Mankind has spent the entire last century making itself louder. A great deal louder. But why? And what are the consequences? The gramophone, the radio, then TV, cassettes, CDs, MP3 players: they all have sound amplification as their basis. But in the last century alone the lower threshold of human hearing has gone up by four decibels. This may not look much until you realise that this means a 66% deterioration in hearing quiet sounds!

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From BBC World Service: The Noisy Ape