With a fixed focus transducer, what two factors determine the focal depth?

With a fixed focus transducer, what two factors determine the focal depth?

• A. Transducer diameter and Frequency of the sound
• B. Transducer diameter and Temperature
• C. Frequency and Beam width
• D. Transducer material and Frequency

Answer: (A)

Focal depth in a fixed-focus transducer is determined by the aperture geometry and the wavelength of the sound it emits. For a circular aperture with a curved, lens-like surface, the focal length scales with D^2/λ, where D is the transducer diameter and λ is the acoustic wavelength. Since λ = c/frequency, increasing frequency shortens the wavelength and moves the focus deeper, while a larger diameter increases the focal depth as well. Temperature can slightly change the speed of sound in tissue and thus the actual depth, but the primary determinants are the transducer’s diameter and the frequency. Transducer material mainly affects efficiency and bandwidth, not the fixed focal depth.

Focal depth in a fixed-focus transducer is determined by the aperture geometry and the wavelength of the sound it emits. For a circular aperture with a curved, lens-like surface, the focal length scales with D^2/λ, where D is the transducer diameter and λ is the acoustic wavelength. Since λ = c/frequency, increasing frequency shortens the wavelength and moves the focus deeper, while a larger diameter increases the focal depth as well. Temperature can slightly change the speed of sound in tissue and thus the actual depth, but the primary determinants are the transducer’s diameter and the frequency. Transducer material mainly affects efficiency and bandwidth, not the fixed focal depth.