For an unfocused transducer, two near zone lengths are equal to the:

An unfocused transducer creates a beam that diverges much more rapidly than a focused transducer, influencing how we understand its near zone. The near zone, also known as the Fresnel zone, is the region closest to the transducer where the sound beam is relatively narrow and more collimated. The distance to the focus and the characteristics of the active element also play roles in determining the beam's profile, but they do not determine the lengths of the near zone in the same straightforward way as the transducer diameter.

In the case of an unfocused transducer, the near zone length is directly tied to the diameter of the transducer. Mathematically, the near zone length can be described using the formula that involves the wavelength and the diameter of the transducer. Since for an unfocused transducer, the near zone lengths are equal to the diameter, the relationship is direct and indicative of how the beam's characteristics are outlined.

Understanding that the diameter of the transducer governs these near zone lengths is key, as it influences how the sound wave behaves in imaging applications. This central characteristic of unfocused transducers is essential for ensuring optimal imaging and interpretation in sonographic practice.