Sound is caused by the vibration of particles but not all vibrations can be heard as sound. Common ideas about sound come from the limited range of vibrations that human ears can detect.
The frequencyThe number of waves produced each second. The unit of frequency is hertz (Hz). of a sound wave is related to the pitchThe frequency of a sound. Sounds with a high pitch have a high frequency. that is heard:
high frequency sound waves are high pitched;
low frequency sound waves are low pitched.
The amplitudeThe 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.
oscilloscopeA device used to record signals that change regularly, such as sound or other vibrations. traces showing the following sounds:
quiet, low pitch sound
loud, low pitch sound
loud, high pitch sound
The cochleaPart of the inner ear that contains nerve endings that transmit sound vibrations to the auditory nerve. 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 Hz to 20,000 Hz (or 20 Hz to 20 kHz).