MANY firefighters in the US can no longer hear their colleagues amidst the noisy maelstrom of a fire rescue. The problem? Their brand new digital two-way radios.
The US has been equipping its emergency crews with digital radios because they take up half the radio spectrum of the old analogue ones. But fire crews complain that they cannot hear what their colleagues are saying.
It turns out the problem is in the “vocoders” that digitise speech and then compress the bits into a 12.5-kilohertz band of radio spectrum. Vocoders are designed for normal human speech, so their output degrades in the presence of loud background noise,…
