Contents of this post
Notes from today
- Metronome: A device that keeps the rhythm; aka the “beat”
- The shorter something is, the faster it vibrates.
- We had a demonstration of the vibrating bar from the fall final; the shorter the bar was, the faster it vibrated.
- Both string and wind instruments depend on lengthening or shortening the material that the sound is produced by to create different notes.
- In some cases, the string is thicker (lower notes) or thinner (lower notes).
- Our ears have hearing nerves: The long ones detect low notes, and the short ones high notes.
- As we get older, our short cells tend to die off more than our long ones, so kids and teenagers can often hear sounds that adults can’t
- A dog whistle is similar: The frequency is so high that people can’t hear it, but dogs can.
Sound is the rhythmic motion of air particles. So, similar to thermal energy, it is a type of kinetic energy.
Humans are said to be able to hear from 20 to 20,000 Hz (cycles per second). Test your hearing range with the video below. (I can hear from about 60 to 13,000 Hz.)
When the ball hits the tuning fork:
- Kinetic (ball moving towards tuning fork) moves from the ball into
- Sound energy from the tuning fork.
The video below shows a tuning fork being lowered into a glass of water, shot with a very high speed cameras (about 50 times faster than most cell phone cameras, and even faster than the slow-mo option on phone cameras).
Sample instruments
In the instruments below, notice how the length and/or thickness changes to make a range of notes.
Piano
The longer strings are placed above the shorter ones for space efficiency.
Trombone
Clarinet
Flutes and recorders use a similar system.
Percussion instruments
Ukulele
