Specifying Duration of sound(tone) created with WaveTone() in NAudio

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C#

audio

I want to play a sound(tone) at specified volumes and frequencies but want the duration of playback fixed say 2 seconds.

My code is similar to one given here.

double freq, volume;
WaveTone tone = new WaveTone(freq, volume);
stream = new BlockAlignReductionStream(tone);
output = new DirectSoundOut();
output.Init(stream);
output.Play();

I tried to use latency in DirectSoundOut() above but it did not work as desired. I have to change freq and volume dynamically for each playback. So I need to know the exact duration of playback of tone. Thanks.