Do we only hear sounds? Or can we also hear silence? These questions are the subject of a centuries-old philosophical debate between two camps: the perceptual view (we literally hear silence), and the cognitive view (we only judge or infer silence). Here, we take an empirical approach to resolve this theoretical controversy. We show that silences can “substitute” for sounds in event-based auditory illusions.
I don’t have access to the full paper (I probably wouldn’t understand it anyway), but the idea that we can “hear” silence is pretty mind-blowing to me.
There’s an article about it in the New York Times which apparently goes into much more detail, but I don’t have a subscription- https://www.nytimes.com/2023/07/10/science/silence-sound-hear.html
It is excerpted in this Slashdot post, however, and that may give you enough information to understand it better: https://science.slashdot.org/story/23/07/10/2343221/silence-is-a-sound-you-hear-study-suggests
To sum up, it’s not about total silence, it’s about perceiving gaps in louder sounds as “sound” rather than the lack of sound.
Having read the NYT article (with the PNAS paper still not available through a certain hub), I think a useful analytical framework would perhaps be to think of silence as a negative space. E.g., take some background noise (this could be the environmental noise averaged over some time scale) at certain overall intensity as “zero” (or reference level), then complete silence will have the same frequency content as that background but with negative intensity. From there one can start talking about various forms of “partial silence” as different spectral compositions of negative intensity. I’d even posit that some of the illusions they discovered would work in a similar fashion with positive intensity boost as well (e.g.two disjoint boosts vs one sustained boost). It is probably more about the frequency content than the intensity relative to the reference level.