This is the traditional microphone that is built into hearing aids. It picks up sounds from all directions.

See Otitis Media with Effusion.

A two-to-one relationship between frequencies. Thus 1000 Hz is one octave above 500 Hz.

Agency responsible for administering industrial safety standards set by the Occupational Safety and Health Act in the USA. This includes safe noise levels.

A change in the acoustical properties of the ear that results from the physical presence of a hearing aid in the ear canal. The result is that the person feels like they are talking inside a barrel—natural sounds seem muffled. Some modern hearing aids can largely overcome the occlusion effect by using “open fit” ear […]

Measurement of hearing sensitivity based on predictions made from physiologic responses such as ABR. The child’s participation is not required.