Ikiru (1952)

Both the Toho and Criterion blu-ray audio tracks have been cleaned up quite a bit, but Criterion did a better job of it. Its noise floor is lower and its bass frequencies are intact. The complete absence of these frequencies on the Toho is most noticeable with all music and during the scene exactly 2 hours into the film -- the rumble of the tractor has been wiped out on the Toho. Both tracks have had their high-end subjected to noise reduction, at the expense of some dialogue clarity.

The opening music demonstrates the biggest difference - the upper brass notes have been chopped off due to noise reduction on the Criterion blu-ray, whereas on the Criterion DVD they're vibrant (albeit distorted) and much more alive. Both tracks were no doubt originally transferred from the same limited optical elements--and it's actually quite likely that they're the exact same transfer, only with different post-processing/mastering--but the dialogue on the DVD sounds less hollow. The differences here aren't nearly as discernible as they are with the flawed Shochiku restorations, but they are still audible.

Bass frequencies on the DVD are intact and quieter than on the blu-ray, and it's obvious to me that they were EQed to be more prominent on the blu-ray.

I should emphasise that the DVD audio is very hissy and has a substantial amount of 'selective crackle' marking all dialogue. Still, I much prefer it for its untampered-with high-frequency detail, warts and all.

Update (8/26/2021): Added the BFI blu-ray and Amazon/BFI Player download. Both are the same mastering and sound better than the Criterion DVD.