Spectral broadening in a Doppler waveform is most commonly associated with?

• A. Laminar flow
• B. Turbulent flow
• C. High velocity
• D. Low resistance

Answer: (B)

Spectral broadening in a Doppler waveform arises when the sampled volume contains a range of flow velocities rather than a single, uniform velocity. In a smooth, orderly flow (laminar), the velocities across the beam are relatively uniform and Doppler shifts cluster around one dominant value, so the spectrum stays narrow. When flow becomes turbulent, though, there are many eddies and rapid velocity fluctuations within the beam, producing a wide variety of Doppler shifts. This mixture of speeds fills out a broader range of frequencies, smearing the spectrum. High velocity by itself shifts the spectrum but doesn’t fundamentally broaden it unless there’s a broad distribution of velocities; low resistance doesn’t directly cause broadening. Therefore, spectral broadening is most closely associated with turbulent flow.