How to use it
- Set the Frequency with the slider or type it in the box. To use a note, choose it under Note and press Use this note.
- Choose a Waveform, then set the Volume and the Balance.
- Pick a Duration, or tick Sweep to rise from one frequency to another, then press Play.
- Press Stop when you are done.
How the sound is made
An oscillator makes the waveform at the frequency you set. A sine wave is one pure tone. Square, sawtooth and triangle waves also contain harmonics, so they sound brighter, with the square wave the buzziest. The volume is capped at half of full scale, about -6 dBFS, so a moderate setting stays quiet. The balance turns the left or right side down in proportion.
Frequency, notes and A4
The slider is logarithmic: each step changes the pitch by the same ratio, the way the ear hears pitch, so the middle of the slider is the geometric middle of 1 Hz and 20 000 Hz, about 141 Hz. Notes use equal temperament with A4 at 440 Hz. Each semitone is the twelfth root of two, so C4 (middle C) is 261.63 Hz and C8 is 4186.01 Hz.
frequency = 440 × 2^((n − 69) ÷ 12), where n is the note number (A4 = 69)Keep the volume low
Loud sound held for a long time can damage hearing, and a tone is harder to judge than music. Start with the volume low, adjust it with the device's own volume control, and stop a loud tone as soon as you no longer need it. This page is not a hearing test: a hearing test needs a calibrated setup and a professional. The NIDCD notes that sounds at or above 85 dBA can cause hearing loss with long exposure.
Example: the middle of a sweep
A sweep from 20 Hz to 20 000 Hz over 10 seconds is at 632.46 Hz after 5 seconds: the geometric middle of 20 and 20 000, the square root of their product. Each octave takes the same time, so the octave from 20 to 40 Hz takes as long as the octave from 10 000 to 20 000 Hz.
Frequently asked questions
Can I use this tone for a hearing test?
No. The page makes plain tones on your device, but it is not a calibrated audiometer and does not measure hearing. A hearing test needs a calibrated setup and a qualified professional.
Why can I not hear 20 Hz on my laptop?
Small speakers cannot reproduce very low frequencies. Headphones or a subwoofer can play them, and how loud a tone sounds depends on the device as well as the setting here.
What is the difference between a sine and a square wave?
A sine wave has only one frequency. A square wave adds odd harmonics, at one third, one fifth and so on of the level, which makes it sound sharper and buzzier at the same pitch.
Why does the volume stop at half?
The page caps the tone at half of full scale, about -6 dBFS, so that a moderate setting stays quiet. Above 50 % a warning appears, and the cap holds whatever value you type.
What does the balance control do?
At the centre both sides play equally. Moving it left turns the right side down, and at the far left only the left side plays. Check the balance in your system sound settings if one side is still silent.
Does the tone generator record or store anything?
No. The tone is made in your browser, and nothing is recorded, stored or uploaded. It stops when you press Stop, when the duration ends, or when you leave the page.
Sources
- Web Audio API, W3C specification (oscillators and waveforms)
- Equal temperament, Wikipedia (twelfth root of two)
- A440 (pitch standard), Wikipedia
- Cent (music), Wikipedia (logarithmic pitch scale)
- Noise-induced hearing loss, NIDCD (National Institutes of Health)
Figures and text last checked on Tuesday, November 10, 2026.