Test speakers & headphones
Run a slow sweep from 20 Hz upward to hear where the bass actually starts, and listen for rattles, buzzes and distortion along the way.
- StudioEars
- Tone generator
Free online tone generator
Tone generator. Any frequency, 20 Hz to 20 kHz.
Pure sine waves and more, with note names, frequency sweeps, pink noise and left, right and polarity tests. Built for checking speakers, rooms and headphones, tuning by reference, or just hearing what 12 kHz sounds like.
- Free, no signup
- 6 waveforms
- Log sweeps
- L / R & polarity
Tone generator
Hz
Space play/stop ← → ±1 Hz Shift + ← → ±1 semitone
Waveform
Output
Frequency sweep (logarithmic)
Presets
Start quiet. Pure tones can be louder than they sound, especially at high frequencies, and square or saw waves at high volume can damage tweeters. Set your system volume low, press play, then raise it slowly. Take breaks.
Uses
Six things a tone generator is great for
Find room modes
Sweep 30–200 Hz from your listening position. Notes that boom or vanish point to room resonances that bass traps or speaker placement can fix.
Check stereo & polarity
Send the tone left, right or both. Flip the polarity on a low sine: correctly wired speakers sound fuller and centred in normal mode, thin when inverted.
Tune by reference
Play A4 at 440 Hz, or any note from the chart below, and tune your instrument until the beating disappears.
Set levels with pink noise
Pink noise is the standard signal for matching monitor levels with an SPL meter and for comparing speakers, because it sounds balanced across the spectrum.
Hear the spectrum
Want to know what 63 Hz or 8 kHz sounds like on its own? Pure tones teach you the pitch of each frequency band, a great companion to EQ ear training.
Waveforms
Sine, square, saw, triangle and noise
The shape of a wave decides which harmonics it contains, and that decides how it sounds. Switch waveforms above and watch the oscilloscope while you listen.
| Waveform | Harmonics | Sounds like | Good for |
|---|---|---|---|
| Sine | None, a single frequency | Pure, smooth, flute-like | Testing, tuning, room modes, hearing a single frequency |
| Square | Odd harmonics, falling as 1/n | Hollow, buzzy, retro game console | Synth sounds, testing distortion (use low volume) |
| Sawtooth | All harmonics, falling as 1/n | Bright, brassy, buzzy | Synth leads and pads, hearing harmonic content |
| Triangle | Odd harmonics, falling as 1/n² | Soft, between sine and square | Gentle test tones, mellow synth sounds |
| Pink noise | Every frequency, equal energy per octave | Balanced "shhh", like a waterfall | Level matching, speaker comparison, EQ ear training |
| White noise | Every frequency, equal energy per hertz | Bright hiss, like TV static | Sound masking, technical measurements |
Reference
Note frequency chart
Frequencies in hertz for equal temperament with A4 = 440 Hz. Each octave doubles the frequency. Click any note to play it. Middle C and A4 are highlighted.
| Note | Octave 1 | Octave 2 | Octave 3 | Octave 4 | Octave 5 | Octave 6 | Octave 7 |
|---|---|---|---|---|---|---|---|
| C | |||||||
| C♯ / D♭ | |||||||
| D | |||||||
| D♯ / E♭ | |||||||
| E | |||||||
| F | |||||||
| F♯ / G♭ | |||||||
| G | |||||||
| G♯ / A♭ | |||||||
| A | |||||||
| A♯ / B♭ | |||||||
| B |
Hearing range
What can you actually hear?
Human hearing is usually quoted as 20 Hz to 20 kHz, but that's the best case for young ears. The top end drops with age and noise exposure, and many adults hear little above 14 to 16 kHz. That's normal, and it matters less than you'd think: the range from about 60 Hz to 8 kHz carries most of what we care about in music.
At the bottom, tones below about 40 Hz are felt as much as heard, and most laptop and phone speakers can't reproduce them at all. If a sweep goes silent at 150 Hz on your laptop, that's the speaker, not your ears.
Our ears also aren't equally sensitive at every frequency. We're most sensitive around 2 to 5 kHz, which is why a 3 kHz tone sounds much louder than a 50 Hz tone at the same level.
Not a hearing test
Browsers, headphones and speakers all colour the sound and don't share a calibrated level, so this tool can't measure your hearing. Use it out of curiosity, and see an audiologist if you notice changes in your hearing.
Protect your ears
- Start every session with your system volume low.
- High frequencies can be uncomfortable before they seem loud. Stop if anything hurts or rings.
- Square and saw waves at high volume put a lot of energy into tweeters. Keep them quiet.
- Take regular breaks when testing or training.
StudioEarsEar training for iPhone & iPad
Hearing a tone is easy. Naming it is a skill.
StudioEars trains you to recognise frequencies, EQ moves, compression and more by ear, in a short daily session. The tone generator and metronome come built in.
Download on theApp Store- Frequency Quiz UnitName the boosted frequency band
- Equalizer Control UnitHands-on EQ frequency faders
- Built-in studio toolsTone generator, metronome and BPM tapper
- Daily sessions & streaksTwo fresh units a day, picked for you
More free tools
Keep training
FAQ
Tone generator questions
What is an online tone generator?
A tone generator produces a test signal at a frequency you choose, usually a pure sine wave. It's used to test speakers and headphones, find room resonances, check stereo wiring, tune instruments and explore how different frequencies sound. This one runs entirely in your browser with the Web Audio API.
What frequency is A4 and middle C?
A4, the A above middle C, is 440 Hz in standard concert pitch. Middle C (C4) is about 261.63 Hz. Each octave doubles the frequency, so A5 is 880 Hz and A3 is 220 Hz. The note chart on this page lists every note from C1 to B7.
What is a frequency sweep used for?
A sweep glides smoothly from one frequency to another. It reveals rattles and buzzes in speakers and furniture, resonances and dips in a room, and the point where a speaker or your hearing stops responding. A logarithmic sweep spends equal time in every octave, which matches how we hear.
How do I test left and right channels and speaker polarity?
Use the Left and Right buttons to send the tone to one side at a time. For polarity, play a low sine around 60 to 100 Hz on both channels and toggle the polarity switch. With correctly wired speakers, normal polarity sounds fuller and centred, and inverted sounds thin and diffuse. If it's the other way round, one speaker is wired out of phase.
Can a tone generator damage my speakers or hearing?
Yes, at high volume. Pure tones can sound quieter than they are, especially at high frequencies, and square or sawtooth waves send a lot of energy to tweeters. Always start with the volume low, raise it gradually, and avoid long exposure. This generator caps its output, but your system volume still matters.
Can I use this as a hearing test?
Not as a medical test. Headphones, speakers and devices have very different frequency responses and output levels, so results aren't calibrated. It's fine for curiosity, such as finding the highest tone you can hear on your setup, but see an audiologist if you have concerns about your hearing.