The Listeners by Jordan Tannahill

While lying in bed next to her husband one night, Claire Devon hears a low hum that he cannot detect. And, it seems, no one else can either.

This innocuous noise begins causing Claire headaches, nosebleeds, insomnia, gradually upsetting the balance of her life, though no obvious source or medical cause can be found.

When Claire discovers that a student of hers can also hear the hum, she and the boy strike up an unlikely and intimate friendship. Finding themselves increasingly isolated from their families and colleagues, they fall in with a disparate group of neighbours who can also pick up the sound.