Which intensity descriptor has the lowest numerical value for characterizing a pulsed-wave ultrasonic field?

Which intensity descriptor has the lowest numerical value for characterizing a pulsed-wave ultrasonic field?

• A. Sata
• B. Spta
• C. Satp
• D. Sptp

Answer: (A)

The thing being tested is how the four intensity descriptors differ in space and time. The smallest value comes from averaging over both dimensions: spatial and temporal. So the descriptor that is spatial-average temporal-average yields the lowest numerical value. In a pulsed beam, you have peaks in time and/or space, which raise the reported intensity when you don’t average in both dimensions. The other descriptors capture either a temporal peak, a spatial peak, or both, and those peak values are larger than the fully averaged one.

The thing being tested is how the four intensity descriptors differ in space and time. The smallest value comes from averaging over both dimensions: spatial and temporal. So the descriptor that is spatial-average temporal-average yields the lowest numerical value. In a pulsed beam, you have peaks in time and/or space, which raise the reported intensity when you don’t average in both dimensions. The other descriptors capture either a temporal peak, a spatial peak, or both, and those peak values are larger than the fully averaged one.