Once the spaces are selected, they are acoustically tested by world-leading acoustic consultants Arup. The acoustic test is a common test used in acoustic surveys of concert halls and other acoustically critical spaces: A ‘sine sweep’ is played into a room; a pure tone that rises from 20hz to 20khz over 20 seconds. The sweep is recorded, and then analysed for a spaces acoustic properties, reverberation, clarity, definition etc. The locations of the speaker; and the receiving microphone, are called the ‘source’ and ‘receiver’ positions respectively. These also represent the spatial relationship between a performer and a listener, or audience.
The acoustic parameters are interesting to acousticians and architects, and work very well on a technical level, what is critical, is for a musician to use their ears, and develop an intuitive response to a space. So in addition to the acoustic parameters, the sine sweep can produce what is called an ‘impulse response’. This is a computer generated retort, or snap, that contains spatialized acoustic data from the space. On its own, it’s fairly meaningless, but when dropped into a convolving reverb effect in a studio environment, it allows a space to be ‘convolved’ in real time, simulating the effect of a space digitally.