Uneven wave form....why?

[dastrick]

Why are waveforms uneven (from top to bottom)? This is spoken word. A countryman mic -> mixer -> 2 aux sends (L & R) -> CD recorder.

Only the spoken word is uneven. The music that was recorded has even waveforms.

And btw, it sounds fine. I'm just wondering what's going on.




Thanks,
Dwayne

 

[Track Rat]

Don't worry about how it "looks", just how it sounds.

 

[Bobbsy]

Some voices and, indeed, some instruments, simply have non symmetrical waveforms with more energy in the negative-going direction or vice versa. It's nothing to worry about and quite normal.

However, on the other hand, if you see a waveform where the "centre line" is displaced upwards despite the waves being symmetrical around it, that generally means you have some DC offset. This is caused by a small amount of DC electrical current present on the signal along with the alternating current sound information. Most DAWs have a function to correct for DC offset and it's worth running this if only to make amplitude changes in you mix more effective--with DC offset present, you maximum level is governed by the higher side of the waveform.

 

[VomitHatSteve]

I've often wondered about this (though I guess I've never been worried about it).

So what makes these sound waves have greater energy going one direction than the other?

 

[Bobbsy]

I believe it is to do with the phase relationship between the harmonics which are a natural part of the timbre of acoustic instruments (including voices). Some instruments produce a more symmetrical waveform than others--but even on a particular instrument the symmetry can vary depending on the note played and the technique of the player.

Some people have noted that non-symmetrical waveforms are often the most pleasing to the ear. I was once told that Larry King's voice (and a lot of the deep, resonant announcer voices) are particularly non-symmetrical. I've never had a chance to check that out though!

This is all different from the DC offset I mentioned--with DC Offset the symmetry of the waveform isn't changed, it's just that the zero crossing point is moved upwards from where it should be.

 

[RawDepth]

This is entirely different from DC Offset, which can occur when the mic preamp or interface introduces DC current into the AC audio signal.

I think your problem is more frequency related. This can happen when additional frequencies that are not harmonically related become part of your recording. (Let us say 1000Hz and 3763Hz, for example) Perhaps some noise such as the wine of a computer fan or a running air conditioner has been picked up by the mic. Or maybe your hardware is adding noise to the signal. I don't know. I am guessing.

The waveform below shows how unrelated frequencies interact, or should I say, don't interact. (Image stolen from the Internet) The peaks below the centerline represent the fundamental frequency and the peaks above the line represent some higher frequency. It is also possible that the lower the affected frequencies, the more obvious the lop-sidedness appears.

 

[Bobbsy]

Exactly what I said, Raw Depth! Your graphic illustrates it nicely though.

I'd take issue with one thing in your post: calling it a problem. The harmonics and their phase relationship with the fundamental are simply a natural part of sound, not a problem to worry about. Indeed, as I said, I've seen it argued that some of the richest, nicest sounds have very non-symmetrical waveforms because the "richness" is lots of harmonics.

 

[RawDepth]

Exactly what I said, Raw Depth! Your graphic illustrates it nicely though.

I'd take issue with one thing in your post: calling it a problem. The harmonics and their phase relationship with the fundamental are simply a natural part of sound, not a problem to worry about. Indeed, as I said, I've seen it argued that some of the richest, nicest sounds have very non-symmetrical waveforms because the "richness" is lots of harmonics.

You are correct. I shouldn't have called it a problem, (unless there is audible noise in the track.) Many times I have had lopsided waveforms and left them alone because they sounded fine. As with all things in nature, being different is not a bad thing. Thanks again Bobbsy.

 

[MariosParadisis]

It's not a problem at all, it has to do with the phase of your audio material and it should not make you worry. Instruments like violins for example can produce this kind of uneven waveforms.

 

[salcedocarlo]

Why are waveforms uneven (from top to bottom)? This is spoken word. A countryman mic -> mixer -> 2 aux sends (L & R) -> CD recorder.

Only the spoken word is uneven. The music that was recorded has even waveforms.

And btw, it sounds fine. I'm just wondering what's going on.


View attachment 72086

Thanks,
Dwayne

This happened to me just last nite while mixing in Logic. The culprit in my case is the compression i used for the snare. I noticed this bec the downward peak happens only on the snare. I adjusted the attack of the compression, it kinda helped but not entirely. I think when the comressor's attack is too fast, the snare has no time to sound the other half of the waveform, creating a peak on just one side. But this is just the case in this particular mix, there could be other causes just like in your case, a voice recording.

 

[ashcat_lt]

Assymetry can be a problem in that it basically wastes headroom. It is true that many deep male voices can be particularly assymetrical, but part of what makes them sound so good coming out of a radio or television is a little trick they call Phase Rotation which is really just an allpass filter or two which causes a change in phase at different frequencies without actually changing the volume relationship of those frequencies. That has the effect of redistributing the energy and making the waveform more symmetrical. By itself it sounds like an extremely subtle form of compression that ever so slightly smoothes the voice a bit, but it also allows compressors and limiters that follow to work more predictably and consistently and actually lets you get away with less overall compression. Every voice you hear on radio and tv will have had this effect applied. I use it on my vocals all the time, and while it's no magic bullet, it makes them noticeably easier to work with.