Plot[Piecewise[{{Sin[2*Pi*(-10Log[1- t/800])],t<=600},{Sin[Pi*20Log[4]+Pi*(t - 600)/10],t>=600}}],{t,0,800}]

Uh oh! Wolfram|Alpha doesn't run without JavaScript.

Please enable JavaScript. If you don't know how, you can find instructionshere.Once you've done that, refresh this page to start using Wolfram|Alpha.