Definition

audio introduction

Part of the Multimedia and graphics glossary:

This page provides a brief overview of audio and its production for computer users. It contains embedded hypertext links to all of the audio-related terms on whatis.com. After reading this page, you should have a general idea of what audio production involves and some ideas about where to learn more. Topics include production devices, MIDI, multi-media desktop production, surround sound playback for consumer and professional use, audio for film and video, and music on the Internet.

Modern audio production involves an ever-expanding set of specialized tools. Each year, there are the number of applications using audio increases. You'll find many possible tools and technologies. In addition to what you may already have in your computer, you'll find an abundance of shareware and freeware music and audio software available.

In the past 20 years, audio has moved from analog recording with LPs (long-playing records) and tape cassettes as the playback medium to totally digital recording using computers with digital surround sound playback. Once, music could only be recorded by a live group of players. Today, the Musical Instrument Digital Interface (MIDI), the sequencer, sound cards, and synthesizers allow anyone to create music right on their desktop. Even a modest setup can create surprisingly realistic audio tracks. You probably have many of these tools in your computer already.

Even if you're not a musician, the technology surrounds you. Songs can be downloaded as MIDI files that will play on your computer's soundcard. Computer-based audio files can now deliver your favorite songs over the Internet. Download a group of your favorite songs as MP3 files and then create a custom CD to listen to at your next party. Create greatest hits collections of your favorite tunes to share with your friends; add a soundtrack and sound effects to your latest video recording.

How is it possible to download a 3-minute pop song without growing old and gray in the process? The current crop of audio delivery methods include RealAudio, Shockwave, MP3, and others. RealAudio and Shockwave are designed to allow real-time playback of audio directly from a Web site. MP3 is one of the most popular delivery formats for downloadable audio. At the heart of this technology is a compression scheme that reduces the file size of a recorded piece of music that has been stored in a computer.

What about creating your own music and audio files? If you are a budding composer, the most basic setup would include a keyboard and some MIDI sequencing software. Using this combination you could play individual piano, bass, drums and horn parts right from your desktop, using the computer's soundcard to play the sounds of your "band". Edit the parts until you have your masterpiece. Saving the music data as a standard MIDI file, you can send your composition to anyone on the Internet and they can play the same piece of music on their PC.

Of course, this sounds easy. What's the difference between this modest setup and a professional setup? As a personal music studio starts to grow, the user expands the sound production possibilities, the palette of sounds, and the recording tools. The music studio is an expanding set of tools. But one thing is essential; good ideas. Without them, no amount of expensive gear can make you a pro.

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Just for fun, here's an illustration of a project that uses as many of the whatis.com audio definitions as we could think of:

You are hired to write and produce some music and sound effects for a new CD-ROM release. When the first brilliant idea pops into your head, you race over to your trusty computer, and start your favorite MIDI sequencer software application. Selecting a tempo of 95 BPM, you choose a cool synth patch (by sending Program Change 73, of course) on your favorite multi-timbral synthesizer, and start recording.

The first pass yields a great idea, but the performance is a little rough. You need to clean it up a bit with the software's quantize feature. For the next musical part, you need to design a never-before-heard sound. You start flailing away at the parameters of your synthesizer: adjust an oscillator here, a bit of filter with some resonance there, tweak the ADSR for the amplitude envelope, then adding just the right amount of reverb and a bit of chorus. Ah, a masterpiece of sound design! Perfect for adding the melody to your piece. While you're at it, you better save that synth sound masterpiece by sending some system exclusive data to your synth patch librarian.

But this music needs a human touch, too. How about a live acoustic guitar? Patch the condenser mic (Cardioid pattern) into your tube mic pre-amp (with the proper XLR cable, of course), turn on the 48v phantom power, select a channel on your ADAT 8-track MDM, and you're ready to jam along in sync with the MIDI tracks you just laid down. You did remember to connect the SMPTE time code to the digital audio workstation, right? Good. Arm a track for an overdub, and start strumming. Get a good hot level, to maximize your use of the dynamic range!

Now it's time to mix your music. Of course your fancy new mixing console has automation, so you'll be able to make the mix perfect and recall it later if the client needs a small change. Each track that you've recorded comes up on its own fader on the console. You adjust the parametric EQ (notching out 6 decibels at 500 hertz, with a Q of 1.2 octaves, patch in a bit of compression with a channel insert, and pan each sound to a unique position in the mix. Since you have plenty of digital signal processing horsepower, you experiment with using some flanging and phaser effects patched into the Aux sends of the mixer. Nice. Adding a bit of hall reverb (with a 40 msec pre-delay) completes the process.

Ok, you have a great stereo mix. It's time to record it. Of course, you'll want to use your fancy analog-to-digital conversion as you lay down the mix to Digital Audio Tape. Patch the balanced outputs of the converter to the DAT machine from your patchbay, set a level, and lay the mix down to tape.

But wait, there's more! Now you have to edit the mix. Transfer that mix from DAT to your digital audio workstation using the S/PDIF digital interface. Trim the file so that it starts precisely on time. You might as well normalize it, too, and then run it through the peak limiter to get maximum level and impact.

No, you're not done yet. Your contract requires you to deliver the audio as computer files for inclusion on a CD-ROM. You'll need to convert the files to both Wave file and AIFF formats for this application. You also need to provide low-fi and hi-fi versions of the files: by sample rate converting them to 22.5 kHz and 11.025 kHz. Don't forget to dither! (See dithering.)

Congratulations, your project is a success; you're on your way to becoming the most sought-after audio specialist in town.

This was last updated in May 2008
Posted by: Margaret Rouse

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