February 2017 Newsletter:

Signal to Noise – An Explanation

The relationship between signal to noise is something we environmental scientists, engineers and geophysicists need to understand and work with on a regular basis. But it is an important issue in all aspects of engineering and in life.  What is exactly do I mean when I talk about the signal to noise relationship? Generally, we can think of the signal as the desired target result of an experiment or test. In contrast, the noise can be viewed as the background interference, or really everything else that can get in the way of focusing on the signal. More practically, let’s take Valentine’s Day as an example. You decide to buy your wife a new shovel for this romantic holiday. When you ask her what she thinks of it, she responds, “it’s fine.” There is a good deal of “noise” incorporated into the result of this experiment. By finding a way to remove the noise and focus on only the true result, we may see that her true signal response is something more like, “what do you think, dear?” Marriage can be the ultimate experiment in interpreting signal to noise ratios.

When I was studying geophysical data processing, I had an instructor that defined noise as unwanted sound. Another practical example would be if your stereo emits a hissing sound as you try and listen to your favorite album. Here, the music is the signal and the noise is…well the noise. Similarly, during a geophysical seismic test we are trying to record a specific noise signal (let’s call this the music playing), and at the same time eliminate all other background sound vibrations (or that pesky unwanted hiss in the background). If done correctly, it is quite amazing what a concerted effort to reduce noise vs signal can accomplish.