Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!watmath!clyde!burl!ulysses!allegra!princeton!orsvax1!pyrnj!caip!daemon From: roberts@nbs-vms.ARPA Newsgroups: net.micro.amiga Subject: white and pink noise Message-ID: <1637@caip.RUTGERS.EDU> Date: Wed, 26-Mar-86 06:33:31 EST Article-I.D.: caip.1637 Posted: Wed Mar 26 06:33:31 1986 Date-Received: Thu, 27-Mar-86 07:39:49 EST Sender: daemon@caip.RUTGERS.EDU Organization: Rutgers Univ., New Brunswick, N.J. Lines: 38 From: "ROBERTS, JOHN" About 8 or 10 years ago, Popular Electronics ran an article describing the properties of white and pink noise, and telling how to build generators. It seems to me that white noise was made by generating random numbers at regular intervals and using them to represent amplitude of the waveform, indexed from a base value. Pink noise was generated by computing random numbers at regular intervals, putting in an offset, and using the resulting value to increment or decrement the amplitude value from the previous interval. The maximum frequencies of either would of course be a function of the sampling frequency (and the nonlinearities of the generating equipment). Clearly, such a white noise generator would put out a lot more energy around the sampling frequency than would the pink noise generator. It has been said that an ideal white noise generator puts out the same It has been said that an ideal white noise generator puts out the same power per unit bandwidth across its spectrum (i.e. .15mW/Hz) while an ideal pink noise generator puts out constant power per logarithmic frequency range (i.e. 300mW/Octave). By this description, white noise would have more emphasis on high frequencies, and ators are widely used more emphasis on low frequencies. Pink noise generrators are widely used to test audio systems. I think knowledge of the implementation of such features is definitely important to those who wish to take advantage of the Amiga as a sound generator. (Question: If the Amiga gererates sound only by repeating a previously programmed waveform, can it ever generate good random noise? How rapidly can the waveform be updated?) (Standard disclaimers. Before you make a million of them, I suggest you read the article. Also, I'm sure the IEEE must have published something at some time [perhaps in audio engineers' journals] that discusses the issue in detail.) "It turned out to be one of those John Roberts all-night wicker places...." -Police Squad roberts@nbs-vms.ARPA ------