LEGO Guitar

In our second Light & Sound unit we learned about what sound is, how it is made and heard, how it travels, and other fundamentals of sound. I am most proud of the science concepts learned such as how to graph sound waves and learning what each variable stood for. Our action project is about about creating sound waves and making an instrument that can be played by the Landfill Harmonic. We were each instructed to build a guitar from scratch. This would show how sound is produced and amplified.

The guitars we built work like a normal guitar: the strings vibrate the air, and the body amplifies the vibrations, projecting a louder sound. When you press on the strings you change the length of the vibrating which changes the pitch. The lower on the neck you go the higher the pitch.

The sounds the guitar makes show all the principles we learned. Sound waves are molecules contracting and expanding, which is shown on the guitar with the vibrating strings. They make vibrations in the air which are just contracting and expanding molecules. Wavelength is the distance from one peak/crest/trough to the next peak/crest/trough. The shorter the guitar string length the shorter the wavelength. Pitch/frequency is how fast a wave travels (how many cycles there are per second). Each string has a different pitch, and if you change the length of the string by putting your finger down, it will change the pitch. Amplitude is how high/low the wave is, the guitar’s body demonstrates this by amplifying the sound the strings make.The amplitude is how loud the sound is, the higher the amplitude, the louder the sound is.

All the dimensions are shown in the picture below. The rubber band width was .26 mm and the fishing wire width was .47mm. The volume of the body was 74 7/32 squared inches and the volume of the sound hole was 15 5/8 squared inches.

AG Guitar Sketch (2015)

After building the guitar we also found the frequencies and wavelengths of the open notes and the octave notes of both strings. The rubber band string was a G note, the open note frequency was 403.4 Hz and the wavelength was 185.8 cm, the octave note frequency was 806.8 Hz and the wavelength was 92.9 cm.The fishing wire string was an A# note, the open note frequency was 455.9 Hz and the wavelength was 657.6 cm, the octave note frequency was 911.8 Hz and the wavelength was 328.8 cm.

AG Guitar Front (2015)

AG Guitar Side (2015)

Another thing we learned about in this unit was the Doppler Effect; this is the phenomenon that makes a sound’s pitch seem to get higher as it travels towards you and lower as it travels away from you. Really the pitch stays the same the whole time, but it sounds like it changes because the waves get pushed together and overlap when the sound is moving towards you, and spread out when moving away from you.

I really enjoyed this action project and had fun making the guitar. However, if I could do this project again I would add more strings and add tuning pegs so I could change the tension of the strings as well. That way it would be even more like a real guitar.