There is a tympanic membrane between the outer and middle ear. It maintains air pressure balance between the two, aids hearing and prevents the ingress of contamination. So as long as it is intact, the air cannot enter the body through it!
What might be the possible reason behind the recommendation to cover the ears –
In ancient India, Parda pratha (Covering the face lower down with Ghungat) was a social practice to ensure the safety of females from molestation.
Ghungat was not only nuisance and uncomfortable to mothers, but it used to interfere in newborn care too. Also, in cases of emergency, the mother would not be able to recognize in time and act fast to safe guard the baby.
So our elders logically proposed to replace the Ghungat with a cover on head and ears to aid in baby care without interfering with the sanctity of rituals and social beliefs.
The information is shared to create awareness towards Pregnancy and Childcare to reduce maternal and child deaths. Atmost care has been taken by the author to include the verified information from authentic sources. However, kindly discuss the same with your health care provider before implementation.