How the pinna collects and funnels sound
The pinna (auricle) is the visible flap of the ear that gathers sound and directs it into the ear canal, the tube leading inwards.
Remember
The pinna gathers sound and directs it into the ear canal; the parts deeper in the ear carry and convert that sound rather than collect it.
The pinna, also called the auricle, is the visible flap of the ear, found at the side of the head. It gathers sound from the surroundings and guides it into the external acoustic meatus, which is the ear canal, the tube that leads inwards towards the eardrum.
Most of the pinna is elastic cartilage, a springy, flexible cartilage that holds the folds in shape but still bends. Those folds act like a funnel. The concha is the hollow bowl just outside the canal opening, and it helps direct sound into the canal. Other landmarks to know are the tragus (the small bump of cartilage in front of the canal opening), the helix (the outer rim) and the lobule (the earlobe), the only part with no cartilage.
Once the pinna has gathered the sound, the canal carries it to the tympanic membrane (the eardrum, a thin membrane at the inner end of the canal), which vibrates. The ossicles, three tiny bones of the middle ear, relay those vibrations onwards to the cochlea, the coiled hearing organ of the inner ear, where hair cells change fluid movement into nerve signals.
The pinna has no part in relaying vibration, equalising pressure or detecting sound. The Eustachian tube, which links the middle ear to the nasopharynx (the upper throat behind the nose), equalises middle-ear pressure, and the hair cells that detect sound lie in the cochlea.
Key facts
- Job
- gathers sound from the surroundings and directs it into the ear canal.
- Tissue
- mostly elastic cartilage, which lets the folds bend and return to shape.
- Landmarks
- the tragus, helix, concha and lobule.
- Direction cues
- the curved, ridged surface changes sound according to the direction it arrives from, which gives the brain cues for localisation (working out where a sound comes from), especially of height.
- Canal shape
- the canal is S-shaped, and pulling the pinna backwards and upwards in an adult straightens it so the eardrum can be seen.
- Next steps
- the eardrum vibrates, the ossicles pass the vibration on, and the cochlea turns it into nerve signals.
Exam traps
- The ear canal is the route that sound enters, not the funnel that gathers it, although its skin lining protects the passage.
- The eardrum receives sound that has already travelled down the ear canal, so it is not the structure that gathers sound.
- The pinna does not make sound louder by vibrating its cartilage, because its contribution comes from the shape of its folds, which collect and direct sound.
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