Daniella, Jovanny, Sergio Mentor: Jakub String telephone Daniella, Jovanny, Sergio Mentor: Jakub

DIFFERENT STRING TELEPHONES Cans Soda Cans Paper cups Sort of worked, but you couldn’t understand anything through it. Didn’t work at all. Worked best of all the three, you could actually hear the other person talking.

What are we trying to find out? What happens to sound when it goes through a string telephone?

Experimental Setup Microphone Paper cups Speaker String LAPTOP COMPUTER

Experimental Setup Photos

Results – Sounds like experiment Can you hear me now? CLICK ME -> Playing sounds just like our experimental program did – here just samples from 200 Hz to 20,000 Hz every 1100 Hz.

Results - Raw Data This is how our raw data looked like after reading it from the microphone. These are measurements of loudness of sound at many different times. We were taking 44,100 measurements PER SECOND, which is equivalent to CD sound quality.

Results - Raw Data (close up) Here is a close up of the raw data. You see that the sound wave goes up and down, and because the frequency is 1102 Hz it means that each second it goes up and down 1102 times. Here you see 1/100th of a second, so the wave goes up and down approximately 11 times.

Results- Power spectrum The raw data was then trasnformed by Fourier Transform to tell us how loud was the frequency that we emitted. You can see it as this large spike at around 1000 Hz. The height of the peak tells us how well this wave was transmitted by the string phone.

Results Comparison On this plot you see our final results. Green points show what happens when you have a string telephone and red when you don’t. You can see that the sound going through string phone has much lower loudness for frequencies above 6000 Hz because the string cannot transmit those frequencies. This is called the ‘cutoff frequency’ of the system.

Results Comparison However, if you look at the lower frequencies you see that at around 300-1100 Hz the sound going through the string telephone was actually amplified. This is because it was close to the natural frequency of the cup, i.e. a frequency at which it likes to oscillate. Because this is the range of frequencies used by people to talk, you can actually hear others through the phone.

Our Experiences Learned about sounds: what they are and how they travel. Built the experimental setup - string telephones - styrofoam box for sound insulation Run the PC program running the experiment Checked that we can hear beyond 17,000 Hz but Jakub can’t because hearing degrades with age.