The speed of sound in air increases when
- A. the pressure alone increases at constant temperature
- B. the temperature increases
- C. the humidity falls
- D. the frequency of the sound increases
Explanation
Speed rises by roughly 0.61 m per second for every degree Celsius, because hotter molecules move faster and transmit the disturbance more quickly. Changing pressure alone has no effect, since density changes in the same proportion and the two cancel. Speed is also independent of frequency, which is why a distant band is heard in tune rather than smeared out.