09/11/2018 Sound and Hearing

ALL SOUND IS CAUSED BY VIBRATIONS! Investigating Sounds ALL SOUND IS CAUSED BY VIBRATIONS! Put your hand on your throat and talk. What can you feel? Your throat VIBRATING. Put your hand on a loudspeaker that is producing sound. What can you feel? The loudspeaker VIBRATING. Strike a tuning fork against a wooden block. What can you see? The prongs of the tuning fork VIBRATING. Place a ruler half over the end of a table and flick the ruler. What can you see? The ruler VIBRATING. Pluck a string on an instrument. What do you see? The string VIBRATING. 09/11/2018

Sound and Vibrations All sound is caused by VIBRATIONS. How does sound travel from a vibrating object to your ear? The vibrating object makes the AIR PARTICLES VIBRATE. The vibrations are passed along from air particle to air particle in the form of WAVES. Sound travels in waves. The air particles make your EAR DRUM vibrate. Your ear drum makes three small bones, called OSSICLES, vibrate. These are connected to your COCHLEA that contains thousands of SMALL HAIRS. These small hairs DETECT the vibrations. The AUDITORY NERVE carries messages to your BRAIN which are interpreted as SOUNDS. 09/11/2018

How sound travels… 09/11/2018 As we know, sound waves are formed when something vibrates. But how does the sound reach our ears? Air molecules 2) The vibrations pass through air by making air molecules vibrate 3) These vibrations are picked up by the ear 1) An object makes a sound by vibrating

Travelling sound 09/11/2018 Sound travels by particles vibrating. To understand this better you need to remember what the particles look like in a solid, liquid and a gas: solid liquid gas Which state does sound travel fastest through? Why? In which state are the particles closest together? Sound travels fastest through solids because the particles are closer together than in a liquid and a gas, so the vibrations are more easily passed from particle to particle. solid In which state are the particles furthest apart? gas

Speed of sound 09/11/2018 The speed of sound in air is around 330 m/s. What happens when sound travels through different materials? Speed of sound (in m/s) Material Conclusion – the denser the material, the faster sound travels through it

Making Sounds A sound is made when an object or material VIBRATES. 09/11/2018 A sound is made when an object or material VIBRATES. Take, for example, a guitar. To make a sound with a guitar a string has to vibrate. We can raise the pitch of the sound a guitar makes by doing three things: 1) _________ the length of the string 2) _________ the string 3) Using a _________ string We can make the sound louder by ________ the string harder Words – tightening, thinner, increasing, plucking

Sound and Vacuums Sound can travel through solids, liquids and gases. SOUND CAN NOT TRAVEL THROUGH A VACUUM. If you were in space you would not be able to talk as there is NO AIR TO VIBRATE. If you were in space and there was an explosion you would not be able to hear it. 09/11/2018

The Bell-jar experiment What happens when the air is removed from the bell-jar?  Sound waves are vibrations and so need a substance to travel through.  With air inside, the sound can be heard. With nothing inside [a vacuum], the sound can’t be heard.

Parts of the Ear Oval window Semi-circular canals Ossicles Auditory nerve Ear drum Cochlea Pinna Eustachian tube 09/11/2018

Loudness and Distance The FURTHER AWAY a sound is, the QUIETER a sound is. I can’t hear it - it’s too quiet! What beautiful music! 09/11/2018

What are the effects of noise on your body? What is NOISE? A NOISE is UNWANTED SOUND. What sorts of noises could damage your hearing? Loud music. Machinery. Explosions. Aircraft. How can you protect yourself from loud noises? Ear protectors. NAUSEA HEADACHES LOSS OF HEARING DEAFNESS Double glazing. What are the effects of noise on your body? Putting machinery into separate rooms to workers. Turning down the volume of music. 09/11/2018

How does the ear work? 09/11/2018 1) Sound waves are “funnelled” into the ear by the pinna 5) The electrical signals are then sent to the brain 3) These vibrations make the ear bones vibrate 4) These vibrations are turned into electrical signals in the cochlea 2) These vibrations make the ear drum vibrate