The Barry Box is one of those devices that just has to be heard to be believed. The device provides all that is needed to store and reproduce the most realistic speech and sound. Geoff Bains has been exercising his vocal chords.

Paul Hardcastle's song of last year not only brought the number 19 to the public's eye but also the idea of digital sound sampling. That record was made with equipment that converts a noise into digital values that may be manipulated by a computer. Now the Barry Box gives BBC micro owners the same facilities.

The Barry Box itself is a small black plastic case with cables to connect it to the Beeb's 1MHz bus and auxiliary power supply. A microphone (supplied) plugs into the box and an extension speaker or amplifier can be connected too, if the Beeb's own sound system is not to your taste. Of course, the software to run it all is supplied on ROM.

The hardware consists mainly of fast ADC and DAC chips. The ADC (Analogue to Digital Converter) samples the input from the microphone several thousand :imes a second, and converts this into digital form. The Beeb can store and manipulate these values, and the DAC (Digital to Analogue Converter) can turn them back into sound.

The Barry Box can be used in two modes. In Direct mode a *BAR. command puts the Beeb under the command of the software and gives you several options, all selectable with the function keys.

1. Sample a sound (key triggered) 2. Sample a sound (sound triggered) 3. Playback sound 4. Playback sound backwards 5. Load or Save sampled sound to tape, disc or sideways RAM 6. Display waveform 7. Display frequency analysis 8. Display amplitude envelope 9. Frequency smoothing 10. Amplitude smoothing

The frequency analysis is particularly impressive. Complicated mathematical calculations are used to reduce your sampled sound into a graph of frequency against amplitude. The sampling rate can be altered allowing your own choice of compromise between quality of sound (from good to appalling) and length of sound sample (up to about ten seconds).

Such facilities make the Barry Box an obvious choice for demonstrating the nature of sound in schools. However, the Barry Box isn't just good for serious stuff; it's great fun too. If you thought that the sound of your own voice was entertaining then try it backwards.

In Program mode all these facilities of the Barry Box are available to a Basic program with a series of * commands. These commands are given names to tie in with the Direct mode (e.g. playback is initiated by pressing f2 in Direct mode and with *BAR2 in Program mode), making them easy to remember. Sampled sounds can be easily strung together or chopped around from Basic. The short but comprehensive manual gives a few example programs. A simple 10 line Basic program produces a reasonable facsimile of the 'N-N-N-Nineteen' effect. Whether for study or fun, the Barry Box, though expensive, is an impressive piece of equipment.