Sounds through Air and Water

Physics of SoundInvestigation 3, Part 1

Student sheet no. 13 called Sounds through the Air Student sheet no. 14 called Sounds through Water Tone generator with 9-V battery Megaphone Paper fasteners Large plastic bags Tuning fork Listening tube Rubber bands Wood block Basin/bucket Stethoscopes Alcohol Cotton balls Paper towels Water

Materials

Sound through AirRoll tagboard into tubes and secure with paper fasteners at

each end, and 2 rubber bands in the middle.Put listening tube, tuning fork, and wood block in bag.

Sound through WaterFill 4 basins about 2/3 full of water.Set 2 stethoscopes near each basin.Keep a supply of paper towels, alcohol, and cotton balls at

station.

MegaphoneCurl the fan shaped piece of tagboard into a cone and

fastening with 3 fasteners.

Preparation for teacher

Wind chimes dance in the breeze, collide, and begin to vibrate. The tinkling sound travels from the chime to your ears through the air.

Male humpback whale calls to a mate by creating vibrations in his respiratory system. His song travels a great distance through the water to a listening female.

A bird watcher hears a wood pecker busy at work high in a cluster of trees. Which tree is the wood pecker in? Bird watcher places his ear to each trunk, until he hears the loud hammering sound traveling down through the wood.

Back ground

Wind chime, whale, and pecking bird = sound source

Ears = sound receiverSound can travel through solids, liquids, and

gases as go from a source to a receiver.Sounds travel faster and seems louder when

hear it through a solid or liquid than when we hear them through the air.

At great distances, we can observe that sound travels faster through solids than liquids and slowest through the air.

Sound Travel

2 people are on a deserted railroad track.One person with an ear to the solid metal track.Another person standing up with an ear to the air.Both people have stopwatches in their hands.1500 meters down the track is another person with a big

hammer and a red flag.The flag and the hammer come down at exactly the same time.The hammer strikes the track to make a loud noise.When the 2 people see the flag come down, they start their

stopwatches.When they hear the sound of the hammer hitting the track,

they stop the watches.The person with an ear to the track should hear the sound

much sooner than the person with an ear to the air.

Train

Most of the time, we are close to sound sources, so we tend to think of sound as an instantaneous phenomenon.

Air is a pretty inefficient medium for transmission of sound energy, and becomes increasingly poor as the temperature drops and the elevation increases.

Colder molecules have less energy to begin with, and air molecules are farther apart at higher elevations.

In space, where heat is negligible and molecule density near zero, sound does not travel.

Background

To move from one place to another, sound needs a medium through which to travel.

The medium can be solid like a railroad rail, liquid like water, or gas like air.

If there is no medium, sound cannot travel and so cannot be heard.

Sound will not travel to the ear if the listener does not want to hear the sound.

Transfer of sound traveling from sound source directly to an ear in a continuous straight line.

Sound needs an unobstructed line of sight to get to an ear. If it is blocked, the sound will not be hear, or it will be heard softly.

Misconceptions

When the school bell rings, what is the sound source?

How does the sound get from the bell to your ears?

Do you think it travels through the walls or through the air?

If this room were filled with water, would you still be able to hear the bell?

Can sound travel through water?

School Bell

Every time we hear something, the sound has to travel from the sound source to our ears.

Sound is invisible.

Today, we will find out if sound travels through water and air.

Overview

Remind how to use tuning fork.

Demonstrate how to hold by stem and strike on wood or bottom of shoe with little force.

Demonstrate how to use the listening tube to direct sounds to your ear.

Sound through Air

Stethoscope – instrument for listening to sounds in the body.

Demonstrate how to use a stethoscope.

Show how to clean the earpieces with cotton ball and alcohol.

Stethoscope amplifies sounds, so do not strike it hard while listening.

Show how to snap.

Sound through Water

Distribute

Read the instructions

15 minutes at stations

Record observations

Clean up before switch stations

Share observations

Student Sheet

Begin with audible volume.

Slowly decrease the volume until only students in front can hear the sound.

We have a problem here.

The volume is very soft.

Is there anything you can do at your seats that will allow you to hear the sound? (megaphone, listening tube, cup hands over ear)

Tone Generator

Make sound louder

Megaphone – funnel shaped device that can amplify sounds at a receiver

How do you think this megaphone works?

Amplify Sound

Outer ear – made of flesh and cartilageCollects and directs sounds much like a megaphone

or a listening tube.

Middle ear – inside ear

Inner ear – inside earNerves carry the sound message to brain

Ear Function

Stethoscope – used by doctor to amplify sounds produced inside body

Megaphone – amplify sound at the source or receiverOuter ear – flap of flesh and cartilage that directs sound

vibration to the inner earInner ear – where nerves transmit messages to the brainCan sound travel through water? (Yes, and it is louder

and clearer.)How can sound be amplified in air? (With tubes and

megaphones, which gather and direct sound at either the source or receiver.)

How do ears assist hearing? (Outer ears are designed to receive, focus, and amplify sounds.)

Science story – Moving Along

Review

The End!!!