Methods


Equipment List


For our group, most of the equipment are reusable and eco-friendly. Here is a list of the equipment we use:
  1. 5 gallon water carboy (filled with water) x1
  2. Rubber bands x20
  3. Smartphone/iPhone with Signal Frequency app x1
  4. 1 metre plastic tube x1
  5. Metre ruler x1
  6. Calculator x1


Diagrams of experimental setup  



Figure 1: Tube in the water carboy (set-up with rubber band at the tip of the carboy)

Procedures


Start by  filling a 5 gallon water carboy with water.


Place the tube in and mark the plastic tube with a rubber band at the tip of the water carboy, you will need to download a sound frequency app in your smartphone.
  • Audio Tone Generator Lite by TOON, LLC (App Store)
  • Signal Generator by XYZ Apps (Google Play Store)


After downloading the apps, we can begin the experiment.


Set the signal in your signal frequency app to 500 hz. Place the smartphone/iPhone on top of the plastic tube and raise the tube until you hear a high pitched sound.


After you hear the high pitched sound,  look at the point where the water touches the tube. Then, you pause the sound and take out the tube to mark it with a rubber band at the point where the tube comes into contact with the water.


After measuring the distance between the rubber band marked at the tip of the water carboy, we record the results in Table 4.


We will move on to 750 Hz of frequency and repeat the same process. But, this time we take the first and second highest pitch sound and mark both sounds with a rubber band each. Record the distance between the two rubber bands and we mark it.


It applies the same for 1000, 1500, 2000 and 2500 Hz.


After recording the results, we use Table 1 as a reference for the formula to calculate the speed of sound. (See Yavuz, A., 2015)


Table 1: How to calculate the speed of sound
Physical value
Symbol
Unit
Formula
Frequency
f
Hz = 1/s
f = c / λ
Wavelength
λ
m
λ = c / f
Speed of sound
c
m/s
c = λ × f

Risk Assessment and Management  

Table 2: Risk Assessment and Management Table
Risk
Assessment
Management
The smartphone may drop and its glass screen may shatter, causing it to cut your finger.
Low
Always have a layer of tempered glass on the screen and have a spare smartphone.
We might drop the carboy container, causing it to hurt our foot.

Medium
Pour water in the water carboy only when starting the experiment to lighten the weight of it.
We might spill some water out from the water carboy and students may slip and fall.
Medium
Be careful with the water and be sure to not pass it around too much.
When holding the metre ruler, we might hit someone if we turn around too quick.
Medium
Return the metre ruler immediately to the lab personnel after using it.

Data Analysis
As our experiment is more of a trial and error, we decided to come out with a table questioning the following questions through our results.
  1. Was our hypothesis correct (If speed of sound is 340 m/s)?
  2. What is the average wavelength after 3 tries of each frequency?
  3. What is the speed of sound after conducting our experiment?

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