Day 3

After awakening from whatever sleep we could get, we headed straight for the jetty. The setup of the equipment was the same as day 2. Our supervisor, Shane, did make some minor changes to eliminate the annoying electrical noise interfering with our result taking yesterday. Here are some photos of the setup:

Firstly, we took a depth measurement with the marked rope. The depth of water today was 1.9m.

The transmitter was then suspended in the water by attaching the two ropes on its sides to the sides of the jetty. A wire was connected from the transmitter to the signal output, which was set up on the table alongside a laptop plus a signal generator.

(System)

A underwater microphone was linked to an amplifier that was also connected to the laptop, thus the laptop recorded both the signal output and the signal recording. We then used the depth meter to actually drop the underwater microphone and hang it directly in front of the transmitter, with the depth meter being used as a measuring device for the distance between the transmitter and the mircophone.

Data Collection
The independent variable was the distance between the transmitter and the mircophone
The dependent variable was the time taken for the microphone to receive the signal
The control variable was the strength of the signal, the depth of the transmitter and the microphone.
With the distance varied every 20cm, and 20 pulses emitted for a duration of an average of 25 seconds, we are able to record through the microphone, thus able to later view the track's on laptops through a program that visualise the waveform of sound.

Problems encountered 
1) Water current- The water current would inadvertently cause the microphone and the transmitter to oscillate back and forth, and not exactly in phase, causing fluctuations in the distance between the two
2) Snapping shrimps- The underwater microphone is extremely sensitive, thus picking up the bursting of bubbles created by the shrimps, interfering with the signal and causing problems in identifiying the signal recieved.
3)Ships passing- Jetty ships, speedboats, all cause underwater sounds just as much as in air. But as sound travels way faster underwater, the underwater microphone is able to detect ships' movement literally miles away.

Outcome
Altogether 23 tracks of recording were collected, with about 5 of them being duds. We were able to then identify between the interference and the signal recorded in each track. Collecting data of the tracks is important to identifying the trend in signal recieving