3.5: Hearing (Auditory Sensation)

FREQUENCY:

• frequency (pitch): Dimension of frequency determined by wavelength of sound… measured in hertz (Hz)

• Humans can hear sounds at frequencies from about 20 Hz to 20,000 Hz.

• Hearing is best at around 3,000 to 4,000 HZ, where human speech is centered.

  

INTENSITY:

• Intensity (loudness): amount of energy in a wave determined by amplitude; related to perceived loudness.
• Loudness is measured in decibels.

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

Theories of Hearing (Audition):

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.

Place Theory suggests that sound frequencies stimulate basilar membrane at specific places resulting in perceived pitch.

Localization of Sound: Because we have two ears sounds that reach one ear faster than the other makes us localize the sound.

HEARING LOSS:

Just as when you drive a new car off the lot, it depreciates in value due to its use, your ear’s hearing ability decreases with use.

Noise-Induced Hearing Loss- the progressive inability to detect higher frequency sounds due to damage to the hair cells accrued over time and with use.

• generally any sound loud enough to produce tinnitus (ringing of the ears) causes some damage (85db)

High intensity (loud) sounds can actually tear off the hair cells of the inner ear

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

COCHLEAR IMPLANT:

• 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.
• 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.