anaswer question on the video

https://www.youtube.com/watch?v=URrEtyFSENc&feature=youtu.be
Watch & listen to the video. 

1) Adjust the volume on your speakers or headphones to a comfortable level.  You can use the ad at the beginning of the video for this.  Watch the video in “full screen” mode.

2) Listen to the video and observe the oscilloscope  showing sine waves that correspond to the changing frequency on the screen.  (Do not change the volume on your speakers!)

3) Answer the following questions:

a) What happens to the oscilloscope tracings as the frequency of the tones increase from 20 to 20k Hz? Why?

b) What happens to sound as the frequency changes through the range of 20 – 20k Hz?  why?

eg.  Were you able to hear all the frequencies?  Were some frequencies inaudible?  Were some frequencies loud and some softer?

  Why or why not?