[untitled worksheet]

Target Language or Knowledge:

Sound is a mechanical wave that results from the back and forth vibration of the particles of the medium through which the sound wave is moving. However, the speed of sound varies from substance to substance. Sound travels faster in liquids and non-porous solids than it does in air. At normal atmospheric pressure and a temperature of 20 degrees Celsius, a sound wave will travel at approximately 343 m/s; this is approximately equal to 750 miles/hour. It travels about 4.3 times as fast in water (1,484 m/s), and nearly 15 times as fast in iron (5,120 m/s), as in air at 20 °C. Low pitch sounds are low in frequency, and high pitched sound are high in frequency. Frequency is measured in Hertz (Hz). The range of human hearing is generally considered to be 20 Hz to 20 000 Hz. The primary advantage of having two ears is the ability to identify the direction of the sound. Human listeners can detect the difference between two sound sources that are placed as little as three degrees apart, about the width of a person at 10 meters.