September 19th, 2010, 07:20 AM  #1 
Newbie Joined: Sep 2010 Posts: 2 Thanks: 0  Sine wave question
Hello, My name is Driehoek and I'm new to this forum. To learn the math involved I'm programming a software synthesizer. I can't find the answer for one problem though: Let's say I have a function that desribes a sinewave making one rotation per unit: [color=#FF0000]f(x) = (sin (x * pi * 2))[/color] I then want a wave that rotates 4 times per unit, I simply do: [color=#FF0000]h(x) = f(x * 4)[/color] My problem comes if I want to shift the frequency of the wave from i.e. 4 to 0: First I thought I'd make just a function describing the shift: [color=#FF0000]g(x) = 4  x[/color] and then simply plug it into the wave function: [color=#FF0000]h(x) = f(x * g(x))[/color] The result of this is an undesired one however (the frequency goes down and then up again) this is presumably because "x * g(x)" describes an inverted parabola. ...so finally the question, can somebody hint me, answer me or explain me how to create a sine wave slowly shifting from one frequency to another? This a been troubling me for over a week. I Thank you, Driehoek 
September 19th, 2010, 09:47 AM  #2 
Newbie Joined: Sep 2010 Posts: 2 Thanks: 0  Re: Sine wave question
I think I solved it myself: h(x) = f((x * a * (d  x)) + (x * b * x) / d) where: a is the starting frequency, b is the ending frequency and d is the duration of the wave. 

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