I'm doing a piece of A-level physics coursework at school at the moment and seens I do Maths as well this shouldn't be hard for me, but I just can't get my head around it. So, any help would be really apprieciated! For my coursework, I'm testing different materials for sound-proofing and then looking at the structure of the material - seeing which works best and why. One side I have a signal generator with a speaker set a set distance away from a microphone and an oscilloscope (that measures the potential difference, or the voltage). In between the gap I insert materials and measure the change in the voltage (for example, with just air in the gap I recieved a reading of 20mv, when cardboard was inserted it dropped to 10mv). After my first practical I realised a problem...I didn't even think to take into account the thickness of the material, and they were all of different thicknesses! I spoke to my Teacher about this and he came up with the idea of using an equation using logs to find a constant that would over come this problem. He said: He said that plotting the Voltage (from the material) against thickness would result in an exponential curve and hence you could state: Vm = Vo x e^(-ct) Where Vm is the voltage from a material (the reading), Vo is in air, c is some unknown constant and t is the thickness. He then took logs (simple enough): lnVm = lnVo - ct lnVo = lnVm + ct Then apparently you can plot lnV against t to get a gradient, which is C. Could someone please explain how you get from that final equation to plotting that graph? And also how I would reapply the answer with the constant to my old data to form the new more exact data. Thanks, Rich. Sorry about the long read!