Ray Dolby was one of the true audio pioneers and his “A” Noise Reduction system became an industry standard. In the age of digital recording it’s obsolete, but creative engineers find ways to use equipment in alternative ways – like the “Dolby Trick”
Used this way, Dolby A becomes an expander, lifting high frequencies more than low ones, and can impart a soft, breathy quality to voices. It’s a frequency- and level-dependent effect, hard to duplicate without Dolby hardware. These cat.22 A cards have been modified to disable the lower two frequency bands, enhancing the effect
Once you hear it, you’ll want it!