Abstract: An audio recording may be repaired by implementing a processor to process the harmonic signal content of the audio recording; calculating a difference signal from the harmonic signal content by subtracting a predicted harmonic signal from a detected harmonic signal, the predicted harmonic signal being obtainable by a predictor means and the detected harmonic signal being detected by the processor; defining a threshold for the difference signal above which the difference signal indicates the occurrence of one or more acoustic excitation events; and thereby producing an events display which allows an operator to visually distinguish between indicated excitation events that are present as a result of a disturbance in the audio recording and indicated excitation events that are present as a result of natural harmonics in the audio recording; and repairing one or more of the displayed excitation events by a repair circuit which is in communication with the processor.

Abstract: An audio recording may be repaired by implementing a processor to process the harmonic signal content of the audio recording; calculating a difference signal from the harmonic signal content by subtracting a predicted harmonic signal from a detected harmonic signal, the predicted harmonic signal being obtainable by a predictor means and the detected harmonic signal being detected by the processor; defining a threshold for the difference signal above which the difference signal indicates the occurrence of one or more acoustic excitation events; and thereby producing an events display which allows an operator to visually distinguish between indicated excitation events that are present as a result of a disturbance in the audio recording and indicated excitation events that are present as a result of natural harmonics in the audio recording; and repairing one or more of the displayed excitation events by a repair circuit which is in communication with the processor.

Abstract: Audio processing apparatus in which a payload signal is inserted into a primary audio signal comprises a noise generator operable to generate a noise signal in dependence on the payload signal; a level detector for detecting a signal level of the primary signal; a modulator for respectively increasing or decreasing the level of the noise signal in response to an increase or a decrease of the detected signal level of the primary audio signal, to generate a modulated noise signal; a combiner for combining the primary signal and the modulated noise signal; and a signal delay arrangement; the modulator operating with respect to the signal delay arrangement so that a decrease in the level of the noise signal is time-advanced with respect to the corresponding decrease in the signal level of the primary audio signal.