Keeping an ear to the sky

An air traffic control system that uses acoustic sensor technology to ‘hear’ aircraft as they take off and land is ready for full-scale testing.

The EU-funded Safe-Airport project uses acoustic sensors that are claimed to be able to detect and track aircraft up to six miles away to complement conventional radar-based control systems in the immediate vicinity of airports.

The sensors consist of two banks of 512 phased-array microphones able to pick up acoustic waves from the aircraft within a specific frequency range. The signal is transmitted to the control centre computer system via fibre optic cables. The computer’s software is then able to guide the array towards a specific acoustic target by steering the microphones to lock on to the strongest signal.

One of the major problems the project’s engineers had to tackle was the effect that differing wind angles might have on the signal and make allowances for it in the development of the software.