Audacity overloads at -6dB or 50%. I know why. How?

Everybody Knows if you record mono from a stereo Interface Audacity will try to reduce the recording volume by half or -6dB. This regularly kills people trying to record a mono microphone into a mono audiobook with a stereo interface.

How? Where is that 6dB reduction produced? This was only of fuzzy interest until people started to experience very serious recording volume damage—almost like that 6dB reduction thing went nuts.


What’s effectively happening is that you have an input like this:

but “recording mono” Audacity mixes it down like this:

This is the same behavior as Mix Stereo To Mono has; the tracks essentially get averaged.

It seems like we’ll be exploring a fix for this in more detail during the next development cycle. It coincides with multi-track recording capabilities, in particular recording desktop audio and your own mic at the same time - or recording 2 USB mics at the same time.

I have some designs for this already:

The question now is whether this is a technically easy change, or whether it involves more massive restructurings like we’ve had creep up on us during the last couple releases.

From the point of view of the performer:

They just bought a good quality microphone that they’re using through a good quality stereo interface in a quiet, echo-free room. They always have to apply a change. Record in perfect stereo, convert to two-track mono, and lop off the dead track --or-- Record in mono at half volume with double the noise, and apply a volume boost.

Everybody loses.

I wouldn’t mind a single, secret, hidden setting that stops this process.

[X] AudioBook

The Obsessive Engineer standing behind me wants a sensor that if there’s nothing on the right channel, it automatically checks that box.

We’re ignoring him.


And just when you thought it was safe.

I have a Behringer U-PHORIA UM2. “mono” interface. It will record in either stereo or mono with the same microphone volume.



Oh, and before we wander too far off from the real problem. We need to resolve the issue of creating massively reduced recording volume for no apparent reason.

Screen Shot 2023-07-28 at 11.18.53 AM

The right-hand blob is yelling into the microphone with everything turned up.

This one is converting Audacity into Unfit For Purpose. There doesn’t seem to be any way to fix it. We have already had one user throw in the towel and go for a different program.


This looks like the same problem except a 4 channel interface.

In each case, I agree that the automatic mixdown is really opaque, and we should just let people select the channel in question instead.

This is why you wear the robe, pointy hat, and fuzzy slippers. I would never have through of that.


That illustration was from this posting.


Probably because I don’t own a quad or higher interface, or even know anyone who does.

But not all the errors come out even like that. Some show a much more serious reduction in volume. That’s what happened to the one poster who jumped ship and went with a different program.

“Thanks but I really need to start recording so if there aren’t any solutions it’s best I try another software.”

And that’s when I called “Unfit For Purpose.”

One common thread seems to be “This used to work OK and now it doesn’t.” So this isn’t someone who plugged a new microphone in and it didn’t work.


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