37.5khz Meant to Locate CVR & FDR Within a Crash Site. Not for Finding a Crash Site.
"bobcat4: Why use 37kHz when lower frequencies travel longer in water? I'm just curious."
The main reason is the ULB was never meant for finding a crash site. It was meant to find the black boxes within a crash site, and a higher frequency is easier to pinpoint, and less likely to be confused with lower frequency noises from ships and other equipment. Also, it uses less battery power than lower frequencies.
Back when 37.5khz was established as the frequency in ULB's, people figured if a crash was so far out in the ocean, where you didn't know where it went down, it would be too deep to get to anyway. Now that the use of deep diving robot vehicles is not uncommon, maybe it would be a good idea to add an 11khz ULB to locate a crash site, since 11khz travels farther through water than 37.5khz, and common sonar can hear 11khz, so you wouldn't need special equipment.
Last edited by Coagie; 29th Mar 2014 at 17:05.
Reason: Punctuation