La chienne (1931)

From the Cinémathèque Française:

The Bitch was restored in 2014 by Les Films du Jeudi and La Cinémathèque française, with support from the CNC and the Franco-American Cultural Fund - DGA - MPA - SACEM – WGAW.

The restoration of the sound was carried out at the L.E. Diapason studio in order to recover the intelligibility of the dialogues whilst preserving the sound of the film typical of the beginnings of speaking films.

From the Criterion booklet:

The original monaural soundtrack was remastered from the 35mm optical soundtrack negative and restored by L.E. Diapason.

One should expect a track taken straight from the 35mm optical soundtrack negative to sound better than it does on the Criterion blu-ray, which does not present the soundtrack restoration as L.E. Diapason intended.

Noise reduction has been applied -- enough to quality as extreme noise reduction -- and the dialogue and music sound muffled. Ambient street sounds are mostly gone, or at least attenuated to the point of being too faint to be audible at normal volumes.

The French M6 Vidéo blu-ray* presents L.E. Diapason's sound restoration without any downstream filtering. It sounds much more detailed than the Criterion and is not muffled. 

Update (9/12/2021): Added the Opening DVD, as well as a comparison video. The DVD generally sounds better than the Criterion blu-ray despite being much noisier and sourced from higher-generation elements. The M6 blu-ray still sounds better overall, though.

*This disc does not have English subtitles. It also has one redundant stray black frame at 01:13:21.