Oscilloscope Lab Worksheet Oscilloscope Lab
Mapping Pitch and Volume to Wave Anatomy
Name:
Date:
Mission Objective
Use a digital oscilloscope to visualize sound waves. You will manipulate tone generators to determine exactly how physical wave properties (amplitude and frequency) change the sound we hear (volume and pitch).
1
Amplitude & Volume
Set your generator to a constant frequency (e.g., 440 Hz). Start with the volume at 10% and increase it to 90% while watching the screen.
Observation: How does the visual wave change?
Sketch the "Quiet" Wave:
Spacer
Sketch the "Loud" Wave:
2
Frequency & Pitch
Keep the volume constant. Sweep the frequency from 100 Hz up to 2000 Hz. Watch the density of the waves on the screen.
Observation: How does the visual wave change?
Sketch the "Low Pitch" Wave (200Hz):
Spacer
Sketch the "High Pitch" Wave (800Hz):
?
Analysis
1. Define the relationship between Amplitude and Volume:
2. Define the relationship between Frequency and Pitch:
3. If you double the frequency of a wave, how does its wavelength change visually?
Sound Anatomy Slides Wave Anatomy
The Physics of Sound Perception
Lesson 01: Pitch & Volume
Can you hear this?
Humans typically hear between 20 Hz and 20,000 Hz.
The Challenge:
Close your eyes.
Raise your hand when you hear a sound.
Lower it when it disappears.
TONE GENERATOR ACTIVE
Wave Anatomy 101
Amplitude
The height of the wave from its resting position. This determines how much energy the wave carries.
Subjective: VOLUME
Frequency
The number of cycles per second (measured in Hertz). How "tightly packed" the waves are.
Subjective: PITCH
Lab Briefing
01
Open your oscilloscope app/software and ensure your microphone is active.
02
Observe your own voice. Try a whisper vs. a shout. Try a low growl vs. a high squeak.
03
Sketch the wave patterns on your worksheet. Accuracy in scale matters!
Wave Anatomy Teacher Guide Teacher Guide
Lesson 01: Wave Anatomy and Sound
REF_ID: AC-L1-TG
Lesson Narrative
This lesson bridges the gap between the sensory experience of sound and the physical reality of longitudinal waves. By using oscilloscopes, students transition from "hearing" to "seeing" sound, allowing for a concrete mapping of subjective terms (pitch, volume) to objective physics variables (frequency, amplitude).
Essential Question
How do changes in a wave's physical structure manifest as changes in auditory perception?
Quick Specs
Duration: 60 Minutes
Materials: Tone Gen App, Oscilloscope App, Tuning Forks
Key Terms: Amplitude, Frequency, Hertz, Pitch
Pacing & Facilitation
0-10m
The Hook: Hearing Sweep
Use a tone generator to sweep from 20Hz up. Have students raise hands. As frequency increases, hands will drop (typically around 15k-18k for teens, lower for adults). This highlights the limits of the biological detector (the ear).
10-25m
Direct Instruction: Wave Mapping
Deliver slides. Focus on the direct correlation:
25-50m
Lab Investigation
Students work in pairs with the Oscilloscope Lab Worksheet. Circulate and ensure they are zooming the oscilloscope correctly to see 2-3 full wave cycles. If the wave looks like a solid block, they need to increase the time-base (zoom in).
Critical Misconceptions
Misconception:
"Higher pitch waves travel faster."
Reality:
Wave speed is determined by the medium. Pitch (frequency) and wavelength adjust to maintain that constant speed.
Misconception:
"Loudness changes the frequency."
Reality:
Amplitude and frequency are independent variables. A loud sound and a quiet sound can have the same pitch.
Debrief Questions
"Why does your voice look more complex on the oscilloscope than the tone generator?" (Timbre/Harmonics)
"If we moved this lab to the moon, what would happen to our data?" (No medium = no wave propagation)
Doppler Shift Slides The Doppler Shift
Frequency in Motion
NNNNNEEEE-RRRRROOOOOMMM
Think of a race car or an ambulance passing you. Why does the pitch drop as it goes by?
Does the driver hear the pitch change?
Observation Mode: Moving Source
Discussion: Is the car actually changing its sound?
The Physics of Motion
A
Front (Approaching)
Waves are compressed. Wavelength decreases.
High Pitch
B
Rear (Receding)
Waves are stretched. Wavelength increases.
Low Pitch
Beyond the Siren
Weather Radar
Determining the speed and direction of storm cells by shifting microwave frequencies.
Red Shift
Proving the expansion of the universe by observing light from distant galaxies stretching to longer wavelengths.
Speed Cameras
Calculating vehicle velocity based on the frequency shift of returned laser pulses.
Doppler Mapping Activity Doppler Mapping
Analyzing Apparent Frequency Shifts
Name:
Date:
1
The Siren Scenario
An ambulance is parked with its siren on. The source frequency is 800 Hz. Sketch the wave fronts (concentric circles) reaching the observers.
Observer A
Observer B
Obs A Apparent Freq:
Obs B Apparent Freq:
The ambulance now moves Right at 30 m/s. Sketch the compressed and stretched wave fronts reaching the observers.
Observer A
Observer B
Obs A (Receding):
Obs B (Approaching):
?
Experimental Design
If the ambulance driver is inside the car listening to the siren, will they hear a frequency shift? Why or why not?
A star is observed through a telescope. Its light is "Red-Shifted" (stretched to longer wavelengths). Is this star moving toward Earth or away from Earth? Explain.
Could a Doppler shift occur if the source is stationary but the observer is moving? Explain your reasoning.
The Doppler Math
\( f = f_0 \left( \frac{v + v_r}{v + v_s} \right) \)
\(f\) : Observed Frequency
\(f_0\) : Source Frequency
\(v\) : Velocity of waves in the medium
\(v_r, v_s\) : Velocity of receiver and source
Note: Sign changes depending on direction!
Doppler Mapping Answer Key Answer Key
Doppler Mapping Activity
REF_ID: AC-L2-KEY
1. Wave Pattern Guidance
Static Scenario
Drawing: Perfect concentric circles centered on the source.
Apparent Freq: Both observers hear 800 Hz. No relative motion = no shift.
Moving Scenario (Right)
Drawing: Circles bunched up on the right; stretched out on the left.
Obs A (Receding): Frequency < 800 Hz. Pitch drops.
Obs B (Approaching): Frequency > 800 Hz. Pitch rises.
2. Critical Thinking Responses
Driver Perspective:
No. The driver and the source are moving at the same velocity (\(v_r = v_s\)). There is no relative motion between them, so the wave fronts reach the driver at the same rate they are emitted.
Red-Shifted Star:
Away. Longer wavelengths correspond to lower frequencies (red end of the spectrum). Just like the rear of the ambulance, the stretching of waves indicates the distance between Earth and the star is increasing.
Moving Observer:
Yes. The Doppler effect depends on relative motion. If you run toward a stationary speaker, you will encounter wave fronts more frequently than if you stood still, resulting in a higher apparent pitch.
GRADING TIP: Look for the center of the wave circles in Part 1. They should be offset in the direction of travel to demonstrate the source "chasing" its own waves.
Vibrational Resonance Slides Vibrational Resonance
When Energy Aligns
The Power of Wind?
In 1940, the Tacoma Narrows Bridge collapsed. It wasn't just "strong wind." It was a Mechanical Failure of wave alignment.
"The wind provided the energy, but the bridge provided the rhythm."
Tacoma Narrows Footage
How can a 40mph wind destroy thousands of tons of concrete?
1. Natural Frequency
Every object has a frequency at which it wants to vibrate.
Affected By:
Mass (Heavy = Low Freq)
Stiffness (Tight = High Freq)
Shape (Geometry matters)
EVERYTHING VIBRATES
What is Resonance?
"When the frequency of an external force matches the natural frequency of an object."
Forced Input
Natural Frequency
=
MASSIVE AMPLITUDE
Tacoma Narrows Analysis Worksheet Bridge Breakdown
Case Study: Tacoma Narrows Resonance
Name:
Date:
The Incident Report
On November 7, 1940, the Tacoma Narrows Bridge in Washington State collapsed during a windstorm. Despite winds only reaching 42 mph—a speed the bridge was theoretically designed to handle—the roadway began twisting and undulating with massive amplitude before finally tearing apart.
1
The Matching Frequency
Identify the "Source Frequency" and the "Natural Frequency" in this case study.
Source Frequency Provider:
Resonating Object:
2
Energy Transfer
Why did the bridge undulations grow in size (amplitude) over time rather than staying at a small, constant flutter? Use the concept of constructive interference in your answer.
3
The "Singer and the Glass" Connection
How is the collapse of the Tacoma Narrows Bridge physically identical to an opera singer shattering a wine glass with their voice?
4
Structural Engineering Solution
If you were the engineer redesigning this bridge, how would you prevent this from happening again? (Hint: Think about how to change the bridge's natural frequency or disrupt wave alignment.)
Lesson: Vibrational Resonance
Physics Strand: Waves & Acoustics
Document: Case Study WS-03
Sonic Speed Slides Sonic Speed
Waves Through Media
~343 m/s
The Squeaky Voice
Why does breathing helium make you sound like a cartoon character? It's not because your vocal cords are moving faster...
The Secret:
Sound travels 3 times faster in helium than in air.
Medium Density Matters
Speed vs. Medium
Gases
Slowest. Molecules are far apart. Hard to pass kinetic energy.
~340 m/s
Liquids
Medium. Molecules are touching, but slippery.
~1,500 m/s
Solids
Fastest. Rigid bonds snap back quickly. Instant energy transfer.
~5,000 m/s
Temperature Check
Sound moves faster in WARM air than in COLD air.
The Calculation
\[ v \approx 331 + 0.6 \cdot T_c \]
Where \(T_c\) is the temperature in degrees Celsius.
Sonic Speed Lab Worksheet Velocity Lab
Calculating the Speed of Sound via Resonance
Name:
Date:
Mission Parameters
Determine the speed of sound in the classroom by finding the resonant length of a closed air column.
Required Gear
Resonance Tube (Graduated)
Tuning Forks (Diverse Frequencies)
Water Tank
Thermometer (Celsius)
The Lab Equation
\[ v = f \cdot \lambda \]
For a 1st harmonic closed tube: \( \lambda = 4L \)
Part A: Data Collection
Trial Freq (\(f\)) Hz Resonant Length (\(L\)) meters Wavelength (\(\lambda = 4L\)) Calc Speed (\(v\)) 01 02 03 AVG -- -- --
Theoretical Speed
Measure the room temperature and use: \( v = 331 + 0.6(T_c) \)
Room Temp (\(T_c\)):
Theo. Speed (\(v_t\)):
Error Analysis
\( \% \text{Error} = \left| \frac{\text{Theoretical} - \text{Experimental}}{\text{Theoretical}} \right| \times 100 \)
Calculation:
Conclusion Questions
1. As the tuning fork frequency increased, what happened to the resonant length (\(L\)) of the tube? Explain why.
2. Identify one major source of experimental error in this lab. How could you improve the measurement?
Laboratory Note: Remember that sound is a longitudinal wave. The air in the tube is vibrating back and forth, creating high-pressure nodes and low-pressure antinodes. Resonance occurs when the antinode aligns with the opening of the tube.
Harmonic Standing Waves Slides Harmonic Math
The Geometry of Music
Sound You Can See
When a metal plate vibrates at a specific frequency, sand on its surface migrates to the NODES—the places where the plate isn't moving at all.
Higher Frequencies = More Complex Geometry
Chladni Plate Demo
Standing Wave Anatomy
Node (N)
Points of ZERO displacement. Total destructive interference.
N
Antinode (A)
Points of MAXIMUM displacement. Total constructive interference.
A
A
Instrument Physics
String (Closed)
Fixed at both ends.
Always starts and ends at Nodes.
Fundamental: \( L = \frac{1}{2} \lambda \)
Air Column (Open)
Open at both ends.
Always starts and ends at Antinodes.
Fundamental: \( L = \frac{1}{2} \lambda \)
Instrument Design Workshop Worksheet Instrument Architect
Applied Acoustic Engineering
Name:
Date:
Workshop Challenge
Design a musical instrument that uses a standing wave in an air column or a string. You must calculate the physical dimensions required to produce a specific musical note.
1. Mechanism Selection
Closed String (e.g., Guitar)
Open Pipe (e.g., Flute)
Closed Pipe (e.g., Pan Flute)
Why did you choose this mechanism?
2. Target Note Analysis
Select a target frequency (e.g., A4 = 440 Hz):
Target Freq (\(f\)):
Medium Speed (\(v\)):
343 m/s (Air)
Required Wavelength (\(\lambda = v/f\)):
3. Dimensions & Standing Wave Map
Calculate the length (\(L\)) of your instrument for the Fundamental Frequency (1st Harmonic).
Show your work here...
Sketch Your Instrument:
Scale drawing & label N/A
4. Performance Control
How will your instrument play different notes?
Describe the physical change (e.g., covering holes, pressing frets) and how that change affects the wavelength and resulting pitch.
Volume Control:
How will the player increase the amplitude of the waves without changing the frequency?
Architectural Summary
Total Length: __________ cm
Mechanism: __________
Acoustic Mastery Assessment Unit Assessment
Acoustic Lab: Resonance & Waves
Cadet:
Score: ____ / 40 Class: 9-PHYS
Section 1: Signal Identification
1. If a sound wave's frequency is tripled while its speed remains constant, what happens to its wavelength?
It triples in length.
It stays the same.
It is reduced to one-third.
It becomes nine times longer.
2. Which of the following determines the speed of a sound wave?
The amplitude of the source.
The frequency of the source.
The pitch of the sound.
The properties of the medium.
3. A point on a standing wave that experiences zero displacement is called a(n):
Antinode
Node
Crest
Rarefaction
Section 2: Tactical Calculations
4. The Doppler Shift Scenario
[6 POINTS]
A police car siren emits a constant 1200 Hz tone. You are standing on the sidewalk as the car approaches you, passes you, and drives away. Describe the apparent frequency you hear at each stage. Explain WHY the frequency shifts using wave compression/stretching.
5. Speed of Sound Calculation
[6 POINTS]
On a warm day (30°C), a student claps their hands near a large canyon wall and hears an echo exactly 2.4 seconds later. Calculate the distance to the canyon wall.
Final Answer:
Section 3: Structural Resonance
6. Explain the concept of "Natural Frequency" and how it relates to the phenomenon of resonance. Provide one example of resonance being Useful (e.g., an instrument) and one example of it being Destructive (e.g., a building or bridge).
End of Acoustic Mastery Assessment // 9th Grade Physics Unit 04
