© oxford university press 2011 ip1.29.3 sounds around us sounds around us

8
© Oxford University Press 2011 IP1.29.3 Sounds around us Sounds around us

Upload: walter-casey

Post on 31-Dec-2015

212 views

Category:

Documents


0 download

TRANSCRIPT

Page 1: © Oxford University Press 2011 IP1.29.3 Sounds around us Sounds around us

© Oxford University Press 2011

IP1.29.3 Sounds around us

Sounds around us

Page 2: © Oxford University Press 2011 IP1.29.3 Sounds around us Sounds around us

© Oxford University Press 2011

IP1.29.3 Sounds around us

Introduction to sound waves

Sound waves are longitudinal waves. Sound waves are created whenever an object vibrates. Sound waves can travel through all solids, liquids and gases. The denser the material the sound travels through, the faster

it travels. Sound can’t travel through a vacuum. There are no particles

in the vacuum to vibrate.

Page 3: © Oxford University Press 2011 IP1.29.3 Sounds around us Sounds around us

© Oxford University Press 2011

IP1.29.3 Sounds around us

Speakers vibrate in and out when they receive an electric current. These vibrations create the sound.

Page 4: © Oxford University Press 2011 IP1.29.3 Sounds around us Sounds around us

© Oxford University Press 2011

IP1.29.3 Sounds around us

A musical instrument often has a string, a column of air or a reed. This causes vibration that creates sound waves.

Page 5: © Oxford University Press 2011 IP1.29.3 Sounds around us Sounds around us

© Oxford University Press 2011

IP1.29.3 Sounds around us

A tuning fork delivers an exact pitch which depends on the length of its two prongs. If you put a tuning fork in a glass of water you can confirm that sound is caused by vibrations.

Page 6: © Oxford University Press 2011 IP1.29.3 Sounds around us Sounds around us

© Oxford University Press 2011

IP1.29.3 Sounds around us

Ultrasound has a frequency too high for the human ear to detect. It is mostly commonly used for medical imaging.

Page 7: © Oxford University Press 2011 IP1.29.3 Sounds around us Sounds around us

© Oxford University Press 2011

IP1.29.3 Sounds around us

If a note of the correct frequency is played for long enough it will cause a glass to vibrate and eventually break.

Page 8: © Oxford University Press 2011 IP1.29.3 Sounds around us Sounds around us

© Oxford University Press 2011

IP1.29.3 Sounds around us

Sound waves and the human body

When you talk, your vocal chords vibrate. You can feel them if you gently press the front of your throat whilst talking.

When vibrations reach our ear, they make our eardrum vibrate and we detect this as a sound.

Humans can hear sounds up to a frequency of 20 000 Hz. Sound waves above this frequency are called ultrasound.

As you get older you lose your ability to hear high frequency sounds. By the time you are twenty you will only be able to hear 16 000 Hz; this falls to 13 000 Hz at thirty.

Listening to music that is too loud does permanent damage to your hearing.