How Quiet is Too Quiet?
For things that humans hear with 0 decibels being absolute silence and 120 decibels being the threshold for pain. The limit of how quiet things can be on our planet: -23 decibels, which is the amount of noise made by air molecules bouncing off one another. Of course, it's much quieter in space — silent, in fact. But going to space is cheating since there's no air to propagate sound.
Human hearing full range representation
Digital sound uses a reverse scale and put 0 dB as a reference level before distortion becomes audible (or the loud parts of the sound wave are clipped). In such case -120 dB is the absolute silence or the limit of human hearing.
What is DTS-HD Master Audio
DTS-HD Master Audio is a combined lossless/lossy audio codec commonly used for surround-sound movie soundtracks. According to the DTS-HD White Paper, DTS-HD Master Audio contains 2 data streams: the original DTS Core stream and the additional "residual" stream which contains the "difference" between the original Master Audio signal and the lossy compression DTS Core stream.
DTS-HD Master Audio and DTS Core visual representation
DTS-HD MA supports up to 8 channels, while DTS Core limited by 6. The layout for 8 channel named 7.1 and for 6 - 5.1. The essential and the most popular layout is 5.1 as for today. But 7.1 setups is the studio standard for the best cinematic sound. The most Blu-ray soundtracks are 5.1, and a few of Blu-ray soundtracks that contain 7.1 channel information. Even though this amount increasing with a time.
The highest size correlation between the original DTS Core stream and the additional "residual" stream is around 25% to 75% or 1.3 GB to 3.7 GB for recent 2 hours movies with 7.1 layout. For regular 5.1 layout average correlation is about 40% to 60% or 1.3 GB to 2.0 GB. There are smaller correlations for the classic movies from the Golden Age of Hollywood. The ones, made more than 30 or 40 years ago, or from the 1930s, 40s, 50s and 60s.
We'll try to figure out how much audible information this additional 75% or 60% hold.