Musical Waves Project

Purpose

The purpose of this project is to is to engineer a device that will help students understand the relationship between the vibrations of an instrument, and the sound waves it produces.

Background Info & Design Task

All sound waves are created by vibration. Nearly all musical instruments have more than one vibration system. For example, in a violin, the string vibrates and the sounding board vibrates. In a clarinet, the reed vibrates and the column of air vibrates.

Engineering Design Task

Your task is to design and build your own instrument that can play “Mary Had a Little Lamb.” You will present your instrument to the class, including an explanation of how it produces sound.

The instrument can only be created with objects found in your home, garage, or here at school. You may not spend money on this project. The recycle bin is a great place to find materials, as is the “junk drawer.”

Helpful Videos

Basics

Tuning

Physics of Guitar

How to Make Notes

Musical notes represent different frequency sound waves. As the notes move up in frequency, they also increase in pitch.

Here is an example of a simple Xylophone. Each note is represented with a different size wooden or metal key.

Notice how each of the notes on the Xylophone is also represented in the chart above.

To make a new note, you have to change the natural frequency of the vibration you are making. In this case, it is the size of the key. Each instrument has its own natural frequency that is changed by the musician either by changing their hand positioning or plucking/hitting a different object.

To find what frequency your instrument is playing, you can download an instrument tuner app for your phone – there are many free ones (this is optional, but may help you find accurate notes).

Playing "Mary Had a Little Lamb"

How to Play “Mary Had a Little Lamb”

“Mary Had a Little Lamb” is actually one of the easiest songs to play! All you need is 3 notes (frequencies or pitches). These notes can be any 1st, 3rd, and 5th note in a row on a frequency chart. Musicians usually give these frequencies letters that repeat from A -G.

The tune is simply this pattern:

5, 3, 1, 3, 5, 5, 5, Mary had a little lamb

3, 3, 3, 5, 5, 5 Little lamb, little lamb

5, 3, 1, 3, 5, 5, 5, Mary had a little lamb

5, 3, 3, 5, 3, 1 It’s fleece was white as snow

(5 = higher pitch, 1 = lower pitch)

Music Project Brainstormer Template

What type of sound do you want to create? (What instrument makes the sound you want to make?)

What mediums do you think would make the vibrations you are looking for?

List some potential materials you may need to make these sounds based on the materials available to you.

*Remember you need to make 3 notes*

Draw a prototype to use as inspiration for your instrument. Put it below

Create a list of steps you will need to complete your instrument. Include materials, and building processes.

Number each step as you go. Make your instructions neat and organized.

Explanation Template

Scientific Explanation:

Medium

∙ Explain what medium(s) within the instrument are vibrating to produce sound.

∙ Explain how the sound waves are transferred to your ear.

“Pitch” of Sound

∙ Explain how sound waves are different for the different notes, correctly using the words wavelength and frequency.

Volume of Sound

∙ Explain how you increase the volume of your instrument.

∙ Explain how sound waves are different for the different volumes, correctly using the word amplitude.

Predicting/Applying

∙ Explain how you would have done this differently with an unlimited budget. What mediums would you use? Why? Talk specifically about the natural frequency of the mediums chosen.

Student Example: 3 String Guitar

Materials Tried:

Wood 2x4 - 2ft

Wood Screws (4)

Cotton String

Plastic Fishing line

(3 strengths)

Cardboard

Hot Glue

Final Materials:

Wood 2x4 - 2ft

Wood Screws (6)

Metal Bolt (2)

Plastic Fishing Line

Cardboard

Hot Glue

Steps of creation:

First, I decided I wanted to make a string instrument. I found a 2x4 that was 2ft long for the “neck” of my instrument.
I used some cotton strings that I stretched out on the plank of wood.
I tied the 3 strings to the ends using screws to hold them in place. I then turned the screws to tighten the strings.
The strings were too close to the wood and didn't make a lot of sound. I added spacers under the string with some bolts. This helped.
I found some plastic fishing line and used 3 different strengths instead of the cotton string. This was hard to tune.
I ended up switching the different strings out for all the same type of string for consistency.
I then wanted to make my instrument louder because I couldn’t hear it very well. So I added a cardboard box under the “neck” of my instrument and cut holes in it to let the vibrations out. This helped to increase the amplitude of the sound produced.

How I created my different notes:

I used the screw to tighten/loosen the strings until I found the frequencies I was looking for. The tighter I made the string the higher the frequency of the sound. I used a tuning app to help me identify the frequencies I was looking for. I used the frequency ratio of 1:3:5 for my composition of “Mary had a little lamb”.

Scientific Explanation:

Medium

∙ Explain what medium(s) within the instrument are vibrating to produce sound.

My instrument is made up of wood, cardboard, and fishing line. When I pluck the string, it sends a vibrational longitudinal wave along the string. The soundwaves then vibrate inward from the point where the strings meet with the instrument. In my case I used a bolt as the “bridge” of the guitar. The vibration bounces around inside the instrument vibrating the air inside the box. The vibration of the box also plays a role in the sounds produced by the strings. Different materials vibrate at different natural frequencies. The box then sends the vibrations outwards through the holes.

∙ Explain how the sound waves are transferred to your ear.

The vibrations move from the instrument through the air as longitudinal waves. These waves push the particles back and forth in the air at a specific frequency and amplitude. The vibrations then hit your ears and your brain recognizes the difference in pressure from the vibrations.

“Pitch” of Sound

∙ Explain how sound waves are different for the different notes, correctly using the words wavelength and frequency.

Each note I play has its own wavelength and frequency. Higher frequency waves come from strings that are tighter and smaller in diameter. This is because the strings can vibrate faster and create higher pitches. High frequency waves have shorter wavelengths and push the air faster than low frequencies. My thicker strings vibrate slower and have a lower frequency giving me lower pitches. The length of the strings also plays a role in the frequency of sound waves that is produced. Shorter strings will bring higher pitch as well. That is why the neck of the guitar is important.

Volume of Sound

∙ Explain how you increase the volume of your instrument.

To increase the volume of an instrument, you need to increase the force acted upon the strings themselves. The more force put into vibrating the string, the higher the amplitude will be.

∙ Explain how sound waves are different for the different volumes, correctly using the word amplitude.

Each sound wave has a different volume which decreases with distance. The amplitude of the wave determines how loud the sound will be. The amplitude is also the highest number of particles that are displaced within the compression of the longitudinal wave. These waves of high pressure is what is shown as amplitude when looking at voice recordings.

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