1. Sound Wave Creation
Sound is created when something vibrates—like vocal cords, a drum, or a speaker. These vibrations cause the surrounding air particles to move in waves of alternating high and low pressure. These waves travel through the air (or another medium) toward our ears.
2. Outer Ear: Sound Wave Collection
Pinna (Auricle): The visible part of the ear that captures sound waves and funnels them into the ear canal.
Auditory Canal: Directs sound waves toward the eardrum. The shape of this canal helps amplify certain frequencies.
3. Middle Ear: Mechanical Vibration
Tympanic Membrane (Eardrum): Vibrates in response to the incoming sound waves.
Ossicles (3 tiny bones):
Malleus (Hammer)
Incus (Anvil)
Stapes (Stirrup)
These bones amplify the vibration from the eardrum and transmit it to the oval window of the cochlea. The ossicles are the smallest bones in the human body.
4. Inner Ear: Mechanical to Electrical Conversion
Cochlea: A spiral-shaped, fluid-filled structure lined with thousands of tiny hair cells (called stereocilia) on the basilar membrane.
As the stapes pushes on the oval window, it creates waves in the cochlear fluid.
These fluid waves move the basilar membrane.
Different frequencies stimulate different parts of the membrane (tonotopic organization).
Hair Cells: Detect motion of the membrane. When they bend, ion channels open, causing electrical signals to form.
Outer hair cells amplify and fine-tune the vibrations.
Inner hair cells convert motion into neural impulses.
5. Auditory Nerve: Signal Transmission
The auditory nerve (cochlear nerve) carries these electrical signals from the cochlea to the brainstem and then to the auditory cortex in the temporal lobe of the brain.
The brain decodes the signals into recognizable sounds like speech, music, or noise.
6. Brain Processing: Understanding Sound
The primary auditory cortex processes pitch, loudness, and location.
The Wernicke’s area helps interpret meaning in speech.
The brain also integrates sound with memory, emotion, and attention.
how can you differentiate between different types of sound? explain.