Properties of Sound They are three fundamental properties of sound : Speed Frequency Loudness Speed The speed of sound is 330 metres per second in dry air in room temperature. Sound moves faster through liquids and solids than air, since liquids and solids can be pushed together more. Sound cannot travel through a vacuum, which is a space without any air or matter. The speed of sound is affected by temperature. It travels slower at low temperatures, for example in the stratosphere Frequency An important measurement of sound is the frequency. This is how fast the sound wave is oscillating. Frequency is measured in hertz. • • • • Audible sound has frequencies between 20 Hz to 20 kHz. Human beings can hear audible sound. Sound waves with frequency above 20 kHz are called ultrasound waves. Sound waves with frequency below 20 Hz are called infrasound waves. Human beings cannot hear ultrasound waves and infrasound waves, but some animals, like bats and dolphins, use them. Older people have an even smaller hearing range. • People are best at hearing sounds between 1000 Hz and 6000 Hz. Loudness Loudness refers to how loud or soft a sound seems to a listener. The loudness of sound is determined, in turn, by the intensity of the sound waves. Intensity is a measure of the amount of energy in sound waves. The unit of intensity is the decibel (dB). Characteristic of Sound #1 Sound travel Sound waves travel through air, water, and solid objects as vibrations. #2 Sound can be reflected (bounced) Sound waves can reflect off surfaces. We hear sound reflections as echoes. Hard smooth surfaces are really good at reflecting sounds – this is why empty rooms produce lots of echoes. #3 Sound can be absorbed Sound absorption is the loss of sound energy when sound waves comes into contact with an absorbent material such as Fibrous materials and other objects, as a result of which, the sound is not reflected back into the space. #4 Sound can be modified Sound can be changed to alter the pitch of a sound. To be able to modified what sound looks like when we change the pitch or loudness. #5 Sound is caused by vibrations Sound is a type of energy made by vibrations. When any object vibrates, it causes movement in the air particles. These particles bump into the particles close to them, which makes them vibrate too causing them to bump into more air particles. Trivia Questions 1.Can sound travel under the water? Yes sound can travel under the water. It moves four times faster through water than through the air. It can travel such long distances that whales can hear each other when they are nearly a hundred miles apart. 2.Is there sound on the moon? No, there is no sound in space. Sound needs something to travel through like air or water. 3.What is the speed of Sound? Sound travels through air at 1,120 feet (340 meters) per second. Thank you