The audio industry does not have a standard for playback system calibration, but in the movie industry a calibration standard has been defined by the Society of Motion Picture and Television Engineers (SMPTE).^[6] The standard states that a single channel pink noise signal with an RMS level of -20 dB relative to a full-scale sinusoid^[7] should be reproduced at 83 dB SPL.^[8]

ReplayGain adapts the SMPTE calibration concept for music playback. Under ReplayGain, audio is played so that its loudness, as measured using the procedures described in Loudness measurement above, matches the loudness of a pink noise signal with an RMS level of -14 dB relative to a full-scale sinusoid,^[9] also measured using the procedures described above.

In ReplayGain implementations, the reference level is described in terms of the SMPTE SPL playback level. By the SMPTE definition, the 83 dB SPL reference corresponds to -20FS dB system headroom. The -14 dB headroom used by ReplayGain therefore corresponds to an 89 dB SPL playback level on a SMPTE calibrated system and so is said to be operating with an 89 dB reference level.

SMPTE cinema calibration calls for a single channel of pink noise reproduced through a single loudspeaker. In music applications, the ideal level of the music is actually the loudness when both speakers are in use. So, ReplayGain is calibrated to two channels of pink noise.^[10]

Here is "official" reference wav file:

http://replaygain.hydrogenaudio.org/proposal/ref_pink.wav

Its track gain should be +6.0 for 89 dB reference level.