14.2 Sound Intensity and Sound Level

• A useful quantity for describing the loudness of sounds is called sound intensity.
• In general, the intensity of a wave is the power per unit area carried by the wave.
• You may have noticed that when people talk about the loudness of a sound, they describe it in units of decibels rather than watts per meter squared.
• While sound intensity (in W/m2) is the SI unit, the sound intensity level in decibels (dB) is more relevant for how humans perceive sounds.
• Hearing is the perception of sound.
• The perception of frequency is called pitch, and the perception of intensity is called loudness.