E-Learning 1.0 Recording Professional-Sounding Audio on a Budget By Mike Doyle So you've moved into e-learning or e-something else and you want to begin working with digital audio. Maybe you’re a presenter and want to create an online demo or multimedia presentation; maybe you want to prepare lessons in PowerPoint and include your voiceovers describing each slide. Here’s how digital audio works and how you can set up your own studio to record professional-sounding audio on a reasonable budget. How does digital audio work? When you emit sound from your vocal chords, you send vibrations (sound waves) into the air as analog sound data, with infinite combinations of frequency, tone, volume, and distortion possible. In the old days of vinyl and cassette recording (you remember that, don't you?), the analog sound waves were etched onto vinyl or stored magnetically on tape; there was no need to convert the analog data into digital data. With the invention of the CD in the late 1970s and the proliferation of computer multimedia in the 1990s, the world of audio began a dramatic revolution towards digital audio storage. So, how does it work? Doing the wave The world is full of analog data. The only way to store any type of analog data in digital format (0s and 1s, or more precisely, electric pulses and lapses) is to capture samples of that analog data at regular sampling intervals and gradations of detail. To understand sampling, let's talk about a sampling device you're probably familiar with: the scanner. Scanners operate by sampling light waves (analog data) that reflect off a document or image. You can scan at various sampling intervals (for example, 72 or 600 dots-per-inch) and various gradations of detail (for example, 256 colors or millions of colors). Higher sampling intervals and gradations of detail result in higher-quality digital reproductions. Laugh 'til it hertz In the audio world, the sampling device is called an analog-to-digital converter, which is contained inside a sound card. When you feed analog audio into the sound card, it samples the analog data at specific intervals called hertz, the unit of measurement for the number (frequency) of wave signals per second. When you convert analog audio to digital audio, you typically specify the interval in terms of kilohertz, a thousand samples per second. CD-quality audio is typically 44.1 kilohertz, or 44,100 samples per second. In addition to the frequency of the samples, another determining factor in audio quality is the bit rate, which determines the gradations of detail, or range in audio lingo. Bit rates for digital audio (sometimes called resolution) are 8-bit, 16-bit, and 32-bit. CD-quality audio is typically 16-bit. When you record audio you can choose between mono and stereo. Mono audio plays a single track of audio over all speakers; stereo plays two tracks of audio, sending different tracks to different speakers. If you’re recording a single voice, you only need a mono recording (in fact, recording in stereo would just be a waste of storage space and download time). If you’re recording from multiple inputs (multiple microphones and vocalists, an instrument, or a stereo feed), then use stereo. When you record audio intended for digital delivery, I'd highly recommend you record at CD level -- you can always convert later to lower frequencies and rates to save storage space, but you can never add what you didn't initially sample. A codec moment Once you start working with audio (or video for that matter), you’re going to run into the term codec. A codec, which is short for coder/decoder (or compression/decompression, depending on who you ask), is a technology for compressing audio and video data so that it can be stored and transported in smaller sizes. To understand that, let's take our CD audio example. At 44,100 16-bit (2 byte) samples per second, a single second of uncompressed audio would chew up about 88,200 bytes of storage space per second. That means that a minute of audio would chew up almost 5 megabytes of storage. That's a lot of space for a minute of audio! Codecs reduce the amount of storage required for audio files by compressing them using different algorithms, or rules for processing. Three common codecs are WAV (Windows Audio), AIFF (Macintosh audio), and MPEG (an ISO standard). However, there are many others. Before you store your digital audio, make sure that the codec you select works with the application into which you insert that audio. For example, Microsoft PowerPoint 2002 can import sounds in the MID, RMI, WAV, AIF, AIFC, AIFF, AU, and MP3 formats. Macromedia Flash MX can import sounds in the AIFF, WAV, and MP3 formats. If you have QuickTime 4 or higher installed on your system you can also import AIFF, QuickTime movie sounds, and AU. The least proprietary of the sound formats is MP3, which is based on an ISO-standard called MPEG Layer 3. PowerPoint, Flash, and many other presentation and software demonstration tools let you record audio directly into them. A word of caution, though: Most of those tools don’t allow you to edit the resulting audio stream. If you choose that path, I would strongly urge you to read from a script to … ummm … eliminate … ummm … distracting … ummm …you get it, don't you? Purchasing and setting up your equipment If you've ever been in a professional recording studio, you know that the sheer mass of equipment there (and exponentially, the sheer quantity of knobs and dials) is mind-boggling. The good news is you can replicate near-professional quality (if not the number of options) for about US$500 retail, and less if you shop on the Web. You need six components to record high-quality audio: a microphone, mixer, sound card, speakers, cables, and microphone stand. Don't be frightened by the model numbers— they'll help you easily locate and price-compare equipment. And remember that in the audio world, like many others, you're only as good as your weakest link. Microphone. My recommendation is for a Shure SM58, which is used for vocals by many recording artists (Alice Cooper, Susan Tedeschi, and Blues Traveler, to name a few). The SM58 is a cardioid microphone, which is a directional microphone that eliminates peripheral sounds and is perfect for vocals. Retail is $188 (www.shure.com). Mixer. In addition to mixing multiple input sources, mixers amplify the weak signal feeding from the microphone. I use a Fender PD-250, which retails for $1,149.99, but you don’t need to buy such an expensive system. You can get good quality mixers for much less. A great starter mixer is the Behringer MX802A Eurorack Compact Mixer. Retail is $129.99 (www.behringer.com). When you select your microphone and mixer, make sure that the mixer inputs use the same type of connector as the microphone output. For example, the Shure SM58 has an XLR output (3 prongs), and the Behringer has XLR inputs. Sound card,which takes the input from the mixer and converts the analog signals to digital signals; it also converts sound output from digital signals back to analog signals and sends them to your speakers. The leader in the sound card arena is Creative Labs, founded in 1981 and considered the originator of the computer sound revolution. A great product is their Sound Blaster Live 5.1 card. Retail is $69.99 (www.creativelabs.com). Make sure that your sound card has a Line In connector, because that’s the jack you'll use to connect the mixer to the sound card (not the microphone jack). Second, make sure that the sound card can handle CD-quality sampling rates (44.1 kilohertz, 16-bit rate). If your system already has a sound card with a Line In connector, try it out; you may be able to skimp on purchasing a new one if it already handles CD-quality sampling rates. Speaker system. Your recording may be great, but how will you know it if it plays through sub-standard speakers? A great brand is the Logitech Z-640 speaker set, which includes a subwoofer, 5 satellite speakers, and Dolby Digital surround sound. Retail is $99.95 (www.logitech.com). Cabling. You'll need two cables: one to connect your microphone to the mixer (if you go with the Shure SM58, it uses an XLR-connector). And you'll need an audio cable, which connects the mixer to the sound card. The audio cable is typically a Y-Adapter audio cable, connecting the two output jacks on the mixer to a single input jack on the sound card. Typically the output jacks on mixers are 1/4 inch or 1/8 inch, and the Line In jack on a sound card is almost always ¼ inch. Just bring the specs to Radio Shack and you'll be able to pick up both cables for $30 to $50 (www.radioshack.com). Microphone stand. You can pick up a table-top model at any music store for around $20. Whew! Now that you've spent about $500 and have all this equipment, you’re ready to set up. It's not that difficult. In fact, the most difficult part of the process will be the installation of the sound card. I'd recommend adding the sound card first; if you're not comfortable opening your PC and popping it in, call around to computer stores to see if anyone will install it for free -- or at least for minimal expense. Figure 1 shows my setup. Remember, the mixer I have is rather ostentatious; the Behringer is much more compact and costs a lot less money. Notice that the single cable feeding into the mixer is the microphone XLR cable; the double cable feeding out is the Y-Adapter, which connects to the sound card's Input Line jack. Figure 1: A sample setup of microphone and mixer Recording tips Now that you’re ready to step up to the microphone, here are a few recording tips that'll make a world of difference (and if you think back on famous artists in a recording studio, you'll see they generally follow these tips when recording). Get intimate with your microphone. Don't be afraid. Your mouth should be between 3 to 6 inches away from the microphone when you record. Position the microphone so that the head of the microphone is at nose level or a little higher, but pointed at your lips. Don't speak into the microphone at dead center; move it slightly to the left or right to avoid popping. Record and listen to snippets before you record in earnest. You may need to adjust mixer or software settings to optimize the sound. To get into the spirit of professional recording, yell "sound check" periodically! Onto production If you decide to purchase audio editing software, check out the low end leader--a product called Cool Edit, shown in Figure 2. Retail is $69. (Download a 30-day trial version at www.cooledit.com). Figure 2: Cool edit lets you edit digital sound data Cool edit lets you record mono or stereo. Figure 2 shows two separate tracks, indicating a stereo recording and demonstrating the space wasted in recording a voice in stereo, since the two waves are virtually identical. Cool Edit can record up to 192 kilohertz, with a bit rate up to 32. Of course, remember that the recording capabilities of any software application are ultimately limited by the capabilities of the sound card. No matter how much you try, you can't get four lanes of traffic on a two-lane highway! After you've recorded your audio, you can easily highlight and cut unwanted audio, amplify pieces, filter noise, and transform snippets. You can even mix other audio clips, including music and sound effects--search the Web for royalty-free ones. Once you’re happy with your audio production, you can save that audio in over a dozen different formats, including WAV, AIFF, and MP3. Now, how does that sound? Published: July 2003