Why is it when you have a cold or allergies which block up your sinuses and ears, noises close to you – within the same room or a few feet – are extremely loud, but background noises and noises some distance from you – the next room over – are so muted?
Your ears have tubes that go into your throat. These can be blocked by congestion, and get covered themselves.
This blockage limits that airflow that the ears use to detect sound. Louder sounds and sounds of certain frequencies overcome this blockage, or are impacted less, but others cannot.
Kind of like getting water in your ears, but the other side of the eardrum.