A new'hush house'just completed by British engineers for the Portuguese Air Force will drastically cut the noise of jet engines on ground tests to no more than a loud hum.

The facility, located at one of the main strike bases at Monte Real, 130 km north of Lisbon, has been designed to test engines in F-16 and A-7 jet aircrafts and has managed to cut noise emissions from more than 140 decibels to just 70 decibels. The main test cell measures 25 x 20 m. The inner walls are made of perforated stainless steel for maximum sound absorption and corrosion resistance.