The frequency of a sound wave determines what people hear as pitch. A higher frequency has a higher pitch, and a lower frequency is heard as a lower pitch. The frequencies that humans can hear range from 20 to 20,000 Hertz.
Frequencies below 20 Hz are called infrasound, and those above 20,000 Hz are ultrasound frequencies. Animals like dogs and dolphins can hear at lower and higher frequencies than humans. For example, dolphins hear frequencies between 0.25 and 200,000 Hz.
A wave's frequency is defined as the rate at which a particle vibrates through a medium or material. Hertz is the unit of measurement used for frequency; 1 Hertz is equal to 1 vibration per second.
Loudness, which is another component of sound waves, is determined by a sound wave's amplitude. A large amplitude represents a louder sound.