Sound is a kind of energy which is detected by the ears of living beings. Sound travels in the form of waves through the material medium and reaches our ears. These waves make our eardrums vibrate. From the inner ear, nerve messages travel to the brain and we hear the sound. Sound cannot travel without a material medium. It is of great importance to us.
Sound is a result of vibrating energy
Sound is produced only by the vibrating bodies but our ears cannot detect all the vibrations. Human ears are sensitive to the vibrations ranging in frequencies from 20 Hz to 20,000 Hz. This range of frequencies is called the audible range. Beyond this range of vibrations, our ears are not sensitive. However, some animals like dogs can hear the frequencies even beyond this range. The word, sound is called only to those vibrations for which our ears are sensitive.
Pitch of sound
The range of audible frequencies differs slightly from person to person but the common range lies between 20 Hz to 20,000 Hz.
More is the frequency of vibrations, the sharper is the sound. High frequency voices are called high pitched sounds while low frequency sounds are called hoarse sounds. Our ears are more sensitive to the frequencies from 1000 to 4000 Hz. We can distinguish some 400,000 kinds of different sounds.
The sounds having frequencies below 20 Hz are called infrasonic while those having frequencies above 20,000 Hz are called ultrasonic. Ultrasonic waves are very useful in scientific laboratories, diagnostic instruments and ultrasonic machines. These ultrasonic sounds can be heard by dogs, bats etc. sound is produced through many sources. Infact, any vibratory thing can produce sound. Musical instruments also produce different kinds of sounds. The sound which is not pleasant to the ears is called noise. Reference: Children’s Science Library by A.H.Hashmi.