Why do people go partially deaf when they have cold?

Answer 1

Sometimes, more so in some people than others, a cold will result in swollen Eustachian tubes along with the typical swollen sore throat and swollen sinuses and nasal congestion. If you blow your nose with force when congested, especially if you hold one nostril closed as you blow, sometimes the nasal drainage is forced into the Eustachian tubes from the nasopharynx. These tubes connect the nasopharynx to the middle ear (also known as pharyngotympanic tubes). When these swell, they can allow fluids, that would normally drain from the ear and tubes, to accumulate and not drain. This can muffle sounds due to the retained fluid behind the ear drum and in the middle ear. This accumulation of fluids can allow bacteria to grow and cause ear infections, as well.

Answer 2

When people have a cold and their estuation tubes can get swollen with the pressure of mucus in ones head. When there is swelling or pressure it makes the sound harder to get through to the ear drum.