Online Tone Generator
A sine wave and frequency generator from 20 Hz to 20 kHz that doubles as a pitch generator for any musical note, with square, triangle and sawtooth (saw) waves too, plus white, pink, brown, blue and violet noise, frequency sweeps and a polarity check, on the left, right or both channels. Everything is generated in real time by the Web Audio API with nothing to install, and any signal saves as a 5-second WAV. The page makes the signal digitally; how clean it reaches your ears is up to your DAC, amplifier and speakers or headphones.
Waveform
Musical note
Nearest note: B5 at 987.77 Hz, 21 cents sharp. Middle C is C4 (261.63 Hz); A4 is 440 Hz.
To check an instrument against its note, the online tuner listens through your microphone and says how many cents off it is.
Start with your volume low. dBFS = decibels below digital full scale: 0 dBFS is the loudest a file can be, and −12 dBFS is a safe testing level. A 1 kHz sine is the standard alignment tone, usually at −18 dBFS (EBU R68) or −20 dBFS (SMPTE RP155).
Pink noise is the usual signal for matching speaker levels. Speaker calibration guides commonly start at −20 dBFS RMS.
Sweep range
Duration & mode
Generates a short click pulse - listen in both channels at once. Correctly-connected speakers produce one "pop" with bass energy; reversed polarity sounds thin and bass-anemic. To check a pair for left, right and phase with what each result should sound like, run the speaker and headphone test.
The noise generator's five colors
- White noise
- Equal energy at every frequency. Sounds like TV static or heavy rain. Used for masking ambient noise and speaker frequency response testing.
- Pink noise
- Equal energy per octave (falling 3 dB per octave). Perceptually "flat" - the closest noise to music in spectral balance. The standard for room acoustic measurements.
- Brown noise
- Falls 6 dB per octave. Heavy bass emphasis - often described as a waterfall or deep rumble. Very popular for sleep and focus.
- Blue noise
- Rises 3 dB per octave. High-frequency emphasis - sounds bright and hissy. Used in dithering algorithms to push quantization noise out of the audible band.
- Violet noise
- Rises 6 dB per octave. Extreme treble emphasis. Rarely used in audio but appears in some dithering applications and tinnitus research.
Frequency landmarks worth remembering
Pin these tones to your ear. Sweep the generator above between any two of them and you start to hear the structure of the audible band - and where every "warm," "bright," "muddy," or "harsh" complaint actually lives.
| Frequency | Landmark | What it does in music |
|---|---|---|
| 20 Hz | Lower hearing limit | Felt rather than heard. Pipe organ pedal, EDM sub. |
| 41.2 Hz | Bass guitar low E | The bottom of most rock recordings. |
| 50 / 60 Hz | Mains hum | Ground loop frequency. Listen for it on quiet passages. |
| 82.4 Hz | Guitar low E | Body / chest of the rhythm guitar. |
| 200-250 Hz | "Muddy" zone | Boomy male vocals; cup/proximity effect on mics. |
| 440 Hz | Concert pitch A | Tuning standard. Where instruments meet. |
| 1 kHz | Reference tone | SPL meter calibration. Voice intelligibility center. |
| 3-4 kHz | Ear sensitivity peak | Fletcher-Munson minimum. Sibilance starts here. |
| 6-10 kHz | Sibilance band | "S" and "T" consonants. Bright cymbals. |
| 15 kHz | Adult upper limit | Most adults can't hear above this; kids reach 18 kHz+. |
| 20 kHz | Theoretical upper limit | The Nyquist target. Few adults hear it cleanly. |
What test tones and noise are for
A pure sine wave contains exactly one frequency, which makes it the cleanest way to ask a system a single question: can it reproduce this, at this level, without adding anything. Anything you hear that is not the tone - a buzz, a rattle, a second pitch - was added by the room or the equipment.
Noise asks a broader question. White noise has equal energy in every hertz, which makes it sound bright because the upper octaves each contain far more hertz than the lower ones. Pink noise corrects for that with a 3 dB per octave tilt, giving equal energy per octave, which is why it is the standard signal for level matching and room measurement.
Sweeps combine both approaches by walking a tone through the range, which reveals where a response dips, where a resonance rings, and where a driver or a cabinet starts to buzz - things a static tone at one frequency would walk straight past.
The ideas behind the controls
- Waveform
- A sine is one frequency alone. Square, triangle and sawtooth add harmonics at whole multiples of the pitch: odd ones only for square and triangle, every one for sawtooth, which is why they sound buzzier at the same note.
- Cents
- A hundredth of an equal-tempered semitone, so 1,200 cents make an octave. The note readout uses them to say how far a frequency sits from the nearest note.
- Polarity check
- A test that reveals whether both channels push in the same direction. Reversed polarity thins the bass and destroys the center image.
Audio signal generator FAQ
What can I do with an online tone generator?
Play test tones to check speakers and headphones: a sine sweep finds rattles, resonances and where the bass rolls off, pink noise shows how a room colors sound, a tone on the left or right channel alone checks the wiring and balance, and the polarity check catches a speaker wired out of phase. It is also a pitch reference for tuning and a noise generator for masking. The page only makes the signal: to measure frequency response or distortion you also need a microphone and analysis software.
Can it replace a function generator?
For audio work, often. It plays the four classic function-generator waveforms, sine, square, triangle and sawtooth, anywhere from 20 Hz to 20 kHz to a hundredth of a hertz, through your computer's or phone's audio output. It is not a lab instrument: it has no DC offset, no pulse-width or duty-cycle control and no output above the audio band, and the output level and impedance are whatever your sound card or DAC provides. For an oscilloscope check of an amplifier, a square wave from here into the amp's input does the classic job.
What is the difference between white, pink, brown, blue, and violet noise?
White noise has equal energy per Hz; pink noise has equal energy per octave (the standard for room measurement); brown (Brownian) drops 6 dB per octave for deep low-end testing; blue rises 3 dB per octave; violet rises 6 dB per octave. Pink and brown are the most useful for audio work; the others appear in DSP testing and synth design.
What are square, triangle and sawtooth waves for?
A sine is one frequency with no harmonics, which is why it is the reference test tone. The other three add harmonics in fixed proportions, so each one is a known spectrum. A square wave carries the odd harmonics, falling 6 dB per octave; its flat tops and fast edges make clipping, ringing and a slow slew rate easy to see on an oscilloscope, which is why it is the classic amplifier test. A triangle carries the same odd harmonics falling 12 dB per octave, so it sounds close to a sine with a slight buzz. A sawtooth carries every harmonic, falling 6 dB per octave, and is the brightest of the four. All four are generated band-limited, so no harmonic above half the sample rate folds back into the audible band, and the WAV download is rendered the same way.
Can I use it as a pitch generator to play a musical note?
Pick a note and an octave under the frequency controls and the tone moves to that pitch in equal temperament, tuned to A4 = 440 Hz: middle C (C4) is 261.63 Hz, a guitar's low E string (E2) 82.41 Hz and its high E (E4) 329.63 Hz. The line under the picker also names the nearest note to any frequency you type or slide to, with how many cents sharp or flat it sits, so 445 Hz reads as A4, 20 cents sharp. A sine is the plainest reference to tune an instrument against by ear; a sawtooth carries more harmonics, which can make a bright instrument easier to match.
Can I download the tone as a WAV file?
Yes. The WAV download button saves five seconds of whatever is selected as a 44.1 kHz, 16-bit WAV: a tone at its waveform and frequency, any of the five noise colors, a sweep between the frequencies you set, or the polarity click. A square, triangle or sawtooth tone is rendered through the same band-limited oscillator the Play button uses, so the file holds the signal you heard, without the aliasing a sample-by-sample square wave would add. Nothing is uploaded; the file is built in your browser.
How loud should test tones be when measuring speakers?
Start at −20 dBFS in the player and adjust the amplifier so a 1 kHz sine measures around 80 dB SPL at the listening position. Sweeps and pink noise can stay at the same RMS. Never go above 95 dB SPL for sustained tones. It is not pleasant for ears or speakers.
Can I use it to calibrate a VU meter or an audio interface?
No. It is fine for checking a speaker, a cable or channel polarity, but the browser adds its own volume stages, so the level at the converter isn't the level you set here. For meter alignment or interface calibration, use a generator plugin in the same DAW as the meter. The x42 Test Signal Generator, for example, plays a 1 kHz sine at −18 dBFS by default, the EBU R68 alignment level.
Does the tone generator work for ear training?
It can, but the dedicated frequency-training tool is built for that purpose, with scoring and a record of your rounds. Use the tone generator when you need a specific tone or sweep on demand; use the trainer when you want guided practice and progress tracking.