Acoustic Velocity Estimation of Salmon Fish Scales Using Acoustic Microscope

Scanning acoustic microscopy (SAM) with a high-frequency 30 MHz polymer transducer was used to determine the longitudinal velocity and the thickness of healthy salmon fish scales. SAM is a non-destructive ultrasonic imaging technique that has been used for evaluating properties like the hardness, thickness, velocity of sound in the sample, subsurface defects and, stiffness. The velocity of sound in fish scales can indicate fish quality and provide early signs of meat deterioration for the fishery industry. It can also be used to deduce the other mechanical parameters of fish scales for bio-mimetic applications. SAM has also been previously used for ultrasonic imaging of biological tissues but has not been used for determining the properties of salmon scales. The reflection of the waves from the front and the back of the sample is recorded as a function of the transducer-sample distance V(z,t), and their time of flight (TOF) is determined. From these values, the longitudinal velocity and the thickness of the fish scale are calculated.