PHY 113: Speed of Sound- Resonance Tube Student’s name: Ilian Valev Lab partners: Jayanthi Durai, Susan Berrier, Chase Wright Date of experiment: April 15, 2010 Section SLN: 17742 TA’S name: Alex Abstract: This experiment tried to determine the speed of sound waves. To determine the speed, a resonance tube full of water was used and two different tuning forks of known frequency. Each fork was struck above the water level and the water level was slowly moved down until a resonance was heard.
The distance where the resonance occurs were recorded and the speed of the waves were determined. The experimental speed of sound was then compared to the calculated theoretical speed of sound. The results obtained were very close to the theoretical speed of sound thus proving that they were precise. I. Objective. To measure the speed of sound waves in air. II. Procedure. This lab utilizes the following materials: resonance tube, tuning forks, rubber mallet, wooden mallet, measuring tape and thermometer.
Fill the tube with water to about 10cm to the open end of the tube. To adjust the level of the water in the tube, move the side bucket up and down in the vertical direction. Use two different tuning forks and the appropriate head of the mallet. If the frequency is below 1000 Hz use the rubber head of the mallet, if above 1000 Hz use the rubber mallet. Strike the tuning fork with the appropriate mallet above the open end of the tube and slowly start lowering the side bucket so the water level goes down until you hear an increase in sound which is called resonance.
Record the location where the resonance occurred and record the height. After you get the first resonance, repeat by lowering the water further down the tube until you get a total of three resonance recordings. Repeat the experiment with a different tuning fork and record the appropriate data. III. Results. Please see the attached raw data. f ? v H2 mm/sdisc% |480 Hz |0. 708 m |339. 8 ±1. 9 m/s |1. 7% | |1024 Hz |0. 31 m |338. 9 ± 4. 1 m/s |2. 0% | . IV. Data Analysis. The theoretical speed of sound is given by Vtheo = 331. 5 + 0. 606 T m/s where T is the room temperature. Vtheo = 331. 5 + 0. 606 (23. 5 ° C) Vtheo = 345. 7 m/s The wavelength ? and speed were determined from the raw data in the following way: For 480 Hz tuning fork: ? = L2 – L1 ? = 87. 3 cm – 16. 5 cm ? = 70. 8 cm ? = 0. 708 m Vexp = ? * f Vexp = 0. 708 * 480 Vexp = 339. 8 m/s ?V = f * 2 ?
L where ? L = 0. 002 m ?V = 480 * 2 *0. 002 ?V = 1. 9 m/s For 1024 Hz tuning fork: ? = L2 – L1 ? = 39. 8 cm – 6. 7 cm ? = 33. 1 cm ? = 0. 331 m Vexp = ? * f Vexp = 0. 331 * 1024 Vexp = 338. 9 m/s ?V = f * 2 ? L where ? L = 0. 002 m ?V = 1024 * 2 *0. 002 ?V = 4. 1 m/s V. Discussion and Conclusion. The discrepancy between the experimental and theoretical speed of sound were: ? Vdisc = (V– Vthe) / Vthe X 100 where the Vtheo was 345. 7 m/s For 480 Hz tuning fork: ?Vdisc = (339. 8– 345. 7) / 345. 7 X 100 ?Vdisc =1. 7%
For 1024 Hz tuning fork ?Vdisc = (338. 9– 345. 7) / 345. 7 X 100 ?Vdisc =2. 0% The experimental results agree with the theoretical results since the discrepancies were really low. The discrepancy for the 480 Hz tuning fork was 1. 7% while for the 1024 Hz tuning fork was 2% which is low thus proving that the results were precise. The most probable sources of error were the limitations of the measuring process. The measurements relied of human ear to listen and determine when the sound got louder which is highly subjective.
When the experiment was conducted there were other people making noise in the room which slightly could have skewed the results since there was noise interference that could affect the person’s judgment of where the sound got louder. Additionally, the level of the water had to be visually estimated which could have skewed the results a few centimeters. To improve this experiment, it is advisable to use computer measuring tools that could determine when resonance occurs such as a sound wave monitor and computer tools to determine the precise water level.
