Tonal quality matters in terms of perception of noise, not just amplitude. We've all experienced the noisy, rattle-trap air con in hotel rooms before. The lower-pitched hum of the compressor doesn't bother us, but you better believe that plastic grille rattling away at a higher pitch most certainly does. A mosquito is tiny and relatively quiet, but one flying around your room will keep you awake. I've run into similar issues with sound reinforcement (large PA systems). I've had times where the solution for noise complaints was larger, full-range drivers instead of the small, frequency-restricted drivers they had installed.