Behind the Sounds of Black Mirror: an Interview with Stefan Henrix

Black Mirror is a TV show that wants to make you uncomfortable. It wants you to coax you with the promise of tech-driven utopias, plant false assumptions in your mind, convince you of them, and then tear them apart in front of your eyes. A modern take of The Twilight Zone, Black Mirror has captured audiences around the world by bringing wired worlds much like our own to dystopian endings.

Through recognizable technology and scenarios that unfold in the not-too-distant future, the sights and sounds of Black Mirror make us question whether these are the conclusions we’re headed for.

Stefan Henrix was the supervising sound editor for three episodes of Black Mirror Season 3: “Men Against Fire,” “Shut Up and Dance,” and “Nosedive.” I called him in his cutting room in London to talk about creating eerie soundscapes, balancing sound design with music, and more.

While each episode of Black Mirror has a different flavor, the show on the whole conveys a cynicism for how technology affects people’s lives. When you’re editing sound from one episode to the next, how do you sustain that darkly sarcastic tenor?

That is the challenge—the visuals obviously help us. In “Nosedive” there was a lighter feel. Joe [Wright] had shot it in lovely pastel colors—incredibly rich, color-wise. That lent itself to giving me a texture to work with. I had to make it feel brighter by the sounds I used, whereas “Men Against Fire” was a lot darker. The house had an underlying menace: you make it speak, it moves, creaks. This soundscape gives the impression of claustrophobia.

They were all incredibly challenging in their own ways. In “Nosedive” I was trying to find electric vehicle sounds, but there was just nothing out there that fit my criteria. So I had to create the vehicle sounds, finally settling on sampled jet dragsters.

The ringtones and text messages were the biggest challenge. The editors had used Apple iPhone tones in the guide track, which we did not have permission to use in the final mix. You listen to an Apple text message and ask, how are these made? I had to recreate these to match the original samples which was no easy task—sorry no trade secrets to give away here. Of course, now I should license them!

"RX is so easy to use. You can see the frequency, and you just take it out."

Black Mirror is a sci-fi show, but its sense of dark humor comes from the viewer's ability to recognize realities that are not too unlike their own. Charlie Brooker, Black Mirror's creator and writer, said of Nosedive, “It’s basically the world we live in.” How do you balance science fiction and reality through sound? What techniques do you use to create a soundtrack that viewers can both recognize and be awed or frightened by?

It’s a good question. How do you answer that? I’ll have to think about that one.

For example, in “Shut Up and Dance,” the protagonist, Kenny, is receiving text messages. We all know the sound of an incoming text message, but I noticed it was kind of a creepy clown noise or something.

Yes, that was an old bulb car horn. There was a lot of discussion about this. It’s interesting you picked that one up because Charlie [Brooker] was very unsure. Is it too comedic? Are we going too far? We tried different variations but we kept coming back to the original. This made it into the final mix, which pleased James [Watkins] the Director because he was particularly fond of this sound.

That’s the thing, the sound had an eerie, unsettling undertone to it. In that particular show, it was about making you feel uncomfortable. Seeing Kenny from the computer’s perspective, we are with the person who is watching—we are watching. There are strange movements and vocal sounds to represent a voyeur’s view—this gives a subtle uneasiness.

Were there parts of the episode where you found that silence worked better in place of a sound? Did you have to pair back various scenes?

We were of aware of it. For example, in the scene on top of the cark park, James said, “We know we’re on top of a car park, but I don’t want it to sound like we’re on top of a car park. I don’t want to hear the city.” All that’s up there is wind and a few leaves and a paper coffee cup blowing around, otherwise it’s quite silent. You are meant to feel Kenny’s loneliness—that’s the idea. The sound that breaks this moment is the motorbike we hear approaching. The only other external sound we hear is at the end of the scene, a police siren. You’re asked the question as an audience, is this connected to him, or is it just in the background?

I really enjoyed that episode. You kind of feel sorry for Kenny, and then the twist at the end is quite unbelievable. Charlie Brooker is a genius, each one of these episodes could quite easily be turned into a feature film

Did you use RX on the car park scene to remove city noise? How do you use it in your work?

I normally use RX if I am cutting dialogue, but saying that, there are times when I would use it to get particular frequencies out of an FX track. It’s so easy to use. You can see the frequency, and you just take it out. This sort of technology is beyond me, and I don’t know how it works, but it’s incredible.

"RX is the Roll’s Royce of the plug-in world for audio repair. It’s the one we all go to."

Do you use other iZotope products?

In “Men Against Fire” I used it to create some of the ambiances with Iris, taking wind tracks and running them through it. With Iris, there are some great presets, but you need to play with them. Iris is a bit more time intensive, but you can get some great original sounds if you persevere. There are quite a few Iris-based sounds that are in that episode, running underneath the music.

With sound design you can often create sounds that are musical, so you have to be careful that you are not treading on the composer’s toes. It’s nice when you can have a collaboration, when you can get your material to the composer, which I did on “Men Against Fire.” I would send them things that I had created, and they would work with it or ask me to remove it depending on what they were doing. Fortunately, most of the time they loved what I did and worked with it.

What were those conversations like?

The big sequences are always the most contentious. In “Men Against Fire” there’s the sequence when Stripe has been shot and gets pulled out of the Humvee. There are Iris sounds running through this scene. So you talk to the composer and say “I’ve got this tonal undertone and I am going to highlight some key points with sound”—for example, the vegetation and the girl falling into the hole. Stripe is in an unconscious state, so the scene is very dreamlike, and the sounds represent that. You don’t want to clash—you are trying to find a balance. Both music and sound effects can be playing at the same time, but they have to be harmony so they do not overpower each other.

Were there any unusual sources that you turned to when creating sound for these episodes?

I can’t say there are particular sources of unusual sounds. Sometimes you have to think outside of the box to create a sound that will represent what you are looking at—for example, the electric cars in “Nosedive,” created from a jet dragster. Each episode of Black Mirror is individual, and that is the challenge. Sound is not a five-minute job. It’s about selecting sounds, playing with them, manipulating them. You might spend an hour or two on one sound and then dislike it; you throw it away and start again!

Are there particular modules you use more than others in RX?

They all just work so incredibly well, but the modules I mainly use are Spectral Repair, Instant Process, Ambiance/EQ Match, and Dialogue De-noise. De-noise is an incredible piece of software used in many post facilities.

What other shows are you working on?

I’m doing a show called Britannia for Sky. It’s one of their big productions this year.

I recently cut dialogues on a Pilot for Amazon Prime called Oasis. I got to use RX a lot, creating ambiance, EQ matching, matching ADR. It’s the Roll’s Royce of the plug-in world for audio repair. It’s the one we all go to.