Understanding Lopsided Audio Waveforms

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Why an audio waveform is lopsided?

In A Nutshell

in a nutshell Most {if not all} of these “lopsided” looking audio waveforms are actually symmetrical in terms of amplitude over time and they have no effect whatsoever on sound quality. Therefore, one shouldn’t worry about them at all . Most importantly, this is not caused by a DC Offset problem in your recording system.

 

Look closely and you will usually see a higher amplitude positive side and a lower amplitude negative one {thus a lopsided waveform} on any waveform. If you sum the area between each side of the waveform and its null crossing, you would find that these areas are actually equal. Check your level meter, if you take a lopsided waveform and invert it, it shouldn’t look any higher. Lopsided waveforms are not caused by DC offset problems, their zero crossings are not shifted from the baseline.

Example: Asymmetrical bi-directional waveform.

a typical lopsided waveform

The waveform you see is correct for what it is, but it is not averaging the sound through the whole waveform, rather just generating values at each sample and calculating the values on a one in one out basis.

Long explanation

All bi-directional Waveforms are calculated by the amplitude of the signal over time. A waveform contains the harmonic content and its additional frequency components such as distortion and noise across the sound spectrum. The sum of of all of these frequency components or partials generate the waveform that you usually see in your digital recording software.

There maybe multiple instances where the harmonic content becomes uncorrelated with each other generating different looking waveforms. This can be sometimes observed when capturing bass, voice and synthesizer sounds. Thus, when your digital software creates an overview waveform display, it usually generates harmonics at different frequencies, and the addition of those harmonics can create a waveform that appears to have the top side looking one way, and the bottom one looking another.

If the top side of a waveform is larger than the bottom one, chances are that it’s the result of a problem in the the transfer function. That shape of waveforms is usually dependent upon the RC time constant of a resistor/Capacitor combination. Some people also theorize that this problem can be compounded by in phase /out of phase problems where harmonic content, in relation to the predominant frequencies, register higher in amplitude when they are in phase, and the opposite at the bottom side or below the axis when out of phase.

At the top of the waveform {positive pulse}, the harmonics that exist are adding to the waveform because they are in phase with the sound. At the bottom of the waveform {negative pulses}, the harmonics that exist are out of phase therefore subtracting from the waveform overview.

Whether it’s a problem with the harmonic content of sound, or the transfer function of a device such as an amplifier, a condenser mic or any analogue vacuum tube gain stage, etc, it’s not a DC offset problem. In fact, it’s not a problem at all if you are mixing or mastering audio/music.

The harmonic content of two different looking waveforms can sound almost the same. Conversely, two similar looking waveforms can have completely different harmonic content. Waveforms are not the best way to determine sound, however, spectrum analysis can be as long as it’s correlated to the sound of the source.

The audio waveform above has relatively the same spectral content, which is what you actually hear. The waveform you see is correct for what it is, but it is not averaging the sound through the whole waveform, rather just generating values at each sample and calculating the values on a one in one out basis.

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