Tens of cycles per second, we won't recognise the very short (If the difference in frequencies is greater than a few This is the acousticalĮxample of the phenomenon of interference beats. So we should hear a wave of intermediate frequency, The frequency of the blue wave is, if you lookĬarefully, about halfway between that of the red and the Well, provided that the difference in frequency is smallĮnough, the resultant wave will sound loud when the twoĬomponents are in phase and soft or absent when they are out If the waves are sound waves, what will this sound like? At this point, the two component wavesĬancel out, and the amplitude of the blue curve is near zero.Īfter an equal interval of time, they get back in step again, One, so it gradually gains on it, and eventually gets one halfĬycle out of phase. Slightly higher frequency than that depicted by the purple Waves start out in phase, so that they add up, as shown at the
BEATS AUDIO ACOUSTIC ECHO CANCELLATION PLUS
In this plot, the wave depicted by the red graph plus thatĭepicted by the purple one gives that represented by the blueĬurve. Maths, we can see what will happen by looking at the diagram. Same amplitude A, and frequencies f 1 andį 2 that are not very different. What it has to do with Heisenberg's Uncertainty Principle (separate page).Using beats and harmonics to tune a guitar.Interference and consonance (with video clips).Varying the beat frequency (with video clips).Sample sound files (beats and Tartini tones for a range of pure sine waves).This background page to the multimedia chapter Interference gives sound files and derivations. (It is also worth looking at for the insight it gives to Heisenberg's Uncertainty Principle, as we shall see below.) Both are useful and important in practice for measuring frequencies and for tuning musical instruments. When sound signals interfere, the beat signal can sometimes be heard as a separate note: the Tartini tone. The beat frequency equals the difference between frequencies of the beating signals. B eats are often observed between two vibrations with similar frequencies.