Phase, also known as position, refers to the orientation of a cyclical waveform in time, relative to another cyclical waveform. Phase shifting is measured in degrees and it ranges from zero to 360º. To determine the phase degree, it is essential to have a reference waveform. Because of this, it is crucial to know exactly where the zero degrees is placed in order to measure the phase degree.
Phasing, also known as phase interference, is a phenomenon that describes interactions between two or more almost identical sounds that are performed at the same time. It’s worth mentioning that phasing directly affects the amplitude’s pressure or power. There are three types of phase interference: constructive, destructive, and comb filtering.
The constructive type happens due to synchronized phase relationships than range from zero to 360 degrees. This causes the amplitude to multiply and resonate. Producers tend to use this effect to boost frequencies. The destructive type happens due to the phase relationships of 180 degrees and causes the waves to cancel each other out. This effect is typically used to eliminate frequency content from any given sound. The comb filter type triggers constructive and destructive peaks and nulls due to uneven phase relationships. The comb filter is typically used to add special effects in electronic music production.
Everything around us is related to sounds. Reflected sounds are usually filtered copies of the initial impulse, so phase interference arises when they bump to each other in the air. This tends to be a problem when trying to capture genuine sounds inside a room because it is impossible to predict when and where the phasing will occur in an acoustic space. Some experienced engineers and producers are able to determine the type of interference that will occur by comparing the position of the reflected waves to the incident waves. They do this by calculating the time it takes each wave to arrive at the receiver, taking the difference, and translating the result to a correlating phase degree.