Have you ever noticed how some sounds catch your attention and others do not? For example, you are driving down the road thinking of your plans for the day and all of a sudden you hear a squeak in the dashboard. It draws your attention immediately, while the air conditioning fan likely does not. The squeak is intermittent (and likely tonal, but that’s a topic for another blog) and therefore stands out over the more constant sound of the fan. This reaction is similar to vision, where our attention is drawn by moving objects much more so than stationary ones.
This phenomenon can be observed with noise in buildings also. Some people are not bothered by the constant fan noise from an air handling unit, but they key into the compressor sound, which cycles on and off. That is, unless the air handling unit noise is too loud, and that is again another topic. Similarly, open plan office occupants are often distracted by the sounds produced by others (talking, ringing phones, rolling carts) but are typically tolerant of electronic sound masking systems (constant background sound that helps reduce distraction).
Next time a sound catches your attention, consider what type of sound it is, constant or intermittent. If it is a continuous sound, how long did it take you to notice it? If it is intermittent or varies with time, did you hear it against a backdrop of continuous noise or under some other condition? I hope you have fun with this bit of acoustical training.