The word pitch is used to describe how high or low a sound is. A songbird chirping is a sound with a high pitch. A soprano voice or a melody played on a piccolo are also examples of high pitched sounds. Examples of sounds with a low pitch include a man speaking with a deep voice or a cello playing.
Pitch is determined by the frequency of the sound wave. We learned that frequency is used to describe how often a wave occurs. The frequency is the number of vibrations of an object per second. We also learned that frequency is measured in hertz, or vibrations per second. When we look at sound waves, the higher the frequency, the higher the pitch of the sound. In other words, the faster the sound wave is vibrating, the higher it will sound to you. Be sure to understand that a high frequency doesn’t mean the sound wave is traveling any faster - it just has more vibrations per second.
Humans are able to hear pitch in a range between 20 hertz (low frequency, low pitch) and 20,000 hertz (high frequency, high pitch). Animals have a wide variety of ranges. Elephants and some whales can hear extremely low frequencies, and bats and porpoises can hear frequencies up to 150,000 hertz! If you think about all the noise you hear every day, imagine how noisy it would be if you could even come close to all the noises that are really out there!
CHRISTIAN DOPPLER (1803 - 1853)
Austrian Physicist and Mathematician
Doppler’s earliest writings were in mathematics. He achieved recognition, however, for his discovery of the effect velocity has on the frequency of light and sound waves. Born in Salzburg, Austria, Doppler was educated at the Polytechnisches Institut in Vienna. In 1842, he published his paper “Concerning the Colored Light of Double Stars,” notable because it was his first statement of what has come to be known as the Doppler effect. The Doppler effect describes how pitch, or frequency of sound waves, changes as the source of the sound waves moves closer or farther away from the hearer. Doppler’s “effect” has had an enormous “effect” in the areas of navigation, astronomical measurement, radar, plasma measurements, military detection systems, and a host of other applications.
