These lobes are sound energy traveling from the transducer array in a direction different than the main beam.

• A. Near-field artifacts
• B. Grating lobes
• C. Specular reflections
• D. Comet-tail artifacts

Answer: (B)

Grating lobes occur when an array transducer’s geometry causes additional directions of energy radiation besides the intended main beam. The description given—sound energy traveling from the transducer array in a direction different from the main beam—matches this phenomenon exactly, since grating lobes are secondary maxima in the radiation pattern that push energy off-axis. They arise when element spacing is too large relative to the wavelength, producing these extra lobes. To reduce grating lobes, you’d use smaller element spacing (less than half a wavelength) or apply apodization to suppress side lobes. In contrast, near-field artifacts come from complex beam behavior in the Fresnel zone, specular reflections follow angle-of-incidence rules from smooth interfaces, and comet-tail artifacts are reverberations from strong reflectors.