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Sounds of Music

From Science Olympiad Student Center Event Wiki

Though this event is gone for now, it is likely to come back in future years so I might as well write down some basic information while it is still fresh in my mind.

Sounds of Music is an event in which two participants build two instruments, play two songs in a performance that's less than 4 minutes, and explain the physics of sound through an interview or written test.

1 The Instruments
2 Technical Interview
3 Previous Winners
4 Instrument Instructions

The Instruments

There are four basic classifications of instruments. For the best score as possible in this event, you will need to build two instruments from different families.

Chordophones

In Chordophones, sound is produced by a vibrating string. The vibration of strings produces standing waves producing fundamental frequency as well as harmonics (the relative abundance of these make up the timbre of your instrument). Resonators added to the string will enhance the sound by vibrating sympathetically with them.

In chordophones, the wavelength made is twice the length of the string. Since we know that velocity equals frequency time wavelength, after assuming that the velocity of sound in the string will remain constant, we find that when one doubles length, frequency will be cut in half (note goes down an octave). Because the relationship between length and frequency is exponential we know that for every increment one goes up in a scale (1/12), the note increases by a factor of the 12th root of two. You can use this fact for starting your tuning. Unfortunately, you'll need some fine tuning and many hours to get your instrument to play accurate notes due to imperfections in string and to the fact that there will be different amount of tension on different strings (when playing different notes on single guitar string, there will be different amounts of tension). This will result in different velocities of sound in the string...making this form of tuning less reliable.

Examples of chordophones include

Guitars
Violins
Harps
Zithers
Lyres

Idiophones

In idiophones, the vibration of the instrument itself is what creates sound. They are generally the percussion instruments that are hit, shaken, or rubbed to create sound. Resonators can also be added to these instruments to create a sound.

In this event, the major type of idiophones created are xylophones, marimbas, or chimes. So when you double the length of a bar, you cut the frequency in a fourth (put it down two active octave). So in these instruments, to go down an increment of the scale, you must decrease the note length by a factor of the 24th root of 2. These also require you to fine tune (sand/file).

Examples of idiophones include

Xylophones
Bells
Steel Drums
Wine Glasses

Membranophones

In membranophones a vibrating membrane over a resonator creates sound. This would be rather difficult to build, and I wouldn't advise it.

Examples of membranophones include

Tuned drums
Timpani
Kazoo (not sure whether your judge would like it though...and you'd need perfect pitch)

Aerophones

In aerophones, sound is produced by a vibrating column of air within the instrument. Pitch is changed by changing size of vibrating air.

Examples of aerophones include

Flutes
Pan Flutes
Tubas
Trombones
Horns/Trumpets

Technical Interview

The technical interview generally becomes more important as the year goes on (and the competition becomes tougher). This is because your opposition usually gets tougher as well and many more instruments sound 'real'. Because of this, the interview will become a huge separator of teams. Make sure you understand the physics of sound and wave theory, basics of resonance, basics of tempering, and go into as much depth as possible into how your own instruments function. Many people take this part of the competition lightly, but 30 points is nothing to scoff at.

The following website provides much of the knowledge needed for the technical interview portion of sounds of music: http://www.phys.unsw.edu.au/jw/basics.html