ap psych study guides

🤔  Unit 5: Cognitive Psychology

👶  Unit 6: Developmental Psychology

🤪  Unit 7: Motivation, Emotion, & Personality

🛋  Unit 8: Clinical Psychology

3.5 Auditory Sensation and Perception

#sensation

#perception

#pinna

#eardrum

#cochlea

⏱️  4 min read

written by

Dalia Savy

dalia savy


🎵 Audition

Your sense of hearing is often called audition, but how do we hear sound? Sound waves that happen from the vibration of molecules enter your ear. Each vibration causes molecules to compress and expand, which is often called one sound wave. The greater the compression, the higher the altitude, and the louder the sound. 

Another characteristic of a sound wave is frequency, the number of complete wavelengths that pass a certain point in one second. The frequency determines the pitch, which is how high or low a sound is. The shorter the frequency, the higher the pitch.

👂Parts of the Ear

Your outer ear, which is often called the pinna, is the first part of the ear that the sound waves reach. Then, a mechanical chain reaction sends the sound waves down through the outer ear to the eardrum. The eardrum is a tight membrane, and when sound waves hit it, it vibrates. Right after hitting the eardrum, three bones in the middle ear (hammer, anvil, stirrup) pick up the vibrations and concentrate them, transmitting them to the cochlea.

https://firebasestorage.googleapis.com/v0/b/fiveable-92889.appspot.com/o/images%2Fear.png?alt=media&token=7f9e9a73-2bfe-4a58-bc2e-5c939fa55c47

Image Courtesy of Research Gate.

The cochlea is the part of your ear that is similar to the retina. It is a tube in the inner ear that triggers neural impulses to the brain. Vibrations from the middle ear cause the oval window (cochlea’s membrane) to vibrate, pushing the fluid inside the cochlea. In the cochlea is the basilar membrane lined with hair cells that are bent by vibrations. These hair cells transduce mechanical energy into neural impulses, similar to the process that happens at the retina in the eye. 

Basically, each hair cell is associated with a specific pitch. The hair movement triggers impulses in nearby nerve cells that form the auditory nerve. Similar to the optic nerve, the auditory nerve sends messages to the thalamus, which are sent to the auditory cortex in the temporal lobe.

Note: The inner ear contains the semicircular canals and the vestibular sacs, along with the cochlea. These have to do with your vestibular sense.

🔇 Hearing Impairment

Just like you could lose your sense of sight, you could lose your hearing sense.

There are two major types of hearing loss:

Sensorineural hearing loss, aka nerve deafness, is caused by damage to the cochlea’s cells or damage to the auditory nerve. Therefore, the signal is transferred to the cochlea, but not to the brain. This hearing loss is often caused by heredity, aging, and being exposed to too much noise (rock and/or rap concerts).

If someone has nerve deafness, they could have a cochlear implant inserted. This device converts sounds into neural impulses, just like the cochlea would if it functioned properly. This is the only way of restoring the sense of hearing, but it is not very effective in adults.

Conduction hearing loss is caused by damage to the system that conducts sound waves to the cochlea. This may be damage done to the eardrum or the middle ear bones (anvil, hammer, stirrup). A hearing aid is used for this less common form of hearing loss.

🤔 Theories of Pitch Perception

How do we hear different pitches? Two different conclusions were made about this phenomenon:

The place theory explains how we hear high-pitched sounds. It links pitch with the location of the basilar membrane, and it is stimulated because certain hair cells are attuned to certain pitches. As the hair cell twitches, the sound is produced.

The frequency theory explains how we hear low-pitched sounds. It states that the “rate of neural impulses traveling up the auditory nerve matches the frequency of a tone, thus enabling us to sense its pitch” (Definition of Frequency Theory). The fluid in the cochlea causes nerves to fire.

These two theories explain why we hear low and high-pitched tones, but what about mid-tones? The volley principle explains that since neurons cannot fire more than 1000 times in a minute, some neurons alternate firing. These neurons then fire in succession so fast that they create a combined frequency above 1000 waves/second. 

Quick note: We measure sound in decibels. 0 decibels = absolute threshold for hearing.

🔊 Localization of Sound

Having two ears, just like having two eyes, is much better than having one. The placement of our two ears on different sides of our head allows us to enjoy 3D hearing.

We can easily hear a sound coming from our left and right and figure out where the source of sound is coming from, but when the sound is coming from behind you, above you, in front of you, or below you, it is much more difficult to locate a sound. Therefore, tilt your head to help you locate a sound. Doing so gives your ears different intensities of the sound, making it easier to locate the source.

🎥 Watch: AP Psychology - Auditory Sensation and Perception

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