What Is a Tone Generator?
A tone generator produces a continuous audio frequency at a fixed pitch. Engineers use them to calibrate equipment, test the frequency response of speakers and rooms, and align audio systems. Musicians use them for tuning instruments and ear training. Hobbyists use them for casual hearing range tests.
Our online tone generator uses the Web Audio API's OscillatorNode to produce mathematically pure waveforms. There's no audio file involved: the tone is synthesized in real time on your device, ensuring perfect accuracy without compression artifacts.
The frequency range spans 20Hz (lower limit of human hearing) to 20kHz (upper limit). You can enter exact frequencies, drag the slider for quick adjustment, or use musical presets that map to common reference pitches.
Four standard waveforms are available: sine (pure, no harmonics), square (bright, odd harmonics), sawtooth (rich, all harmonics), and triangle (soft, weak odd harmonics). Each has its uses depending on whether you want a reference tone (sine) or to stress-test equipment with harmonic content (square/sawtooth).
Waveform Types Explained
Sine waves are mathematically the simplest: a single frequency with no harmonics. They sound smooth and 'pure', like a tuning fork or a clean test tone. Engineers prefer sine waves for measurement because problems in the audio chain show up as added harmonics that wouldn't exist in a clean sine.
Square waves have a flat top and bottom with instantaneous transitions. Mathematically they contain the fundamental frequency plus odd harmonics (3rd, 5th, 7th, etc.) at decreasing amplitudes. They sound bright and buzzy: think early video game music or analog synths.
Sawtooth waves have a linear rise and instant drop. They contain all harmonics (odd and even) at decreasing amplitudes, making them the richest waveform. Sawtooths are the basis of brass and string synth sounds.
Triangle waves are similar to sine but with slight angular shape. They contain only odd harmonics like square waves but at much lower amplitudes. The sound is softer and more 'flute-like' than square.
Hearing Range Tests with a Tone Generator
Adults gradually lose the ability to hear high frequencies starting in their early 20s: a process called presbycusis. By age 30, most people can't hear above 17 kHz. By age 50, many can't hear above 13 kHz. This is normal and not a hearing defect.
To test your hearing range, start at 1 kHz at a comfortable volume. Slowly raise the frequency. Note the highest frequency at which you can still hear the tone clearly. This is your high-frequency hearing limit.
For a low-frequency test, start at 100 Hz and lower. Most adults hear down to 20 Hz, but very low frequencies require good speakers or headphones. Laptop speakers and earbuds typically can't reproduce below 80–100 Hz.
Warning: high-frequency tones at high volume can damage hearing. Always start at low volume and increase gradually. If you experience ringing or temporary hearing loss after testing, you went too loud.
This is a casual test, not a clinical diagnosis. For real hearing concerns, see an audiologist for a proper audiogram.
Speaker and Headphone Testing with Tones
Frequency sweeps reveal speaker and headphone limitations that music masks. Music contains so many overlapping frequencies that gaps or peaks in your equipment's response get hidden. A single sine wave makes them obvious.
To find your speaker's low-frequency rolloff, start at 200 Hz and slowly drop the frequency. The tone should remain audible and consistent in volume. When it suddenly drops or disappears, you've found the speaker's low-frequency limit. Small computer speakers often roll off above 100 Hz; subwoofers extend to 30 Hz or lower.
For distortion testing, play a sustained tone at moderate volume and listen carefully. Buzzing, rattling, or 'crackly' sounds indicate either driver damage or loose components vibrating sympathetically with the tone.
For stereo imaging tests, play the same tone in both channels and walk around your speakers. The sound should appear to come from a single point directly between them. If it shifts or appears to come from one speaker only, your speaker positioning needs adjustment.
Musical Pitch and Concert A
The reference pitch in Western music is A4 = 440 Hz. This is the A above middle C. Every other musical note's frequency is calculated from this reference using a logarithmic 12-tone equal temperament scale.
Some orchestras tune slightly sharp (442 or 443 Hz) for brighter sound. Baroque music is sometimes performed at A=415 Hz, a half-step lower than modern concert pitch.
To tune an instrument with our generator: play A4 at 440 Hz, then play the same note on your instrument. Adjust the instrument's tuning until the two pitches match. Beating (a slow wavering sound) indicates the pitches are close but not exact: adjust until the beats stop.
For reference: middle C = 261.63 Hz, A3 (octave below A4) = 220 Hz, A5 (octave above A4) = 880 Hz. Each octave doubles the frequency.