SOUND SCIENCE GRADE 4

SCIENCE SUMMARY

GRADE 4

TOPIC : SOUND
 Sound is produced by vibrations.

 Vibrations can be felt and seen.

 The volume or loudness of sound is measured in the unit decibels (db).

 The volume of sound can be measured using a sound level meter or a decibel meter.

 The louder the sound is, the higher its decibel rating.

 Sounds can travel through gases, liquids, and solid because the particles in solids, liquids and gases can pass on the vibrations.

 Sounds travel fastest through solids and slowest through gases.

 Sounds cannot travel through a vacuum as there are no particles to pass on vibrations.

 Vacuum is a volume of space without any matter.

 Outer space is a vacuum. Thus, sound cannot travel in outer space.

 We can reduce the loudness of sound using soft materials such as carpets, curtains and foam cushions. These materials can absorb some of the vibrations to reduce the loudness of the sound.

 We can prevent ear damage by wearing ear plugs or ear defenders.

 The ear defenders are lined with foam that helps block loud noises.

 How high or low a sound is, is referred to as pitch.

 All musical instruments use parts that can vibrate to produce sounds.

- String instruments include guitar, violin and harp. When the stretched strings are plucked, bowed or     stuck, they vibrate, producing sounds.

- Wind instruments include flute, trombone, recorder. These instruments have a tube or pipe              containing a column of air that vibrates.

 Changing pitch in musical instruments

PITCH IN STRING INSTRUMENT

 A trombone player has to vibrate his lips while blowing into the mouthpiece. The pitch of the sound in trombone can be changed by extending or shortening the length of the tube. The farther the slide is pulled out, the longer the column of vibrating air to produce a lower-pitched sound.