TECHNOLOGY

1. Software

2. Hardware

3. Sensor Interface

1. Software

The installation programmed was written using Pd running under LINUX.

The audio classification is programmed in C and compiled to run under Pd within the main software. It involves a three-stage process:
(a) "Essense" - a real time FFT implementation analysing incoming sound and outputting real time amplitude, pitch and brightness information.
(b) "Vecstat"- statistics analysing the output of essence and calculating nine parameters over a time chunk: amplitude mean, amplitude variation, amplitude dynamics, pitch mean, pitch variation, pitch dynamics, brightness mean, brightness variation, brightness dynamics.
(c) "Statlib" - a statistical library that stores information from "Vecstat". "Statlib" has a user controllable threshold value. When the distance between an incoming data set is greater than this value "statlib" sends out a 'new' message and a log number for that data-set. When the distance between an incoming data-set is less than this value "statlib" sends out a 'old' message and the log number of the data-set that the incoming information is closest to. The new log number is used as a name for new stored sound. The old log number is used to retrieve an existing sound.

"Essense", "Vecstat" and "Statlib" were written by Řyvind Hammer.

2. Hardware

42-channel audio matrix distributor.

A 4-in-42-out computer controlled audio matrix distributor has been designed to spatialise sound over the small loudspeakers. If this work were to be done only by the computer, a 56 channel sound card would be needed, and extreme CPU speeds. Instead, the computer directly controls spatialisation over the 14 main loudspeakers, and sends just control messages to the matrix distributor for spatial sound positioning on the small speakers. The matrix card has been constructed such that it can be easily repaired should it fail in years to come, where as off the shelf hardware would need to be completely replaced.

The audio matrix distributor was designed and build by Řyvind Hammer, based on his earlier design on the SONOMATRIX.

3. Sensor Interface

On-off messages from the 21 motion sensors are converted to MIDI by the NoTAM-MIDI box, and sent to the computer.