Keyframing audio levels

I want to keyframe audio going from silence to some audible level. I set the stop watch for audio levels at the beginning of a wave form and drag the level slider down, and move the CTI later into the track and increase the audio at that point by dragging the audio level slider,, though when the CTI hits the waveform it is still playing the audio even though I tried making the audio silent at the first keyframe. What do I need to do to make the audio not audible on the first keyframe? Thank you