Determine Signal/Noise Ratio

Signal/noise ratio (SNR) can be found in the the tape recorder's specification, along with the measurement conditions. The desired measurement condition for this app is: relative to 0 dB without noise reduction. If the specified SNR is given under a different condition, adjustment will be necessary. For example, if the SNR is specified relative to the maximum saturation level, it should be adjusted by subtracting the headroom.

If the tape recorder's specification is unavailable, the SNR can be approximated. For a cassette deck, pick a number between 50 ~ 55 dB; for a reel-to-reel deck pick a number between 55 ~ 60 dB. The SNR doesn't have to be accurate as it only suggests a rough range for the audio compressor.