PSY 214 Lecture 16 Topic: Sound, auditory system, & pitch perception Chapter 11, pages 268-288 Corrections: None needed Announcements: At the beginning of class, we went over some demos from the virtual lab CD that related to many of the topics discussed in the previous lecture. The first demo was called Effect of Harmonics on Timbre. This showed how harmonics add to make the sound richer, so adding harmonics adds timbre. The second demo called Timbre of a Piano Tone Played Backwards was able to demonstrate the quick attack and slow decay of a piano. To look at these demos or to try other demos, the virtual lab CD is located outside of Dr. Achtman s office. Filled out course evaluations at the end of class Lecture Notes: Anatomy of the Ear (review) Outer ear = pinna and auditory canal Ear drum separates the outer and middle ear Middle ear contains the ossicles (3 bones) Oval window separates the middle ear and inner ear Inner ear = cochlea and auditory nerve Basilar membrane of the cochlea contains hair cells Tectorial membrane (gel-like substance) and basilar membrane move in opposite direction to bend the hair cells (transduction occurs) Written by: Lauren Sullivan, lsulliv8@mail.naz.edu Page 1 of 5
PG. 269 Figure 11.11 (Slide 3) Anatomy of the ear Inner Ear Stapes= 3 rd ossicle Scala tympani and scala vestibuli = fluid filled (vibrations cause rippling in the fluid) Organ of corti = basilar membrane and tectorial membrane Cilia = top of hair cells Hair cells have long axons that form the auditory nerve to go to the cortex PG. 270 Figure 11.15 (Slide 4) Partially Uncoiled cochlea Written by: Lauren Sullivan, lsulliv8@mail.naz.edu Page 2 of 5
PG. 271 Figure 11.16 (Slide 5) Cross-section view of cochlea How we hear different frequencies 2 major theories (good evidence that they are both correct) Place theory = location on the basilar membrane do the neurons (hair cells) fire Frequency theory = how quickly the neurons are firing (only true to a certain level because of refractory period) Slide 6 a) Which fibers fire b) How fibers fire Place Theory The place on the basilar membrane where the signal is sent from signifies the frequency Base of cochlea = near the oval window (signals high frequency sounds) more narrow than the apex Apex of the cochlea = near the coil (signals low frequency sounds) Tonotopic maps = mapping of different tones (tend to lose higher frequency tones first with age) Written by: Lauren Sullivan, lsulliv8@mail.naz.edu Page 3 of 5
PG. 275 Figure 11.25 (Slide 12) Tonotopic map in cochlea Hearing Loss Conductive hearing loss = blockage of sound from the receptor cells / not passing on the signal / sound never reaches the receptor cells Sensorineural hearing loss = problem or damage to the hair cells, auditory nerve, or brain (neural problem) Usually conductive can be fixed (ex: ear drum can grow back) Sensorineural are more lasting problems because neurons can t regenerate (can be caused by continued exposure to loud noises) Cochlear Implant Consist of microphone, sound processor, transmitter, receiver, and implanted electrode Transmitter and receiver (magnets) Implanted electrode wraps around the coils of the cochlea Doesn t work if auditory nerve is damaged (works for damaged hair cells) Doesn t work for everybody (depends on the damage) - Huge individual differences in success rate - For adults, it works best if they have previous hearing experience - Mixed results for children May or may not work - Was the surgery successful - Was there too much damage - Can they make sense of what they hear (the sound of the language is unfamiliar and they may not be able to decipher it) Written by: Lauren Sullivan, lsulliv8@mail.naz.edu Page 4 of 5
PG. 286 Figure 11.46 (Slide 26) Cochlear Implant For more information: This is a link to a website similar to the hearing loss simulator we looked at in class where you can listen to what a sentence sounds like with a cochlear implant as opposed to original speech. http://www.utdallas.edu/~loizou/cimplants/cdemos.htm MTV s true life did an episode I m Deaf focusing on two individuals who were born completely deaf. One is a sixteen year old who chooses to get a cochlear implant and the other is a dancer whose career may be stunted by her limited speaking skills. For a preview of the episode click the following link. http://www.youtube.com/watch?v=tkjo-krjjny To watch the full episode click this link. http://www.mtv.com/videos/true-life-imdeaf/1590956/playlist.jhtml#series=2211&seriesid=5232&channelid=1 Real-life example: Our discussion of hearing loss is applicable to everyone in that almost everyone will experience at some point. Sensorineural hearing loss is the most damaging due to the fact that these cells cannot regenerate. This can be caused by an over exposure to loud noises, which is not an uncommon occurrence. This gave good reason to take caution and take care of your ears. Written by: Lauren Sullivan, lsulliv8@mail.naz.edu Page 5 of 5