LESSONS: Sound

The majority of lesson ideas below require minimal resources other than the smartphone, and are relevant to introductory physics in high school and college. However, creative individuals are using smartphone science in more complex ways, with drones, engineering kits, and much more. Follow us on Twitter @PhysicsToolbox and see our Publications page for additional content.
Surface Waves and Couder Spheres

What do physical WAVES look like?

Try This

Use the Tone Generator, a speaker, and a small tray of liquid to observe Faraday waves and Couder spheres.

Related Resources

Waveforms Produced by Sound

What kind of WAVEFORMS are representative of HIGH/LOW PITCH and HIGH/LOW VOLUME?

Try This

Use the Oscilloscope to observe waveforms for produced by simple tones (such as tuning forks) and more complex sounds (such as your voice). 

  • Draw a sketch for a high/low frequency sound

  • Draw a sketch for a high/low amplitude sound

  • Compare sounds of the same tone that have a different timbre

Natural Resonance of Sound

What is the relationship between resonant FREQUENCY of a bottle and the LENGTH of the resonating air column? (or the PROPERTIES of a resonating rod?)

 

Try This

Acquire a bottle with a small mouth that can easily resonate by blowing over it. Using the Tone Detector tool, record the resonating frequency produced by the bottle. Record the pitches produced in the bottle at various length (measured with a meter stick) modified by adding or removing water from the bottle. (It is also possible to study the physical properties of resonating rods, including their density/material, length, and Young's Modulus value).

 

Challenge Yourself

  • Create a graph of Frequency  vs. Length of the resonant column of air, and derive a mathematical expression for this relationship.

  • If there are any constants in this mathematical expression, explain their significance.

  • Try the experiment again, and do this instead with a resonating wine glass, using your wetted finger to make the glass resonate. (Note: In the case of wine glass resonance, it is the actual glass - not the column of air - that resonates). Consider how it might be appropriate to measure the variable in question. Try this with glasses of various shapes, sizes, and thicknesses.

 

Related Resources

Forced Resonance of Sound

How many harmonics can be created in a straw?

Try This

Use the Tone Generator at around 800 Hz. Submerge one end of a large straw (such as a "Giant Pixie Stick" straw) into a cup of water so that you can easily modify the length of the closed-end tube. Place the smartphone speaker near the end of the open part of the tube. What length of tube is necessary to generate resonance? Why?

 

Challenge Yourself

  • How many harmonics can be created in a straw with only one tone?

  • What happens to the necessary length of tube as the frequency of the Tone Generator is increased/decreased?

 

Related Resources

Interference

What is the relationship between POSITION between two sound sources and INTENSITY?

Try This

Use the Tone Generator tool on a single smartphone with attached earbuds at 3440 Hz. Separate the earbuds by about 40 cm, and fasten them to a meter stick. Pull the meter stick with the attached earbuds along the length of your ear. What do you hear? Do the same, but pull it along the microphone of another smartphone that records the intensity with the Sound Meter tool. You will notice that the sound intensity increases and decreases multiple times along the length between the earbuds. Why?

 

Challenge Yourself

  • What happens to the interference pattern when the frequency is higher or lower? Why?

 

Related Resources

Beats

What is the relationship between TWO FREQUENCIES played at once and the observed BEAT?

Try This

Use the Tone Generator tool on two different smartphones (ideally, they should be similar phones, so that the microphones are as similar as possible). 

Related Resources

  • Student worksheet from Vieyra Software Beats

What is the speed of sound in air?

Speed of Sound in Air

Try This

Use the Tone Generator tool to cause resonance in a column of air. Use the Oscilloscope to visually observe resonance. Determine the speed of sound in air by measuring the length of a fraction of a wave as it resonates in a column. 

Related Resources

Image provided by https://t.co/96hM9HtwKL

Ambient Noise

How loud is my environment?

 

Try This

Using the Sound Meter tool, measure the average intensity of ambient noise to determine the level of noise pollution that surrounds you. Record values in quiet and loud environments, and compare these values to charts online to determine if hearing damage might result in particular environments. 

 

Challenge Yourself

  • What is the quietest environment that you can possible find?

  • What is the loudest environment that you found?

 

Related Resources

Noise Insulators

What types of MATERIALS block out sound waves?

 

Try This

Using the Sound Meter tool, construct a sonically insulated box using any materials available to you. 

 

Challenge Yourself

  • What materials are best at insulating noise? Why?

Natural Scale

What is the relationship FREQUENCY and NOTE number in the natural scale?

Try This

Using an instrument, play through at least two full octaves of the natural scale. For each note, record the frequency using the Tone Detector or Wave Analyzer.

 

Challenge Yourself

  • Observe the difference in frequency from note to note. What is the pattern in change of frequency from note to note (if any?)

  • Plot a graph of frequency versus note number. What is the relationship?

 

Harmonics

What is the relationship FREQUENCY and HARMONIC number?

Try This

Play a note on an instrument. Observe the FFT graph produced by the Spectrum Analyzer mode.

 

Challenge Yourself

  • Record the main frequency of the note "fundamental," as well as the frequencies of any harmonic(s) produced while the note is played.

  • Compare the frequency of the fundamental to the frequency of the harmonic(s).

Sound Intensity

What is the relationship between the SOUND INTENSITY and DISTANCE from a point source of sound?

Try This

Create a constant sound source by using the Tone Generator tool on one mobile device. Record the sound intensity with another mobile device by using the Sound Meter tool. Using a meter stick, measure how the sound intensity changes as a function of distance from the sound source.

 

Challenge Yourself

  • Create a graph of Sound Intensity  vs. Distance from the sound source, and derive a mathematical expression for this relationship.

  • If there are any constants in this mathematical expression, explain their significance.

  • How would this experiment be different if the tone produced was louder or had a different frequency? Explain.

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