Why this creepy sound effect plays before movies begin

[00:00:00]You probably heard this sound before.

[00:00:09]>> [music] >> This is known as the THX deep note. It's been used in countless films during the section before the action movies begin especially theaters since the 80s. But how did it come to be used everywhere?

[00:00:22]And what makes the sound so creepy? So the short answer to both of those questions is Star Wars. Basically in the 80s when director George Lucas was making the Star Wars film The Empire Strikes Back, they previewed at a local theater in San Francisco and realized how catastrophic the sound system was in reproducing what was intended. And of course the sound system quality varied by theaters but they were all differing levels of bad.

[00:00:45]>> Vader's Now I'll listen.

[00:00:49]>> So George Lucas decided to create a new high-quality sound system standard to be followed by movie theaters around the world and recruited his audio engineer friend Tomlinson Holman for the job. He defined a series of criteria like a frequency response of 20 hertz to 20 K hertz, the human hearing range, without distortion or like precise speaker placements in the theaters for a consistency. And he named these tests the Tomlinson Holman experiment or THX for short, a name he came up with after George Lucas's first film THX 1138.

[00:01:19]George Lucas then demanded that theaters become THX certified or risk not being able to show the new Star Wars movie, Return of the Jedi, in 1983 leading most theaters to upgrade their sound systems.

[00:01:31]>> Vader's here.

[00:01:33]Now I'll listen.

[00:01:35]>> Now one really important criteria that George Lucas requested is for the theater sound systems to be able to recreate a deep bass sound. So another Lucas film audio engineer James Moore ran with it and created the THX deep note, a name he coined taking inspiration from the character Deep Thought from the sci-fi book The Hitchhiker's Guide to the Galaxy as a way to test THX certified sound systems.

[00:01:57]With this sound making its debut in 1983 with its theatrical release of the Star Wars Return of the Jedi movie.

[00:02:25]Now let's look at the sound itself, how it's designed to be creepy. Here's the chart showing what's going on. Okay, I know it looks really complicated, but it can generally be broken down into two parts. The initial chaotic part and the final big shimmering resolution part. It is said that the Lucasfilm audio engineer James Moore who created the sound was given the prompt to create a sound that comes out of nowhere and gets really really big, which perfectly describes what's going on. So in the first half, James Moore programmed 30 voices moving at random pitches between 200 hertz and 400 hertz slowly. It makes the sound very chaotic at the start.

[00:02:59]A cool thing here is that since James Moore programmed the sound with allegedly 20,000 lines of code versus recording directly with instruments, this first part with random pitches between 200 hertz and 400 hertz sound different every time it's played in the theater versus just having one pre-recorded version that's played every time. The best way to think about this first half is controlled chaos versus total chaos. A quite common trick done in pop music as well.

[00:03:27]The reason for that is to set up the second half where the sound opens up to between tens of hertz to over 10k hertz with the sound effect getting louder and louder, too. And the 30 voices settling on different target notes that no longer go randomly between different pitches for a grand comforting resolution.

[00:03:47]So cool. The sound goes from controlled chaos of 30 sounds moving around different pitches to settling on different notes across a wide range of pitches. But, what makes this THX section sound so big? I mean, even The Simpsons parody how huge the second half of the deep note sounds a while back.

[00:04:06]Well, it might be easy to come to the conclusion that since they're all notes at the end, it's going to sound big, but it's only part of the equation. There are a few really cool tricks they use.

[00:04:14]So, if I were to play 11 random notes on my piano, it's going to sound like this.

[00:04:18]>> [music] >> Now, as it stands, but if I were to play these exact 11 notes as outlined here on the chart, they'd sound more like somehow more uplifting and wide. And that's because these 11 notes make up what's known as a major chord, a series of notes that when played together tend to sound brighter and more open versus for example a minor chord, which doesn't sound as open. The same trick of using major chords to make a sound effect huge can be heard elsewhere like on >> [music] >> That's not all. Notice how there are only 11 notes here, but there are actually 30 voices that occupy these 11 notes. So, each note is played roughly three times, but all of them slightly detuned to sound a little bit different from each other.

[00:04:59]So, in reality, there are all these hidden notes in between that show on this chart that make the sound more full.

[00:05:05]Not to mention the sounds played through a synthesizer cello sound.

[00:05:10]The reverb used synth cello combined with the 30 different voices occupying 11 notes of the major chord create this gigantic effect. Now, for better or for worse, starting in the mid to late 2010s, it's becoming more rare to hear this THX deep note sound with THX logo visuals in movie theaters. A huge reason for this is the rise of competing audio certifications like Dolby Cinema with their popular audio format Dolby Atmos, which screen more premium to the average viewer nowadays versus THX. Not to mention, even though a lot of movie theaters upgraded equipment initially to meet THX certification standards, a lot of them then later decided that they no longer needed to keep meeting these uh THX certification standards and paid high maintenance costs just to receive that badge since THX certification requires that movie theaters go through routine inspection and recalibrations that can cost them thousands of dollars per year plus potential equipment upgrades that can cost even more. And even if a theater is indeed still THX certified, they're not required to play the THX logo visual with that THX deep note sound before every movie. And nowadays with no one knowing what THX is since it's been around for so long, theaters will oftentimes rather prioritize showing logos like IMAX or again Dolby Atmos that speak more to the quality of a theater to the modern viewer.

[00:06:28]Doesn't sound as iconic as a THX deep note to me, but THX is still alive today, just more diversified. So, THX extended its certifications to DVDs in the '90s and later on to Blu-rays too in the 2000s. And by 2000, THX certified home theater equipments including TVs became really popular. The 2000s really was the peak for THX with even like car systems and laptops gain certifications too. And all these certifications are still ongoing and new ones are still being rolled out. In 2016 with the gaming equipment company Razer purchasing THX. In 2020, they announced THX game mode certification to certify displays that are suitable for gaming.

[00:07:05]It's not just THX certifications getting updates, the THX deep note sound itself is still getting updates too with modern audio equipments improving. The most recent release was in 2026 titled a spark which makes use of spatial audio technology.

[00:07:24]The visuals also got crazier. I never really thought much about the THX deep note whenever I would catch a film with my friends in middle and high school, but now that it's gone, it really feels like something's missing whenever I watch a movie in theaters these days.

[00:07:36]One of those things where I don't appreciate enough until it's gone. If this is the first time you're watching my channel, I'm Jack and I make videos about hidden popular sounds, whether it's like a melody, a beat, or a chord used in pop culture that once you notice just cannot unhear, with occasional music commentary and covers, too. So, look around if you're interested. I'll see you guys in the next one. Thanks.

[00:07:56]>> And uh it's generated in a scientific way. So, it has the satisfaction of music, but it has the foundation of science. So,