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--- marvin:lab3 [2008/09/19 12:23] – deva
+++ marvin:lab3 [2008/10/09 21:33] (current) – rieper
@@ Line 1: / Line 1: @@
-=== Lab rapport 3===
+===== Lab rapport 3=====
 **Date:** September 19th 2008\\
 **Duration of activity:** 8-12\\
 **Participants:** Bent and Johnny\\
-In this lesson we will use the NXT sound sensor to turn the LEGO 9797 car into a sound controlled
+**Purpose** In this lesson we will use the NXT sound sensor to turn the LEGO 9797 car into a sound controlled
 car.
@@ Line 43: / Line 43: @@
 The sound was that of Bent speaking directly into the microphone, thus utilizing the entire span of the power spectrum.\\
 The recorded samples can be seen below (MatLab plot):\\
-{{:marvin:Lab3-micsamples.png}}
+{{:marvin:Lab3-micsamples.png}}\\
+Notice that the time resolution is poor due to the low sampling time. When playing back in Wave format it is impossible to recognize any spoken words. Yet the microphone is suitable for recognizing clapping sounds and the like, where you basically just want to measure the amplitude level.
-====Sound Control====
+====Sound Controlled Car====
 Below is the source code we used for testing the sound control:
 <code java>
@@ Line 86: / Line 88: @@
 	    waitForLoudSound();
 	    LCD.drawString("Left    ",0,1);
 	    LCD.refresh();
 	    Car.forward(0, 100);
@@ Line 103: / Line 105: @@
 The code was modified to break out of the innermost loops upon ''ESCAPE.keyPressed()'', instead of using a ''ButtonListener'', since the button listener seemed a bit overkill for the apparent application.
+We tested the program with a threshold of 50, but the car activated the next state by the noise of the motors.\\
+We measured the motors running at about 40-60 in noise level, and changed the threshold to 80 accordingly.
+Click the image to see a movie of the sound controlled car in action:\\
 [[http://www.youtube.com/v/o1V42sYXdH8|{{:marvin:lab3-movie.jpg}}]]
+====Conclusion====
+The microphone was sensitive towards the direction of the sound, see the figure under "Test of the Sound Sensor". We also found that the sampling time was far too low for recoring of speech, but the purpose of the microphone in this exercise was to detect clapping sounds, which it handles very well. By measurements on the readings from the sensor we found that the motors noise level was about 40-60, and therfore the threshold for handclap detection was set to 80.