Science Buddies: "Ask an Expert"

My experiment involves testing different frequencies to see how well they penetrate an A4 writing pad. My results have shown that the higher frequencies were affected less by the barrier (eg. they had less change between the level I recorded without the barrier and the level with the barrier).
I have tried to research why this is the case. Sources say that higher frequencies have a higher energy but is that directly relatable to the dB reading on the other side of the pad?
Is there a varying natural amplitude for each sound file that means the results are like they are?

Hi lachlananderson,

A few things:

1. My first concern would be that an A4 writing pad isn't really "big enough" for this project (I assume you are referring to this Science Buddies project: https://www.sciencebuddies.org/science- ... p029.shtml). The writing pad is small enough that sound might just go around it pretty easily, making the results harder to see.

2. Every sound wave has a frequency and an amplitude (you can read more about that in the background section and bibliography of the project if you don't know what I mean). Amplitude is what we think of as "volume" (or the measured dB level) - and ideally that should be the same for each one of the test frequency files.

3. The detailed physics of this are pretty advanced, and involve how vibrations travel through materials and how energy is lost when that happens. As you probably know from reading the background material, sound waves travel through a material because molecules can move slightly and bump into each other. When this happens, some energy is lost, which makes the sound get quieter (decreasing the dB reading) as it moves along. Exactly how much energy is lost depends on the material and the frequency. Atoms in some materials "like" to vibrate at certain frequencies more so than others (this depends on the density and "elasticity", or stretchiness, of the material). So, if you did this experiment with other materials besides the legal pad, you might get different results - there is no general rule like "high frequencies will always get through because they have higher energy." In theory, some materials might be better at blocking high frequencies, but let lower frequencies through. It depends on the individual material.