voice on red light alert

Here are the things to look for: The file name of the audio file must match the file name of the red light csv file except for the extension EXACTLY. If you added a new red light file with a slightly different name, then either the csv file or the audio file must be renamed. Also, the audio file must be in the same directory as the red light csv file when the file is reloaded, just because it was there in the past is not enough. If you took the audio file out of the directory after loading it the first time, then you don't get the audio alert. And, although you apparently got the names correct the first time, it is very important to not hide the file extensions for known file types so as to be sure that you don't have double file extensions. Turn off that Windows "feature" if you have not already done so.

Frovingslosh has it right. The file name for the sound file must be exactly the same.

I believe I read that the mp3 sound file has to be exactly the same as the gong file -- same length of time, bits, etc. I would like to replace the gong file with the sound of diving submarine, but the gong seems to be very, very short. Can it be replaced with a somewhat longer mp3 file?

file length (or time) is not important. The thing to be sure of is that the name of the audio file must match the name of the POI file exactly, with the exception of the 3 letter file extension, which should be mp3 for mp3 audio files (or wav for users without mp3 support, which also requires use of sox.exe). I urge you to turn off the "feature" in Windows that hides file extensions for known file types. Most problems with custom audio see to be caused by this "feature" in Windows that is otherwise quite useless.