Centering Asymmetrical Audio?

[KenTheriot]

I have a vocal recording that is quite asymmetrical - most of the waveform is on the top part of the center line. Here is a pic of it:

I've never seen this before. Is there a way to center it, making it symmetrical, such that an equal amount of the waveform appears above and below the center?

The audio sounds OK. And Normalizing putting a tick in the DC Bias box at 0% does nothing other than normalize the level. Symmetry remains same.

Thoughts?

Thanks!

[SteveG_AudioMasters_ · Accepted solution]

It's supposed to be like that! When people breathe and speak at the same time, the forward motion of the air has the effect of shifting the microphone's response to accentuate the positive side of the waveform. The same thing happens with a brass instruments, and indeed any sound with the same carrier properties.

Generally it isn't an issue, but it can in some circumstances limit the peak amplitude that you can use. Generally a little light limiting will overcome this. It's also possible to reduce the effect using an all-pass filter (alters the phase response), but that sometimes sounds a little strange to my ears; limiting, if applied sensibly, can yield other improvements too, and is a much better way of increasing the effective overall level of the speech.

[KenTheriot]

Thanks Steve. That does make sense from a theoretical point of view. But I've not seen it to quite this degree before. Like you say, though, it isn't a problem from an audio quality standpoint. The only real issue is like you said, it limits how much headroom you have to play with for normalizing, say. And also as you said, that can always be dealt with by a little dynamics adjustment.

But I recently bit the bullet and purchased iZotope RX 6 and used the Phase tool to "rotate the signal phase." Their preset of "adaptive phase rotation" makes the audio symmetrical with no audible artifacts. That leaves a more balanced amount of space on BOTH sides to use for level increases if desired. I wondered if Audition had a similar tool to RX's phase rotation tool?

BTW, just for context, this is not my vocal. I help VO folks with home recording and of all the files I've worked with, I've not seen one this off-center to date.

Thanks!

[SteveG_AudioMasters_]

KenTheriot  wrote

I wondered if Audition had a similar tool to RX's phase rotation tool?

No it doesn't, but you might want to look at this: PhaseNudge | Airwindows

BTW, just for context, this is not my vocal. I help VO folks with home recording and of all the files I've worked with, I've not seen one this off-center to date.

I've seen them that bad before! You have to bear in mind that there are several factors at work that will determine how extreme this will be. How close, what sort of angle the talent has WRT the mic, and the type of mic itself all play a factor. Technically you are more likely to see this from an omni mic, as these are the ones that have an extended bass response and would be more sensitive to pressure effects. Also, the form of windshield can influence this; the less shielding there is, the more likely you are to see it.

[KenTheriot]

Awesome! Thanks.

[KenTheriot]

Just wanted to let you know I tried PhaseNudge and watched the video on the AirWindows site. Interesting but it does not do what I am looking to do. The phase rotation in RX seems to do just what I need and I don't know exactly why PhaseNudge doesn't do the same thing. But the inner workings of both effects are a bit beyond me :-).

[SteveG_AudioMasters_]

Well, if you've got access to the RX one and it does what you want, then use that! I haven't tried the PhaseNudge, but it looked interesting so I thought I'd mention it in passing, just in case... As I mentioned earlier, I wouldn't bother with the all-pass filter method of dealing with asymmetry anyway, because of the artifacts.

[KenTheriot]

Steve, if this were for me, yeah. Obviously I already have RX. But this is for a student. He doesn't have AA or RX :-P. HOWEVER...

I discovered a way to do this in Reaper using a stock plugin - the EQ! Someone on the Reaper forum, in an unrelated thread of mine, offered correction of asymmetrical voice recordings as a way to help get a more "in yer face" effect. He said phase rotation is essentially an all pass filter, which can sort of randomize the phase issues. So I chose a single band in the EQ (which is a parametric EQ), and selected "All pass" as the band type. Left the single target frequency at 1KHz and the Gain adjustment at 0 dB and bingo! It had the same effect as the RX tool!

Now I need to see if I can do that in Audition, just for my own edification.

[huttumi]

More info: https://www.soundonsound.com/sound-advice/q-why-do-waveforms-sometimes-look-lop-sided