Noiz2
Sound Ninja
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The thing is we are probably listening to an optical track as well which by it's very nature is narrow band, you can also hear some of the gating effect that optical also gives.
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Actually if your not listening to 5.1 or SDDS, you are almost certainly listening to an optical track.
In 57 it was probably a mono optical and that was pre Dolby and such so yes small bandwidth and pretty noisy.
Today it would be "stereo" (generally "Dolby stereo" which is a matrixed 4.0 mix) and Dolby SR encoded and really pretty close to full bandwidth and very little noise.