Unit 9: Sound and Waves continued

In continuation of unit 9 we learned more about sounds and waves. Sound is the longitudinal wave from vibrations. We learned the range of sound for humans. Humans range of hearing usually is around 20Hz to 20,000Hz. Ultrasonic sounds, sounds that are over 20,000Hz are very high pitched and are what bats and dogs hear. In fact, bats use ultrasonic sounds to communicate. Infrasonic sounds are sounds that are below 20 Hz and are used by elephants to communicate. These types of sounds are so low pitched that we can't hear it. That is why animals can sense things happening, like natural disasters, before they actually happen. So, if I ever see my dog going nuts, I will run for my life (I'm just being dramatic).

We also learned that refraction is the bending of waves due to the change in medium and reflection is the bouncing of waves. Resonance is the building up of energy and dispersion is the spreading of waves. we also learned that sound travels fastest in solids, next fastest in liquids and slowest in gases.

In class, we did a lab using tuning forks. We filled a graduated cylinder with water and had a tube inside. We then jolted the tuning fork so that it would begin to vibrate. Then we held the fork over the tube while moving the tube up and down to find the perfect length of 1/4 of a wave. Each tuning fork has a specific note that it makes when vibrating. After finding the 1/4 of a wave we multiplied it by four to find the length of one whole wave.

In the picture above, I am making music with the wine glass with water in it. I am making the glass vibrate so that it creates a sound with different pitches depending on how full the glass is of water. Pich is the frequency of sound Unfortunately, I just lied to you because the wine glass in the picture is made out of crystal and doesn't have the same effect.