1-5 Oscillations
Are physical objects elastic in character?
When asked this question our first instinct is almost always no. We can't imagine a steel rod or piece of wood having the same elasticity of a coil spring.
However, let's think about a block suspended from a spring. If we pull the block straight down and release it, the block itself will oscillate up and down with simple harmonic motion.
This can be seen here: Simple Harmonic Oscillator
Also let's consider a column filled with air. The cyclinder contains a piston that can slide up and down the cylinder at will. If we pull out the piston we stretch the air column. However, since the pressure is greater outside the cylinder it is hard to hold the piston out at this position. Once we release the piston it will shoot back to equilibrium position because of the elasticity of the air in the column.
Clearly, any object which is compressed or stretched from its equilibrium position will oscillate with simple harmonic motion.
Oscillations in Music
When an object goes through deformation due to an external force it will oscillate with definite frequencies called their natural frequencies.
Can you think of some examples where instruments are being deformed by an external force?
You may have envisioned a drum head being struck by a drum stick, a string being plucked by a finger, or a reed vibrating from the air being blown on it. These are all examples of a physical object being set into simple harmonic motion by an external force.
You can find other examples from other students here:
Please read through the list and add any other examples of an external force starting simple harmonic motion in music.
Resistance
As oscillations continue there are resistant influences which will use up the energy required to oscillate.
What do you think are some common resistant factors?
Air is a common resistant factor in music. Also, real oscillators will always lose energy to friction.
As the oscillations meet resistance the amplitude (size of the wavelength) will decrease until oscillations have stopped altogether. At this point you would hear no more sound coming from the instrument.
Continue: #REDIRECT 1-6 Sound Waves
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