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Monday, February 27, 2012

22

How to Deal With Microphone Feedback

check, one two. check check, one two twooooo.Did anyone else want to turn off the Oscars last night not because of how boring they were but because of the microphone feedback? Did you notice that every few seconds when someone would speak either a high-pitched zingy squeal would happen or a quiet but creepy robotic ghost noise would follow their words? You may remember theses sounds from such moments as your 6th birthday party when you'd stand too close to the boombox with your Mr. Microphone. I am not a scientist, so I will not attempt to tell you exactly how microphone feedback works, but I will run down a few of the simpler fixes you can try at your next Bat Mitzvah, karaoke night, or Academy Awards telecast.

1. Move the microphone closer to peoples' mouths.

One way you get feedback is by the sound that's being amplified making it's way back into the microphone it originated from. The farther away the microphone is from your mouth, the more room there is in front of it for other noises to get in. Much of the time last night the main presenter microphone was setup kind of low or far away from the folks doing the talking. And speaking of the mic being too low on the stand...

2. Turn down any speakers that are near the microphone.

At a live event, you always have these speakers called "monitors" sitting on the stage that point back toward the performer and are meant to help them hear what they sound like to the audience. If those speakers are too loud or if the mic is too close to them, you'll get feedback. Step away from the monitors and put the mic back up near your face.

3. Keep microphones away from each other and turn offstage  microphones off when they're not in use.

I think this was to blame for much of the noise last night. For some mysterious scientific reason, when mics are on and pointed at each other at just the right angle they can create that terrible sound. Many of the presenters last night had wireless mics pinned to their chest so we could hear them as they walked out or goofed around away from the main presenter mic. But then they would walk over and talk right into the mic on the stand with their lav (industry term, babe — short for lavalier which is one of those mics pinned to your shirt) still on. Or, a presenter would only use their lav and then the recipient would use the mic on the stand while the presenter stood like three feet away in the shadows, again, with their mic still on.

Of course there are plenty of others, but these are the three easiest fixes. And I know what you're thinking: but how does a band, for example, all stand on stage together with mics and monitors and not have this happen? It takes a lot of finagling and futzing around with where everyone is standing and how hot the speakers are and how hot the mics are and all that. Avoiding feedback is one of the reasons your favorite band is spending an hour doing their sound check before coming on stage. Maybe don't wear heels next time?

22 Comments / Post A Comment

Mrs. Hutchinson

To us the Oscar feedback sounded like a swordfight backstage? These tips are cool. As an audience member I always go into an internal mini-panic when feedback happens. IS IT GOING TO GO ON FOREVER?!?!?

maevemealone

@Mrs. Hutchinson Except it really did go on forever, and ever and ever, which describes most Oscar telecasts anyways. To me it sounded like morse code being typed out. I actually thought I was listening in on a closed captioning typist transcribe the entire thing.

maevemealone

@meganmaria I assume someone was already told they'd never work in that town again.

Emby

Jane, I suspect you know what are the mysterious scientific reasons why having two mics near each other can cause feedback, but to spell it out a little further:

The two (or more!) microphones pick up the sound at very slightly different times, causing what's known as a comb filter in the audio signal -- certain parts of the sound signal get cancelled out and others get amplified. Some of that amplification can get picked up in the monitors and create feedback.

Also, having two microphones creates weird little "hotspots" that aren't nearly as predictable as using a single microphone. In these spots, the acoustics just get funky and you get the mics picking up all kinds of reflective sound you never predicted. If you have on a lav AND are speaking into a stationary mic (especially if it's an omnidirectional mic that picks up from ~360 degrees), then that hotspot just jumps around and changes all the time. And you will get feedback.

I don't miss being a sound tech. Stressful, thankless work.

Lenora Jane

@Emby I have had this explained to me many a time by my techie sister and for some reason it has just now clicked in a way that made sense. Thank you!

Jenny Cox

@Emby Is that why my phone makes a weird little ghost noise before it rings AND SOMETIMES WHEN IT DOESN'T EVEN RING AT ALL when it's near a speaker?

angelinha

@jenny_ You might have a cell phone ghost. @melis should be able to determine for sure.

Biketastrophy

@jenny_ GSM phones (ATT&T-mobile) use whats called "Time division multiplexing" meaning each phone gets a certain time block to send its signal to the tower. So basically your phone transmits every x seconds and this pulsing ends up happening at a frequency which is in the hearable spectrum

isitisabel

@Emby I actually enjoy my on-campus sound tech job, because it's usually really simple setups. But it does mean that anytime I hear feedback (or really any kind of bad sound mixing) I get twitchy, not because it's a nasty nasty sound, but because my immediate impulse is to FIX IT NOW.

a5ouncebird

OHMYGODITWASTHEWORST.

swirrlygrrl

I'm not anticipating being asked to do technical production on next year's Oscar ceremony, but I enjoyed this article immensely anyways. And now off to karaoke! *I wish*

LaLoba

I was losing my marbles over this and no one else I was with could hear it!!!! At least it was real?

Cara Motts@twitter

Oh thank god. I asked other people and no one else noticed, so I just blamed it on my super-awesome hearing skillz.

Craftastrophies

@Cara Motts@twitter If it's a high pitched noise, older people probably won't hear it. High frequency hearing is the first to go, because of the hairs in your ears. Or whatever.

isavedlatin

@Craftastrophies Truth. I was watching it with my parents (I'm THAT cool) and The Olds said they couldn't hear it.

Mira

Ahhhh I heard this LAST YEAR and no one else agreed with me that it was happening, and this year it was so much worse and finally everyone heard it, and I no longer feel like I might be crazy!

(And thank you for the tips! I am not cool enough to hang out around a lot of live shows, but I do have to manage a lot of conferences and this will definitely come in handy.)

cuminafterall

@Mira YES YES YES. Last year I just thought I was nuts, this year I am happy to find out I'm not (not because I hear noises at the Oscars, anyway).

Nelson Trautman@facebook

That noise was not microphone feedback.

It was a series of distinct tones. It was intentional, but I'm sure whatever contractor sold the technology to the network promised it would be inaudible.

I'm not sure if it's some kind of audio watermark or timecode, but I think it has something to do with synching the live feed.

It was definitely not feedback though.

twinkiesandwine

I just thought it was the aliens trying to take over my brain again...

jackeemarie

Fiance and I thought it was from his TV, so he put the audio through the stereo instead of the TV speakers. I still heard the noise, but he didn't...so I just pretended not to. ANNOYING.

Zeki Yol@facebook

great work, thank you. i always follow web sites. thanks for sharing. Fıkra .

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