Sound is, simply put, weak but rapid fluctuations in air pressure: The air becomes a tiny bit denser, a tiny bit thinner, denser, thinner, and so forth. These fluctuations start at sound sources, for example loudspeakers, and spread out like waves. At the sound wave’s peak, the air is at its densest, while at the wave’s trough, the air is at its thinnest.
When these sound waves hit our ears, our auditory system translates them into something that we can perceive consciously — and thus, we hear that the sound is there. Still, it is difficult to describe, compare, and process these subjective experiences. For example, would you and I agree that this sound is stronger than that sound? And if so, how much stronger is it?
To make sound into something that we can measure, describe, compare, and handle, many different acoustic quantities have been introduced. We use these to make sound into something that we can discuss in a more concrete and objective manner. These quantities affect us all, not least because noise regulations use them to describe how much sound e.g. airports, roads, and concerts are allowed to make. In this article series, we will therefore go through the most important acoustic quantities. In this first part, we begin by discussing what decibels are. This is a fundamental quantity used everywhere where sound is described quantitatively. …
Acoustic quantities, part 1: What are decibels?Read More »