Hello everybody and welcome back to my blog. Last Thursday I posted a post about Frequencies and the Spectrum and Friday I saw a post on Facebook that I so wish I would’ve seen before the post so I could include it in it. So I decided to go a little further on the topic. This is what I saw in the post:
This video gives an awesome example of what a sound wave looks like. You will notice that the lower sounding strings(top) is at a lower frequencies, therefore the wave is longer. The higher sounding or frequency strings vibrate faster. Another thing that you might notice is that the louder the sound or the harder he strums the strings, the more vertical range there is to the wave. This is called the amplitude of the wave.
Going along with this same type thing, lets talk a little about resonance. Resonance is the frequency at which an object vibrates. Have you ever seen a flag pole that is shaking in the wind? The pole is shaking because the speed that the wind is blowing is causing the pole to shake at it’s resonant frequency.
I’m sure many of you have heard how some singers claim to be able to break a glass just by singing, or see it in the movies or something. Some of you may wonder if it is even possible. I guess anything is possible, but breaking a glass with just your voice is not very probably. However, breaking a glass with sound is a different story. By using the resonant frequency of the glass, it came be done, and rather easily. Most glass resonates at about 50hz. You can hear the resonant frequency of a glass by taking it and rubbing your wet finger around the brim of it. I’m sure all of you have done this at one point in time in your life. So if you take this frequency and put it in a frequency generator and put a speaker next to it aiming at it and turn up the amplitude, or volume, of it, eventually it will break. Want to see it done? Check out the video below…
All of this being sad, just how destructive can sound waves be? Unfortunately the citizens of Tacoma Washington found out very fast on November 7, 1940. Much like a flag pole or a glass, other structures have the same thing, a resonant frequency. Watch the video below. All it takes is a little push and this bridge really gets going. The winds on the day this happened were blowing at a steady 42 mph. This caused the bridge to start to vibrate and sway at just the right frequency where it produced a very large example of a sin wave. Check it out, particularly look at the sides of the bridge, you will see a very well defined sin wave.
Tacoma Bridge Collapse in 1940
I hope that yall have enjoyed my last post. Has anyone seen any other practical examples of frequencies or resonance? Please share them with us in the comments.
As always, thanks for stopping by. Please share this post with your friends, like me on facebook and follow me on Twitter, Google+ and LinkedIn. Until next time, stay thirty my friends…oh wait, sorry couldn’t help myself, it just jumped into my head…
73 de Curtis, K5CLM
Creator and Owner of Everything Ham Radio
Owner of 2xC Products at 2xcproducts.com