What is sound?
This blog is about auditory perception, or the perception of sound. But what exactly is sound?
It's a silly question, of course, because it's quite difficult to imagine anyone being unfamiliar with the concept. I would even go so far as to suggest that most people could provide a decent definition. It's something about vibrations in the air, isn't it? Yes.
Cambridge Emeritus Professor Brian Moore defines sound as follows (2013; p. 2).
Sound originates from the vibration of an object. This vibration is impressed upon the surrounding medium (usually air) as a pattern of changes in pressure. The atmospheric particles, or molecules, are squeezed closer together than normal (called condensation) and then pulled farther apart than normal (called rarefaction). The sound wave moves outward from the vibrating body, but the molecules do not advance with the wave: they vibrate about an average resting place. The vibrations occur along an axis that is aligned with the direction in which the sound is propagating. This form of wave is known as a "longitudinal wave". The sound wave generally weakens as it moves away from the source, and also may be subject to reflections and refractions caused by walls or objects in its path. Thus, the sound "image" reaching the ear differs somewhat from that initially generated.
What I especially like about this definition is the use of image in the last sentence, which foreshadows something that psychoacousticians often do in their research, namely use vision as an analogy for audition.
Sound has several distinct meanings in modern English, but it described the physical phenomenon first. The word appeared in the 13th century. It comes from Latin sonus via Anglo-French son and the Middle English soun.
Merriam–Webster provides the excellent following trivia.
English contains several sound homographs, all with distinct histories. For example, the sound that means "something heard" descends from Latin sonus ("sound"), whereas the sound that means "to measure the depth of water" traces to Middle French sonde ("sounding line"). Another sound, as in "of sound mind and body," is the contemporary form of Old English's gesund. Gesund is related to several words in other languages, such as Old Saxon gisund ("sound"), Old Frisian sund ("fresh, unharmed, healthy"), and Gothic swinths ("sound" or "healthy"). Another relative is Old High German's gisunt ("healthy"), which led to modern German's gesund, the root of gesundheit.
References
Merriam-Webster. (n.d.). Sound. In Merriam-Webster.com dictionary. Retrieved May 6, 2022, from https://www.merriam-webster.com/dictionary/sound
Moore, B. C. J. (2013). An introduction to the psychology of hearing (Sixth edition). Brill.