How to isolate voice in a 2-mic setup

Hey folks,

I’m producing an interview podcast. The interviews will be face-to-face in the same location. We did a test interview, using two microphones and a standalone recorder, recording on separate tracks. When I import them into Audacity, I can hear both voices on each track. (On one track, the interviewer is loud and clear, but I can still hear the interviewee faintly in the background. Vice versa for the other track.) How do I go about cleaning up each track so it only has one voice on each?

Thanks so much!

If you want “only” one voice per channel, you need the two people in separate rooms when you record, or record each person separately (not real-time).

If “mostly” one voice per channel, physically separate the two people as much as possible, and get the mics as close as possible to the people talking. Directional microphones will help.

“Cleaning up” the recording after the event is a non-starter (as I assume you are discovering).

You could try squelching what should be silence, but where you can hear the other person talking …
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This is how Charlie Rose does it.

The “Famous Table” is not an accident. That’s how the sound people keep the two performers apart. That and yes, limbo lighting is dramatic and something of a trademark for him, but the real point of the WNYC studio is it’s dead quiet with no echoes. They’re wearing bright, close-talking lavalier microphones and that’s about as good as it gets. I assume there’s still a little cross-leakage, but it’s so low that it can be ignored.

So yes, the two microphones and two-channel recorder was a good idea, but I bet you shot in a live room with the actors too close and the microphones are picking up each other’s wall echoes in addition to direct leakage.

You can get directional lavaliers and I enjoyed a show shot wild in New York City with them. It came off very well with the performers announcing perfectly, literally in the middle of Grand Central Station, but one of the performers tried to do something a little out of the ordinary and the track went straight into the toilet. Directional lavaliers are rough to use.

Isn’t post production fun when you have cross-talk like that?


and you can also automate that using the “Auto Duck” effect (Auto Duck - Audacity Manual), but whether manually or with Auto Duck you are relying on only one person talking at a time. In real life there is almost always overlap in places.

All these tricks only work when the voices are separate during the exchange. If they like to interrupt and step on each other, that’s the end of the world. Audacity cannot reliably separate instruments, voices and sounds in a mixed performance.

This is another way to shoot these things.

That’s a long-distance shotgun microphone used in close proximity for interviews. Ira Glass was one of the first people to do that on This American Life. Everybody looked in horror and said it would never work. Now everybody does it that way.

There’s probably a Sennheiser MKH 416 inside that wind sock.


A friend of mine did a voice job on one of these in Biscayne Bay. He was on the floor of the boat with a shotgun pointing up at the performer.

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Thanks for the assistance, everyone. I still have a lot to learn.

Thanks for the assistance, everyone. I still have a lot to learn.

Field interviews have all the problems of exterior theatrical production plus multiple microphones. People who can routinely pull that off are production heroes.

Remember if you record in a restaurant you can’t use anything with copyright music in the background.

About a year ago I talked to someone doing an interview here.

I thought he was nuts. He said it was intentional and he did it for the obvious signature of the plane noise, but he was using one blast-proofed microphone in this instance (it’s also windy there). Newsies use one, long-handled microphone and swap it back and forth, but they’re not doing long-form interview. I’m with you. Two mics are a good idea, they just have to be managed carefully.


Ok, here is how we do it at The Ratfiles Podcast, and it works as well as any studio could hope for. We have our recording studio/room fairly soundproofed. Using Behringer mics (XLR), we join the twin microphones with an XLR ‘Y-cable’ and then run them into a top-end laptop’s USB input (using Ubuntu 14.04…works best, for some unknown reason, better than 16.04) and record using Audacity 2.1.2.

Our end result is a very nice, clean quality recording of two hosts sitting in a room 3-feet apart, without ANY reverb or cross-talk (although, we do sometimes try to talk over each other, that’s etiquette, not bad recording properties). Clean-up is easy in post-processing. The only ‘downside’ is that since we only have one audio track (one per session, instead of per-mic, per-person), we have to get the gain fairly synchronized between the mics before we start recording - and luckily (or unluckily) we do this by mouth-to-microphone distance, which is fairly easy to do using this specific 8500 model Behringer microphone. I can get us within say, 2-3 db’s of matching gain by pre-show sound-checks…and then if I need to ‘tweak’ post-production, I can simply go into effects, do a ‘noise reduction’, then some ‘on timeline’ gains or reductions if I have any peaks or spikes.

Now, knowing this, go check out our podcast and see what you think. (homepage)

for the sake of a couple hundred dollars in mics, cables, and a decent 3.5ghz laptop with 8gb RAM and Audacity. I’m telling you, the real magic is in the Ubuntu/Linux, not the other gear…I can’t get this same quality with my Windows-based server, and it is running a quad-core Intel chip and Win7Pro…it just doesn’t sound the same in the final MP3 file.

join the twin microphones with an XLR ‘Y-cable’ and then run them into a top-end laptop’s USB input

You’re missing a step. How did you get the XLR cable into the USB input? That step can cause major problems.


we do this by mouth-to-microphone distance

Going back to the “Y” cable technique, there is no other way to set individual volumes, particularly if the performers like to talk over each other.

How are you holding the microphones up? Short booms?

Are the performers listening on headphones?


Since all recording situations are different, each one may require a slightly different approach. This is what I would suggest. Since you will be doing your interviews in the same room, try and do a little cheap room treatment. Heavy curtains for the windows, move to the center of the room when recording, use directional dynamic mics, make sure the room has carpet on the floors as well as furniture in the room. Purchase some acoustical foam to place around the mics. All of this will help with what is referred to as mic bleed as well as help prevent adding an artificial reverb or echo effect.

Once you do this, you should be able to apply a gate to each track to clean up any cross bleed. You will need to listen to your interview to make sure your gate settings are correct to prevent any chopping of the words being spoken. You can do quite a bit of sound treatment for your recording studio for under $100.00 and it makes a tremendous difference. You can purchase a Face Shield for your mics that cost around $125.00 each or build your own for around $50.00 for both.

The ATR 2100 is a good mic for recording several tracks in the same room. It cost $79 and you can view the specs here. I bought mine on sale at GC for $59.00 each. I purchased 4 to do the same thing your doing.

I use furniture moving pads.

For paid recordings, I use two pads, front and back. I have enough stuff to make an 8 foot box “studio.”

One poster did it with hardware store plastic pipes jammed together.

If you’re using the table mount and have trouble with furniture or floor noises, you can help that with the book/towel technique.

Once you kill the room echoes and noises, you’ll be stunned how much better the sound is, and how much easier it is to clean it up.


You Sir, are the reason I have promoted the “Moving Pad” idea for the last 2 years or so. You said this in another post back in 2014 or 15. Such a simple idea with dramatic results! Pay $6,000 to $12,000 and up for a dedicated sound booth or less than $200.00 DIY concerning moving pads and PVC pipe with 99.9% of the same results using your recommended system. Now, I will not credit you with coming up with this idea, BUT I do credit you with the person who turned me on to this idea. BRILLIANT!

I suggest your advice at least once a week while talking to Podcasters. I spent $30.00 for my PVC pipe and $59.00 for my moving blankets. I built it and recorded a demo then took it down. (The wife made me do it, it was her guest room). When people ask me how I came up with this idea, I simply tell them I did not, it was from some cat name Koz over on the Audacity forum. Cheers. Happy 4th!

I will not credit you with coming up with this idea

Why not? I designed the original one many years ago when I had to record voice tracks and all I had was a quiet “live” room, borrowed from another division of the company. So whatever I did had to go from a pile of stuff to a sound booth in about 40 minutes and come down in the same time.

That’s one piece of wood duplicated multiple times where any piece can go in any position, and they’re symmetrical. You can change the height in 6" jumps to whatever you need. You don’t need to “find a cross-brace.” Just pick up the next piece of wood. The large holes on the ends and rope are to tie the corners of each panel together. Put pads on the floor and you don’t have to worry about ceiling reflections.

I recorded many voice tracks with that setup and it got me out of trouble when I couldn’t find a quiet room. I should go back to the date stamps on the photos. 2010? 2009? Putting pads on the walls is old news, but you can’t do that if you have to shoot in somebody else’s house. Even moving pads is not that common, although I did get that from somebody else lost in the mists of time.

That’s the first known application of this technique. That’s a film editing table with Audacity sitting on top. I’m shooting a voice track for an animation promotion between film cutting jobs.

The PVC Studio was from an audiobook reader here on the forum. That was a take-off on my original idea. I got them to post pictures. I need to go find them and the dates.

It is remarkably effective and it folds up in a neat pile in the back of the garage.

“Koz? What are all those sticks hanging up near the ceiling.”
“That’s a sound studio.”



The original photos are dated October 2009, so the folding studio concept is 8 years old.

Found another one. The assembly can be a little floppy (not designed for outdoors) so you can use one of the sticks as a cross-brace.
The company moved into a much larger building with a soundproofed conference room, so I didn’t need the moving pads so much. That’s how I shot this.

That’s actually two sound shoots (I’m the one on the left). The soundproofing is built into the walls except for the pad on the table. Many shoots went through that room. The only downside was wrestling with actual conferences. Make nice with the room scheduling people.


Well, shucks. I can’t find the poster who made a studio out of hardware store plastic pipes.
Still looking.


Got it.

Odd. She calls it “PVC Pipe.” I wonder why it didn’t show up on a forum search. I got it through a painful, round-the-barn search.

She used duvets, not furniture moving pads. So that’s why that didn’t work.