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#8: Using a USB Audio Capture Device

By | January 13, 2007

Edirol UA-25I’m gonna assume that you’re using some type of USB audio capture device that supports XLR input and that you’ve got a large diaphragm condenser mic hooked straight into it. You can get a good sound with a simple setup like this. Your hardware isn’t gonna pickup a lot of noise, and your mic cable will be quiet too since it’s a low impedance XLR.

Since obviously there are dozens and dozens of different scenarios that you could have, I can’t offer a step-by-step guide for each situation so here’s what I’m gonna do. I’m gonna take you through my production process. Again, I’m using Adobe Audition to record and mix my audio. I’m using an Edirol UA-25 as my audio capture device. You don’t have to have this exact piece of hardware, and even if you’re using an internal sound card, no big deal, but what we will have to assume is that whatever you’re using, it is working with your software.

In Audition, you can check your levels by pressing F10 before you record. This will show a level indicator and you should see it move around when you’re talking. On the front of my Edirol I have a knob labeled SENS and that stands for sensitivity. It’s actually gain but that’s a little more foreign to most novice computer people. It’s sorta like volume, or at least for now you can think of it that way. It determines how sensitive the mic is.

Mic Settings
If your mic has an adjustable gain, set it to 0dB. The other settings are usually for recording something very loud like a guitar amp or drums. I think most USB sound devices have a clip or compressor. I’ve also got a Creative Labs 0404 and it actually has LED lights that indicate level. You want to turn the gain knob up so until your normal ‘loud’ voice just barely triggers that clip light, or the yellow-red area if you’ve got LEDs. Clipping is bad and it won’t sound good, so you want to adjust your gear so that clipping is minimized. The Edirol has a peak limiter that does a pretty good job, but still, try to set your levels so that it’s not needed in normal use.

As I said, in Audition you can monitor the levels before you actually record. Once you set your levels, you’ll probably leave them alone unless you use your mic to record other things or for example you recorded something much louder like singing. With Audition, the level indicator should come close to peak, but never hit it. There are some squares on the right side of the indicator and they turn red if your signal peaks. If this is happens, lower your gain a bit and click on those red squares to reset them. Then do some practice talking again. Make sure you’re not clipping. Don’t just do the old ‘Testing…1..2..3..’ either. Really talk. Just like you’re going to when you record. Position yourself about 6 inches from the mic and point it so that it is not straight into your mouth. Depending on how good the mic is, you’ll get different tonal sounds with different positions. You can experiment a bit making recordings with different positions and different distances from your mouth. For example, position the mic 6 inches from your mouth, at a 45 degree angle and then record, in your normal talking voice, ‘This is what I sound like with the mic 6 inches away at 45 degrees’. Then move the mic to another position and say ‘This is what I sound like x inches away at xx degrees’. Do several of these while recording and then you can listen to the whole thing and decide which makes your voice sound better.

Record Your Podcast
Go ahead and record your podcast. Once you’ve finished, edit it. Audition will let you take out everything from gaps of silence, to ‘um’ and noise as well. Here’s what I do.

Look for a long gap of silence where you didn’t say anything and there is no noise except for the natural ambience of the room you’re recording in. This will probably show up as just a small level of sound. When you play back this part, you’ll hear ‘noise’. You might have to turn your speakers up a bit. It will likely sound a bit ‘hissy’. Fortunately, I don’t have a lot of noise because I’ve got good gear, put even if you do have noise, you can get rid of most of it.

With a silent section visible, hit F9 and you’ll go into Spectral view. This view lets you see frequencies. Use the marquee selection tool and select just the low frequencies for that period of silence, and those frequencies will appear on the bottom. If you have high frequency sounds, you might want to select them as well and you might want to try to find the source of any strange noise and eliminate it. After you select the ‘noise’, right click it and select ‘Capture Noise Reduction Profile’. You have to select a second or two worth of audio, but then Audition is going to use that noise as a sample, and go through the entire audio file and remove those specific noisy frequencies.

Hit F9 again to go back to normal view and select the entire file. Then go to Edit -> Noise Reduction -> and again Noise Reduction. The profile you just captured will be loaded, and then you can click OK.

Now play your file back and you’ll probably find that it sounds a lot cleaner. If you want, you can also preview the noise reduction and adjust the level of reduction before you click OK. Sometimes you can use too much noise reduction and your audio will sound very digitized. I can’t go into all the options in the Noise Reduction dialog, but if you have specific questions, you can post them and I’ll try to get back with you.

Once you’ve got the noise out of the file, go through it and clean up gaps or mistakes. If you fumble over your words when you record, just stop talking, keep recording, take a deep breath and regroup your thoughts, then continue. This is the point where you can edit it out and make it sound like it flows very naturally. Editing in Audition is very easy, you just click and drag with your mouse and hit the delete key. One thing that speeds up this process is making sure that the play transport controls are assigned to keys on the keyboard. That way you can play and stop the file with quick keystrokes instead of moving the mouse a lot, it’s just a lot quicker.

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Topics: Audio Hardware, Audio Recording Software, How to Podcast | No Comments »


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