Pressure Level refers to:

• A. The loudness perceived by the human ear
• B. The power level of the sound wave
• C. What noise measurement instruments display in decibels
• D. The frequency content of the noise

Answer: (C)

Pressure level is the amplitude of the acoustic pressure expressed in decibels relative to a reference pressure (20 micropascals in air) and is what sound level meters display. This makes it an objective physical quantity: it tells you how strong the pressure fluctuations are in the air, regardless of how it is heard. The human perception of loudness depends on the ear’s sensitivity across frequencies, not just the raw pressure, so pressure level isn’t the same as perceived loudness. It’s also not the total power of the sound wave, since pressure level focuses on pressure amplitude rather than energy carried. And it doesn’t describe the frequency content, which would require a spectrum analysis. So the display in decibels on measurement instruments corresponds to the pressure level.