Alarm Suggestions

[Broz]

I'm working on a project for indoor RC aircraft that requires a loud alarm. The alarm will be installed inside the RC aircraft and needs to be heard over the electric motor and propeller noise for a distance of possibly more than 50ft. I have some piezo alarms that are pretty close to working out for me, however I'm afraid the noise of some motors/propellors will drown out the noise of the alarm.

My available voltage will be between 11 and 12 volts. I would like a system that would be as loud as a smoke detector. However, it has to be small and light weight. Any sound emitting device that's much bigger than a quarter will be too large. Anything that requires a transformer or other such coils or magnets will be too heavy. It looks like piezo buzzers are the way to go for this application, but I'm open to any ideas. How can I make a small, light weight alarm that is obnoxiously loud?

 

[audioguru]

A piezo beeper that is operated from DC has its own oscillator inside. It has feedback to the oscillator that causes it to oscillate at the loudest resonance. They are in a resonant tuned cavity.

The size of a quarter is too small to be heard 50 ft away when there is noise.

 

[Broz]

I was afraid of that. That's basically the same conclusion I came to in my testing, but I was hoping I might get some advice to the contrary. I think I'm going to a visual alarm, flashing LED's. I'm looking into some high power LED's used for flash photography. Right now I'm looking at Luxeon power LED's used in flash photography. I'm doing the research for components myself but any advice you have on high intensity flashing LED's would be appreciated. I need the bright flash in a small package. Thanks again.