How to use the tone generator
Type a frequency or pick a preset, choose a waveform and press Play. Start with your device volume low and raise it slowly. The tone fades in over a quarter of a second, so nothing clicks or blasts, and you can change the frequency while it plays.
- Turn your device volume down. The tool starts at 25% volume.
- Set the frequency. Type it in hertz, drag the slider, or type a note such as A4 or C#5.
- Choose a waveform. Sine is the pure tone; the others sound brighter.
- Press Play. Fine-tune with the buttons: ±1 Hz, half, double, or one semitone.
- Go further. Open Sweep to glide between two frequencies, add up to 3 more tones, download a WAV file, or copy a link.
With the tool focused, Space plays and stops, ← and → change the frequency by 1 Hz (Shift: 10 Hz), [ and ] by 0.01 Hz, ↑ and ↓ by a semitone (Shift: an octave), W switches the waveform, and Esc stops all sound.
How the tone generator works
This frequency generator uses your browser’s Web Audio engine. An oscillator calculates the waveform at your device’s sample rate, usually 44,100 or 48,000 samples per second. That’s why 22,000 Hz is the practical top of any hz generator in a browser: the sample rate has to be more than twice the frequency.
The pitch is as accurate as your device’s audio clock, which is plenty for tuning and testing. An electronics frequency generator outputs voltages for circuits; this one outputs sound through your speakers or headphones.
You can type a note name instead of a frequency, which makes it a simple piano tone generator: C4 gives 261.63 Hz. The A4 reference changes every note at once. To practice singing a note, play it here, then match it with the voice pitch analyzer. A “tone generator and probe” is something else: an electrician’s tool for tracing cables.
Sine, square, sawtooth and triangle waves
A sine is one frequency and nothing else, which is what a sine wave generator makes. Square and triangle waves add odd harmonics (3, 5, 7 times the frequency), and sawtooth adds all of them, so they sound buzzier.
At the same peak level, a square wave carries more energy than a sine and its harmonics sound louder. The tool lowers square waves by 6 dB and sawtooth waves by 3 dB, so switching waveforms doesn’t make a sudden jump in loudness.
Frequency sweeps and several tones at once
A sweep glides from one frequency to another over 1 to 120 seconds. A log sweep spends the same time on each octave, the way you hear pitch. A linear sweep moves the same number of hertz per second, so it races through the low notes. Use a frequency generator sweep to find rattles and to hear where a speaker’s sound fades out. Repeat it once, in a loop, or up and down.
As a multiple tone generator, the tool plays up to 4 tones at once, each with its own frequency, waveform, level and balance. Play intervals and chords, or put two tones a few hertz apart to hear beats: 440 and 443 Hz pulse 3 times per second. For a tone in each ear, use the binaural beats page.
Testing speakers, subwoofers and headphones
Low tones from 20 to 120 Hz show how deep a subwoofer goes and what rattles. For a guided check with sweeps, marks and a phase test, use the subwoofer test. As a frequency generator for speakers, play a tone and move the balance slider to hear each side, or check the channels with the left right sound test.
Phone and laptop speakers roll off below about 100 to 200 Hz, so low tones may be silent on them. Human hearing is usually described as 20 Hz to 20 kHz, and the top end falls with age. Dog whistles work mostly above 20 kHz, beyond what phones and laptops can play.
To see which frequencies are in a sound, such as a hum or a whistle, use the spectrum analyzer. For a full check of your headphones, use the headphone test.
Volume and safety
Start low. Set a comfortable level on a 1 kHz tone, then stay near it while you change frequency.
Very high tones can sound quiet even when they’re loud, so don’t keep raising the volume to hear them. Loud high tones can harm hearing and tweeters. Low tones push small speaker cones hard, so listen for buzzing and back off.
The tool asks before you go above 50% volume with very high, very low, square or sawtooth tones. It can’t tell you anything about your hearing; it only plays tones.