Online Tone Generator — Free Tool

An online tone generator plays a precise sine, square, sawtooth or triangle wave at any frequency from 20 Hz to 20 kHz, synthesized live in your browser with the Web Audio API. Nothing is uploaded or recorded, and output level is reported in dBFS relative to digital full scale.

How to use it

1. Press Play tone, or tap Space. The click opens the AudioContext, because browsers suspend audio until a user gesture.
2. Drag the tuning dial to set frequency. The pointer sweeps a 300° logarithmic scale while the readout tracks hertz, the nearest note, cents and the period. At 440 Hz the period reads 2.27 ms.
3. Flip the RANGE switch between decades. ×1 covers 20–200 Hz, ×10 covers 200 Hz–2 kHz and ×100 covers 2–20 kHz. FINE slows the drag; NOTE snaps to the nearest equal-tempered pitch.
4. Choose one of the four waveform shutters. Sine, square, sawtooth and triangle each draw on the live scope; the chart plots the primary frequency over the last eight seconds.
5. Set the output level and balance, then listen. OUTPUT LEVEL defaults to −9.1 dBFS and tops out at −6.0 dBFS; the meter reports RMS and peak, with a clip lamp that lights at −0.1 dBFS. BALANCE pans left to right, and Mute silences the output.
6. Add Channel B for two-tone work. Switch on CHANNEL B · MIX, give the second oscillator its own frequency and wave, and the two signals sum. Copy link shares the state; Download WAV saves a 2-second render.

The dial, the range switch and the readout

A laboratory signal generator tunes in decades, and this dial does the same: the pointer sweeps 300° of logarithmic scale spanning one decade, while RANGE multiplies that dial into the next band. The readout pairs hertz with the nearest equal-tempered note and the cents error; cents are pitch ratios with 100 cents to a semitone, so 442.5 Hz reads +9.8 ¢ against A4 = 440 Hz.

Keyboard moves are exact: ↑/→ and ↓/← step one semitone, Shift ten, R cycles the range, and Space starts and stops.

What the four waveforms contain

A sine wave holds one frequency and no harmonics, which is why it is the reference for level and hearing checks.

Waveform	Harmonic content	Crest factor (peak/RMS)	Typical test use
Sine	Fundamental only	3.01 dB	Level calibration, hearing threshold checks, distortion references
Square	Odd harmonics (3f, 5f, 7f) falling at 1/n	0.00 dB	Polarity checks, tweeter stress, clock and logic paths
Triangle	Odd harmonics falling at 1/n²	4.77 dB	Preamp linearity, gentle harmonic excitation
Sawtooth	All integer harmonics falling at 1/n	4.77 dB	Speaker and pickup character, filter sweeps

Sine wave generator and audio frequency generator

A sine wave generator is this instrument with the sine shutter selected, and it is the cleanest signal for checking a driver because no harmonic can be mistaken for distortion. An audio frequency generator is the broader name for the dial: 20 Hz to 20 kHz on one control, reading in hertz and naming the nearest note.

• 20–200 Hz: subwoofers, port chuffing, room modes and cabinet rattles. A 20 Hz tone has a 50 ms period and needs real excursion, which phone speakers rarely produce.
• 200 Hz–4 kHz: most speech and music fundamentals; use it for midrange balance and crossover seams.
• 4–20 kHz: tweeter response, hiss and the ceiling of your hearing. If 15 kHz is silent but 8 kHz is clear, that is normal roll-off, not a broken speaker.

Every frequency on the dial has a period (T = 1/f) and a nearest note; the table collects common reference points at A4 = 440 Hz.

Frequency	Nearest note	Cents off	Period	Common use
20.00 Hz	E0 (20.60 Hz)	−51 ¢	50.00 ms	Sub-bass limit and excursion check
41.20 Hz	E1	0 ¢	24.27 ms	Low E of a 4-string bass
82.41 Hz	E2	0 ¢	12.13 ms	Low E of a standard guitar
110.00 Hz	A2	0 ¢	9.09 ms	Low male vocal fundamental
440.00 Hz	A4	0 ¢	2.27 ms	Reference pitch (ISO 16)
1000.00 Hz	B5 (987.77 Hz)	+21 ¢	1.00 ms	Calibration standard for meters
20000.00 Hz	D#10 (19912 Hz)	+8 ¢	0.05 ms	Upper edge of the audible band

Stage mode, shareable setups and WAV export

Stage mode expands the instrument to the full viewport and requests a wake lock so the display stays on; Escape exits. The URL carries the setup (freq, wave, mode, b, bwave, pan, level), so Copy link reopens the same tone elsewhere, and Download WAV renders a 2-second 16-bit file offline.

Accuracy, limits and troubleshooting

• The generator is a source, not a meter: pair it with the Audio Oscilloscope or Audio Spectrum Analyzer to measure what the driver actually produced.
• dBFS is digital full scale, not sound pressure: the same −9.1 dBFS tone can be whisper-quiet on one system and very loud on another. Never push the level up to hear a tone, and step up slowly above 6 kHz.
• Volume and processing sit after the generator: Windows enhancements and some macOS filters can compress or EQ the signal, so switch them off for reference work.
• Wireless output adds buffering: Bluetooth headphones and speakers routinely delay playback by more than 100 ms, so use wired output for timing tests.
• Laptop and phone speakers roll off at both ends: a 30 Hz tone may move air you cannot hear, and 18 kHz can be inaudible on small drivers even when present.
• The dial stops at 20 Hz and 20 kHz. Those limits are deliberate, and the Sweep Generator covers timed glides across the band.

Related tools

• Sweep Generator — run a logarithmic or linear glide for driver and room checks.
• Noise Generator — white, pink and brown noise for masking, level setting and room excitation.
• Waveform Generator — draw and play custom periodic shapes beyond the four standard waves.
• Audio Frequency Check: play stepped tones and track which frequencies you can still hear.

Aliases covered on this page: tone generator, frequency generator, audio frequency generator, and sine wave generator.