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by rwnspace
2963 days ago
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I only think I get what you mean by "beating", could you clarify for us/me? I'm thinking of the particularly sonorous pulsing you sometimes get when playing those intervals. Having played guitar from a really early age I'm pretty lucky to able to get tuning pretty much bang-on from ear, plus some double-checking it still sounds okay further up the neck. The main downside is that the open G string never, ever sounds right. |
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When the fifth is in tune, it will sound uniform. When the interval diverges from a fifth you will begin to hear a pulse, a sort of wobble...slow at first (when very close to the right pitch) and faster as they get further apart (and then, eventually, if you go far enough in any direction the beating will get slow and stop again as you approach another perfect interval).
To visualize it, you can maybe think of sine waves at certain frequency ratios of each other (a fifth is a 3:2 ratio, fourth is 4:3, octave is 2:1; these are the "perfect" intervals that don't audibly beat when played together, and are not considered at all "dissonant"). The phase cancellation between this is regular enough and frequent enough and not complete so we don't perceive it as beating, but as a specific singular sound of its own. Most people aren't hearing two independent notes when hearing these intervals, though people with some training or with perfect/absolute pitch can recognize it for the combination of notes that it is.
But, as they drift out of tune, the phase cancellation happens in a shifting pattern up and down, so you end up with very clearly audible changes; this is called "beating" (at least, that's what I've always called it, and I believe it is the proper term in physics, audio research, and music...pretty much anywhere we talk about the phase of waves, I think?).
Here's a page with some diagrams of the basic idea of what is happening and what you're hearing, as well as audio samples of what it sounds like (it's more complex with the complexity of a guitar's timbre, but the principle is the same): http://www.animations.physics.unsw.edu.au/jw/beats.htm