Tone Generator
Generate a pure tone at any frequency, with the waveform and level under your control.
Volume warning
This test plays tones that can be loud and may damage hearing or speakers. Turn your volume down before starting, then raise it gradually.
How this test works
A Web Audio oscillator generates the waveform directly from the audio hardware's sample clock, so the frequency is exact rather than approximated. Four waveforms are available: a sine wave contains only the fundamental, while square, triangle and sawtooth add harmonics in different proportions, which is why they sound progressively harsher at the same frequency. Level changes and start and stop are ramped over a few milliseconds rather than switched, because an abrupt change in a waveform produces a click that contains every frequency at once — audible, and hard on drivers. Frequency changes while playing glide rather than jump for the same reason.
What the results mean
- Frequency
- Hertz — cycles per second. Accurate, because it is derived from the audio clock rather than from a timer.
- Nearest note
- Where this frequency sits in equal temperament with A4 at 440 Hz, and how many cents away it is.
- Waveform
- Sine has no harmonics. Square, sawtooth and triangle add them, which is what makes them sound brighter and harsher.
- Actual loudness
- Reported as not measurable, because it is. The output level is relative to digital full scale, before every analogue stage.
Common problems and fixes
- I cannot hear the high frequencies
- Above 15 kHz that is most often age rather than equipment — high-frequency hearing declines steadily from the late teens. Below that, check whether your speakers actually reproduce it; many small drivers roll off early.
- Low frequencies sound quiet or absent
- Most speakers and nearly all laptop drivers produce very little below about 80 Hz. The tone is being generated correctly; the driver is not moving enough air to reproduce it.
- There is a click when I start or change frequency
- There should not be — starts, stops and frequency changes are all ramped. A click that persists usually means the audio output is being resampled or a Bluetooth codec is re-syncing.
Frequently asked questions
Is a tone generator safe for my speakers?
At moderate levels yes. Sustained high-frequency tones at high level are the risk, because tweeters handle much less continuous power than woofers and a pure tone gives them no rest. Start quiet and raise gradually.
Why does a square wave sound louder than a sine at the same level?
Because it contains harmonics above the fundamental, and those add energy in the region where hearing is most sensitive. Same peak amplitude, considerably more perceived loudness.
What frequency should I hear up to?
Textbook human range is 20 Hz to 20 kHz, but that describes a young ear in ideal conditions. Losing everything above 15 kHz by middle age is entirely normal and not a sign of damage.