Tone generator
Pick a frequency, choose a waveform and press Play. Drag the slider or type an exact value in hertz, or choose a note from C1 to C8 tuned to A4 = 440 Hz. The volume starts low; raise it slowly, because pure tones can sound much louder than they seem.
Runs in your browser: nothing you enter is sent anywhere.
How to use it
- Set the Volume low, then press Play.
- Drag the slider or type a number in Frequency. The pitch changes smoothly while playing.
- Pick a Musical note to jump to its exact frequency. The page also names the nearest note to whatever frequency you set and how many cents sharp or flat it is.
- Choose a Waveform and press Stop when you finish.
How it works
The tone comes from one Web Audio oscillator in your browser. Its output goes through a gain stage with a short fade in and out to avoid clicks. The volume control is squared and capped at half of full scale, so the lower half of the slider has fine steps and square waves keep some headroom. The default is 15 %. The tone runs only while it is playing.
Worked example
Middle C is MIDI note 60, nine semitones below A4: 440 × 2^(−9/12) = 261.63 Hz. An octave up (note 72) doubles it to 523.25 Hz.
Tips
- To test a speaker’s low end, try 40, 60 and 100 Hz at a low volume and listen for the point where sound disappears.
- Use the sine wave to tune an instrument; the other waveforms contain overtones that make the pitch harder to judge.
Frequently asked questions
What frequencies can I actually hear?
Healthy young ears reach about 20 Hz to 20 kHz, but the range narrows with age, and most speakers and headphones cannot reproduce the very lowest or highest ends. Below about 50 Hz a laptop speaker will be silent even though the tone is playing.
What is the difference between the waveforms?
A sine wave is a single pure frequency. Square, sawtooth and triangle waves add harmonics, which makes them sound brighter or buzzier. Square and sawtooth waves sound the loudest at the same volume setting.
Why is the slider logarithmic?
Pitch is perceived in ratios, not in equal steps of hertz. On a logarithmic slider each equal move changes the pitch by the same musical interval, so the middle of the slider is about 141 Hz, not 10 kHz, and low frequencies are easy to set.
How are the note frequencies worked out?
Each semitone is a factor of 2^(1/12) in equal temperament. With A4 fixed at 440 Hz, the frequency of a note is 440 × 2^((n − 69) ÷ 12), where n is the MIDI note number and A4 is 69.