To maximize detection of small flaws near the surface, which transducer characteristic is most suitable?

• A. Very low frequency transducer.
• B. Moderate frequency transducer.
• C. High frequency transducer.
• D. Transducer frequency does not affect detection.

Answer: (C)

When you want to detect small flaws right under the surface, you need the transducer to provide the finest resolution possible. Higher frequency creates a shorter wavelength in the material, which improves both axial and lateral resolution. That means echoes from tiny near-surface flaws stand out more clearly from the surrounding material, making those small defects detectable.

There is a trade-off: higher frequency also means greater attenuation, reducing penetration depth. But for defects near the surface, that reduced penetration isn’t a problem and the enhanced sensitivity to small features is the key advantage. A very low frequency would blur small flaws due to longer wavelength, and a moderate frequency wouldn’t offer as much near-surface detectability.