What is sound pressure?

What is sound pressure?

• A. The energy carried by the sound wave
• B. The speed of sound
• C. The difference between normal atmospheric pressure and the actual pressure
• D. The frequency of the sound

Answer: (C)

Sound pressure is the fluctuation in air pressure caused by a sound wave—the difference between the instantaneous pressure and the surrounding ambient atmospheric pressure. In air, the sound wave makes the pressure locally go a bit higher or lower than P0, and that deviation p is what we call the sound pressure. The louder the sound, the larger this pressure deviation. We quantify it with the sound pressure level using a reference pressure (about 20 micropascals in air). The other ideas—energy carried by the wave (related to intensity and to the square of the pressure fluctuation), the speed of sound (a property of the medium), and the frequency (which relates to pitch)—are distinct concepts.

Sound pressure is the fluctuation in air pressure caused by a sound wave—the difference between the instantaneous pressure and the surrounding ambient atmospheric pressure. In air, the sound wave makes the pressure locally go a bit higher or lower than P0, and that deviation p is what we call the sound pressure. The louder the sound, the larger this pressure deviation. We quantify it with the sound pressure level using a reference pressure (about 20 micropascals in air). The other ideas—energy carried by the wave (related to intensity and to the square of the pressure fluctuation), the speed of sound (a property of the medium), and the frequency (which relates to pitch)—are distinct concepts.