How Do We Hear?

Introduction

• Presenter enjoys combining music and science.
• Main questions:
  • How can we play and hear music?
  • How can we move while playing music without losing balance?
  • What is sound?

What is Sound?

• Basic Explanation:
  • Sound creates vibrations in the air, which our ears process into signals the brain interprets as sound.
• Detailed Process:
  • Vibrations beat against the eardrum.
  • Pushes tiny bones that move internal fluids against a membrane.
  • Triggers hair cells that stimulate neurons, sending action potentials to the brain.

Importance of Ears

• Ears not only provide hearing pleasure but crucially maintain equilibrium.
• Balance allows activities like dancing, walking, standing without falling.

How Sound Works

• Sound Transmission: Key is vibration.
  • Vocal folds, table slaps, or guitar strings vibrate and cause air particles to vibrate too.
• Sound Waves:
  • Frequency: Number of waves passing a point in a given time (high-frequency = high pitch, low-frequency = low pitch).
  • Amplitude: Difference between high and low pressures (higher amplitude = louder sound).

Anatomy of the Ear

• Divisions: External, middle, and inner ear.
  • External and middle ear: Involved in hearing.
  • Inner ear: Involved in both hearing and equilibrium.
• External Ear: Pinna (auricle) catches sound and funnels it to the auditory canal.
• Middle Ear: Tympanic membrane (eardrum) and auditory ossicles (malleus, incus, stapes) amplify sound waves.
• Inner Ear: Labyrinth (bony and membranous) converts vibrations into electrical impulses and maintains equilibrium.

Inner Ear and Hearing

• Cochlea: Converts physical vibrations to electrical signals (snail shell shape).
  • Basilar Membrane: Reads sound within human hearing range, has fibers resonating at different frequencies.
  • Organ of Corti: Contains hair cells that trigger sodium channels leading to action potentials.
• Transmission to Brain: Cochlear nerve sends signals to the cerebral cortex for interpretation.

Equilibrium

• Vestibular Apparatus: Includes sacs and canals detecting head movements.
  • Fluid movement in semicircular canals corresponds to different rotations (sagittal, frontal, transverse planes).
  • Utricle and saccule have hair cells sensing fluid motion, sending signals about head acceleration.
• Sensory Conflict: Discrepancy in sensory inputs (e.g., motion sickness on a boat or spinning).

Closing

• Summary of key points about hearing and balance.
• Thanks to supporters and contributors.
• References to more educational resources.