There is a frequency where touch – the most intimate of the senses – and hearing meet: 20 Hz. And 20 Hz is considered the normal low frequency limit of human hearing (and below: just the rumbling realm of infrasounds).
Sound and touch. A sound that becomes touch, a sound that touches: intimacy (sonic). That is an interesting starting point.
Also because: “the ear is arguably the most underrated and underexplored erotic organ, connecting directly to the imagination – the phantasmatic center of the libido.” 
Phantasm; ghost: back to infrasounds.
“Some scientists have suggested that this level of sound may be present at some allegedly haunted sites and so cause people to have odd sensations that they attribute to a ghost”. 
So: hauntology. Is it just a matter of infrasounds? Maybe infrathoughts? What is the sound of fading past cultures? Is there any (meaning more than what’s already recorded and stored, which is only here and now schizophonically  – c’est à dire like a ghost, somehow)?
Odd sensations: is this how we live in our time (of epidemics and infodemics)?
Too many questions.
But we can look for answers in sounds, tactile sounds that can become tactical: a strategy for our present, now that we lost futures: “is it still possible for us to cultivate shadows?” That seems the most interesting soundscape to explore: “search for the edges of our world, fringed, abandoned places”. 
Away from the ASMR pop bubble (is it?), more of “female voices launched from undetectable locations”, defying and terrifying the power – which, by the way, is always male and noisy. Also: keeping up a collective intimacy  that creates community.
And that’s about the concept and its frame – just scratching the surface. Big work is on content and format. But I reckon I needed to start soundwhere.
 D. Pettman, Sonic intimacy, Stanford University Press, 2017
 Infrasound linked to spooky effects.
 R. Murray Schafer, The soundscape, Destiny Books, 1977/1994. “Schizophonia refers to the split between an original sound and its electroacoustical transmission or reproduction.”
 M. Fisher, A time for shadows, in K-Punk, Repeater, 2018
 F. Arminio, Geografia commossa dell’Italia interna, Bruno Mondadori, 2013 (my translation)
 D. Pettman, idem
 S. Tartaro, Ascoltatori, add editore, 2019 (my translation)
The image is Old school radio by Dimplemonkey on Flickr (published with CC licence BY)