Phase is the relationship of sound waves to one another. This can get really nerdy and will be handled 99 out of a 100 times by your producer or creative director.

What is a sound wave actually?

A sound wave is made up moving air that your ear and brain interpret. It is depicted below. The wave has peaks and troughs that can be measured in two ways linearly: amplitude (vertical dimension) and frequency (horizontal).

The amplitude of the wave corresponds to the loudness of the wave. The greater the gap between the peaks and troughs of the wave is perceived as loudness.

The frequency of the wave is the measurement between the peaks and troughs of the wave, which is measured in cycles per second (also called hertz, or Hz). The human ear can hear and interpret sound waves between 20 Hz (which are low, big sounds) and 20,000 Hz (which are high sounds).

What is phase?

When multiple sound waves are summed together (I.e. “mixed”) they interact with one another according to their amplitude and frequency. There is a phenomenon called “phase” where two captured instances of the same wave interact in a specific way. For example, a snare drum is typically mic’ed with two microphones: top and bottom. They are capturing the same source from two different locations, so they are capturing the same sound wave.

This is a good thing when the two waves are being played back at the exact same time: in fact, when two waves from the same source are played perfectly in time (I.e. their peaks and troughs are aligned with each other), there is a doubling of its amplitude that sounds good. If, however, the two captures are not perfectly in sync or “in phase,” there will be degradation to the sound. In fact, two identical waves played perfectly out of phase (with peaks aligned to troughs) will cancel out the sound completely.

These diagrams demonstrate the phase two waves—first in perfect phase, then second perfectly out of phase!

MxU Video (6:51)

https://www.youtube.com/watch?v=LBYaY64FEVs

Typical Phase Troubleshooting

• Drum snare mics (top and bottom)
  • The solution is usually just to phase-reverse the bottom mic
• Drum overheads
  • Because there is more physical distance between the close mics of the drum kit and the overheads, it is easy to misjudge the height of the overheads to the point where they are out of phase with the rest of the kit. There are ways to correctly measure the height to get them in-phase. This video from Attaway Audio explains at around the 9:30 mark.

https://www.youtube.com/watch?v=4UzX7LqnSjg

Application

On the M32 mixing board, phase can be flipped on the preamp section. Feel free to experiment on how this changes a sound, but make sure it goes back to where it started.

The Bottom Snare mic is phase-reversed so it plays back in phase with the Snare Top microphone.