Muting the Drum – a Reverberation Challenge at Cranford House School, Oxford
It’s not often the team at Amadeus are shocked; however, we were astounded when we first heard the acoustic characteristics of the relatively new multi-purpose hall at Cranford House School…the room acted like an enormous drum.
Hard surfaces such as floors, walls, ceilings and glazing are standard and are common contributors to an area’s resonance; less common was the hollowness of this area’s floor and a large storage area running the entire length of the space. Sound was travelling beneath the floor, into the storage area and was amplified by this space…just like an enormous drum! The moment anyone uttered a word, walked or ran across the room, or bounced a ball, the sound became dramatically amplified to the point where it was impossible to discern speech at a distance of over 1 metre. Teaching in this space was all but impossible and games of any sort were painful on the ear and vocal chords!
The first thing we needed to do was to understand how the room was behaving acoustically and so our talented acoustician, Ricardo Sanles, performed a thorough survey. Having analysed the data carefully, he calculated that the addition of ‘mass’ to the walls all the way around the space would reduce the room’s reverberation times from just under 9 seconds to around 2.5 seconds. To achieve this, he designed a family of slotted resonators, more than 70 of which were fixed around the walls of the hall by the Amadeus installation team.
As one can hear in the video and see from the graph below…mission achieved!
For the first time, the Head of Sports was able to coach and inspire in the hall without having to raise her voice and the school was delighted.