How to generate sin wave in AS3 without clicks?

Question

I have started using sound to synthesis audio, I don't know why I get those noisy clicks sounds within the sounds?

My loops is:

for(i in 0...2048)
{
var phase:Float = position / 44100.0 * Math.PI * 2;
position+=1;
sample = Math.sin(phase * v);   // where v varies between 200 to 400
event.data.writeFloat(sample); // left
event.data.writeFloat(sample); // right
}

Any idea?

EDIT

What I need to do is to interpolate frequency within the loop:

var phaserad:Float= 2*Math.PI/44100;
var delta:Float = current_v - new_v;
var p:Int= 2048;
for(i in 0...2048)
{
p--;
v = new_v + delta * (p / 2048); // v will interpolate from current_v to new_v
position += v * phaserad;
sample = Math.sin(position);    
event.data.writeFloat(sample); // left
event.data.writeFloat(sample); // right
}

current_v = new_v;

but, I couldn't hear anything, I tried another approach:

var delta:Float = current_v - new_v;
var p:Int= 2048;

for(i in 0...2048)
{
var phase:Float = position / 44100.0 * Math.PI * 2;
position+=1;

p--;
v = new_v + delta * (p / 2048); // v will interpolate from current_v to new_v

sample = Math.sin(phase * v);   // where v varies between 200 to 400
event.data.writeFloat(sample); // left
event.data.writeFloat(sample); // right
}

but, the frequency will keep going up, and it won't stop at expected new_v

Do you change either `position` or `v` between calling these loops? Also, if you increase range to 8192, will it decrease the number of clicks? — Vesper, Jul 04 '14 at 05:21
I need to have the range to minimal to keep my app responsive — simo, Jul 04 '14 at 09:21

score 0 · Answer 1 · answered Jul 03 '14 at 19:41

0

If you want a continuous sine wave your phase needs to from 0 -> 360 -> 0 -> 360 degrees etc.

answered Jul 03 '14 at 19:41

Tyler Eaves

12,879
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but why I get click sounds? – simo Jul 03 '14 at 21:28
Because if the phase isn't smooth the waveform will jump. Write your sample data to a wave file and open it in an editor like audacity...it should be immediately obvious where the discontinuities are. – Tyler Eaves Jul 03 '14 at 21:45
please see EDIT above – simo Jul 04 '14 at 09:38

score 0 · Accepted Answer · answered Jul 04 '14 at 05:26

0

You have your wave generator set about right, but the approach with saved position requires your v to be constant and position unaltered. Given your description of v, you change it during your playback somehow, but changing v results in sine form to be disrupted. So, instead of recalculating position from scratch, you should accumulate phase and add current shift based on v to receive an uninterrupted waveform.

const phaserad:Number=2*Math.PI/44100;
for(var i:int=0;i<2048;i++)
{
    position+=v*phaserad; // requires this var to be "Number" type
    sample = Math.sin(position);   // where v varies between 200 to 400
    event.data.writeFloat(sample); // left
    event.data.writeFloat(sample); // right
}

answered Jul 04 '14 at 05:26

Vesper

18,599
6
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Please see EDIT above – simo Jul 04 '14 at 09:36
A sound 2048 samples long is 0.05 second length. You need to calculate desired length of your sound prior to running loops, then have your `v` assignment to be divided by the calculated length instead of 2048. Length in samples is `(length_in_seconds)*44100`. – Vesper Jul 04 '14 at 09:41
I am writing a simulator, frequency changes about 40 per second, I will try to do it, thanks – simo Jul 04 '14 at 10:50

How to generate sin wave in AS3 without clicks?

2 Answers2