Thanks Andy-I have played with sound recorder before and what you have described would certainly work,but I have found an easier way (I think from somebody here),and that is to open the sound folder for the plane,open sound cfg with notepad,scroll down to overspeed warning,and add a couple of forward slashes on each line,like this:
//[OVERSPEED_WARNING_SOUND]
//filename=baover
//maximum_volume=9900
then save and exit-course you'll have to do this on each plane that HAS an overspeed warning section