Project on Sound Absorption: Investigating Results

[Cyan]

Hi. As part of our physics course we have to make an independent investigation into a subject of our choice. I took a simple sound absorption idea.
Basically, i took a signal generator, a speaker, and a decibel meter. With the speaker and the decibel meter 30 cm apart and a material in the middle to measure the relative sound level detected.
That was the first experiment i did. In an ajoining small room, in an english science lab. so all the walls and floors are hardwood or brick. The readings seem kinda erratic, as the different readings are all out of phase. I really don't know what to pin the readings down to, so i don't know what I'm measuring here.
I thought that the peaks and troughs on the graph could be attributed to minimums and maximums of the waveform. But then after a long, painful, amount of time i think i was just getting mixed up and of standing waves (where the minimums and maximums would remain stationary and not move through the air?)

I'm supposed to be analysing that data but I really don't know what im' doing and I'm getting kinda desperate.

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after taking those readings i hadnt graphed them because they looked too random. (stupid mistake) so i moved into a different room (bigger room with less clutter) and took another set of readings. this time, i was fortunate to have a laptop with me so i took waaay more readings as most of it was automated.
I get something completely different, the amplitude drops dramatically below 250 hz periodically. i was thinking that the speakers were so positioned that an echo within the room created a standing wave that destructively interfered making the amplitude drop. ... but then why isn't there constructive interference too?

i'm sort of worn out, and I'm afraid i mightn't have explained things very well. help is appreciated though. i attached some graphs i made on-the-fly, just so you can see what I've been murmuring about.

 

[wais]

Hi there,

It sounds like you have been working on a very interesting project on sound absorption. It can definitely be a challenging topic to investigate, so it's great that you have taken on this independent project.

From your description, it seems like you have already done a good job setting up your experiment with the signal generator, speaker, and decibel meter. However, it sounds like you are having some trouble interpreting the data you have collected.

Firstly, it's important to make sure that all of your equipment is properly calibrated and that you are taking accurate readings. It's also a good idea to repeat your experiment multiple times to ensure consistency in your results.

Regarding the erratic readings, it's possible that they could be due to external factors such as background noise or interference from other sources. It's also important to make sure that your materials are set up in a way that accurately simulates real-life situations.

In terms of the peaks and troughs on your graph, these could indeed be attributed to standing waves. Standing waves occur when the sound waves reflect off of surfaces and create areas of constructive and destructive interference. The stationary points, or nodes, of the standing wave correspond to the minimums and maximums on your graph. It's possible that the different readings you are getting could be due to changes in the positioning of your materials or the setup of your experiment.

Moving on to your second set of readings, it's interesting that you observed a drop in amplitude below 250 Hz. This could potentially be due to the phenomenon you mentioned of echoes within the room creating standing waves that interfere with the sound waves produced by your speaker. It's possible that the positioning of your speaker and the dimensions of the room are causing this effect. However, it's also worth considering other factors such as the materials used in the room and any obstructions or objects that could be affecting the sound waves.

Overall, it seems like you have already made some great observations and have some interesting data to work with. It's important to continue exploring and considering different factors that could be influencing your results. Don't be afraid to reach out for help and guidance from your teacher or other resources if you are feeling stuck. Keep up the good work!