mac built in mic - panned right?
March 14, 2019 10:31 PM   Subscribe

i have a 12 inch macbook that has dual microphones on the right side of the laptop. they're literally on the side, where the headphone jack is, not on the flat surface with the keyboard. when i record through that mic my voice sounds dead center to me, but since the mics are slightly to the right, shouldn't i be hearing my voice panned slightly right? i feel like this is a really dumb question. am i just not hearing it or is there some reason the audio is in the center even though the mic is to my right?
posted by january to Technology (9 answers total) 2 users marked this as a favorite
If both mics are in more or less the same spot on the chassis, then they'll both pick up the same sound (more or less) so when you play it back through headphones, both channels will sound similar (roughly centered). The audio recording/playback apps will not pan everything to the right channel because the mics happened to be on the right -- all they get is two signals, they don't have any info about where the mics are/were physically.
posted by Alterscape at 10:36 PM on March 14 [1 favorite]

The dual microphones are used to cancel background noise and ultimately produce a single (mono) input audio signal.
posted by perihare at 11:28 PM on March 14 [3 favorites]

I thought the way it worked was that if you stood way to the left of a mic and sang, then the vocals would show up mostly in the left ear of the headphones. All a mic cares about is distance? It always puts the vocals in the center? Is this because it's an omni mic? Like, if you wanted to use one mic to record a roomful of musicians and capture that person A was on the left and person B was on the right, can you do that with a certain kind of mic?
posted by january at 11:49 PM on March 14

You're describing a stereo mic which is actually 2 mics. Where you perceive a sound in terms of a left-right stereo image has only to do with how an audio signal is routed to 2 (stereo) speakers -- and your spatial relation to the speakers.
posted by Jode at 2:24 AM on March 15 [2 favorites]

There are various ways to mic a sound source that will be perceived as stereo on playback, if played back in stereo. This explains it fairly simply.

Outside of studio trickery, generally that means two microphones at different angles to the sound source. It can be done with two omni mics (a lot of orchestral recording is), but generally spaced farther apart than most of the other techniques. Two microphones of the same type/polar pattern, right next to each other, pointed directly at the source, won't create something your ears will recognize as directional.

The conceptual part it seems like you may be missing is that each of these techniques records two separate audio tracks. If you recorded a single track, it will be playing back on both channels at equal volume, even if you play them back on a binaural system. Your ears interpret distance based on volume, reverberation, and a whole lot of other cues, so even cloning that track and panning the clone one side hard left and original side hard right will not give you a stereo signal (although on a single source like your voice, panning half of the stereo field to the left, while leaving the other side alone, should change your perception of where the voice is coming from.)
posted by aspersioncast at 5:09 AM on March 15 [1 favorite]

Ok, thanks for the link. It actually helps clarify my question, which, as you can see from the title, was not very clear in the first place.

It's actually not that I want to hear audio positioned in different places in the audio field - it's that I want to avoid it. If I'm singing into an omni mic and I accidentally turn my head a bit or get up and sit down and I'm a foot away from where I was, will I hear a difference in the audio?

It seems like I could hear a difference in volume and/or frequency, but not position. I just want to be able to move relatively freely and naturally while singing and not be locked into a rigid position.

(Super ironically, I actually have a home studio with nice mics and a nice audio interface, but I've always done everything by the book without knowing why I was doing it. I'm asking all this because I'm trying to simplify everything I do. I get that the mac mic being omni has a worse noise floor and all sorts of things that make it not the ideal mic, but I can live with that for my purposes. I just need to know if I'm wasting my time if I get away from sitting perfectly pointed to the mic each time I sing.)

((Sorry for chat filter.))
posted by january at 7:16 AM on March 15

Yeah, if you move closer or farther from a single mic, all you’ll do is affect the volume. I’ve been involved in recording 3D audio; it’s expensive and requires special hardware. You won’t do it on accident.
posted by Andrhia at 7:50 AM on March 15 [1 favorite]

IANArecordingengineer, but I took some classes in college: You're right that you'll hear a difference in volume and tone as you move relative to a fixed (single channel) mic in a studio, but not position.

When you're singing, you've got interactions between your body, the sound waves in the air, and whatever microphone you're using. Your lungs, throat, vocal chords, neck and mouth act a little like a somewhat-directional loudspeaker -- acoustic energy is radiated out of your mouth, most strongly in the direction you're looking (but also everywhere else, at slightly diminished power). So when you change your orientation relative to the mic, you're essentially sending a slightly different part of the sound your body produces towards it.

Sound vibrations in the air follow, more or less, an inverse square law sort of like light. If you imagine a single moment of sound expanding from you as a rough sphere, the surface area of that sphere gets MUCH larger as the radius increases, so the energy that's present in any particular point, like, say, the diaphragm of your mic, rapidly falls off. This half of why it's so noticeable when you change your distance relative to the mic (even holding your orientation and relative angle constant).

The other piece is that mics have distinct pickup patterns -- cardioid, hypercardioid, omni, etc. . Depending on how the mic is physically structured, sound from some directions will be (relatively) amplified and sound from some directions will be (relatively) diminished. Your mics' manuals probably have plots of response vs. angle. This is the other part of why changing your position can change the sound quality -- suddenly the sound your body is producing is coming from a different point relative to the mic's pickup pattern, so getting different gain and maybe frequency response (tho less this). You shouldn't notice this if you shift back and forth in front of the mic (right in the sweet spot), but if you, say, move from the front to the side of a mic during a take, that'll probably have an impact.

So I think it's pretty hard to move freely and have great sound, unless you have a dude or dudette with a boom (hi, 10-years-ago-me) following you around! There are probably recording setup tricks to get you closer to what you want, thoug, and that's where my knowledge falls down and hopefully other people can pick up!
posted by Alterscape at 8:14 AM on March 15 [1 favorite]

If I'm singing into an omni mic and I accidentally turn my head a bit or get up and sit down and I'm a foot away from where I was, will I hear a difference in the audio?

Yes, your distance from the microphone will always matter. That's fundamental to the nature of how microphones (and sound) work.

Omni patterns have a number of interesting characteristics that make them less susceptible to certain aspects of poor mic technique than, say, hypercardioids. But a difference of a foot is going to be audible on pretty much any source unless you're miking something loud from several feet away. Which I wouldn't recommend for voice work.

To be able to do what you describe, you'll generally need a lavalier or headset that moves around with you (there are other ways, but they are going to get bonkers expensive very quickly). This should be adequate for general voice work not meant for professional production. If you are singing, or doing professional overdubs or something, there's simply no substitution for learning good mic technique, which means generally keeping the mic in pretty much the same place relative to your face.

Pickup pattern doesn't really have much to do with noise floor. The quietest mic I own is a multi-pattern I usually use in omni. Smaller diaphragm mics will tend to be a bit noisier than LDCs.

Based on your update, if you're hearing a lot of self-noise, I would suspect that you're cranking the gain in order to get the mic to pick up your voice from multiple positions - in general people tend to record way too hot. But your internal mics running through your built-in soundcard are always going to be pretty noisy compared to even a cheap interface or USB condenser.

If you're going to be doing a lot of recording, I strongly recommend getting a copy of David Huber's "Modern Recording Techniques," and reading the section on microphones.
posted by aspersioncast at 8:19 AM on March 15 [3 favorites]

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