Heavy hiss and bass reduction on the original Japanese blu-ray (released by Studio Ghibli) and on the StudioCanal blu-ray -- both tracks are ostensibly the same. The later 'Hayao Miyazaki Collection' Japanese blu-ray has less high-frequency noise reduction and leaves the bass frequencies intact. The Japanese tracks on the old DVDs (both Japan and US) and the Disney blu-ray are unfiltered and sound much, much better.
Note: The waveforms of all of the above look identical -- no egregious compression/clipping.
English track:
Here, the first Japanese blu-ray, the StudioCanal blu-ray, and the Disney blu-ray use the same mastering with noise reduction. The second (Miyazaki Collection) Japanese blu-ray has much less NR, and the old Disney DVD has none.
More interestingly, every edition except the old Disney DVD exhibits a high level of clipping. Minor clipping, unlike noise reduction, isn't audible to most people, but the amount here absolutely should be.
