How does your ear tell a high note from a low note?
After you watchHow does your ear tell a high note from a low note?
The short answer
Your ear tells notes apart with a tiny coiled strip inside it called the basilar membrane. Different spots along the strip are tuned to shake at different speeds, so a high note shakes one end and a low note shakes the other. Each spot fires its own nerve, so your brain knows exactly which pitch arrived.
Try this next
- What if you flatten the LOW-note spot instead of the high one? Flatten the floppy, wide end of the strip, then predict which note goes silent before you play both. Watch which nerve stays dark this time.
- What if a note lands between two spots on the strip? Pick a note partway along the strip and predict: will one spot bulge, or two spots share the wiggle? Play it and watch where the bulge actually peaks.
The whole story
How it works
Sound is a wiggle in the air, and pitch is how fast it wiggles: high notes wiggle fast, low notes wiggle slow. Inside your ear the sound travels along a curled ribbon called the basilar membrane, which is stiff and narrow at one end and floppy and wide at the other. Each frequency makes the strip bulge most at its own special spot, where tiny hair cells turn that motion into a nerve signal. Because every pitch peaks at a different place, your ear sorts a whole song into separate notes, like keys laid out on a piano.
What people get wrong
Many people picture the ear hearing every sound as one mixed lump, so they assume any ear damage just turns the overall volume down. In reality the inner ear lays pitch out by place, so wearing out one stretch of the strip steals one band of notes (usually the high ones) while the rest of your hearing stays fine. That is why hearing loss often takes the high pitches first instead of dimming everything equally.
The catch
Sorting pitch by place is what lets you tell two notes apart, follow a tune, and pick one voice out of a noisy room. The cost is that the layout is fragile: if loud noise or age wears out one stretch of the strip, you lose that band of pitches for good while the rest keeps working. An ear that heard everything as one lump could never go partly deaf to just the high notes, but it also could never sort pitches at all, so speech and music would smear into a buzz.
Questions kids ask
Why does hearing loss often take the high notes first?
High notes are sorted at the base of the inner-ear strip, the end the sound reaches first and the part that takes the most pounding from loud noise and aging. When that stretch wears out, you lose high pitches while lower pitches, sorted farther along, keep coming through. So damage steals a band of notes rather than just turning everything down.
Does each note really get its own spot in the ear?
Yes. The coiled strip inside your ear is tuned along its length, so each frequency makes it bulge most at one particular place. Tiny hair cells at that place fire a nerve, telling your brain which pitch arrived. It works like a piano keyboard rolled up inside your head.
How can my ear hear lots of notes in a song at once?
All the notes arrive mixed together in the air, but they bulge the strip at different spots at the same time, so many places shake at once. Each spot fires its own nerve, and your brain reads them all together as a chord or a tune.
What is pitch, really?
Pitch is how fast a sound wiggles the air. A fast wiggle is a high note and a slow wiggle is a low note. Your ear turns that speed into a place on the listening strip, which is how it tells one pitch from another.
Talk about it
- Before we look — guess where a really high squeak would shake the strip: the narrow stiff end or the wide floppy end? Why?
- If you had to lose either the high notes or the low notes, which would you miss more, and what would sound different?
- Why do you think loud concerts come with a warning about your hearing? What might be getting worn out?
For grown-ups
The strip is the basilar membrane inside the spiral cochlea, and it is mechanically tuned along its length, an arrangement called tonotopy. It is stiff and narrow at the base, which resonates to high frequencies, and floppy and wide at the apex, which resonates to low frequencies. An incoming sound sends a travelling wave down the membrane that peaks at each frequency's own place, and the hair cells there transduce the motion into nerve firing. This is why noise-induced and age-related damage, which hits the high-frequency base first, causes loss of a specific pitch range rather than a uniform drop in loudness.
Keep going
What else makes you wonder?
- If each note has its own spot, what happens at the very edges — is there a fastest wiggle and a slowest wiggle your strip can still catch?
- A dog can hear whistles you can't. Does that mean a dog's strip has spots tuned even higher than yours?
- When two people sing the same note, why do their voices still sound different to your ear?