BY treating speech separately from background noise, a hearing aid developed by US chemicals and electronics company 3M may make it easier for people with poor hearing to hold a conversation in noisy surroundings.
Although people with hearing problems find it difficult to hear quiet sounds, they are likely to suffer the same discomfort from loud sounds as people with normal hearing. Modern hearing aids try to compensate for this with compression: they use strong amplification to make quiet sounds louder, but keep loud sounds in check by reducing the strength of the amplification. The unfortunate side effect is that the device may amplify background noise so that it swamps conversation.
Most background noise has a fairly low frequency, while speech - especially the sibilants that are crucial to intelligibility - is at a higher frequency. So an electronic filter in 3M's new aid splits the incoming sound into two ...
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