useful audio equipment
pa system and headphones
All of these demos make sounds of some kind, so you'll need to connect your computer to a pair of stereo speakers. You'll also need headphones for the Delayed Voice demo.
Desktop computer speakers usually come with built-in amps so they can be plugged directly into the output of your soundcard. Hi-fi speakers usually need to be used with an amplifier.
In a large space, you could hook your computer up to a PA system. A powerful domestic hi-fi might suffice if you don't have a PA system handy.
A microphone
Many of these demos give you the option to use a microphone. You can use a mic with the oscilloscope, for example, to examine the waveform of someone's voice. If you have an external soundcard (one that comes in a box that's separate to your computer) or a higher-quality built-in soundcard, you may have plenty of inputs, some of which are designed to handle signals from microphones.
If you don't have such a set-up, a simple and fairly cheap solution is to buy a USB condenser mic, such as the Samsung C10U. A USB-condenser mic gives you a very reasonable sound quality, ideal for vocal recordings during a live science show. As the mic is powered directly from the USB port of your computer, you won't need any extra hardware or special ins and outs to use it. Condenser mics cost around £45 ex VAT (but do shop around - this figure could be out of date by the time you read this page!).
The cheapest option of all is to buy a karaoke mic - you should be able to pick one up in a shop like Maplins for around a tenner. The sound quality won't be brilliant but it's fine for quick demos. You may be able to connect the microphone directly into your soundcard (possibly using a 1/4-inch jack to mini jack converter). But if the signal level is too low, pass the output of the mic through an amp first (e.g. the amp from your hi-fi or mixer(. There's an option to select the 'line-in', of your computer instead of 'mic' in the patches. Experiment to get the best results.
You can make do with the condenser mic that's built into the case of your laptop computer. However, this can be tricky to incorporate in live shows - users need to hunch over your computer to use it. A built-in condenser mic is unlikely to record with very high fidelity - but it will work with these patches.
CDs or sound files
A few of the demos (e.g. the simple oscillosope) enable you to play and experiment with pre-recorded sound files. You can use any .wav or .aiff files here, including tracks from a CD.