1. The problem statement, all variables and given/known data I had a Physics lab with the following setting: A signal generator is connected to a speaker which is located on one end of a tube. This creates the sound wave. The tube is open on both ends. A micro is movable along the tube and it is connected to an occsilator which displays the sinusoidal wave. With the micro I could find the nodes (no sound) of a standing wave. My length of the tube is L=0.9m Now we are in mode n=2 where I have my node in the middle at about 0.45m at a frequency of about 360Hz. I can calculate the wavelength which is 2L/n = 0.9m and the speed of sound in air v = wavelength * frequency. So far I understand. The tube has 3 holes, one at the center and the other two in the middle of the center and the ends. So the holes divide the tube in 4 parts. Now I have to open the hole in the center with the result that the sound is louder (amplitude goes up). I close the center hole and open the other 2 holes. The sound becomes softer and the frequency it throws off the frequency. My question why is that? Why does it become louder when I open a hole at a node and why does the sound becomes softer when I open the holw which is not at a node? Thanks! 3. The attempt at a solution I tried to understand what happens when I open a hole of the tube. I thought I would shorten the length L of the tube and would receive a new fundamental harmonic which would give me a higher frequency and therefore a higher pitch. I am not sure why the amplitude goes up. and I totally do not understand why there is a difference in opening a hole where there is a node located or not. Thanks for any hint!