smallest lightest beeper

If you only need one, it's probably cheaper to buy a watch than to buy one mail order, pay minimums + shipping. You might want to firm up your specs. First you talk about weight, but then you need size too. What else? Efficiency? Sound level? Frequency? mike

than

Look at this. I remember seeing this from when I was researching a part for a product. They advertise it as "The World's Smallest Audio Transducer"

I understand where you're coming from, but specs like "smallest possible" are simply not helpful. Would you pay $50 more each to make 'em a millimeter smaller? If you would, I've got a grinder and some free time ;-)

At the risk of sounding like a soapbox... The ABSOLUTE MOST IMPORTANT PART OF A PROJECT IS THE SPECIFICATION!!! Many project problems can be traced directly back to poor specification.

If you approach a vendor with a statement like, "just audible from 10-20 feet away with normal human ears"... An excellent vendor will ask, "What does that mean?" A typical vendor will try to sell you something.

By "just audible," do you mean "barely perceptible?" Probably not... but I can't tell. You're too close to the problem. You have preconceived notions that are different from mine. You know what you meant, I heard what you said, but communication didn't happen.

Getting down off the soapbox, Sound is all about air pressure. If the transducer is smaller, it needs to have more displacement. Depending on the frequency, it might be quite directional. Think about ways to increase the coupling to the air. Resonance with the packaging can be your friend. Do some research on horn loudspeakers. There's been some interesting research on vibrating the plastic case on computers to produce sound. MIT Technology Review...I think...is where I read it. mike