Chapter 5: Sensation Hearing

Hearing - Audition Sound Waves - moving molecules of air which are collected by the ear. The ear detects changes in air pressure and transforms into neural impulses- which the brain decodes as sound Sound waves - vary in frequency and amplitude, which we perceive as difference in pitch and loudness Loudness-determined by the strength(amplitude) of a sound wave Frequency- the length of a sound wave, determines the pitch Long waves = low pitch (tuba) Short wave = high pitch (piccolo)

The Intensity of Some Common Sounds Decibels - measuring unit for sound energy, absolute threshold is zero A recent U of Tenn. study found that 60 percent of college students suffer some high-frequency hearing loss Loud music is believed to be the culprit Live concerts—120 + decibels, louder than jack hammer, chainsaw OSHA says that 85 decibels (food processor) 8 hours, 5 days a week will eventually cause permanent hearing loss For each 5 decibel increase, the time it takes to cause lasting injury drops by half Try: hold finger up as if taking a court room oath, rub thumb, finger together and should hear a scrtiching sound---if not, MAY have hearing loss

Outer and Middle Ear Outer Ear - Collects sounds Pinna - cartilage in ear, catches sound and directs it into ear canal Eardrum-vibrates when hit by sound waves Middle Ear – amplify and relay eardrum’s vibrations Three tiny bones (hammer, anvil, stirrup) act like a piston to relay vibrations to the cochlea

Inner Ear (Innermost part of the ear) Cochlea - (looks like snail) contains fluid that vibrates which in turn causes basilar membrane to vibrate Basilar Membrane – (in the cochlea) lined with hair cells which bend, triggering impulses on base of nerve cells Auditory Nerve - carries information (via the thalamus) to auditory cortex where sound is interpreted

The Ear

How Do We Perceive Pitch? Place Theory - the theory that links the pitch we hear with the place where the cochlea’s membrane is stimulated Best explains how we sense high pitches Doesn’t explain how we hear low-pitched sounds Frequency Theory - the theory that the rate of nerve impulses traveling up the auditory nerve matches the frequency of a tone, thus enabling us to sense its pitch Best explains how we sense low pitches

Hearing Loss and Deaf Culture Conduction Hearing Loss - caused by damage to the mechanical system that conducts sound waves to the cochlea. (eardrum punctured or the tiny bones damaged) Sensorineural Hearing Loss (nerve deafness) More common, hair cells are damages due to disease, heredity, aging, or prolonged exposure to noise or music. Older people tend to her low frequencies well but suffer hearing loss for high frequencies.

Cochlear Implants DO NOT NEED TO COPY Cochlear Implants - Electronic device wired into the auditory nerve which translates sounds into electrical signals that convey some info about sound to the brain. Used only with people with nerve deafness; preferable in children. Deaf culture advocates say deafness is not a disability and does not need to be corrected. Some parents help deaf children become bilingual both in sign and spoken language

Hearing Aids A microphone picks up sound from the environment and converts it into an electrical signal, which it sends to the amplifier. An amplifier increases the volume of the sound and sends it to the receiver. A receiver/speaker changes the electrical signal back into sound and sends it into the ear. Then those impulses are sent to the brain. A battery provides power to the hearing aid.

Hearing Aids cont. Hearing aids aren't effective for everyone. Hair cells in the inner ear must pick up the vibrations that the hearing aid sends and convert those vibrations into nerve signals. You need to have at least some hair cells in the inner ear for it to work. Even if some hair cells remain, a hearing aid won't completely restore normal hearing.