I rarely post, but if everyone was like me no one would benefit as I have by others posting.
I followed the instructions and it did not work until I matched the FREQUENCY of the .caf file, which is 44,100 hz. Please note that. What I did was take a Navy Klaxon wave file and increased the pitch and amplified it so I could hear it from two rooms away (using Audacity a free open source sound editor that allows you to set the project rate to 44,100,
http://audacity.sourceforge.net/).
Then I exported it as a .wav file, not mp3, because once you convert it to an .aif from mp3 using Quicktime, the file is twice the kb than a .wav file converted to .aif. I named the file alarm.aif and renamed it to alarm.caf.
Using the free and amazing SSH free iPhonebrowser
http://code.google.com/p/iphonebrowser/, I renamed the original alarm.caf; alarm1.caf. at /System/Library/Audio/UISounds and pasted my newly made klaxon called alarm.caf.
THEN I REBOOTED THE IPHONE, HOLDING BOTH KEYS DOWN UNTIL THE SCREEN WENT BLACK
It works very well and very loud and I am very happy. I don't think you need to jailbreak your phone to do this either. Just use iPhonebrowser.
I have uploaded the alarm.caf in a zip file to make it simple for anyone else.
http://bohen.net/alarm.zip. Just drop it in /System/Library/Audio/UISounds via iPhonebrowser and reboot.
Thank you everyone for contributing and making my life more effecient.
Robert Bohen