Myrddin
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Have a project to do on an acoustic resonance chamber, a loudspeaker attached to a perspex box with a copper pipe, there was a microppohne inside the chamber connected to oscillloscope. We investigating a few variables in most detail was route [1]
[1]damping by chainging materials in the chamber carpet foam etc.
[2] using a birch plywood as the ceiling and seeeing the effects
[3] changing pipe size
in [1] the resonant frequencies were recorded for different materials, then reonance curve plotted to find quality factor, reverberation time, abosorption coefficient, we found the carpet was best absorber. But the resonance posistions changed slight WHY is this? can't find any detail explanation anywhere, is it simply due to the change in dimensions caused by introducing the damping material?
[2] Found the birch plywood had quich high aborbtion coefficient, have deduced this is beceause the energy was transferred out of the system by causing the plywood to vibrate thus transferring sound outside? is this the principle on some musical instruments work
[3] This is the trickiest bit that i don't understand and our results are very inconsistent. Seem to find that the changing pipe doesn't add or removed and resonant frequency but seems to change the amplitude. Such that the smaller pipe has a section of frequencies of very high amplitude resonance, and the longer pipe produces the same resosnances but a different section of the resonance have very high amplitude?
Any help/explanation/ guidance will be grateful! otherwise will end up doing this on xmas eve
[1]damping by chainging materials in the chamber carpet foam etc.
[2] using a birch plywood as the ceiling and seeeing the effects
[3] changing pipe size
in [1] the resonant frequencies were recorded for different materials, then reonance curve plotted to find quality factor, reverberation time, abosorption coefficient, we found the carpet was best absorber. But the resonance posistions changed slight WHY is this? can't find any detail explanation anywhere, is it simply due to the change in dimensions caused by introducing the damping material?
[2] Found the birch plywood had quich high aborbtion coefficient, have deduced this is beceause the energy was transferred out of the system by causing the plywood to vibrate thus transferring sound outside? is this the principle on some musical instruments work
[3] This is the trickiest bit that i don't understand and our results are very inconsistent. Seem to find that the changing pipe doesn't add or removed and resonant frequency but seems to change the amplitude. Such that the smaller pipe has a section of frequencies of very high amplitude resonance, and the longer pipe produces the same resosnances but a different section of the resonance have very high amplitude?
Any help/explanation/ guidance will be grateful! otherwise will end up doing this on xmas eve