SOUND waves can be used to measure factory emissions, say scientists at the Open University in UK. Pollution monitoring systems using light waves are often inadequate and direct sampling of air emissions is time-consuming as well as expensive, specially for smaller firms who need to monitor their own pollution levels as stipulated under European Community laws.

Using pulse emitters and microphones linked to computers, the velocity of sound pulses through polluted atmosphere can be measured and the changes in velocity, as dust and solid particles scatter the sound, recorded.