Intake recommendations for iodine and other nutrients are provided in the Dietary Reference Intakes (DRIs) developed by the Food and Nutrition Board (FNB) at the Institute of Medicine of the National Academies (formerly National Academy of Sciences) [2].
Answer. The ear canal has very delicate skin; even a hair may cause itching in the ear. So no wonder itching or irritation is a common complaint from the hearing aid user who comes in for a follow up visit.
The ear canal protects the eardrum and acts as a resonator, providing about 10 decibels (dB) of gain to the eardrum at around 3,300 Hertz (Hz). The net effect of the head, pinna, and ear canal is that sounds in the 2,000 to 4,000 Hz region are amplified by 10 to 15 dB.