Audio

2010-06-20 21:28:49 UTC

Matt Legend Gemmell tells you what to do and what not to do when making a product page. One point I felt worth expanding upon:

Either have a professional-sounding voiceover, without pauses and “um”s, with great audio quality, or don’t have a voiceover at all. Superimpose explanatory text titles instead. Be honest with yourself about how your voice sounds. If you’re the typical male engineer, your voice is probably going to be a major turn-off, and you probably can’t do talk-along without pausing, making various noises, and restarting your sentences. Get someone else to do it, or use text.

There’s nothing you can do about the innate quality of your voice, and if that sucks, then “get someone else to do it, or use text” is good advice. (Alternatively, you may be able to train yourself or be trained to speak better, depending on your exact problem. Mine used to be that I didn’t open my mouth enough, so everything sounded like I was talking through clenched teeth.)

But audio quality is something you can improve, and it matters. Care about this stuff; your potential customers do.

  • Buy a microphone. Yes, your laptop has one built-in. It sucks.

    The microphone itself may be all right, but it’s in indirect physical contact with a fan, a hard drive, and other noise-inducing parts. It’s also too far away from you. Good enough for voice chat, but not for recording. Buy a separate microphone and record with that.

  • Practice good microphone technique. Get fairly close to the microphone—about 6 inches/15 cm—and talk straight over it. Talking over it will avoid loud spikes (pops) on the recording from plosive sounds, such as the start and end of the word “pop”.

    You could buy a pop-filter and then talk straight into the microphone (through the filter), but I’m trying to keep your monetary and effort expenses low.

    Also, if you’re soft-spoken, speak up, like you’re talking to someone down the hallway. Don’t yell, but do project.

    And no matter what you do, don’t ever, ever touch the microphone, its stand, or its cord.

  • Set your gain. In simple terms, your input’s gain is how hard the microphone is listening. You want to avoid clipping—that’s where the signal maxes out (0 dB) and would go out of bounds if it could. You want the signal to be high enough for your voice to be clearly audible, while never, ever going high enough to clip.

    You’ll generally do this in the Sound pane of System Preferences, but your recording software may have its own control for this. Sound Studio does.

    The only way to find out the right amount of gain for you (and your microphone) is through experiment. Say something over and over while cranking up the gain, then go into actual recording, and when it clips, dial it back down and start over.

    Note that it is pretty hard to set the gain too low, except when it’s obviously too low, but it is very easy to set it too high. Err on the low side.

  • Edit. There are three components to this.

    • Cut out ums, ers, pauses, etc. You can record as much of that as you want—speak as you naturally do in recording. Then edit out anything between words.

      On a related note, pause for a second or so between sentences, both to breathe in and to make it easy for you to edit in re-takes.

      You may also want to write and print out an outline of the points you want to hit in your voice-over, as a map through the presentation for you to follow. Use OmniOutliner or TaskPaper, or pencil on paper (as long as you can read it easily). Read items between sentences; don’t read while you speak. Don’t write a script unless you can pull script-reading off. An outline (or script) will keep you from rambling and focus your sentences, reducing the number of ums, ers, pauses, and pointless sentences you need to cut out.

    • Remove noise. Amadeus Pro has a great tool for this. Use it.

    • Compress the edited recording. I don’t mean use a codec, I mean compress the levels—bring the quiet bits up so that they aren’t quiet anymore, while keeping the loud bits where they are (without clipping them).

      You should also use AUPeakLimiter (one of the built-in Audio Units), or an equivalent, to crank up the compressed levels to 0 dB. The difference with how you set the gain earlier is that you set the gain to keep your levels under 0 dB, whereas here, you’re amplifying to at 0 dB.

      90% of screencasts are not loud enough. I do not appreciate having to crank up my system volume to hear you. You can fix this.

All of this is not trivial, but it’s not hard, either. Practice will make it easier, and the result—clean audio on your screencast (or podcast)—will be worth it.

2 Responses to “Audio”

  1. Jesper Says:

    Didn’t you also use to be a vocal proponent of “normalize”?

  2. Peter Hosey Says:

    Jesper: Yes, but compression and/or peak-limiting is a better way to achieve the desired end result (uniformly loud signal). Normalization fails easily when there’s a peak anywhere in the signal.

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