String Telephones versus Sound tubes... STEM project.... Homemade Science with Bruce Yeany

Hello, I'm Bruce Jania. Today in Homemade Science we're going to take a look at one of the oldest demonstrations I can think of, the string telephone and also the whisper tube. Now we made these out of a lot of different materials to see which ones gave us the best sound. We had about 30 devices that students had to rate for volume, clarity, pitch, and tone. After each test devices were wiped or sprayed down with sanitizer. After collecting results we then tried to draw conclusions based on our findings. The telephone materials fell into three groups, plastics, cardboards, and metals. Now we did try seven different sets of telephones with a metallic diaphragm to them. Now the telephones are set up. I'm going to put a small speaker right inside the can. Quick note, I would like to mention that some of the telephones sound better than they appear, but I've had to filter out the noisy neighbors. Tension of the string of course was a big factor in this. Hello? Anything? Nope. Nothing. We found that the small ones actually worked much better than the larger ones. Next up let's try a couple telephones that were made out of plastic. We also tried various sized plates and bowls. What? How does this thing turn on? We tried making a telephone out of large five-gallon buckets. How does this thing turn on? I don't know. There aren't any buttons on it. I was curious whether this position worked. I'd rather be out here talking on the phone than in class. We also tried using two soda bottles that were cut in half. Is it working at all or not? Definitely Now one of the favorites was actually two containers attached by a long metal spring. The springs were only okay as telephones but made great sound effects. That sounds so weird. It sounds like something from Star Wars. We had a variety of containers made out of cardboard. Various cups of different sizes. We had cardboard boxes. For example here's some cereal boxes that were used and different size containers that had food in them. The cup can hear. Science is my favorite subject. We also tried two-way telephones which worked surprisingly well. We found that the boxes and soda bottles were least effective. We got good results from the Pringles cans, plastic cups, plastic plates and bowls and the best results were from paper cups. Now how does this actually work? What are your plans for today? Now the explanation of course starts with sound chopping as a wave. We can demonstrate the type of wave with a slinky. This is an example of a compressional wave where the particles move forward and backward when the spring is pushed. Now if we take a look at a radio speaker we find that electrical impulses causes this surface to move. It moves forward and backwards to make sound. Now when I talk into this cup the compression waves from my voice causes the bottom of the cup to vibrate just like the speaker did. With two cups connected by the string the string acts to transmit the vibrations from one side to the other and on the bottoms that string causes an opposition of movement. You can see as one moves forward the other one moves backwards. So that opposite side is then acting just like that speaker. Now that we've taken a look at the string telephones let's go on and take a look at the whisper tubes. This is simply a garden hose that I've added two cones on to the ends of it. I'm talking to you with a garden hose. That's kind of weird. But it works great. Yeah we should just replace all the garden hoses. I perfectly agree. My favorite sound tubes is using a pool hose. Now this hose is 40 feet long. It's one and a quarter inches in diameter and you should be able to hear it fairly clearly. Now let's try a little bit of music. This is something that I had set up in my classroom for a number of years. Students could test it as it sat on a shelf or in the hallway. Can you hear me? Uh we can hear you. Okay cool. So how does a whisper tube work? When sound is made in an open area the compressional waves move out in all directions and the wave energy quickly diminishes as you get further away from that sound source. Now when the sound energy is directed inside the tube all that energy is focused in the same direction so it ends up traveling for a much further distance before it dies out. Now our next whisper tube is going to be made out of these cardboard carpet tubes. Hello. Yeah this sounds sounds clearer than a telephone. Hello. Hello. Yeah this is what they must have used before telephones. Yeah this is awesome. Hello. Is correct. Sound tubes were invented way before the telephone and were used in buildings and ships and they're still used today. This is the test of our whisper tube made from carpet tubing. It is four pieces that are 12 feet long. Hopefully you can hear me at the other end. Now let's try some music. Now when students looked at the whisper tubes it was interesting that quite a few of them gave them perfect scores in all four categories. In the future we're going to take a look at the whisper tubes again and also the string telephones. I'd like to see if I can improve its efficiency by changing the size and the type of diaphragm that's used and I also want to take a look at the horn and see if we can come up with a better design that's going to make it. Well I hope you enjoyed this video and please come back and see me again. Okay bye.