Efficient and Stable Acoustical Coupling for GHz Subsurface Probe Microscopy

Many techniques are under development for the detection of subsurface defects or cracks. One such method is GHz subsurface probe microscopy (GHz SSPM). Here, modulated GHz elastic waves are transmitted through the bottom of a sample. The waves are scattered by buried features and detected using the probe of an atomic force microscope (AFM),...

Analysis of underwater acoustic propagation in a harbour environment and its effect on communication

Acoustic underwater communication is an enabler for the use of autonomous underwater vehicles (AUVs). AUVs can operate in acoustically challenging environments, e.g., near offshore platforms and in harbours. To realize robust underwater communication in such environments, the propagation conditions need to be properly understood. In this paper,...

Performance of acoustic communications for AUVs operating in the North Sea

A Hybrid Finite Element/Helmholtz-Kirchhoff-Integral Model for Shooting Range Sound Prediction

National legislation enforces a limit on the Sound Levels of outdoor military shooting ranges observed in nearby residential areas. These restrictions directly influence the number of shots that may be fired at a specific shooting range, which may conflict with the required/ scheduled training capacity for that specific range. If desired, sound...

Passive acoustic detection of closed-circuit underwater breathing apparatus in an operational port environment

Divers constitute a potential threat to waterside infrastructures. Active diver detection sonars are available commercially but present some shortcomings, particularly in highly reverberant environments. This has led to research on passive sonar for diver detection. Passive detection of open-circuit UBA (underwater breathing apparatus) has been...

A blast absorber test: Measurement and model results

A blast absorber test was conducted at the Aberdeen Test Centre from 13 to 17 June 2005. The test was set up to determine the absorbing and shielding effect of a gravel pile, of 1.5 meters high and 15 by 15 meters wide, on blasts from large weapons: e.g. armor, artillery or demolition. The blast was simulated with single brick C-4 charges of 570...

A high frequency transient detector suitable for monitoring marine mammal activity

As part of a program to study the effect of man-made noise on marine mammals an EARS Acoustic Recording System) buoy was deployed in the Ligurian sea. The EARS buoy was deployed at a position with a high probability of marine mammal activity at a depth of around 950 m. It was operating for almost 19 days and collected acoustic data sampled at...

Assessment methods for personal Active Noise Reduction validated in an international round robin [Méthodes d’évaluation des protecteurs auditifs à atténuation active du bruit]

Hearing protection with standard passive earmuffs is for many military applications insufficient. Low frequency noises (diesel engines, helicopter rotor) require increased attenuation. Active Noise Reduction (ANR) is specifically suited for reduction at low frequencies. Assessment of ANR for military applications is an important topic as the...

Reduction of muzzle blast by barriers

Noise pollution around military training facilities caused by firing of explosives, artillery or large caliber guns poses a severe problem to neighbouring communities. One possible way to attenuate the blast is the construction of blast walls close to the explosion center. This paper describes a combined experimental and numerical study of the...

Acoustic Characterization of Ricochets

This presentation describes the activities which have been carried out within the scope of a task appointed by the Ministery of Defence, Dienst Gebouwen Werken & Terreinen. Projectiles fired at a frring range will sometimes undesirably fly over the present bulletstop after hitting the ground surface. The task was to identify these stray bullets...