Sound waves
Sound waves are longitudinal waves. They cause particles to vibrate parallel to the direction of wave travel. The Repeated movements back and forth (about a fixed point). can travel through solids, liquids or gases. The speed of sound depends on the A material through which a wave can聽be transmitted聽(propagate). through which it is travelling. When travelling through air, the speed of sound is about 330 metres per second (m/s). Sound cannot travel through a A volume that contains no matter. because there are no particles to carry the vibrations.
The ear
The human ear detects sound. Sound waves enter the ear canal and cause the eardrum to vibrate. Three small bones transmit these vibrations to the cochlea. This produces electrical signals which pass through the auditory nerve to the brain, where they are interpreted as sound.
The The number of waves produced each second. The unit of frequency is hertz (Hz). of a sound wave is related to the pitch that is heard:
- high frequency sound waves are high pitched
- low frequency sound waves are low pitched
The The maximum height of a wave from the middle of the wave to its peak or trough. of a sound wave is related to the volume of the sound:
- high amplitude sound waves are loud
- low amplitude sound waves are quiet
The cochlea is only stimulated by a limited range of frequencies. This means that humans can only hear certain frequencies. The range of normal human hearing is 20 Hertz (Hz) to 20,000 Hz (20 kHz). Sound waves below this frequency range (<20 Hz) are called Sound with a frequency lower than 20,000 Hz (20 kHz)..