The Big Ear

摘要

Ever wish you could build an "audio telescope" that would let you hear things that were faint or far away? Well, this article shows you how to build such a thing. We call it the Big Ear. The Big Ear is shown in Figure 1. Its most obvious feature is its parabolic dish reflector. The reflector concentrates sound energy onto a microphone that connects to a very high gain amplifier (see sidebar on parabolic reflectors). And believe it or not, it's all assembled on a wood base you can find in a place that sells concrete supplies and tools! More about the wood base later; first we'll discuss the amplifier. The amplifier is built on a printed circuit board (PCB) and mounted on stand-offs inside a small aluminum box along with a nine-volt battery. Jacks for the microphone and headphones - along with an on-off switch and a volume control - are mounted on the box. Input jack J1 accepts a 2.5 mm mono plug that is wired to an electret microphone. Output jack J2 is for a 3.5 mm stereo plug that is standard on many headphones.