A company whose equipment enables soldiers to communicate during shelling or heavy gunfire has been sold for £52 million.

Harrow- based Racal Acoustics gained its second set of owners in less than 18 months when managers bought the business using funds put up by private equity firm ECI Partners.

Racal Acoustics makes headsets, helmets and field communications systems that are used by special forces and army units.

Its products protect hearing as well as cutting out excess noise when the military is travelling in armoured vehicles, planes and helicopters.

Among the best-known military vehicles to carry its systems are the Chinook and Sea King helicopters, Challenger and Warrior tanks and Hawk trainer jet aircraft.

Racal Acoustics - part of the former Racal business that spawned mobile phone giant Vodafone - has around 170 staff and operates from a single site, although it has customers worldwide including in the United States and Canada.

It is being sold from US private equity house JF Lehman & Co, which acquired the business in March last year from French defence giant Thales.

Geof Eeles, managing director of Racal Acoustics, said the business had "a global brand and reputation built up over more than 50 years in a cautious market sector where a track record of product performance and reliability is paramount". ECI said it was backing the deal because the markets served by Racal Acoustics were expanding rapidly and revenues were expected to grow as military spending increases around the world.

ECI said a further £50 million was available to Racal Acoustics to buy businesses selling complementary products.