show more Phase provides you with in-depth training on Audio + Music. Taught by Dave Schroeder as part of the Digital Audio Principles show less
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Another thing that comes up that is good to be aware of when dealing with frequencies, and waveforms, and cycles per second is the concept of Phase. Phase is the relative delay or offset between two sound waves of the same frequency. When there is no offset, the waves are considered coincident and they're In Phase. But when there is an offset, they're considered Out Of Phase. So let's take a look, we have a coincident pair of two sine waves. What you get when you combine those two sine waves is you get more of the same, it just increases the amplitude.

If they're in different phases of the cycle when they're summed, the amplitude of the resulting wave will look something like this. We'll get different increases and decreases in the amplitude based on the offset. If they're at complete opposite stages in the phase, you get what we call Phase Cancellation. Meaning that this side of the phase gets canceled out by the energy of this side of the phase. The result is cancellation, or nothing. Needless to say, this phase cancellation can become a problem when you're working with digital audio.

You'll find that it'll creep up in a few different situations, such as dealing with microphone placement and making sure you have properly wired cables. We'll talk about this a little bit in other sections. But I just want you to be aware of the concept of phase, and the idea that it's the correlation between two sets of sounds, or two sets of waves, and where they are when we hear them. At what stage of a cycle they're in, when we hear both of them, or when they both arrive at the same point, like when two sounds get to a microphone, we want to know what stage of the cycle they're in. Hopefully, they're In Phase.

So we have two waves that are In Phase, we get more of the same. We get greater amplitude, but we get the same frequency, and we get the same intensity. When we have sounds that are slightly Out Of Phase or offset, we get kind of a wavering factor. It sounds like the sound will kind of be bright for a moment, and then dull for a moment. There's actually an effect called a Phase, where we use this to our advantage to kind of add some texture to sounds. But if you're not looking for that texture, like you're trying to record a grand piano, and you don't want it to have the Phaser effect on it, you need to pay attention to this.

You'll usually be able to identify phasing when you hear it, because it doesn't sound quite right unless you're intending for it to happen. Finally, if we have two waves that are completely out of phase, we end up with Phase Cancellation. You can see that if the waves are exactly opposite points in the cycle, the result is cancellation, because the amplitudes cancel each other out, so we don't hear anything at all. This can be a problem, when you're trying to record something, because you want to hear it.

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Phase provides you with in-depth training on Audio + Music. Taught by Dave Schroeder as part of the Digital Audio Principles

Audio + Music
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