Hearing Fundamentals

Hearing

• Sound waves are mechanical vibrations that travel through a medium, like air.
• Hearing involves the perception of these vibrations.
• The ear converts sound waves into electrical signals that the brain interprets as sound.
• The outer ear collects sound waves, the middle ear amplifies them, and the inner ear converts them into electrical signals.
• Different frequencies of sound waves correspond to different pitches.
• The intensity of sound waves, measured in decibels (dB), corresponds to the loudness of the sound.
• Normal hearing range is typically 20 Hz to 20,000 Hz. Exposure to loud noises can damage hair cells in the inner ear, leading to hearing loss.
• Conductive hearing loss occurs when sound vibrations cannot reach the inner ear.
• Sensorineural hearing loss occurs when there is damage to the inner ear or the auditory nerve.
• Presbycusis is age-related hearing loss.
• Tinnitus is a ringing or buzzing sound in the ears that is not caused by an external source.

Vision

• Vision involves the eye's detection and interpretation of light.
• Light enters the eye through the cornea, which bends the light.
• The light then passes through the pupil, which controls the amount of light entering the eye.
• The lens focuses the light onto the retina.
• The retina contains photoreceptor cells (rods and cones) that convert light into electrical signals.
• Rods are responsible for vision in low light conditions, while cones are responsible for color vision and sharp vision in bright light.
• The optic nerve transmits the electrical signals from the retina to the brain.
• The brain interprets these signals as images.
• Nearsightedness (myopia) occurs when the eye is too long, causing light to focus in front of the retina.
• Farsightedness (hyperopia) occurs when the eye is too short, causing light to focus behind the retina.
• Astigmatism is a defect in the cornea or lens that causes blurred vision.
• Cataracts occur when the lens becomes cloudy, making it difficult to see.
• Glaucoma results from increased pressure inside the eye, damaging the optic nerve.
• Macular degeneration is a common cause of vision loss in older adults, impacting central vision.
• Color blindness occurs when certain cones in the retina don't function properly, affecting the perception of colors.
• Visual acuity measures the sharpness of vision.
• Depth perception is the ability to perceive distance and three-dimensional space.