Sound and Hearing

Cecile Savage                   John Farren School
                                5055 South State
                                Chicago IL 60609
                                (773) 535-1440

Objectives:

     To demonstrate that sound travels.
     To explore how sound is reflected, amplified and recorded.   
     To investigate the physical components of the ear and the way it works.
     This lesson is designed for a 5th or 6th grade class.

Materials Needed:

     one cookie box or cake tin
     rubber bands
     uncooked rice
     scissors
     sauce pan or baking tray and wooden spoon
     plastic wrap or balloons
     cardboard tubes
     1 or 2 candles
     modeling clay
     1 tape recorder and microphone
     flashlight
     index cards or pieces of smooth posterboard
     alarm clock or softly ticking metronome
     blindfold
     a blank cassette tape
     2 funnels
     1 yard of flexible plastic tubing

Strategy:


     Sound as waves

     Activity #1: Stretch the plastic wrap or balloon over the cookie tin; 
secure with rubber band(s) and sprinkle a few grains of uncooked rice over the 
plastic.  Hold the baking tray over the can.  As the tray is being hit with the 
wooden spoon, the rice can be seen moving and jumping over the plastic membrane. 
This activity shows that sound travels in waves and reaches our ear drum or 
tympani much in the same way as it vibrates the plastic over the cookie tin. 
     Activity #2: Stretch a piece of plastic wrap or balloon over both ends of a 
cardboard tube; secure with rubber band(s).  Make a little hole in the plastic 
at one end of the tube only.  With the clay, build a short stand that has the 
same height as the candle.  Lay the tube over the stand, with the pierced end 
pointed towards the candle, and just a few inches away from it.  Tap the other 
end with your finger.  The vibrations blow out the candle.  This activity shows 
how the vibrations made by tapping the drumhead move down the cardboard tube and 
push the air out through the little hole at the opposite end, much like they 
travel down our ears.  The pitch or tone of sound waves is measured in Hertz. 

     Waves: direction and reflection.

     Activity #3: this is a game for the whole class room.  The class sits down 
in a circle.  One person volunteers to wear a blindfold and sit in the middle.  
The other players are quiet and a designated student makes a gentle noise, such  
as popping his/her fingers.  The blindfolded student must point in the direction 
of the noise.  Many different players can take a turn at being blindfolded.  
Whose ears have the best sense of direction?                                           
     Activity #4: Use modeling clay to secure 4 equal pieces of cardboard tube  
in an horizontal manner.  They must form a zigzag pattern with an angle of about 
90o between each tube.  Without changing that angle, place a square of 
posterboard facing the adjoining end of the first and second tubes, another 
square of posterboard facing the ends of the second and third tubes, and a third 
piece of posterboard facing the ends of the third and fourth tubes.  Place a 
microphone hooked to a tape recorder at one end  of this contraption.  Set a 
ticking metronome or alarm clock at the opposite end, but away from the opening 
of the first tube.  The tape recorder will record either nothing or a very faint 
sound.  Now, place the metronome right at the opening of the first tube.  The 
resulting recording should be quite clear.  Different experiments can be done: 
change the directions of the tubes and determine which direction give off the 
clearest sound; or replace the smooth cardboard with reflector cards of 
different material or egg cartons.  This activity demonstrates that sound waves 
in air will bounce off a flat, solid surface, like a ball bouncing off a wall. 
If, however, the sound waves are bounced off a surface that is soft or bumpy, 
the waves will break up or fade away.  Volume is measured in decibels. 

     Amplifying and recording sound.

     Activity #5: making a stethoscope.  Take a piece of plastic tubing that 
fits tightly over the narrow ends of 2 funnels.  Attach a funnel to each end. 
Ask a student to put one funnel over his/her chest and another student to put 
the other funnel, at the other end over his/her ears.  He/she should be able to 
hear the other student's heartbeat.  This activity demonstrates how some devices 
can amplify sound.  The shape of a cone is used to amplify sounds whether 
receiving them (stethoscope), or sending them (megaphone). 
     Activity #6: Students face a microphone in a row or two, depending on their 
numbers.  They sing a song together in the microphone, hooked to the tape 
recorder.  The tape will pick up the voice nearest to the microphone drowning 
the rest.  Then, the microphone is tied to the handle of an open umbrella,facing 
the students standing at the exact same place.  Play the tape back.  The voices 
are far clearer than on the first recording.  The same experiment can be done 
recording birds outside.  This activity shows students how the umbrella's shape 
collects the sound waves and reflects them back to the microphone. 

     Make a model that demonstrates how the ear works.

     Activity #7: Stretch plastic wrap over one end of a tube and secure with a 
rubber band.  Roll another sheet of paper to make a cone and insert the smaller 
end into the other end of the tube.  Stand an index card in a vertical way, 
(secure with modeling clay) very near the end of the tube with the plastic wrap. 
Shine the flashlight on the plastic wrap so that the light is reflected onto the 
card.  Then shout or sing loudly into the cone.  Results: the reflected light 
should flicker.  The cone represents the outer ear (pinnea), the tube is the ear 
canal and the wrap represents the ear drum (tympanic membrane).  When sounds are 
captured by the outer ear and travel down the ear canal, the eardrum vibrates. 


Performance Assessment:

     Students should be able to retrace any experiments of their choice step by 
step.  They should know how to explain the following terms: hertz, decibel, 
stethoscope, pitch, volume, outer ear, ear canal, ear drum, amplify, sound wave, 
string, wind and percussion instruments.