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Real time sound rendering: frequency changes aren't smooth

Aug 9, 2011 at 4:05 PM
Edited Aug 10, 2011 at 10:24 AM


I've used the code which can be found on this blog post: to produce a continuous sine wave, where the frequency is updated by the position of the mouse (as I move it up and down, so does the pitch).

However, as I move the mouse, when the frequency changes there is a small pop, meaning that the output is not continuous but sounds like there are discrete levels, whereas I would like the tone to be a smooth glissando between frequencies. I have looked through the other discussions and there doesn't appear to be anyone else using this library to do this kind of thing, but I was wondering if anyone is able to help me out? Here is the relevant code:

(I have used the waveprovider classes as shown on the blog post, without editing them)


internal class GenerateSound
        private WaveOut _waveOut;
        public void StartSineWave(SineWaveProvider sineWaveProvider)
            sineWaveProvider.SetWaveFormat(8000, 1); // 16kHz mono
            sineWaveProvider.Frequency = 1000;
            sineWaveProvider.Amplitude = 0.25f;
            _waveOut = new WaveOut();
            _waveOut.DesiredLatency = 100;

        public void StopSineWave()
            _waveOut = null;

then to play the sound, my main initialises an instance of the sinewaveProvider, then updates the frequency when the mouse is moved by setting sineWaveProvider.Frequency.

I just can't figure out why, when the frequency of the instance of the sinewave is changed, playback stops momentarily before playing the next frequency




Aug 9, 2011 at 4:11 PM

the sine wave provider I wrote doesn't smoothly change frequency, and will likely fill one whole buffer at a time at the same frequency. I'd suggest asking a DSP tagged question on StackOverflow asking if anyone has an algorithm that allows a smooth changing of frequency.


Oct 1, 2011 at 1:10 AM

Hello Matt,

Could you please post your code to solve this problem? I am trying to solve it now...

Take care,