Tones

Hearing is measured with an instrument called an Audiometer. The Audiometer can emit tones of varying frequencies and intensities to the patient via earphones (air conduction) or through a bone oscillator (bone conduction) that is placed on the mastoid bone behind the ear. Air conduction tests all three parts of the ear. Bone conduction directly tests the inner ear by vibrating the bones of the skull and bypassing the outer and middle ear mechanism.

Human speech includes low pitches with a frequency of 250 cycles per second to high pitches with a frequency of 8,000 Hz. The aging process in people gradually reduces their ability to hear the higher frequency sounds, to the extent that by the age of 70 years, most people lose usable hearing above 6,000 Hz.