When was the last time you turned on the subtitles while watching a movie? Does it ever seem like the music and sound effects, especially the explosions, are as loud as ever, but the dialogue’s barely above a whisper? Does it seem like older movies, movies like Jaws and Star Wars, were easier to understand? Are we just getting older and losing our hearing? That’s one possibility, but if the sound quality of your last moviegoing experience resembles the “Empire Strikes Back meets Christopher Nolan” parody video posted on my blog, your ears probably aren’t playing tricks on you:https://www.youtube.com/watch?v=IpWAOM3XC9QCinematic sound has changed dramatically over the past few decades, in some ways for the better and in other ways maybe not so much. Those changes can tell us a lot about the value of sound, all the different moving parts and new technologies that can be involved in creating just the right audio experience, and how even the biggest names in Hollywood can overlook its importance. One of those big names is director Christopher Nolan, and his films in general, and the movie Tenet in particular, sparked debate about whether his distinctive use of muted dialogue and booming music is a good or bad thing. But that question didn't start with him: a Los Angeles Times article from 1996 about the teen horror movie The Craft raises some very familiar-sounding complaints about the trend of music and sound effects drowning out the dialogue, and it suggested that teenagers and new media are to blame. "New media" back then meant loud music videos and the younger generation was Generation X, which just goes to show how long this trend's been developing. Christopher Nolan is, however, something of a unique case, and his movies are often at the forefront of cinematic audio trends. According to sound editors who’ve worked with him, he believes in actively engaging the audience and focusing their attention through the use of sound, and his actors, like many Hollywood actors these days, tend to forego theatrical performances for a more soft-spoken, naturalistic style of speaking that isn’t always easy to pick up on a microphone. He’s also very enthusiastic about digital audio’s potential for crafting ambient soundscapes, and his movies often rely on a unique auditory illusion called a Shepard tone to set the pace and create tension. A Shepard tone is a sequence of tones on three octaves layered together: the highest octave seems to fade as it ascends while the middle and lowest octaves seem to grow louder. Since two out of three octaves are growing louder at any given time, our brains combine them into a single tone that seems to be getting higher and higher, or lower and lower if the tones are played the other way around, without ever really changing. Listening to it can be a dizzying experience, and there’s a link on my blog to a video that lets you hear the effect for yourself. You might also recognize it as a sound that shows up pretty often in Christopher Nolan’s movies, from The Dark Knight to Dunkirk:https://www.youtube.com/watch?v=MShclPy4KvcOne quote from the director in Tom Shone’s book The Nolan Variations, however, gives us a clue about some of the other reasons cinematic sound’s changed in recent years. “I was a little shocked to realize how conservative people are when it comes to sound,” Nolan says, “because you can make a film that looks like anything, you can shoot on your iPhone, no one’s going to complain. But if you mix the sound a certain way, or if you use certain sub-frequencies, people get up in arms.” Some of my listeners might remember a recent interview with...