Introduction: In this project, we created multiple musical instruments and learned about different waves and how they transfer energy like sound and light. Our group, Eliza, Marilynn, Michelle, and I created 4 instruments. Our string instrument was a guitar, and our chime instrument was a xylophone. We used bottles with different amounts of water in them as a wind instrument, and created a drum from a metal trash can, a platter, and a pot lid. This project not only had an cool and interesting final product, but also taught us a lot about sound and waves.
Content: We learned all about longitudinal and transverse waves in this unit. - waves transfer or carry energy and are a form of moving energy Transfer Waves: - Motion is perpendicular to direction of travel. - Anything on the electromagnetic spectrum qualifies as a transverse wave (ex. light, x-ray) - travels fastest through vacuum and slowest through dense molecules Longitudinal Waves: - Motion is parallel to direction of travel - Sound waves are longitudinal - travels fastest through stiff molecules and slowest through gases Doppler effect- sound changes pitch because there is movement towards or away from the sound - There is a higher frequency when the sound is close and lower frequency when the sound is further away
Instruments:
Guitar:Our guitar uses vibrations and tensions to play a 12 note scale. Our guitar classifies as a string instrument and plays a total of 12 notes. It ranges from an F3 to a C4. To reach these notes we have included 4 strings, each having an open note, and two frets to play. Each fret plays one note higher than the last. We tuned the open string by tightening screws that keep the strings in place. We then used the guess and check method with a tuner to place the frets. To find the lengths of the open strings, we used the provided wavelength chart and calculated the length of the longest string. We then just placed blocks of wood on the other open strings to shorten them, and played with the tensions using a tuner. The vibration resonating through the large, wooden box makes the sound louder and the sound waves from plucking of the strings becomes audible. When the string is shorter or tenser, you get a higher not, and when it is longer or looser, you get a lower note.When the string is tight and short the vibration is small and vibrates in a smaller proximity, producing a higher note. When the string is long and loose, the vibration is large and wide, producing a lower note.
Xylophone: Our xylophone is a chime instrument. The longer the pipe is, the lower the note is. We made our xylophone by finding a pre-cut piece of pipe and hitting it with a mallet to see what note it makes. From there we used a chart that told you what numbers to multiply the original length with to create different notes. Our original pipe, the longest one, was 33 centimeters long and an E4. We decided to make our xylophone have one octave of notes. The highest note is E5 at 23.43 centimeters. All of the other pipes are varying in lengths that are between 33 and 23.43 centimeters, but the higher the note is, the shorter the pipe length. The reason why shorter pipes make higher pitched sounds is because there is less time for the sound wave to travel through the pipe. The wave lengths are compressed, which creates a higher pitched sound. That means that the longer the pipe, the more spread out and longer the soundwave will be. If the wave lengths are more compressed, they vibrate faster. The more time they have to rarefy, the slower the waves vibrate.
Drums: Our drums are a vibration instrument, but we did them a little differently. We started out trying to make them like the steel reggae-style drums like the ones in “Under the Sea”, but we had some trouble. We tried to use a cupcake tin to make the note range and were trying to modify the note by hammering it so it would produce a lower or higher sound. This did not work out, and each part sounded like the same metal bang. We also couldn't really get a good read on what note it was making with that metal bang. We decided since we had 3 other instruments that this one would be sort of a background beat, much like a simple drum set with a pot lid as a cymbal, a garbage can as one of the big drums, and a metal platter tray as a sort of snare. We also have two drumsticks made out of wooden dowels and another wooden dowel with a paper towel and duct tape tip on the end for the big drum (it makes a different sound)
The bottles use sound waves, vibrations, and different frequencies to create sound waves, which create notes. Our bottles are classified as wind instruments. For all wind instruments, it is essential to create vibrations. The vibration can be from friction (example: reed in a clarinet), or from splitting air (example: flute). In the case of our instrument, we are splitting the air. Half of the air goes over the bottle and the other half goes into the bottle. This creates each bottle’s unique sound (along with the amount of water/fluid in it). The vibrations created must travel through some kind of tube to actually create a certain note. To find how long the tube must be in order to create a certain note, you take the wavelength of the note and divide it by four. Wind instruments require ¼ th of the original wavelength to create the certain note. To complete one full sound wavelength, the wave must travel from high pressure, to equilibrium, to low pressure, then back up to equilibrium. A wind instrument only uses one fourth of the complete wavelength to create notes. The high pressure is created at the top of the bottle (where you blow into it) and the neutral pressure is where the sound waves exit. If a note has a wavelength of 131.87 cm (middle C), then in a wind instrument the wavelength must be 32.97 cm. This means that the pipe must be 32.97 cm long in order to create that note (can place a hole at same distance for same effect). The bottles we used play notes that range from a C4 to a C5. Our group decided to change the notes by adding different amounts of water into each bottle. The more water that was in the bottle, the higher the note. This is the result of the sound waves vibrating. The bigger the bottle/space provided, the longer it will take for the pressure inside to build up (vibrate) which results in longer frequencies, causing deeper notes. As you add in water, the sound waves’ space becomes restricted and they will start to move faster causing a higher frequency. This results in higher notes.
Reflection: This project taught us a lot about different waves, particularly sound waves. During this project we experimented with different frequencies and created 4 instruments. One thing our group did well was productivity. We were able to work together and eventually finish all of the instruments. For example, we started with the xylophone, and planned out the order that we would make the instruments. Another thing we did well was communication. We had a group chat where we discussed materials and plans. However, we struggled with time management. Each day we did a reasonable amount of work but still ended up having to go in during a few lunches. We also tended to joke around and stray from the task at hand, but this was not a big deal because we still were able to balance the project with having a good time. Overall, this was a fun project, and taught my group and I a lot about sound.