Physics
Sound Intensity
Quick fact
The faintest sound a human can hear has an intensity of about 10⁻¹² W/m², while the threshold of pain is about 1 W/m²—a range of one trillion times in power per unit area.
Why this is interesting
You can hear a whisper from across a quiet room, but a shout from the same distance feels uncomfortably loud. What physical quantity determines that difference in loudness?