SOUND STATIONS LAB Name PROPERTIES OF SOUND Visit each station. Follow the directions for that station and write your observations and the answers to any questions on this handout. You don't have to visit the stations in numerical order, but you must do them in chronological order! STATION 1 Strike the tuning fork against the rubber stopper. Do not hit the tuning fork against any hard object! While you are hearing a sound, dip the ends of the tuning fork into the beaker of water. What is the result? What conclusion can you make about what the tuning fork is doing while it is producing sound? STATION 2 Scrape your finger nails against the side of the sound sensor and watch the oscilloscope pattern. Strike the tuning fork against the rubber stopper. Do not hit the tuning fork against any hard object! Hold the tuning fork near the microphone and watch the oscilloscope pattern. Contrast the oscilloscope pattern made by your nails and the tuning fork. What appears to be the difference between the waves made by noise and by musical sounds? STATION 3 Strike the tuning fork against the rubber stopper. Do not hit the tuning fork against any hard object! Hold it vertically and close to your ear. Spin the tuning fork on its long axis slowly. What do your hear? What can you conclude is happening to the waves of sound coming from each tine of the tuning fork? What do you hear when the waves come to your ear in phase? out of phase?
STATION 4 Compare the volume of sound produced by the bell with and without air in the bell jar. What can you conclude about what is necessary in order for sound to reach your car? STATION 5 Hold the strings and strike the coat hanger with your pen or pencil. Describe the sound you hear. Wrap the string around your index fingers and put your index fingers into your ears (gently). Have your lab partner strikes the coat hanger with his or her pen or pencil. Describe the sound you hear now. Compare it to your partner's sound. Repeat for your lab partner. What do you conclude about the ability of the string to conduct sound compared to the ability of the air to conduct sound? Write a revised conclusion about what is necessary for sound to reach your ear. (instead of the one your wrote for STATION 4.) STATION 6 Blow a stream of air over the mouth of the empty bottle. Describe the sound that is produced. Now do the same for the other bottles 1/4 and 1/2 full of water. Compare the sound produced now to the sound produced when the "empty" bottle. What happens to the sound produced as the amount of water goes up? Describe the change in the sounds you hear when the amount of water and the shape of the bottle is different. Is the frequency of the sound getting higher or lower?
Is the wavelength of the sound getting longer or shorter? (You may have to wait until you have completed STATION 7 to answer these two questions.) STATION 7 There should be two tuning forks on the table. Read the printed frequency on each one. Choose the fork with a higher frequency. Strike it against the rubber stopper. Do not strike the tuning fork against any hard obiect. Hold the tuning fork near the sound sensor. Repeat with the second tuning fork. Compare the patterns you observe on the oscilloscope. How do the wavelengths of the sound created by the two forks compare? Strike one tuning fork and hold it near the sound sensor. Watch the oscilloscope pattern as the sound diminishes. What is the difference in the waves caused by a loud sound compared to the waves caused by a soft sound? Strike one tuning fork and quickly move it closer to and further away the microphone. How does the oscilloscope pattern change? What happens to the frequency when the tuning fork approaches the microphone? What happens to the frequency when the tuning fork moves away from the microphone? What happens to the pitch of the sound the microphone "hears" in each case? STATION 8 Wet your finger and rub it around the top of one of the wine glasses. USE YOUR OTHER HAND TO HOLD THE BASE OF THE WINE GLASS STEADY. Describe what happens. Describe the change in the sounds you hear when the amount of water in the glass is different. Is water necessary in the glass in order for sound to be produced? Try the empty glass. What must be producing the sounds you hear -the water or the glass? Explain how the amount of water changes the sound produced.
STATION 9 Turn on the frequency generator. Put your fingers gently on the uncovered speaker. What do you feel? Now change the frequency. Keep your fingers on the uncovered speaker. Describe what you feel as the frequency increases and then decreases. Write a conclusion about the frequency of the vibrations you feel and the pitch of the sound you hear. STATION 10 (IN HALL) Whirl the vacuum cleaner tube above your head until you hear a distinct sound. Now increase the angular velocity. Describe the change in the observed sound. Write a conclusion about the rate at which your whirl the tube and the frequency of the sound produced. Close off the end of the tube you are holding with your other hand. Now whirl the tube. How does the sound compare to the sound produced when both ends of the tube were open? STATION 11 Cut the ends of a straw into a V as shown at the station. Insert the V into your mouth and blow on the straw to make a noise. Note the sound produced. Have your lab partner cut off small portions of the straw as you blow into the straw. Please - make sure to put the pieces into the waste basket! (Yes. Every single little piece.) There should be no straw shrapnel anywhere after you leave. What happens to the sound produced? Make a conclusion about the length of the straw and the frequency of the sound produced.
STATION 12 Make sure that the two boxes are facing each other on the foam pad - open sides towards each other. Set them about a 3cm apart. Strike one tuning fork with the rubber stopper. After a second or two touch it to make it stop vibrating. What do you hear? What is creating the sound? Wrap four plasti-bands (non-latex binders) around the top of one tine of the second tuning fork. Then strike the first tuning fork again. What do you hear this time? Did it work as well? Suggest a reason why. Strike the tuning fork with the plasti-bands on the end. Touch that tuning fork to stop it vibrating. What do you hear this time? Strike both tuning forks and listen. Do you hear warbling (louder and softer sound)? Remove the plasti-bands before you leave this station. Thanks! STATION 13 Don t touch the spring inside the microphone for any reason. Speak loudly into the microphone while your partner watches inside the cut-away portion of it. What happens while you speak? What kind of waves does the vibrating spring make? How is the sound amplified? STATION 14 Use the sound level meter to estimate the loudness (in decibels): of your normal speaking voice of your shouting voice -
Did you get above 100dB (dangerous to your ear drums) zone? STATION 15 Examine the string instrument. Change the tension of one of the strings. How does the amount of tension affect the pitch of the vibrating string? Change the length of the vibrating string by holding down part of it and plucking the rest. How does the length of the vibrating string affect the pitch? Examine the thickness of the strings. Find two strings of different thickness. How does the thickness of the string affect the pitch? What must be held constant when you make this determination? STATION 16 Look at the keyboard attached to the oscilloscope Examine the pattern of the waves produced when the piano (instrument 00), flute (instrument 70), brass (instrument 55) and organ (instrument 15) are selected. Select instrument 70. Play two notes one-half note apart on the keyboard (two adjacent white keys with no black key between them). Observe the pattern. Play two notes further apart and observe the pattern. Play two notes one octave (eight white keys apart.) and observe the pattern. What conclusion can you make about the pattern of the waves and how close the notes are to each other?