Air detection in an oyster

Yves Mevel

Air in oysters, Crassostrea gigas, is the result of a shock or pathogenic agent. Often it is dead/this often leads to the death of oysters. The pathogenic agent is dangerous for humans. Air must be detected when we want to export oysters. Oysters are in water. An acoustic transducer, with a frequency of resonance of 2,5MHz, is located 7,5cm above the oysters. A pulse is applied to the transducer. The Transducer converses it to an acoustic wave. The wave is reflected by the upper shell, crosses it can be partly reflected by the flesh; but the wave is above all reflected by the lower shell. One measurement is made every centimeter, (6 to 10 measurements according to the oyster length). For standard oysters, the several echoes with all the points, draw a cut of the oyster. When there is air in the oyster, the difference of the impedance between air and the shell induces a complete reflection, which increases strongly the voltage of the first echo, the second echo is vanished. About forty experiments have permitted to verify this solution.

Mots clés: oyster; air; ultrasound; dectection

Domaines: Acoustique [physics.class-ph]

Yves Mevel. Air detection in an oyster. Acoustics 2012, Apr 2012, Nantes, France. ⟨hal-00811153⟩