Retrieval procedures

If a speech file is lost AND its computer backup is also lost (OR the backup was never made!!!) then the digital tape recording safety backup will have to be used. This raises a number of questions. If the recordings are transferred to computer form in the digital domain, then an OROS AI-PCM type interface will be required - but this does not allow a resampling rate of 20kHz-19.8kHz is closest possible. This retrieval method is only possible if the recording was made on a PCM or DAT machine where the pre-emphasis was switched off. The alternative is to copy in the analogue domain, the problems here are:

1. There is normally a degradation of frequency and phase responses and signal-to-noise ratio is reduced (the latter effect is possibly masked by the reported poor signal to noise of OROS A/D board).
2. The gain of the original signal is relatively poorly defined because the gain on the PCM unit is infinitely variable and there is no automatic method of noting the gain set for the microphone channel for each speaker. The calibration signal should be used for this purpose.