What Causes Feedback On Audio Webinars and Teleconferences?

I’ve been on way too many webinars and teleconferences where one of the guests invariably had a bunch of feedback. In many cases, the host couldn’t even hear it, which makes it even worse.

Why does this happen?

I’d venture to guess that the problem is actually quite simple. It’s the microphone that the guest is using.

Microphones tend to have two different “pick-up patterns”: omnidirectional and cardioid.

Omnidirectional mics pick up sound from “all around”, while cardioid mics tend to be more directional. There are also “hyper-cardioid” mics, and they’re even more directional.

A lot of cheap headset mics that you can buy online might sound great, but they’re usually omnidirectional mics. To make matters worse, they tend to have AGC circuits built-in that bosts their gain when you pause for more than a couple of seconds. (AGC = Automatic Gain Control.)

So if you’ve got some kids or dogs making noise in the background, these kinds of mics will pick up all of that noise if you stop talking.

And, if you’ve got your computer set up to play back the audio through external or internal speakers, rather than headphones, then … yes … these cheap mics will pick up and AMPLIFY those sounds as well — which leads to … you guessed it … feedback.

As an aside, I have a course on recording audiobooks where the author spents quite a bit of time at one point extolling the virtues of some particular equipment that he likes and recommends. Which is fine until you come to the part where he also recommends you set up your “studio” in a closet lined with pillows and/or blankets to make sure there’s no background noise on the tracks. Ummm, yeah … can you guess what kind of mic he’s using and recommending? A fancy mic with an omnidirectional pick-up pattern and … built-in AGC. Ugh.

Don’t get me wrong, the mic he recommends is a GREAT mic! The problem is, it’s twice the cost of the Audio-Technica 8HEx-Pro and creates all sorts of problems because it’s an omnidirectional mic.

I sit at my computer with music playing softly on my computer speakers while I’m recording vocals on my 8HEx and you cannot hear ANYTHING in the background tracks! NADA! ZIP!

Ditto for my Sennheiser 441 mics — I’ve recorded people speaking when jet planes flew overhead and you cannot hear the planes at all.

But if I had used omnidirectional mics instead, I’d have all sorts of background noise in my tracks.

If you look around on sites like Sweetwater Sound or Amazon at the various mics, you’ll notice something interesting: most lavalier and headset mics tend to be omnidirectional. I don’t know why that is; what I can tell you is, most of the time when you’ll find the exact same mic in a cardioid pick-up pattern, it’ll cost more … sometimes quite a bit more.

SUMMARY

Unless you have a particular need to bug a room or have a group of people sitting around a table and you want to record everybody from one mic sitting in the middle of the table, I don’t know why you’d need or want to use an omnidirectional mic. Stick to cardioid mics — you’ll be much happier with the results.

One thought on “What Causes Feedback On Audio Webinars and Teleconferences?

  1. Mikey B

    I just graduated from CRAS audio school, it’s awesome that I get to travel the world doing what I love right now. I went there wanting to do music, discovered post production, and 6 months later I ended up doing broadcast. The options are endless.

    Reply

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