What is phase?

Posted by Aaron Groombridge on

Phase - It could be what is pushing you back.

Phase relates to the actual sound wave of what you are recording and mixing. This is why it can be one of the most confusing things to understand in audio engineering.
It is also the source of that unexplainable weirdness and weakness in your mix.
In short, unless you have incredible ear for it or you are crazy lucky, you need to put the time into grasping the concept of phase.

What is phase?

Phase is a way of describing how multiple sound waves are working together; are they helping and reinforcing each other? or are they working against and destroying each other?

What is a soundwave?

Every sound is transported or in fact created by something pushing particles, and those particles then rippling through air, wood, whatever, until it runs out of energy. Hitting a table creates a sudden push of particles through the air and through the wood of the table. The wood of the table moves at a different speed to the air around the table. Slow moving particles sound lower and fast moving particles sound higher. So the sound of the wood is lower and the sound of the air is higher.

What is in phase?

When some things are in phase they are working together.
Imaging several people rowing a boat at the same time.. Like the Dragon boaters I sometimes see on Lake Pupuke, or a Waka down at Petone beach. If their paddles are hitting the water at the same time, then are using the same power and speed for their row, and the boat will heave ahead in a stronger more solid motion.
This is in phase.
This is a good mix.

What is out of phase?

When some things are out of phase they are working against each other.
Imagine if a couple of the rowers described above realised they forgot their lunch and started rowing in the opposite direction.
Imagine also if another rower had a broken wrist, so their rowing was a lot slower and inconsistent to the others.
The paddles will not be hitting the water at the same time, they are using different power and speeds for their rows, and some are actually rowing backwards! The fact is, this boat will still be moving.. But it won’t be pleasant for anyone.
This is out of phase.
This is a bad mix.

One more analogy

The soundwave coming to your ears right now is the result of a massive collection of waves. Have you ever stood knee deep in any of our west coast beaches? Have you experienced the multiple levels of waves coming in from the ocean at the same time? There is a single, slow moving wave, then a stronger surge pushes its way through, but it does not replace the slow wave, and it doesn’t seem to change the slow waves pace, is just kind of moves over it, and you can see the level of the slow wave is added to the fast wave for a moment and then the fast wave moves on to the sand leaving the slow wave as if nothing happened… although it might be a tad higher than it was before. But then the fast wave is pulling back out to sea, but the slow wave is still fighting to have it’s time on the sand….. And then there are waves which have smashed against a rock and are now moving sideways across the slow and fast wave! It’s a mess, a beautiful, satisfying mess. This is what is happening to the sound waves coming from all around you. Some are getting to you sooner, some are reflecting and fighting against other sound waves. Although some of the sounds may be unpleasant, this mish mash of soundwaves is real and is what we like to hear.

So what do I do about phase?

Knowing and understanding that it is a real, this is key - You will read and watch audio engineers telling you it is the enemy, but it is not. If everything you recorded was in phase it would just be a single tone. Our ears don’t like that, we like sounds to be messy in the right way. As an audio engineer you need to understand and be able to control and shape the messiness.

How do I avoid phase issues?

When starting out, it is a good idea to use 1 microphone to record a live sound. Introducing a second mic, you need to hear how the two microphones work together. They will NEVER be 100% in phase, as each microphone will be picking up slightly different reflections off walls and other inconsistencies. Recording a drum kit with 2-20 microphones is where you will really battle with phase, but it is a challenge worth tackling!

Still confused?

It took me many years to develop my phase hearing skills. If you want more information or would like me to come and help you understand and fix phase issues with your gear at your place.