Humans can hear sounds at frequencies from about 20Hz to 20,000Hz. Frequency (pitch): Dimension of frequency determined by wavelength of sound…measured in hertz (Hz) Humans can hear sounds at frequencies from about 20Hz to 20,000Hz. We hear sounds best at around 3,000 to 4,000Hz, where human speech is centered.

Loudness is measured in decibels. Intensity (Loudness): Amount of energy in a wave determined by amplitude relates to perceived loudness. Loudness is measured in decibels.

Richard Kaylin/ Stone/ Getty Images 120dB 70dB

Pinna control vestibular sense…balance collects sound tympanic membrane to the cochlea

Coiled, bony, fluid-filled tube in the inner ear that transduces sound vibrations to auditory signals.

Frequency Theory states that the rate of nerve impulses traveling up the auditory nerve matches the frequency of a tone, thus enabling us to sense its pitch. Sound Frequency Auditory Nerve Action Potentials

Theories of Audition Place Theory suggests that sound frequencies stimulate basilar membrane at specific places resulting in perceived pitch. http://www.pc.rhul.ac.uk

Because we have two ears sounds that reach one ear faster than the other makes us localize the sound. Volunteer needed!

The older we get, we tend to lose the ability to detect the higher frequency (pitch) sounds

Why do we lose the ability to detect the upper frequencies as we age? Due to the everyday sounds we expose our ears to… generally any sound loud enough to produce tinnitus (ringing of the ears) causes some damage (85db) over the years, small amounts of damage accumulate referred to as Noise Induced Hearing Loss (NIHL) High intensity (loud) sounds can actually tear off the hair cells of the inner ear

Damaged…especially “outer” hair cells Healthy…three rows of outer hair cells and one row of inner hair cells are seen.

Conduction Deafness: Hearing loss caused by damage to the mechanical system that conducts sound waves to the cochlea. may be “corrected” with surgery or hearing aides Sensorineural Deafness: Hearing loss caused by damage to the cochlea’s receptor cells or to the auditory nerve, also called nerve deafness. this is a permanent condition

A cochlear implant is a small, complex electronic device that can help to provide a sense of sound to a person who is profoundly deaf or severely hard-of-hearing. The implant consists of an external portion that sits behind the ear and a second portion that is surgically placed under the skin. An implant has the following parts: A microphone, which picks up sound from the environment. A speech processor, which selects and arranges sounds picked up by the microphone. A transmitter and receiver/stimulator, which receive signals from the speech processor and convert them into electric impulses. An electrode array, which is a group of electrodes that collects the impulses from the stimulator and sends them to different regions of the auditory nerve. An implant does not restore normal hearing. Instead, it can give a deaf person a useful representation of sounds in the environment and help him or her to understand speech. Information from…http://www.nidcd.nih.gov/health/hearing/coch.asp

Total cost of surgery = $40,000 Wolfgang Gstottner. (2004) American Scientist, Vol. 92, Number 5. (p. 437) Total cost of surgery = $40,000