Nature of Sound
Sound is a mechanical wave that requires a medium to travel. It cannot propagate through a vacuum and moves fastest through solids, slower in liquids, and slowest in gases.
Sound Wave Types
Sound waves are longitudinal waves where particles vibrate parallel to the direction of wave propagation, creating regions of compression and rarefaction in the medium.
Sound Frequency & Pitch
Frequency, measured in Hertz (Hz), determines a sound's pitch. High-frequency sounds have a high pitch, like a whistle, whereas low-frequency sounds have a low pitch, like a drum.
Audible Frequency Range
Humans can hear frequencies from about 20 Hz to 20,000 Hz. Sounds above or below this range are called ultrasonic and infrasonic, respectively, and are not audible to us.
Amplitude and Loudness
Amplitude determines the loudness of sound. Larger amplitudes make louder sounds. The threshold of hearing is 0 dB, while prolonged exposure above 85 dB can damage hearing.
Speed of Sound
The speed of sound varies with temperature and medium. At 20°C, sound travels at 343 meters per second in air. It's faster in water and even faster in steel.
Reflection of Sound
Sound reflects off surfaces, leading to echoes. The minimum distance to hear an echo is approximately 17 meters, as sound takes time to travel to the surface and back.