Resonance... Resonance... RESONAAAAANCE!

In this lab activity, we had to determine the speed of sound and frequency experimentally. Using a resonance tube setup comprised of a long, glass tube, a water reservoir, and a speaker with adjustable frequency, we were able to measure the lengths at which resonance occurs.

Frequencies at 400, 600, and 800 Hz were sounded via speaker unto the resonance tube. By lowering the water reservoir, the water level also lowers; making the length of the tube (air) longer. At some points on the tube, a loud sound could be heard: this is called resonance. Resonance occurs when there is constructive interference that results to rapid increase in the amplitude of the vibrating body. The points were measured from the tip of the tube and were recorded as Ln. Differences between consecutive lengths were taken to obtain ΔL. These were then averaged and noted as Laverage.

To get the value for the speed of sound, the wavelength should be known, since the frequency is already given. Using the relationship ΔL = (1/2)λ, the average wavelength was obtained for each frequency. Hence, the speed of sound was calculated using the equation Vs=λ/f. Averaging the experimental values and comparing it with the actual value (which is temperature dependent), we obtained a 2.06% error.

In determining the unknown frequency, it was hard listening to the tuning fork because the amplitude of the sound seemed to be lower at longer distances. Instead, we set the speaker at random and did the same procedures as above. Using the speed of sound from the first experiment, we calculated a frequency of 514.8 ± 5.2 Hz.

This experiment tested our patience. Well, we had to go out of the lab because our apparatus was leaking. We did our activity with occasional mopping of the floor (which I quite enjoyed doing :)). It was also hard to listen to the sound especially when outside the class (in this case, steel balls were hurling towards wooden planks -- projectile experiment of another class), so we made about two to three trials for each frequency. However, it was thrilling to calculate and see that our measurements made sense :D