It’s called “dialogue boost” and it turns up the volume on the dialogue track relative to the score, ambient sound or effects.
The catch is it’s only available on a selection of Amazon Prime Video’s originals, including Jack Ryan, The Marvelous Mrs Maisel, Being The Ricardos and Beautiful Boy.
There are already some expensive sound systems and certain TV sets which have a similar feature, but Amazon claims it’s the first streaming platform to roll it out on a global scale.
To turn it on, you select it from the audio and subtitles drop-down menu on an individual title, and it will give you two options: “English Dialogue Boost: High” or “English Dialogue Boost: Medium”.
The title page for a TV show or movie will indicate whether dialogue boost is available.
The feature was originally developed for hearing-impaired viewers, according to Variety.