Volume level of an audio system with the volume at the 0 decibel setting resulting in 85 decibel volume with a test tone and 105 decibel peaks. Dolby reference level is the volume level used in movie theaters for movie presentations (although this level is sometimes turned down). he reference level is set using a test tone generated by a surround sound preamplifier and a sound pressure level meter (SPL meter) to measure the sound output or volume. While providing a realistic and enlivening auditory experience, the reference level is very loud and is often turned down somewhat by listeners. However, surround sound audio systems should be set to the Dolby reference level and all channels properly equalized (each channel putting out the same sound pressure levels with a reference signal) even if the system will not be listened to at the true reference level.