Path: utzoo!mnetor!uunet!lll-winken!lll-lcc!lll-tis!ames!hao!gatech!uflorida!codas!pdn!usfvax2!jc3b21!fgd3 From: fgd3@jc3b21.UUCP (Fabbian G. Dufoe) Newsgroups: comp.sys.amiga Subject: Re: Sonic Tomfoolery Message-ID: <320@jc3b21.UUCP> Date: 1 Mar 88 01:14:49 GMT References: <8802251858.AA21577@cory.Berkeley.EDU> Organization: St. Petersburg Jr. College, FL Lines: 33 Summary: Difference between phase and frequency In article <8802251858.AA21577@cory.Berkeley.EDU>, dillon@CORY.BERKELEY.EDU (Matt Dillon) writes: > Huh, where did this come from? I've played around with sound > quite a bit, and if I generate two tones of slightly different frequencies, > I can hear the phase quite fine thank you. In fact, if I generate two > tones of the same frequency that are out of phase, I can also tell the > difference. This effect is certainly not limited to low frequencies. If you generate two tones of slightly different frequencies you will hear a pulsation caused by the amplitude change that results from the union of the two tones. Sometimes their amplitudes will reinforce one another and sometimes they will cancel one another. The rate at which they do this is called the beat frequency. The closer in frequency the two tones are the lower will be their beat frequency. Phase refers to the relationship between a waveform and its origin. For example, the plot of the sine function is 90 degrees out of phase with the plot of the cosine function. If you generate two sine-wave tones of identical frequency and adjust their phase difference to 180 degrees you won't hear anything. The sum of their amplitudes at each instant will be zero. If the two tones are 90 degrees out of phase their amplitude will be greater by a factor of the square root of two. The resultant waveform will be out of phase with each of the originals by 45 degrees. It's true that you can hear the effect of a phase change if you generate two tones of the same frequency and play around with the phase difference. However, I don't think you could tell they were out of phase unless you could compare the effect of changing their phase difference. --Fabbian Dufoe 350 Ling-A-Mor Terrace South St. Petersburg, Florida 33705 813-823-2350 UUCP: ...gatech!codas!usfvax2!jc3b21!fgd3