Text to speech still plays even after tab or browser close in asp.net

Text to speech still plays even after tab or browser close in asp.net

I'm developing a text to speech application but the voice still plays even
when i close the browser. here is the code :
SpVoice objspeach = new SpVoice();
objspeach.Speak(lbl1.Text.Trim(), SpeechVoiceSpeakFlags.SVSFDefault);
objspeach.WaitUntilDone(System.Threading.Timeout.Infinite);
How can i stop voice after browser close?
Is there any code behind method that i can use?
Thanks