Pick a frequency and waveform, then press play. Start at low volume — especially with headphones.
440 Hz
FrequencyWaveform
Volume
Presets
Hearing check (high tones)
⚠️ Protect your ears: keep the volume low and stop if you feel discomfort.
How to use
Type a frequency or drag the slider (it moves logarithmically, like human hearing), choose a waveform, and press Play. Sine is the pure reference tone; square and sawtooth sound louder and buzzier at the same volume because of their harmonics. Handy uses: A440 for tuning instruments, 100–200 Hz to test a subwoofer, 1 kHz as the standard audio reference, and the hearing-check presets to find the highest tone you can hear — most adults top out between 12 and 17 kHz, and the limit drops naturally with age. Always start quiet: high frequencies can be uncomfortable at volumes that feel fine for low ones.
Waveforms and why they sound different
A sine wave contains a single frequency and nothing else, which is why it sounds smooth and slightly dull — it is the reference against which every other sound is described. A square wave adds odd harmonics above the fundamental and sounds hollow and buzzy; a sawtooth adds every harmonic and is the brightest and harshest of the three. At the same volume setting the square and sawtooth will sound noticeably louder, because the extra harmonics fall in the range your ear is most sensitive to.
The frequency slider moves logarithmically rather than linearly, because hearing works that way. Doubling a frequency raises the pitch by exactly one octave whether you go from 100 to 200 Hz or from 4,000 to 8,000, so equal distances on the slider produce equal musical steps.
Frequencies worth knowing
440 Hz — concert A, the international tuning reference for orchestras and most instruments.
1 kHz — the standard reference for audio measurements, and roughly where hearing is most sensitive.
100-200 Hz — the range for checking whether a subwoofer or a laptop speaker actually reproduces bass.
50-60 Hz — the hum of mains electricity, useful for identifying an earth loop in an audio setup.
Above 15 kHz — the region that fades first with age. Many adults over forty hear nothing above 15,000 Hz at all.
Using it safely
Start with the volume low every single time. A pure tone carries no dynamic variation, so the usual cues that tell you a sound is too loud are missing, and sustained high frequencies at volume are genuinely capable of causing damage. This matters most with headphones, where the sound sits directly against the eardrum.
Keep hearing checks short and treat the result as a rough guide rather than a measurement. Browser output, headphone response and room acoustics all shape what reaches you, and none of them are calibrated. A real audiogram uses controlled equipment for good reason.
Human hearing tops out around 20 kHz in childhood and declines naturally with age — by 40 most people hear little above 15 kHz, and 17 kHz+ is mostly teenagers. Your speakers matter too: many laptop speakers cannot reproduce very high or very low tones at all, so test with headphones before concluding anything about your ears.
What is a safe volume for testing?
Start with the volume slider low (the default is gentle) and your device volume at or below half. A test tone only needs to be just audible — there is no benefit to loud playback, and sustained loud pure tones are harder on ears than music at the same level. Stop immediately if you feel ringing or discomfort.
What are the common frequencies used for?
A440 (440 Hz) is the international tuning standard for instruments. 1 kHz is the reference tone used to calibrate audio gear. 50–80 Hz reveals what a subwoofer really does, 3–4 kHz is where human hearing is most sensitive, and sweeping 8–18 kHz is the classic quick hearing-range check.
What's the difference between sine, square, sawtooth and triangle waves?
A sine wave is a single pure frequency with no harmonics — the cleanest test signal. Square and sawtooth waves stack strong harmonics on top, so they sound buzzy and bright; a triangle wave sits in between. That harmonic content is why the same pitch sounds so different in each shape.
Is 432 Hz really better than 440 Hz?
There's no scientific evidence for special healing effects at 432 Hz. A440 became the international tuning standard by agreement in 1955 — you can generate both here and compare; the difference you'll hear is simply a slightly lower pitch.
What frequencies can dogs and cats hear that we can't?
Humans top out near 20 kHz, but dogs hear up to roughly 45 kHz and cats around 64 kHz — that's how silent dog whistles work. If your pet perks up during a high-frequency test you can't hear, that's why. Keep the volume low around animals.