Defence activities such as firing ammunition, using explosives and driving heavy vehicles can involve such noise that the noise itself is troublesome for defence personnel and people living near a barracks or training area. With a view to limiting this as much as possible, TNO is studying the transmission of noise and the impact of noise on the environment. Moreover, TNO is advising about noise reduction measures.

As well as measuring methods to establish the loudness at source, TNO has calculation models with which to determine the transmission of noise from source to environment and the consequential noise nuisance. The models - which are the result of extensive, accurate research - take account of both meteorological conditions and the type of subsurface. This is because land and water surfaces influence the transmission of noise in different ways. The various weather conditions, too, affect the transmission of noise in their own ways. TNOs calculation models calculate these factors in detail. Even when noise is being transmitted across great distances. In fact, these models make it possible to predict noise nuisance two days in advance.

Weapon and vehicle noise

Firearms, explosives and defence vehicles produce noise and vibrations. When a shot is fired, there are three possible sources of noise:

  • Muzzle noise, which is caused by the explosive firing of the projectiles load.
  • Bullet noise, which occurs when the projectile travels faster than its sound.
  • Detonation noise, which occurs if the projectile has a detonating load.

TNO has developed measuring and calculation methods for establishing the amplitude at the source of these noises and for calculating the noise nuisance. Moreover, with the American Department of Defense, TNO has investigated which noise reduction measures can be taken against the low-frequency noise produced by heavy weapons. The noise produced by Leopard tanks has been studied using several microphones. By placing the microphones one behind the other in an array and measuring the direction taken by the noise, TNO is able to advise about (the placing of) special sound absorbers.

Environmental noise

TNO studies the noise nuisance of screened shooting ranges on the immediate residential neighbourhood and advises about noise reduction measures. Screened shooting ranges are shooting ranges with concrete screens above the shooting area. In the Netherlands these ranges are used for target practice with light firearms and pistols. Finally, TNO measures the vibrations caused by explosions. As well as being transmitted through the air, these sound waves are transmitted through the ground. This can cause buildings to vibrate, giving rise to damage. TNO performs these measurements in order to establish the likelihood of damage.