audio spectrum and having, as a repetitive identifier, brief interruptions of a substantially fixed time period of the wide frequency range signal occurring periodically, wherein the time period of the interruptions is long enough to be heard in a reverberant room yet short enough to avoid disrupting the ear'"'"'s ability to determine the level and spectral content of the wide frequency range signal.
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31. 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.
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35. 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.
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39. 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.
Specification