Introduction to Hearing and Audition

Hearing is the ability to sense sound and process the sensations to gain information about the source and nature of the sound.
In humans, hearing is also called audition, and refers to the perception of sound.
Audition is the transduction of sound waves into neural signals, processed by structures in the ear.
The ability to hear connects people, enables communication, and allows experiencing and understanding sounds around us. It is vital for mental and overall health.

Outer Ear:
- The auricle (pinna) is the outer flap of the ear, composed of cartilage and skin.
- Tragus: A small pointed eminence in front of the concha (the shell-shaped part of the pinna) that aids sound collection from behind.
- Helix: The outer rim of the ear extending from the superior insertion (root) to the earlobe.
- Lobule: The fleshy lower part of the auricle lacking cartilage and with rudimentary muscles connecting it to the skull and scalp.
Middle Ear:
- The space inside the eardrum.
- Malleus, Incus, Stapes: Three tiny bones (ossicles) known as the hammer (malleus), anvil (incus), and stirrup (stapes), transmitting sound vibrations from the eardrum to the inner ear.
- Tympanic Membrane: Also known as the eardrum, a thin flap of skin vibrating when sound hits it, transmitting vibrations to the tiny middle ear bones.
Inner Ear:
- A compartment containing hearing and balance apparatus.
- Cochlea: Shaped like a snail, divided into two chambers by a membrane filled with fluid; vibrations cause the fluid to ripple resulting in hair cells (sensory cells) on the membrane to vibrate and send electrical impulses to the brain.
- Semicircular Canals: Assisting with balance, these canals are lined up at right angles to each other. Their orientation allows the brain to understand the direction of head movement.

Step 1: Sound waves enter the outer ear and travel through the ear canal to the eardrum.
Step 2: The eardrum vibrates, transmitting vibrations to the three tiny bones in the middle ear.
Step 3: The bones in the middle ear amplify the sound vibrations, sending them to the cochlea.
Step 4: The elastic partition (basilar membrane) in the cochlea splits it into upper and lower portions, causing vibrations.
Step 5: Sensory hair cells on the basilar membrane vibrate and send electrical impulses to the brain.
Step 6: The auditory nerve carries these electrical signals to the brain, which processes them into recognizable sounds.

Noise: Unwanted sounds that lack a structured pattern, inducing disturbance. Examples include: Traffic noise, construction noise, and machinery noise.
Music: Produces a 'pleasing' sensation; characterized by harmony, rhythm, and melody, typically employing musical instruments. Examples include Classical compositions, popular music, and folk music.
Subjective Perception: The distinction between noise and music is often subjective, depending on the listener's perspective and context. What one person finds pleasing, another may find irritating.
Conditions Affecting Perception: Factors like volume and competing sounds can influence whether a sound is perceived as music or noise.
Sound Processing in the Brain: The auditory nerve transmits electrical signals to the brainstem, where sound is localized and separated from background noise. Then, the signals are relayed to the thalamus, a relay station in the brain that filters and processes the signals before sending them to the auditory cortex. The auditory cortex, located in the temporal lobe, analyzes the frequency, intensity and duration of sounds, and creates a mental representation of the auditory world.

Ear Infections: Infection of the middle ear, an air-filled space behind the eardrum containing the tiny vibrating bones of the ear; Children are more prone to such infections compared to adults.
Hearing Loss: Occurs when something affects the hearing system, leading to trouble understanding, following, or participating in conversations. Types include: Conductive, sensorineural, and mixed hearing loss.
Tinnitus: A sensation of a ringing sound or other unusual sounds such as roaring or buzzing; it commonly affects individuals with hearing complications.
Vertigo: A sensation of motion or spinning that can be described as dizziness; it may be caused by problems in the inner ear's balance portion.

Music as a unique source of noise-induced hearing loss: Music is a significant source of noise-induced hearing loss, though it is also often categorized as more pleasant and appreciated than other forms of noise. Both noise and music may cause similar damage to the auditory system.

This presentation detailed the process of hearing and described the relevant anatomical structures from the outer ear to the inner ear, how sound is processed and the implications of noise and music on hearing. This information is crucial for comprehending the complex interplay of physical and cognitive processes during sound perception.