New acoustic yarn monitors British military hearing health

Scientists of the Defence Science and Technology Laboratory (Dstl) work with Nottingham Trent University on knitted sensors to guard against hearing loss for troops.

New acoustic yarn monitors British military hearing health
Combat conditions can cause hearing loss (Picture source: BAE Systems)

The Defence Science and Technology Laboratory (Dstl) is supporting the Materials Research Exchange exhibition and conference (MRE), the biggest materials innovation event of the year.

Among projects from industry and academia being presented as part of MRE is acoustic yarn, which has been developed by researchers at Nottingham Trent University. Funded by Dstl through the Defence and Security Accelerator Open Call for Innovation, it has been developed in response to the specific risks to hearing that could be suffered by the military. This work created a textile noise sensor, or dosemeter, suitable for military use.

Overexposure to noise is known to cause permanent hearing damage; as a result, employers are required to implement suitable health monitoring measures when workers will be exposed to loud noises.

A noise dosemeter is the most reliable way to determine a worker’s noise exposure, but commercially available solutions are not suitable for military use. An innovative helmet cover made of ‘acoustic yarn’ means that the sensor does not interfere with kit or with the operational effectiveness of the troops.

Dr Theodore Hughes-Riley, Research Fellow, Advanced Textiles Research Group Nottingham Trent University, said that sound measurements were required from both sides of a helmet cover, as asymmetric hearing damage is known to be more common when firearms are frequently used, compared to general noise exposure, such as in construction. Tiny microphones were soldered onto fine multi-strand copper wire and encapsulated within resin which, with additional packing fibres, was then to be put through a knitting machine to form the acoustic sensor yarn. Finally, the acoustic sensor yarn was incorporated into a knitted helmet cover created using computerised flat-bed 3D knitting technology.