In the late 1890s Harvard University knew they had a problem with the lecture hall in their Fogg Art Museum. The sound was terrible, but in those days there were no acoustics engineers.
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Their first option was to try the physics department, but they thought it was too difficult. Eventually the problem fell to junior staff member Wallace Sabine.
Nobody including Sabine himself had any experience, but he decided he'd give it a go.
Sabine measured the reverberation time and found it was more than five seconds. Imagine what it would've been like - it takes about six seconds to read the opening sentence of this paragraph. If you read it aloud, people at the back of the hall would be hearing "an early" while you lips are mouthing "University". Every word would by out of sync by five seconds.
But it's worse than that because reverberation is stretching the sounds. Each word is smudged for five seconds over the top of whatever follows.
The Fogg Art lecture hall was converting sound into sonic porridge.
Clearly, something had to be done to dampen the reverberation. Sabine's first approach was to experiment with seat cushions to muffle the hard reflecting surfaces.
When this showed some success, he tried other sound-absorbing materials. It took several years, but eventually Sabine came up with an configuration that seemed to work.
Sabine then went on to design the Boston Symphony Hall, which is admired today for its acoustics and it's fitting that the unit of sound absorption - the Sabine - is named in his honour.
Good acoustics is partly about getting the right amount of reverberation - and this depends on the type sound it's designed for.
Salisbury Cathedral has far too much reverberation for most purposes, but I recall visiting while the pipe organ was playing. Twelve seconds is a huge amount of reverberation, but the effect was majestic. There's something magical about the sound of an organ in a venue like this. The organ music wraps itself around and transports you to another world.
This works for organ music largely because of the deep resonate tones, while the thin, reedy notes of a violin would be lost. And, unlike the music of say, a string quartet, it's acoustically simple because there's only one instrument.
For symphonic music, the preferred amount of reverberation is 1.8 - 2.1 seconds, while for a lecture theatre, it's 0.6 - 1.1 seconds.
Salisbury Cathedral's 12 second reverberation is impressive, but it's a long way short of disused World War II oil storage tanks in Ross-shire, UK. It claims the world record by ringing for 112 seconds.
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