Have movies and TV shows tricked you into thinking that your hearing is going downhill? Have you resorted to reading closed captions so you don't have to rewind to know what's being said? Neither is possible when you're sitting in a movie theater. It's not your hearing, or at least it's not only your hearing. Everyone has noticed that actors appear to mumble in movies way more than they did ten, twenty, or more years ago. There are many factors that contribute to this trend. Vox talked to professional dialogue editor Austin Olivia Kendrick to get the technical side of the story. It almost seems like the movie industry as a whole has decided that the realism now possible is more important than the viewer's comfort and comprehension, and if we have a problem with it, we can read captions.
YouTube commenter Chronically Me added some interesting information about captioning.
As a captioner, I cannot "worry a little bit less about picking up every single word that gets said", and I guarantee the vast majority of captioners don't have the highest-end Dolby surround sound. Speech recognition technology is leagues ahead of where it has been, but it still requires a human to come in and fix things, especially when there is background noise or strong accents. If you've ever watched a TikTok or Youtube video with auto-captioning, you know this, especially if it included uncommon names or community-specific language like neurodivergent. Also, captions are available on nearly every platform because they are required to provide them and have been criticized and, in some cases, sued* for not providing them as breaking the ADA in America or similar laws in other jurisdictions.
Also, this is probably nitpicky, but if the language of the words written is the same as the language of the words spoken, it's captions, if they are in a different language, they are subtitles. I know no one else cares, but it is an important distinction because they serve two very different purposes and thus have different requirements. This is particularly important to note when something is dubbed in a new language, the original subtitles are not going to suit the dubbed version because they will not match what's being said and will lack important details like speaker labels and atmospherics (descriptions of a sound that isn't dialogue). This is also why subtitled media often is inaccessible for the Deaf community, since it's assuming you can hear, just not understand, the spoken words.
*The National Association of the Deaf sued Netflix in 2011 for not providing captions in their streaming content. look up NAD v Netflix if you wanna read more about that.
So, when I turn on the words to understand mumbling, it's captioning. When my family watches a movie in Korean and we need a typed translation, it's subtitles. When my daughter watches a movie in German with German subtitles to practice the language, it's captions. If I join in and change the written language to English, it's subtitles. And when filmmakers let you question the quality of your own hearing ability, it's gaslighting.