4th Gen. Focusrite Scarlett Series Interfaces – Solo, 2i2 and 4i4
October 19, 2023
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(fyi, formal definition below)
Generally in podcast production you don’t have to worry about phase issues because phase cancellation mostly happens when two microphones are picking up the same source from different distances. Usually the only times this usually during podcast recording is if there are several people, each with their own microphone in the same room – however if each participant speaks very close to their microphone there won’t be any noticeable phase issues.
As defined in Sweetwater’s comprehensive glossary of audio terms:
Audio waveforms are cyclical; that is, they proceed through regular cycles or repetitions. Phase is defined as how far along its cycle a given waveform is. The measurement of phase is given in degrees, with 360 degrees being one complete cycle. One concern with phase becomes apparent when mixing together two waveforms. If these waveform are “out of phase”, or delayed with respect to one another, there will be some cancellation in the resulting audio. This often produces what is described as a “hollow” sound. How much cancellation, and which frequencies it occurs at depends on the waveforms involved, and how far out of phase they are (two identical waveforms, 180 degrees out of phase, will cancel completely).
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2 Responses
I’m glad you’ve made reference to this. Frankly, there is some misinformation out there regarding phase in general.
I’ve heard people refer to the Adaptive Phase Rotator option in iZotope RX as a tool that may be used to “fix the phase” across a segment of audio. This is inaccurate. The Adaptive Phase Rotator (or any Phase Rotation tool for that matter) does not address and/or correct misalignment that may result in audible cancellation anomalies.
As well, Phase Rotation does not correct Polarity issues. Note that the “Phase” option included on many professional audio devices (and plugins) is often misunderstood as well. For the most part this simply inverts the Polarity of the audio. It does not correct misalignment.
In simple terms Phase Rotation changes the *shape* of waveforms. This restores and optimizes headroom. The process is implemented in broadcast audio chains. And IMHO – it’s a vital option in Podcast production as well.
The reason is as follows:
Many producers now recognize -16.0 LUFS as the “standard” for stereo Podcasts. In order to meet this target in post, a significant amount of added gain may be necessary. Delivery specs. also include a maximum amplitude ceiling. More specifically – a True Peak max. In many cases limiting is applied in order prevent overshoots relative to the defined compliance ceiling.
With all that said, uncorrected asymmetric waveforms will compromise headroom and may result in excessive limiting. This should be avoided, especially when distributing lossy codec audio at low data rates. As noted Phase Rotation will restore headroom and optimize the audio as it moves downstream in a signal (or processing) chain.
-paul.
@produceNewMedia
Thanks Paul!