The A-Zed of Audio

Audio interfaceYou might think Google had figured out how to cure chickenpox or turn coal into gold because of the miracle stories you hear about their Translate app. It may not be that important of a development, but it is pretty nifty. On my recent trip to China, I really got to experience how useful the app was. With the exception of a few translation oddities, I was able to communicate effectively enough to purchase iPad covers of questionable branding origin, request meat-free food, and not only get ripped off by buying an apparent 1 terabyte USB stick, but actually get my money back when I realized I'd been duped. The app enables communication between two people who share only a small amount culturally, and nearly nothing linguistically.

Believe it or not, digital audio couldn't exist without translators like these.

The audio interface, which acts as a translator, isn't exactly the same but it's pretty similar. Recall that the hard drive in your computer can’t store audio. Those gigabytes of MP3s you have filling it up are exactly that: gigabytes. To put it another way, your version of Sgt. Pepper’s Lonely Hearts Club Band is information. In order for a computer to store or compute anything, it needs to be in a language with which it can work. That language isn’t english or swedish or indonesian but numbers instead.

When we talk about analogue recording (vinyl records or magnetic tape being good examples), what we're saying is that the physical phenomenon of a sound – moving air molecules – gets converted into a form that's analogous to the way those air molecules moved physically. As soon as the air molecules touch a microphone, their motion gets converted into electrical impulses. These impulses can do things like power loudspeakers in the case of a live performance, or etch magnetic charges onto tape, in the case of recording. 

But even with recording, we don't store sound. We store an analogue of sound. A translation has happened, and when we listen back we’re not listening to the original sound. Think about those handprints in front of Mann's Chinese Theatre on Hollywood’s Walk of Fame. Suppose you come across an impression of Clint Eastwood's hands. You might be able to reconstruct something that resembles his palm, but you'll be a long, long way from Clint Eastwood himself. This is a great way to think about recording sound – at best, it only goes through one round of translation, like Mr. Eastwood impressing his palm into wet concrete.

Clint Eastwood signatureYet in digital audio, we need to convert our signal once more – like this photo of the impression of his hands – because if you saw tape the last time you looked inside your computer, then you’re probably a long way off from discovering the internet, and certainly not reading this right now. 

Computers need to convert electrical impulses into digital information, and this is where the interface comes in. In the case of recording, we have an A/D converter, or an Analogue-to-Digital converter (also called an ADC). For playback, we need to convert the computer’s digital information into electrical impulses, which then power our speakers or headphones. 

iPhone jack

This is called a D/A converter, or DAC – you guessed it, Digital-to-Analogue converter. Any digital device that allows you to plug headphones into it has a DAC. The headphone jack in your smartphone or laptop relies on a DAC to translate the stored information into what you eventually hear.

But the way this translation actually happens isn't obvious or simple. With entry level interfaces beyond the run-of-the-mill, built-in DACs, a respectable unit can be had for about $200. Yet when I think back to using Google Translate in China, I know there were some pretty wild mistranslations, but in the end the job got done. Instead of using their free app (or whatever cost you calculate, knowing Google is storing every word that I put into it for research, refinement, and perhaps other alchemical motives), would I have paid $1000 for a professional translator? No, certainly not.

But if I were negotiating a million-dollar business deal, or talking a person down from a ledge, having a high-quality translator would be well worth the money. You can probably imagine some of the frightening or humorous possibilities of how important instructions can get miscommunicated in a crucial situation.

This is why audio interfaces can easily cost a few thousand dollars – if you’re making professional recordings, those little imperfections from a lower-end device aren’t acceptable, just like telling the person on the ledge that "birds can fly, you might be able to" when you meant to say, "you really should get down from there."

Archaic computerThe most interesting thing to take away from this is a glimpse into how computers work. They're machines with which we have no direct way of communicating. The advances we've made in the last forty years have just as much to do with interfaces as they do with processing power and information storage. One of the most significant developments – the GUI or graphical user interface – allows for simple translations of the computer's calculations into images that are more in our day-to-day language than strings of arcane code or rows of blinking lights. 

With audio, it's much the same. We have interfaces that allow us to store recordings in digital media, and then play them back or edit them into new concoctions. The mark of success for these interfaces is our general ignorance that they even exist. We believe that computers store sound, images, videos, love letters, and whatever the fox says. Really, all they store are strings of binary information that we could never have a hope of decoding, much less dancing to or crying over.

But the humble interface is like the Matrix – it translates these terrible strings of numbers into virtual reality: Bob Dylan's voice, Fleet Foxes' lush harmonies, Skrillex's insane bass drops, and everything between.

(Click here to see this post without an interface, in its terrible strings of numbers.)

Jordan Mandel is a Digital Media Lab Instructor at the UW Stratford Campus, and writes for this blog regularly. His hobbies include laminating documents, DIY ball bearing manufacture, and artisanal dried apricots. More of his work can be found at, which houses the award-winning satire rag, The Outa Times.

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