There are two main properties of sound: pitch and volume. Pitch measures how high or low a sound is, and volume measures how loud or soft a sound is. Frequency is measured in hertz, and amplitude is measured in decibels. The more force the louder the sound is. The properties of sound are also the characteristics such as "cling, thud, clatter, slap, etc.," sounds that distinguish one object from another.
Sound is formed when matter vibrates. When matter vibrates it creates energy. The word energy means the ability to cause a change. When matter vibrates it pushes molecules back and forth making compressions and rarefactions. These compressions and rarefactions travel out in sound waves.
The human ear is important to us. It allows us to hear. There are three main parts in the human ear. There are the outer ear, the middle ear, and the inner ear. When sound waves hit the pinna they travel down the ear canal to the eardrum. The sound waves make the eardrum vibrate. The vibrations pass through the hammer and anvil to the stirrup. The vibrations travel into the cochlea. Vibrations in the cochlea cause nerve cells to transmit signals to the brain. The brain processes these messages and tells you that you've heard sound.
Musical instruments have three groups. The include wind, string, and percussion. The wind category includes many instruments. Some of these instruments are trumpets, saxophones, trombones, and clarinets. Wind instruments make sound when people blow into them. Percussion instruments have a wide variety of instruments. These include the bongo, the base drum, the snare drum, and many more. Percussion instruments make sound when someone strikes the head of the drum. Finally, there are string instruments. Some string instruments are the guitar and the ukulele. String instruments make sound when people pluck the strings.
Loudness depends on the amplitude (amount of energy) of sound waves. Loudness is measured in units call decibels. Sounds are loudest when we are close to them, and when they are made with a lot of force. Frequency is measured in units called hertz. A sound wave that occurs one time a second has a frequency of 1Hz. The word hertz was named after Heinrich Hertz, the German scientist who discovered radio waves. Noise pollution is any sound that causes problems for people or things. Any sound that is over 80 decibels can cause hearing loss.
Echoes are reflected sound waves. When a soundwave hits a smooth, hard surface it reflects off. When a sound wave hits a soft, irregular object it is absorbed. Sound waves travel through matter. Matter is something that takes up space and has a mass. There are three types of matter: solid, liquid, and gas. when sound waves travel through matter it is called medium. Sound travels at about 750 miles per hour. When sounds are produced it depends on the amount of energy. When a sound wave travels it has compressions and rarefactions. Bats use a special technique called echolocation to find food. Echolocation means locating an object based on an emitted sound and the reflection back from it.