Stereo vs. Binaural Recording

Yesterday, Boing Boing posted a link to an article about surround sound research at UC Davis.

This new technology is a very interesting extension of binaural recording. Binaural is a two channel format that mimics the pick-up pattern of the human ears.

Stereo is two channel as well but it recreates a “wall of sound”. To record in stereo, you take to two mono microphones and position them in a “v” shape. The point is the head of the microphones. They should be at a 90 degree angle to each other. The heads should (obviously) be pointed at the sound source.

When played back from stereo speakers, a stereo recording creates, as I said, a “wall of sound” that is projected out from those speakers. Closing your eyes and facing the speakers, you could imagine the sounds happening just in front of you. Listening to a stereo recording on headphones places that plane of sound in your head. Put on a record that features a lot of stereo panning like Pink Floyd’s “Dark Side Of The Moon”. On headphones, you’d swear the sound was moving right through the center of your head. Here’s a little bit of “On The Run” from that album so you can see what I mean.

Binaural recording, as the article points out, typically uses a dummy head with microphones placed in the ears and positioned at the same angle as human ears. There are also “stealth” binaural recording rigs that put tiny microphones in what appears to be walkman-style headphones. Wearing the “headphones” puts them in the proper location for binaural recording.

The biggest difference between stereo and binaural recording is that binaural can only be played back on headphones. Listening to binaural recordings is like really being there with sounds going on all around you. It records in 360 degrees, so recording a sound of someone walking behind the dummy head would sound exactly like someone was walking behind you when listening on headphones. If you play a binaural recording back on stereo speakers it sounds really strange. It’s hard to exactly put your finger on what’s wrong but you can tell that something isn’t right with it.

This new technology from UC Davis records 8 or 16 microphones positioned in a circle, and during playback mixes the relative strength of each signal in real time based on the positional data from a worn sensor. With normal binaural, the previously mentioned sound of walking behind you would always be behind you no matter where you turned your head. This new technology would allow you to turn your head around to “see” who was behind you and you would then hear the sound of walking as if you were looking at it.

Fascinating stuff.

I worked on an IMAX movie called “T-Rex: Back To The Cretaceous” that had a limited amount of binaural sound in it. Being a 3-D IMAX movie, you were given goggles to wear which would make the 3-D images look correct when you sat in the theater. These goggles were much larger than the standard red and green paper ones that you often get for these kinds of things. There were actually tiny speakers in them that were positioned directly over your ears when properly worn.

When we were on the dub stage mixing the movie, we would actually have to wear these goggles (minus the 3-D lenses) so that we could properly mix the sound for that channel. For those who are curious, it was actually wirelessly beamed to the headset via an infrared signal. The idea was that 3-D visuals plus binaural sound should really place you in the movie. However I found that the soundtrack was so loud with the music and the dinosaurs stomping around that even with the speakers right next to your ears, they were easily drowned out by main speakers in the theater. It was an interesting concept that wasn’t quite realized.

In March 1999 I recorded a rock show at a little club in Los Angeles called Dragonfly. A band I knew said it was ok and I was very excited about the prospect so I showed up with 2 different DAT rigs and a video camera. Two of my friends came along to help me manage it all. One of the DATs included a stealth binuaral headphone setup. During one of the opening bands, I had my friend who was going to use the stealth rig, go practice using it. He didn’t quite understand the concept and he moved around alot. Put on some headphones and you can hear the vocals and instruments move from ear to ear in this recording as he looked around from side to side. (One of the best reasons to use a dummy head instead of a live body.) You’ll notice two things from the recording of Candy Ass covering The Runaways’ “Queens Of Noise”. First, unlike the Pink Floyd song above, when the sound moves it doesn’t pass through your head—it “rotates” around you. Second, if you listen on speakers, it doesn’t sound right.

It’s not a very good example of binaural recording. I know. But it’s the best I could come up with easily.