You know what can make even the most entertaining YouTube video really frustrating? Bad sound.

That is, for audiences who don't rely on closed captioning. Like, what if my voice was all garbled with static, or if my words weren't synced up to the video right now? Annoying, right?

You might look away from a screen if the visuals are jarring, but you pretty much always hear a film - whether it's dialogue that was recorded on set, or a sweeping score added in post-production.

And the sad thing is: you don't often really notice good sound recording and design. Even though it takes just as much technical know-how and artistry as visual storytelling does. 

When sound production is most successful, you're not thinking about the quality of the sound at all. You're feeling it. You're pulled into the story and living in the world of the film. 

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Let's start with the basics: the audience is gonna want to hear the characters they're watching. And that all starts with the sound department on set, which is usually a small crew of two to three people.

Its head is the Sound Mixer, also known as the Production Sound Mixer, Location Sound Recordist, Sound Engineer, or just the "sound guy." This person usually supplies all the sound equipment for the production, and is responsible for recording all the sounds on set. 

Every space has unique acoustics, so a good sound mixer will try to record as much as possible to make the world of the film feel real. That includes the sounds actors make in the scene being filmed - like dialogue...

Batman: Where's Dent?
Joker: Those mob fools want you gone so they can get back to the way things were. But I know the truth. There's no going back. You've changed things. Forever. 
Lily Gladstone: ...slurping their tea...

[slurp]
...or foot stomps as they job down a street. 

[footsteps]
Marion: Hey, what happened? You don't look very happy. 
Indy: Fools. Bueacratic fools.
Marion: What'd they say?
Indy: They don't know what they've got there.

Lily: Plus, it includes wild sound, which is any extra lines that are said or noises that are intentionally created without the camera rolling, to be added into the movie in post-production. 

And lastly, there's room tone, the atmospheric sound in a space filled with silent actors, crew, and set dressing. Having room tone helps the sound editors make the world feel authentic and consistent. 

The sound department's second-in-command on set is the boom operator, or boom op for short. This is the person you'll see holding a microphone on a long boom pole out over the actors.

Actors will often have small body mics hidden on them to record any sounds they make. These are also called as lavalier mics. This is mine...it's not hidden. 

But the boom op is working to capture sound from everyone and everything in each scene. To do their job well, they have to really know the script and the blocking, or how the actors will physically move through a scene. That way, they can position the boom in the best place to pick up sound, while keeping the mic and its shadow out of the camera's view. 

On larger sets, there might be a third person on the sound crew: the utility sound technician, also known as the second assistant sound. This person helps with a bunch of stuff, like: equipment maintenance, mic placement, cable management, keeping everyone quiet while filming or even operating a second boom. 

Now, I already mentioned the two main mics you'll find on a film set: the boom mic and the body mic. But you have to think about a lot more than just where you put a microphone. When you're speaking, you're pushing air through your vocal folds out into the world. That vibrates other air molecules, making sound waves. 

So, microphones nearly always have a windscreen to help record clean sound, and not just loud, whooshing noises from the air. It muffles air being blown directly at it without affecting the mic's ability to pick up sound. A small windscreen is usually enough on an enclosed set, or on a sound-stage, like this one. 

Outdoors, you might need more intense windscreens. And here's a perfect example of how great film crews are at naming things: the big ones are called dead cats...because, well, just look at them. 

The sound department not only has to make sure they're recording good sound, but they have to pay close attention to what they don't want to capture. And they can do that with microphone patterns. A microphone pattern is a shape around a mic where it picks up sound best, and there are a few standard types. Just like the camera department has to change lenses, the sound department might have to change mics from scene to scene.

First, you have omni-directional mics, meaning the mic is recording sound coming at it from every direction. There are a lot of situations where this is ideal, like for recording a conversation where people are sitting and talking all around a table. But on a set, you only want to hear the actors on camera, and not all the crew behind the scenes. So this mic wouldn't be the best choice.

Bidirectional mics pick up sound directly in front of and behind them, while rejecting sound coming in from the sides. Their sensitivity pattern looks kind of like a figure 8. These mics are useful for interviews or duets - any time when two people are directly across from each other with the mic in the middle.

Then, there are cardioid mics, named because their pattern is kind of shaped like a heart. They pick up more sound in the direction you're pointing them, plus a little bit from behind and on the sides. A cardioid pattern is good for recording lines from one person at a time, up close. So lavalier mics - the ones physically attached to actors - are usually cardioid or omnidirectional. 

If you want something a little wider than a typical cardioid, but not as wide as an omnidirectional, there are subcardioid mics. Or, say you're trying to record a conversation where a bunch of people are huddle together and talking.

So you have several mics near each other, and you want each one to only pick up one person. In this case, a supercardioid or hypercardioid might be your best options, because they have even more directional pickup. But they downside is that they also have more sensitivity directly behind them so they can pick up things you don't want to hear in the final film, like chatter from the crew. 

If you need something even more directional, like for the end of a boom pole, you can put something called an interference tube over a supercardiod or a hypercardioid mic. This ideally makes unwanted sound waves from the sides cancel out, and creates a lobar pattern: you can aim them more precisely, and pick up sound from farther away. Because these mics are long and narrow, they're called shotgun mics. 

So on a typical set, there's probably a shotgun mic on the boom pole, and a handful of lavaliers on different actors or hosts. Each of those microphones is picking up part of the overall sound in a scene, and each one feeds into its own track on the audio recorder where the sound mixer is. 

There, the sound mixer can adjust the mic sensitivity and the recording levels. So, in the final film, the audience can hear a soft whisper...

Gandalf: Fly, you fools. 

Lily: ...and understand loud shouting. 

Stansfield: Benny? Bring me everyone. 
Benny: What do you mean "everyone?"
Stansfield: EVERYONE!!!

Lily: And all this is just production sound! We still have a whole world of post-production to explore. Before editing anything, the very first thing you need to do is sync the sound with the camera footage. And if you prepare during production, it's pretty easy to do. 

Remember the 2nd AC? They're responsible for the slate, which marks each take with both a visual and an audio cue. To help keep track of media, the scene, shot, and take number are written on the slate for the camera to see, and are called out for the microphone to hear. 

Nick: Scene 21, take 25!

Lily: And then, the 2nd AC claps the slate shut. [Slate claps] If you don't have a slate, you can clap your hands in front of the camera and the mic to get the same effect. [Clap]

The goal is to the make the audio levels spike, while the camera catches the exact moment the clapper and the board of the slate come together. That way, in post-production, you can manually match up that audio and visual cue and voilà! Your sound is synced.

If you want a faster way of syncing audio and video, we've got you covered too. One way is through a time code sync, if you're using a digital slate. The moment the clapper hits the board, a signal is sent from the slate to the camera and the audio recorder. And the time code of this exact moment is recorded on both devices, which you can use to sync everything up.

The second way is if your camera is recording audio too, which won't be used in the final mix. It's called a guide track. That way, in your editing software, you have your video footage, camera sound, and sound from the audio recorder. And an audio waveform sync program can match them all up. 

Typically, an assistant editor syncs up the sound with the visuals, and then the editing team cuts together the film. Once the film editor and director agree on a picture lock, meaning the visual and story edit of the film is finalized, it's time for the post-production sound team to get to work. 

Like the film editor, the sound editor makes decisions based on things like story and the actor's performances. The best takes for camera aren't always the best takes for sound, though, technically or artistically. And it's up to the sound editor to make sure the best sound takes for the film make it into the final mix. 

On a bigger film, some sound editors will be dedicated dialogue editors. Like the name suggests, their job is to cut for the best dialogue from production sound. Ideally, the audio and video from the same take will both be great. That makes their job easy. Often though, the dialogue editor has to borrow sound from other takes or wild sound, and sync the best takes for sound with the best takes for camera. This only works if the audience can't tell it's been done, like if the camera is on another character, so it takes a lot of skill and creative editing. 

If there's not a great sound take, the crew will bring actors back into a studio and do some Automated Dialogue Replacement, or ADR. Some actors relish ADR. Meryl Streep famously loves it because mixing separate visual and audio performances can add complexity to what her character is conveying. 

Of course, dialogue isn't the only sound in a film. Sound Designers work with sound mixers and Foley artists to create the sound effects that make the world of the film feel rich and whole, from birds chirping to the *pew pew* of lasers.

And music supervisors and composers work with the director to either curate or create the music of the film. Adding music frequently comes at the end of post-production. And when it's done well, it's the finishing touch that solidifies the entire film and brings it to life.

From an actor's whispered lines to the final score woven throughout a film, sound helps us go from watching a story with relatable characters, to feeling what they feel and living in their world. 

Today, we learned about all the artists involved in production sound, and how different microphone patterns are best for different situations. We talked about the importance of post-production sound and the role it plays in deepening our experience of a film, and making the movie the best it can be.

Next time, we'll talk about the people who see everything, from the bigger picture to tiny details that could get overlooked on a film set: producers. 

Crash Course Film Production is produced in association with PBS Digital Studios. You can head over to their channel, check out a playlist of their latest shows, like PBS Infinite Series, Physics Girl, and Reactions.

This episode of Crash Course was filmed in the Dr. Cheryl C. Kinney Crash Course Studio with the help of all these nice people. And our amazing graphics team is Thought Cafe.

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