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Update authored by Steffan Lildholdt's avatar Steffan Lildholdt
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Lesson-3.markdown
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......@@ -18,9 +18,20 @@ The plan is to follow the instructions for Lesson 2 [1].
### Exercise 1 and 2
TBD: Tilføj billede af test setup.
Due to the similarity between exercise 1 and 2 the results have been joined together.
In order to test the sound sensor we made a test setup were the LEGO car was placed next to a computer loudspeaker playing a monotone sound (440Hz sine wave). The leJOS data logger was used to collect the sound levels recorded by the sensor. The setup is seen in figure 1.
![Exercise 2 - Test setup](http://gitlab.au.dk/uploads/rene2014/lego/a6a24b2215/Exercise_2_-_Test_setup.jpg)
Figure 1 - Test setup
By manually lowering the sound level on the computer with a certain interval we expected to see a constant decrease in the sound measurements. The result from this exercise is summarized in figure 2.
![Measured sound level as a function of sound level from a mac pc](https://gitlab.au.dk/rene2014/lego/raw/ffd008e7c3df32eb42b20f306dc2ff655fd9a17b/Week5/Measurements/SoundLevelMeasurements.png)
Figure 2 - Sound level measurements
According to figure 2 we can see the expected step wise decrease in the measurements from time = 0 to time = 25. We noticed that the step size is also decreasing as the sound level is lowered. There could be multiple reasons for this. At the moment of writing we are not sure that the lowering of sound on the computer is performed linearly. In order to test this we need a calibrated microphone which is able to provide us with the exact sound level in decibels. The small variations seen along the measurements are probably caused by quantization noise in the A/D converter.
At time = 28 a high peak is detected. This was caused by a nearby group making a sound which affected our measurements. At time = 35 we stopped the test and began to talk which caused irregularity in the measurements.
### Exercise 3
The SoundCtrCar.java program have four states. Whenever a loud sound is recorded, the state will be change.
......@@ -46,4 +57,5 @@ TBD: Code snippet, video, calibration:-30, raw values are inverted compared to p
## Conclusion
## References
[1] http://legolab.cs.au.dk/DigitalControl.dir/NXT/Lesson3.dir/Lesson.html
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[1] http://legolab.cs.au.dk/DigitalControl.dir/NXT/Lesson3.dir/Lesson.html