Haas Effect — the precedence effect, heard

Listen in headphones

Put on headphones: on speakers both ears hear both sides and the effect is lost. Tap an example to play it, and again to pause. The same clap reaches your right ear a little later each time.

How the Haas effect works

A sound from your left reaches your left ear first and the right one up to about 0.6 to 0.7 ms later, the time it takes to travel round your head. The brain uses that gap to place sounds. Give one ear a delay that small and the clap moves towards the other side.

Longer delays do not sound further left. From about 1 ms to some 30 ms the brain fuses both arrivals into one sound and places it where the first came from: the precedence effect, studied by Helmut Haas in 1949. It keeps rooms from sounding like a hall of echoes; later than about 30 to 40 ms, the second arrival breaks away as an echo.

Good to know

The late copy can be up to about 10 dB louder and the sound still seems to come from the first one. One example here makes the late side twice as loud, 6 dB.
Sound engineers rely on it: delaying the speakers at the back of a hall by the right few milliseconds keeps the sound seeming to come from the stage.
Mixers use it to widen a mono sound: the same track a few milliseconds later on the other side sounds wide but single. Summed back to mono, it can turn thin and hollow.
Where the copy becomes an echo depends on the sound: for sharp clicks it can be as early as 5 to 10 ms, for speech nearer 40 ms, for music later still.

Right ear later by	What you hear	Why
0 ms	One clap in the middle	Both ears agree
0.6 ms	One clap, moved to the left	The gap a sound from the side makes
5 ms	One clap, on the left	Precedence: the first arrival decides
12 ms	One clap on the left, a little wider	The late copy adds body, not a second sound
60 ms	A clap and an echo	Too late to fuse

What is the Haas effect?

Also called the precedence effect: when the same sound reaches you twice within about 30 ms, you hear one sound, placed where the first arrival came from.

Why do I need headphones?

The effect here depends on what each ear alone hears. On speakers both ears hear both speakers, and the delays mix together.

How is the Haas effect used in music?

To widen and place sounds: a copy delayed by 5 to 30 ms on the other side makes a sound feel wide without being heard twice.

Mixes

Pick what you need. One tap to start, change anything and save it as your own.

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

Sound while you breathe

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.

Take it to bed

An app without the app store.

Add Ears & Waves to your home screen and it opens like any app — full screen, with its own icon. Everything it needs is saved on your device, so it keeps playing on a plane, in a tent or with Wi-Fi off.

Preparing offline mode…

Works offlineNo streaming. Sound is computed on your device, forever.
Screen offKeeps playing with the phone locked. The timer fades it out gently.
PrivateNo account, no ads, no cookies. Your mixes stay on your device.

Haas effect.