Audio delay measurement with Tektronix TDS5104B

Hi all,

I would like to measure the delay of an audio signal in an entertainment 
system. I'm sending a 1 kHz sine wave, whose amplitude changes every 3 
sec from 0.99 to 0.10, to the speaker. In two places I pick up the 
signal and send it to the Oscilloscope (Tektronix TDS5104B).
Now I want to set a trigger so that the signal stops exactly when 
changing from low to loud sound and I can see the delay to the second 
signal.
Which trigger should be used for that? It has worked neither with the 
edge, nor transition nor runt trigger. And what's the deal with the 
trigger holdoff? Unfortunately, the user manual of the oszilloscope 
couldn't help me.
Thank you for your help!