Follow one sound from the air outside to the hearing centre of the brain in 8 steps. The close-up under the 3D view shows what happens at each step, slowed down and drawn larger.
The ear has three parts. The outer ear collects sound, the air-filled middle ear passes the vibrations on through three tiny bones, and the fluid-filled inner ear turns them into nerve signals and also senses balance. Click any part of the model, or choose one from the list.
Plays quiet tones from 8 kHz upwards. Press “I hear it” or “I can’t” after each one to find the highest pitch you can hear.
Tones play only when you press a button, for about one second, at a low volume. Use speakers or keep headphones turned down. Many speakers cannot play very high or very low notes, so this is not a medical hearing test.
This slider does not play any sound. It shows how loud sounds affect the hair cells in the cochlea and how long you can safely listen.
3D anatomy: Z-Anatomy (CC BY-SA 4.0), based on BodyParts3D © The Database Center for Life Science (CC BY-SA 2.1 Japan). Simplified and combined for the web by SciSim; the ear canal, the eardrum surface, the Eustachian tube, the vestibular nerve and the hearing pathway are modelled. The model files are shared under CC BY-SA 4.0.
This is the same 3D ear seen from the front, with the skin and skull removed: the view you label in an exam. Switch between the labeled diagram, a blank one to test your memory, and a quiz where you place each label yourself. You can also download both versions or print a worksheet.
Tap a word, then tap the numbered box it belongs to (on the diagram or in the list below). Tap a filled box to take the word back. On a phone, swipe the diagram sideways to see every number.
Tap a card, then tap the box it belongs in. Press Check when all 12 are placed.
A printable worksheet: label the ear, sort the parts, put the steps of hearing in order, multiple choice, calculations (wavelength, decibels, safe listening time) and explain questions, with an answer key.
A vibrating object pushes and pulls on the air, making a longitudinal wave of compressions (air squeezed together) and rarefactions (air spread out). The number of waves per second is the frequency, heard as pitch; the size of the pressure change is the amplitude, heard as loudness. In air sound travels at about 343 m/s.
The pinna funnels sound into the ear canal, which ends at the eardrum. The pressure changes make the eardrum vibrate at the same frequency as the sound. Three tiny bones, the hammer, anvil and stirrup (ossicles), pass the vibration across the air-filled middle ear. Because the eardrum is about 17 times larger than the oval window and the bones act as a small lever, the pressure is increased about 20 times, enough to move the fluid of the inner ear. The Eustachian tube keeps the air pressure on both sides of the eardrum equal.
The stirrup pushes on the oval window of the snail-shaped cochlea and starts waves in its fluid. They run along the basilar membrane, which is narrow and stiff at the base and wide and floppy at the tip (apex). Each frequency makes the membrane swing most at one place: high pitches near the base, low pitches near the apex. There, hair cells are bent, ion channels open and the cells release a chemical that makes the fibres of the cochlear nerve send electrical signals. Through relay stations in the brainstem and thalamus they reach the auditory cortex in the temporal lobes, where we become aware of the sound.
Next to the cochlea, three fluid-filled semicircular canals at right angles to each other sense the head turning. When the head starts to turn, the fluid lags behind and bends a jelly flap (the cupula) with hair cells inside. The utricle and saccule contain tiny crystals that sense gravity and tilting. The vestibular nerve carries these signals to the brainstem and cerebellum.
Press Follow a sound and step through the journey. In Pitch, slide from 20 Hz to 20 kHz and watch the glowing place move along the cochlea, then play a quiet tone and try the hearing range test. In Loudness, find the level where the safe listening time drops below one hour. In Balance, press Spin, then stop and watch the fluid keep moving after the head has stopped: that is why you feel dizzy.
| Region | Parts | Filled with | Job |
|---|---|---|---|
| Outer ear | Pinna (auricle), ear canal; ends at the eardrum | Air | Collects sound and channels it to the eardrum |
| Middle ear | Eardrum, hammer (malleus), anvil (incus), stirrup (stapes), Eustachian tube | Air | Turns sound into vibrations of the bones and increases the pressure about 20 times |
| Inner ear | Cochlea, semicircular canals, vestibule (utricle and saccule) | Fluid | Turns vibrations into nerve signals (hearing) and senses movement and gravity (balance) |
| Part | What it is | Job |
|---|---|---|
| Pinna | Flap of skin-covered cartilage | Funnels sound into the ear canal; its folds help tell whether a sound is in front, behind, above or below |
| Ear canal | Tube about 2.5 cm long and 7 mm wide | Carries sound to the eardrum; glands make earwax that traps dust; boosts sounds of about 2–5 kHz |
| Eardrum (tympanic membrane) | Thin cone-shaped membrane, about 9 mm across (about 55 mm² of it vibrates) and 0.1 mm thick | Vibrates when sound waves hit it |
| Hammer, anvil, stirrup (ossicles) | The three smallest bones of the body, linked by tiny joints | Carry the vibration from the eardrum to the oval window and increase its pressure |
| Eustachian tube | Tube about 3.5 cm long from the middle ear to the back of the nose | Opens when you swallow or yawn so the air pressure on both sides of the eardrum is equal; drains the middle ear |
| Cochlea | Snail-shaped, fluid-filled tube of about 2¾ turns (about 3.5 cm long if unrolled) | Hair cells on the basilar membrane turn vibrations into nerve signals; each place responds to a different pitch |
| Semicircular canals | Three fluid-filled loops at right angles to each other | Sense the head turning (rotation) in any direction |
| Utricle and saccule (vestibule) | Two small sacs with tiny crystals (otoliths) on a jelly layer | Sense gravity, tilting and speeding up in a straight line |
| Cochlear and vestibular nerves | Together the vestibulocochlear nerve (cranial nerve VIII) | Carry hearing and balance signals to the brainstem |
| Auditory cortex | Part of the temporal lobe on each side of the brain | Where nerve signals are recognised as sounds, voices and music |
| Property of the wave | What you hear | How the ear detects it |
|---|---|---|
| Frequency (Hz) | Pitch: high or low | Which place along the cochlea vibrates most: high frequencies near the base, low frequencies near the apex |
| Amplitude (sound level, measured in dB) | Loudness | How strongly the hair cells are bent: louder sounds make each nerve fibre fire faster and bring in more fibres |
| Arrival time and level at the two ears | Direction of the sound | The brainstem compares the two ears: a sound from the right reaches the right ear up to about 0.6 ms earlier and slightly louder |
| Sound | Level | Safe listening time (NIOSH) |
|---|---|---|
| Quietest sound a young person can hear | 0 dB | — |
| Whisper | about 30 dB | No limit |
| Normal conversation | about 60 dB | No limit |
| Heavy traffic | about 85 dB | 8 hours |
| Earbuds at full volume | about 100 dB | 15 minutes |
| Rock concert | about 110 dB | about 1.5 minutes |
| Threshold of pain | about 120–130 dB | Seconds |
| Fireworks or a gunshot close by | 140 dB and more | Can cause instant damage |
The decibel scale is logarithmic: every +10 dB means 10 times the sound intensity, and every +3 dB roughly doubles it, which is why the safe time halves.
The cochlea has three fluid-filled channels. The stapes moves the perilymph of the scala vestibuli; the pressure wave crosses to the scala tympani and is released by the bulging round window. The middle channel (scala media) contains endolymph, rich in potassium ions. When the basilar membrane moves, the stereocilia of the hair cells are pushed against the tectorial membrane; tip links pull open mechanically gated channels, K+ flows in and the cell depolarises and releases glutamate onto the auditory nerve fibres. About 3,500 inner hair cells send almost all the information to the brain, while about 12,000 outer hair cells change their length to amplify quiet sounds (the cochlear amplifier). The hearing pathway runs cochlear nucleus → superior olivary complex (both sides compare the ears) → inferior colliculus → medial geniculate body of the thalamus → primary auditory cortex (Heschl’s gyrus), and each cortex receives input from both ears. Loud noise breaks stereocilia and kills hair cells, first at the place for about 4 kHz; age-related hearing loss (presbycusis) removes the highest frequencies first.
The outer ear (the pinna and the ear canal) collects sound. The middle ear is an air-filled space behind the eardrum with three tiny bones, the hammer, anvil and stirrup, and the Eustachian tube. The inner ear is filled with fluid and contains the cochlea for hearing and the semicircular canals and vestibule for balance.
Key takeaway: outer ear collects, middle ear passes on and amplifies, inner ear detects.Sound waves are funnelled by the pinna along the ear canal and make the eardrum vibrate. The hammer, anvil and stirrup pass the vibrations to the oval window of the cochlea and increase the pressure. Waves in the cochlear fluid move the basilar membrane, bending hair cells, which send electrical signals along the cochlear nerve. The signals travel through the brainstem and thalamus to the auditory cortex in the temporal lobe, where they are recognised as sound.
Key takeaway: air waves → eardrum → ossicles → cochlear fluid → hair cells → nerve → brain.The inner ear is filled with fluid, and moving fluid takes much more force than moving air. Without help, almost all of the sound energy would bounce off the fluid. The eardrum is about 17 times bigger than the oval window, so the same force is concentrated on a small area, and the ossicles work as a small lever. Together they increase the pressure about 20 times.
Key takeaway: a big eardrum pushing a small oval window, plus a lever, gives about 20× the pressure.The basilar membrane inside the cochlea is narrow and stiff at the base and wide and floppy at the apex. High-frequency sounds make it vibrate most near the base and low-frequency sounds near the apex. The brain knows which hair cells are sending signals, so it knows the pitch. For low sounds, the timing of the nerve impulses also follows the waves.
Key takeaway: each place along the cochlea responds to its own pitch: high at the base, low at the apex.Young people can usually hear from about 20 Hz to 20,000 Hz (20 kHz). We are most sensitive between about 2 and 5 kHz, which is important for speech. With age the highest frequencies are lost first, so many adults cannot hear sounds above about 12–15 kHz. Sounds below 20 Hz are called infrasound and sounds above 20 kHz ultrasound; dogs, bats and dolphins can hear ultrasound.
Key takeaway: about 20 Hz to 20 kHz, and the top end falls with age.Sound levels of 85 dB or more can damage hearing if they last long enough. A common safety rule (NIOSH) allows 8 hours at 85 dB and halves the time for every 3 dB more: 1 hour at 94 dB, 15 minutes at 100 dB and under 2 minutes at 110 dB. Very loud sounds of about 140 dB, such as fireworks or gunshots close by, can cause damage at once.
Key takeaway: 85 dB for 8 hours; every +3 dB halves the safe time.Loud sound bends and breaks the stereocilia of the hair cells and can kill the cells. In humans and other mammals hair cells do not grow back, so the loss is permanent. Ringing in the ears (tinnitus) or muffled hearing after a concert is a warning sign. Ear protection and keeping earbuds below about 60% volume help prevent it.
Key takeaway: dead hair cells are not replaced in humans.The Eustachian tube joins the middle ear to the back of the nose and throat. It is usually closed but opens when you swallow or yawn, letting air in or out so the pressure in the middle ear matches the air outside. When the pressure outside changes quickly, for example in a plane, the eardrum bulges and feels blocked until the tube opens with a pop.
Key takeaway: it equalises the air pressure on both sides of the eardrum.The three semicircular canals sense rotation of the head. When the head turns, the fluid inside lags behind and bends the cupula, a jelly flap with hair cells in it, and the hair cells send signals. The utricle and saccule contain tiny crystals (otoliths) that are pulled by gravity, so they sense tilting and straight-line acceleration. The brain combines these signals with what the eyes see and with signals from muscles and joints.
Key takeaway: semicircular canals sense turning; the utricle and saccule sense gravity and tilt.When you start spinning, the fluid in the semicircular canals lags behind and the cupula bends. If you keep spinning at a steady speed, friction drags the fluid along until it moves with the head and the cupula straightens, so you no longer feel the spin. When you suddenly stop, the fluid keeps moving for a few seconds and bends the cupula the other way, so the brain thinks you are spinning in the opposite direction while your eyes say you are still.
Key takeaway: after you stop, the fluid keeps moving and sends a false spinning signal.