Because peak measurements are larger than average measurements, which intensity has the highest value, and which has the lowest value?

• A. SATA
• B. SPTA
• C. SP/SA Factor
• D. SPTP

Answer: (D)

Peak values exceed averaged ones because they capture the maximum power at a location and moment in time, while averaging smooths out those spikes.

The highest intensity is the spatial-peak temporal-peak value, since it represents the greatest instantaneous power at the spatial peak. In contrast, when you average over time, you get a temporal-average value, which lowers the number because it includes off times. If you also average over space, the spatial-average temporal-average value becomes even smaller because it smooths both spatial and temporal fluctuations.

The SP/SA Factor is a ratio that describes how much the peak exceeds the average; it’s not itself an absolute intensity, so it doesn’t rank with the intensity measurements in the same way. Among the actual intensity measurements, the lowest is the spatial-peak temporal-average value.