Which layer is positioned at the face of the transducer and is responsible for impedance matching?

Which layer is positioned at the face of the transducer and is responsible for impedance matching?

• A. Electrical shield
• B. Case
• C. Matching layer
• D. Acoustic insulator

Answer: (C)

Impedance matching between the transducer and the body is essential to transfer as much acoustic energy as possible into the tissue. The layer positioned at the face of the transducer is the matching layer, and it is designed with an acoustic impedance between the crystal and the tissue. This intermediate impedance acts as an acoustic transformer, reducing reflections at the boundary and allowing more energy to enter the tissue. If there were no matching layer, the high impedance of the piezoelectric crystal versus the lower impedance of tissue would cause most of the wave to reflect back, diminishing both transmission and reception sensitivity. The matching layer is also typically designed with a thickness of about a quarter of the wavelength at the operating frequency, which helps ensure that reflected waves from the layer combine constructively in the tissue and that energy transfer is optimized. The other options—electrical shield, case, and acoustic insulator—handle electrical noise shielding, housing, and vibration isolation, respectively, and do not serve the purpose of impedance matching at the transducer face.

Impedance matching between the transducer and the body is essential to transfer as much acoustic energy as possible into the tissue. The layer positioned at the face of the transducer is the matching layer, and it is designed with an acoustic impedance between the crystal and the tissue. This intermediate impedance acts as an acoustic transformer, reducing reflections at the boundary and allowing more energy to enter the tissue.

If there were no matching layer, the high impedance of the piezoelectric crystal versus the lower impedance of tissue would cause most of the wave to reflect back, diminishing both transmission and reception sensitivity. The matching layer is also typically designed with a thickness of about a quarter of the wavelength at the operating frequency, which helps ensure that reflected waves from the layer combine constructively in the tissue and that energy transfer is optimized.

The other options—electrical shield, case, and acoustic insulator—handle electrical noise shielding, housing, and vibration isolation, respectively, and do not serve the purpose of impedance matching at the transducer face.