Spatial pulse length is defined as the wavelength multiplied by what quantity?

• A. The number of cycles in the pulse
• B. The beam width
• C. The focal distance
• D. The transducer diameter

Answer: (A)

Spatial pulse length is the physical length of the emitted pulse in space, found by multiplying the wavelength by how many acoustic cycles are contained in that pulse. So the quantity that multiplies the wavelength is the number of cycles in the pulse. If more cycles are emitted, the pulse lengthens in tissue; if the wavelength is longer (lower frequency), SPL also increases. The other terms describe the beam’s geometry—beam width is the lateral size of the beam, focal distance is where the beam converges, and transducer diameter affects aperture and beam shape—not the length of the pulse itself.