speed of sound

Meaning: Speed of sound is how fast a sound wave, a longitudinal pressure disturbance, travels through a medium. The medium sets it, not the source. Stiffer media (larger bulk modulus) carry sound faster, and greater density slows it. Solids are generally fastest, then liquids, then gases. In air it is about 340 m/s at room temperature and rises with temperature. Sound does not travel through a vacuum.

Equation: v = √(B/ρ) and v = fλ, where v is speed (m/s), B is bulk modulus (Pa), ρ is density (kg/m³), f is frequency (Hz), and λ is wavelength (m). For a solid rod, Young's modulus replaces B.

On the MCAT: Expect a sound wave crossing a boundary, such as air into water. Frequency stays the same because the source sets it, so a change in speed produces a proportional change in wavelength. Other common uses are echo timing with d = vt, and pipe resonance, where warmer air raises the speed and therefore the resonant frequency.

Common confusion: Denser does not automatically mean faster, even though ρ is in the denominator. Water is denser than air, yet sound travels over four times faster in it, because water is far less compressible. Stiffness usually outweighs density when comparing media.