Tone Generator

A test tone is the simplest sound there is: one frequency, held steady. It lets you check a speaker, find the point where a headphone driver gives up, hear whether a subwoofer reaches 40 Hz, tune a string by ear, or discover how high your own hearing goes. This generator makes a tone from 1 to 20,000 Hz in four waveforms, sweeps between two frequencies, and can save the result as a WAV file.

Choosing a frequency

Type a value, drag the logarithmic slider or press a preset: 20, 60, 100, 440, 1,000, 4,000, 10,000 or 15,000 Hz. The slider is logarithmic because pitch is: each doubling of frequency is an octave, so the move from 20 to 40 Hz matters as much as the one from 10,000 to 20,000 Hz. The big readout shows the frequency with the nearest note and its offset in cents, and below the controls are the period of one cycle and the wavelength in air at 20 °C, using 343.4 m/s. Notices warn below 20 Hz, where most speakers cannot reproduce the sound, and above 14 kHz, where tones can be painful or inaudible.

A worked example

Press Sample, which sets 440 Hz, a sine wave, a 10 percent volume and a steady tone. The page names the note A4 with an offset of +0 cents, gives the period as 2.273 ms and the wavelength as 0.780 m. The WAV download is a steady tone as long as the sweep time field, 5 seconds by default, so it contains 220,500 frames at 44,100 Hz, and counting the zero crossings in the file measures 440 Hz. A tuner pointed at the speaker reads A4.

The four waveforms

A sine wave is pure and best for measuring and hearing thresholds. A square wave is the harshest and contains odd harmonics only. A triangle is similar but much softer, because its harmonics fall away faster. A sawtooth has all harmonics and is the bright buzz used as the starting point of many synthesizer sounds. Because they hold energy at higher frequencies, square and sawtooth waves can also reveal distortion or rattles that a sine hides.

Sweeps

Set Sweep up or Sweep down, choose the other end and a time from 1 to 120 seconds, then play. The frequency changes exponentially, so each octave takes the same time. A slow sweep from 20 Hz to 200 Hz is the classic way to find room and cabinet resonances; from 1,000 to 20,000 Hz it shows where your hearing stops. Most adults lose the top of the range with age, and a result well below 20 kHz is normal.

Volume and safety

The volume slider starts low and stops at 50 percent on purpose. Pure tones concentrate energy in one place, so a loud sub-bass or a high 4 kHz tone can damage a small driver, or an ear, quicker than music at the same level. Start at the lowest setting, turn the system volume down, and raise it slowly. Do not play very low frequencies through laptop or earbud speakers; they cannot reproduce them and may distort.

Limits

The WAV file holds a steady tone of the chosen waveform, not the sweep. The output level is not calibrated; it depends on your device, its volume and the speakers. Very low frequencies are inaudible on small speakers, and the highest are limited by the 44.1 kHz or 48 kHz output of your sound card. The tone is created in your browser and the WAV is made on your device.

Related tools

• Note Frequency Chart lists the frequency of every note.
• Online Tuner listens to an instrument and compares it with a reference.
• Speaker Test checks left and right channels with noise and sweeps.
• Sound Level Meter shows how loud a tone is at your listening position.