Lab Assignment 1

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Longwood University *

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Electrical Engineering

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Feb 20, 2024

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Lab Assignment 1: The Nature of Sound (50 points) Name Answers should be typed into the space allocated (blue text) . All drawings of waves should be completed on provided graphs or graph paper. You may handwrite answers. Supplies needed  Slinky  Colored pencils/markers  Dominos  A tub of water  Marble (or something of round of comparable weight [that won’t float])  Two drinking glasses (made of glass)-The thinner the glass the best.  Videos and images provided in module.  An assistant (if possible) to help with Activity 1 and Activity 4. 1. Waves: Slinkys (15 points total) View image: “Wave Created Using Slinky.” Watch video: “Slinky Waves.” a. Label each wave created in the video. (Hint: Wave is either longitudinal or transverse.) (1 pt each) Wave 1: Wave 2: Wave 3: Wave 4: Graph Waveform For this activity, you will draw waveforms. Recall from assigned reading that a waveform is a graphic display that represents the alternating compressions and rarefaction of molecules that make up the longitudinal wave. Review how waveforms are graphed before continuing. Now, with your own slinky, spread the coil along the floor with an assistant, as shown in the video. If you don’t have an assistant, you could clamp it to something. Practice making waves by moving your entire arm from side to side, holding your wrist steady. Try again by only moving your wrist. Lab Assignment 1 1

b. Complete graph.  Label both axes (amplitude and time). (2 pts)  With a colored pencil, draw the wave you created moving your entire arm from side to side, holding your wrist steady on the graph on the answer sheet. (1 pt)  Label a wavelength segment on the wave you drew. (1 pt)  Label the amplitude of the wave you drew. (1 pt) c. Change the frequency of the wave. (As you did when you made waves by moving only your wrist.) Directly over (on top of) the wave you just drew in the graph above, draw the new wave in a different color. (2 pts) d. What did you do to change the frequency? (1 pt) e. Change the amplitude (height) of the wave. Draw the new wave in a third color directly over (on top of) the previous two waves you drew. (2 pts) f. What did you do to increase the amplitude/excursion of the slinky? (1 pt) Lab Assignment 1 2

2. Waves: Water (3 points total) Using a tub of calm water, drop a marble into the water and observe how the wave radiates outward. Notice the reflection of the wave as it hits the sides. a. Draw the wave you created, as it looks from above. (2 pts) b. What type of wave(s) were created? (1 pt) 3. Waves: Dominos (3 points total) a. Line up dominos. Knock them over, demonstrating wave action. What type of wave was demonstrated? (2 pts) b. Phonemes of a certain manner category are made with this type of wave. What manner category? (1 pt) 4. Resonance: Make a Glass Sing (4 points total)  Gather at least two different drinking glasses (made of glass) that can try to make “sing.” (The thinner the glass the better.)  Fill a third cup/container with water that you will dip your finger into.  Wash your hands (you want your fingertips clean).  Fill the glasses that you are going to try to make sing approximately half full with water.  Set the glasses on a flat surface.  Dip your finger in water and hold the bottom of the glass with your other hand.  Slowly start running your finger around the rim of the glass, using the part of your finger between the tip and the second knuckle. Be sure to keep your finger in constant contact with the rim of the glass.  You will have to experiment with the pressure, speed, and where you touch the rim. You may find that you need to use a different finger.  Keep at it until you are successful in creating sound with at least one glass. Lab Assignment 1 3

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a. What creates the sound? (1 pt) b. Add water to the glass. How does the water change the sound? (1 pt) Glass (description) Amount of Water (approx.) How is the sound different from when there is no water? c. Have another person pour water into the glass while you are making it “sing.” What happens to the sound while water is being poured? (1 pt) Why? (1 pt) 5. Intensity (9 points total) Watch the video titled “Sound Level Meter.” It shows measuring of sound intensity (in Sound Pressure Level [SPL]) of 3 different sounds (noted below in table) at 2 different distances. For this activity, you will watch the video and enter the data that they obtained into the table. Note : The Extech SPL meter was utilized to obtain data. This meter has a sensitivity range from 40dB to 130dB. And 300Hz to 8000Hz. Compare the results from the information on sound intensities of common sound with ASHA data, at: https://www.asha.org/public/hearing/Loud-Noise- Dangers/ . The dB listed for each noise represents the average decibel levels at the "typical distance" for the given object. This is what you will enter under ASHA data column. a. Complete the table. (5 pts) Lab Assignment 1 4

Sound At Typical Distance 4 Times the Distance ASHA Data dB Distanc e dB Distance Conversation al Speech ~ 4 ft. ~16 ft. Hair Dryer ~ 1 ft. ~ 2 ft. (did not quadruple) Music from Phone Earbuds 0 Direct Contact ~ 4 in. b. How does distance influence intensity? (2 pts) Select the link below to review how long you should listen to sounds before they will damage your hearing. http://dangerousdecibels.org/education/information-center/decibel-exposure- time-guidelines/ c. How long can you listen to a sound of 85 dB?: (1 pt) d. How long can you listen to a sound of 110 dB?: (1 pt) 6. Understanding Frequency, Amplitude, Wavelength. (16 points total) Wave on a String Go to Wave on a String: http://phet.colorado.edu/en/simulation/wave-on-a-string . (NOTE : This does not work well on an iPad/tablet. Use a laptop or PC.)  Set the parameters on “Pulse” and “Loose End.”  Select “Rulers” and move the vertical ruler so that is lined up correctly with 0 cm adjacent to the green dots at rest.  Set “Amplitude” to 1.0 cm.  Set “Damping” to ¼ of the distance on the scale.  Set “Pulse Width” to .5 s.  Set “Tension” to the middle. Lab Assignment 1 5

a. Draw the pulse wave you created on graph. Be sure to label the axes (amplitude, time). (1 pt) b. Vary the amplitude setting and measure the height of the wave and distance the ring moves on the pole. Complete table. (1 pt) Amplitude Setting Height of the Wave at the Start Distance Ring Moves on the Pole (End) 1.25 cm .5 cm c. What happened to the energy at the end of the wave? (1 pt)  Now select “Oscillate.”  Set “Amplitude” at 1.25 cm.  Set “Damping” at the midpoint on the scale.  Use the ruler to measure the wavelength (remember rulers can be moved if needed).  To make the wave easier to measure and view the wave “step-by- step,” you can pause to stop the motion. When paused a large “play” icon appears, to the right of this icon is an “advance” icon. Click on it multiple times to view the wave “step-by-step.” Lab Assignment 1 6

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d. Insert the wavelengths for frequencies set to 1 Hz and 2 Hz. Complete table. (2 pts) Frequency Setting Wavelength 1 Hz 2 Hz  Now, select “Timer” in addition to “Ruler.”  You will be measuring the # of waves in a 10 second period.  Practice turning on and off the timer while the waves are moving.  Then practice counting the waves as they pass a given point (move the vertical ruler so it is along the wave’s path). e. Count the waves for 2 different frequencies, 3 times each. Complete the table and calculate the average number of waves as shown. (3 pts) Frequen cy Setting Time Interv al Number of waves (1 pt) Ave # of waves per 10 sec (1 pt) Avg # of waves in 1 sec (1 pt) Trial 1 Trial 2 Trial 3 2 Hz 10 sec 1 Hz 10 sec f. Complete the following sentence: These data shows that the higher number chosen for the frequency, the (greater / fewer) the number of waves. (You may change the color of your chosen answer to blue/bold, delete the incorrect choice, or circle your answer.) (1 pt) Lab Assignment 1 7

Sine Waves g. To demonstrate your understanding of frequency and amplitude, complete the following graph.  Label the x and y axes. (1 pt)  Draw a sine wave with 5 cycles in 10 seconds. Label this waveform A. (2 pts)  Directly over (on top of) waveform A, in a different color, draw a sine wave with the same amplitude as waveform A, but with 10 cycles in 10 seconds. Label this waveform B. (2 pts)  Directly over (on top of) waveforms A and B, in a third color, draw a sine wave with the same frequency as A, but with twice the amplitude. Label this waveform C. (2 pts) Lab Assignment 1 8