Yes since the default timeout for pulseIn() is exactly one second that's pretty definitely what's happening.
So it seems that the "sound sensor" isn't creating a pulse. Exacty what "sound sensor" is it? And have you tried adjusting the sensitivity control that most of them have? It may either be too insensitive so it never fires at all or over sensitive so that the output is high all the time. Do you have a DMM so you can measure the voltage on that output?
Try changing the command to pulseIn(7, HIGH, 2500000) and report back if anything changes.