Missing Fundamental — hear a pitch that is not there

Listen to a pitch that is not there

Tap an example to play it, and again to pause. Start with the full tone, then the one without 200 Hz: the colour changes, the pitch does not. The live picture shows which frequencies really play.

How the missing fundamental works

Most sounds with a pitch, a voice, a violin, a horn, are made of a fundamental and its harmonics: for a 200 Hz tone, 200, 400, 600, 800 Hz and up. The pitch we hear is the fundamental. Take it away and the harmonics that remain are still 200 Hz apart, and together they still repeat 200 times a second.

The brain reads that pattern and hears 200 Hz anyway. This is why a phone call sounds like the person you know, even though the line cuts everything below about 300 Hz, and why a small laptop speaker still seems to play the bass line.

Good to know

A phone line cuts below about 300 Hz, so the fundamental of most men’s voices, about 85 to 155 Hz, never reaches you. You hear it all the same.
Audio tools use it on purpose: some add harmonics of the bass so that small speakers seem to play notes they physically cannot.
In 1841 August Seebeck heard a pitch where there was no energy at that frequency, and argued about it with Georg Ohm. It is often called residue or virtual pitch.
Organ builders have used it for centuries: a resultant bass stop sounds two pipes a fifth apart to give a note an octave below the lower one, without the giant pipe.

	Frequencies playing	Pitch you hear
Full tone	200, 400, 600 … 1600 Hz	200 Hz
Without the fundamental	400, 600 … 1600 Hz	200 Hz
Harmonics 5 to 10	1000, 1200 … 2000 Hz	200 Hz
Pure tone	200 Hz alone	200 Hz
A man’s voice on the phone	Only above about 300 Hz	His own low voice, around 120 Hz

What is the missing fundamental?

Hearing the pitch of a tone even when its lowest frequency, the fundamental, is absent. The brain works it out from the spacing of the harmonics that remain.

Why can I hear bass on a phone speaker?

The speaker plays the harmonics of the bass notes, and your brain fills in the fundamentals it cannot play.

Is the missing fundamental made in the ear?

Mostly in the brain. Experiments that mask any distortion in the ear still find the pitch, so it comes from how the brain analyses the pattern of harmonics.

Mixes

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Focus timer

Work in waves.

The Pomodoro rhythm: focus with calm sound in your ears, then take a real break. A soft bell marks every change, so you never watch the clock. Every fourth break is a long one.

25:00Focus · 1 of 4

Silence during breaks

Sound while you work

Breathe

Slow your breathing down.

Follow the circle and the sound: it rises as you breathe in and falls as you breathe out. Choose a rhythm, or set your own, and pick what plays underneath.

Ready

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Noise generator

Any color of noise, from deep brown to bright violet — and everything in between.

Brown noise

Noise volume

Spectrum · 20 Hz – 20 kHz

Sound science

The colors of noise

Same randomness, different tilt. Each color shifts energy between low and high pitches — here is what that sounds like.

White

0 dB / octave

Equal energy at every frequency. Because we hear in octaves, it sounds bright and hissy — the classic "TV static".

Pink

−3 dB / octave

Equal energy in every octave, so it sounds even to the ear. Steady rain, rustling leaves. A favorite for focus.

Brown

−6 dB / octave

Deep and warm, like a distant waterfall or a plane cabin. Masks voices and traffic without any hiss.

Grey

Equal-loudness curve

Shaped around how our hearing works, so every pitch seems equally loud. Balanced and soft.

Blue

+3 dB / octave

The mirror of pink: more treble than bass. Airy, crisp, like a light spray.

Violet

+6 dB / octave

Mostly treble, like hissing water. Sometimes used to mask high-pitched ringing.

Calm

Gentle tones to settle into: singing bowls, a slow warm drone, wind chimes tuned so every note fits.

Frequencies

Famous tones on pages of their own: hear them side by side, with honest facts.

Sound phenomena

How sound bends, shifts, rings and fools the ear, and why space is silent: hear it for yourself.

Nature

Rooms & travel

Animals & countryside

A purring cat, whales and dolphins, a nightingale in the dark, cowbells on a summer pasture. Wonderful in stereo.

For babies

Womb sounds are what a baby heard for nine months: a deep rush of blood flow, and the heartbeat.

Hearing and speaker tests

Check your ears, headphones and speakers, each test on a page of its own with a live picture.

Ear Age · 60 seconds

Test your ears.

Our ears lose the highest pitches first, and it starts early. Find the highest tone you can still hear and see the typical age for it.

Headphones on, quiet room
Set a comfortable volume on the 1 kHz tone
Don't turn it up when a tone disappears — that's the point

20,000Hz

Can you still hear it?

Hearing age test →

More ear tests

Check your headphones, find the deepest bass your setup can play, or play any pitch you like.

Headphones check

Left & right

Each ear should get its own side. It matters for 8D, binaural beats and every stereo sound here.

Headphones on, then tap a side.

Bass test

How low can you go?

Deep tones from 200 Hz down to 20 Hz, the bottom of human hearing. Mostly it tests your speakers or headphones.

Tone generator

Any pitch, 20 Hz – 20 kHz

Hz

Tone volume

Start quiet: high tones and square waves get tiring fast.

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Missing fundamental.