Musical Instruments

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Hearing test

Chladni Patterns

Some sound help
Longitudinal waves
Longitudinal waves are compression waves where each vibration makes molecules of air group closer together and leaves areas of rarefaction or low pressure. The waves travel in all directions from the source of the sound.
Compression (high pressure)
Where the molecules are packed closer together
Rarefaction (low pressure)
Where the molecules are thinly spread.
Oscilloscope is a device which shows a display of sound waves as a wavy line.
Pitch is the number vibrations per second or hertz. This sounds like low or high notes.
Amplitude is the loudness or volume of the sound.
Speed of sound at 20°C
The speed of sound in 20°C in air is 344m per second. So it takes one second for someone to hear a sound from 344m away.
Effect of heat and cold
Sounds travel faster in warm air and slower in cool air.
Speed of sound in water
Sound travels at 1525m per second in water and 5500m per second through steel.
What are echoes and what kind of materials let them happen?
Echoes are reflections of sounds. Echoes happen off of solid, hard surfaces. Soft surfaces do not produce echoes.
Describe Chladni Patterns and think about how they are made.
Chladni Patterns are made when a flat metal plate vibrated over a speaker producing sound waves. As the pitch increases the pattern becomes more complicated.

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