Which units are listed as the three sound measurements in air?

Which units are listed as the three sound measurements in air?

• A. The reference units Newtons per square meter, Dynes per square centimeter, and Microbars
• B. Decibels, Hertz, Phons
• C. Pascals, Bels, Loudness units
• D. Joules per cubic meter

Answer: (A)

Sound in air is described by pressure fluctuations, so the fundamental measurements are units of pressure. The trio listed—newtons per square meter (the pascal), dynes per square centimeter, and microbars—are all legitimate pressure units used to express sound pressure in air, spanning SI and CGS systems as well as a bar-derived unit. The other options mix in quantities like frequency, perceived loudness, or energy density, which don’t represent the direct pressure measurements used for sound in air. Thus, this set correctly reflects the three pressure measurements for sound in air.

Sound in air is described by pressure fluctuations, so the fundamental measurements are units of pressure. The trio listed—newtons per square meter (the pascal), dynes per square centimeter, and microbars—are all legitimate pressure units used to express sound pressure in air, spanning SI and CGS systems as well as a bar-derived unit. The other options mix in quantities like frequency, perceived loudness, or energy density, which don’t represent the direct pressure measurements used for sound in air. Thus, this set correctly reflects the three pressure measurements for sound in air.