Free Online Audio Frequency Generator
Generate sine, square, triangle, and sawtooth test tones.
Keep the volume low and remove headphones before starting. High frequencies at high levels can be uncomfortable and potentially harmful.
About the Audio Frequency Generator
A signal generator produces a controlled tone at a chosen frequency and waveform, and it is one of the most useful tools in audio engineering. This browser-based generator creates precise tones with the Web Audio API, displays the live waveform on an oscilloscope, and reports the output level in decibels relative to full scale. It is handy for checking headphones, measuring room resonances, testing speakers, calibrating a recording chain, or demonstrating the relationship between frequency and pitch.
Frequency and pitch
Human hearing spans roughly 20 Hz to 20,000 Hz, although the upper limit falls with age. Low frequencies are felt as much as heard and are difficult to reproduce on small speakers. Middle frequencies around 1 kHz are where the ear is most sensitive, and high frequencies above 10 kHz provide air and detail but are easily attenuated by obstacles. The logarithmic slider makes it easier to sweep across the audible range, because equal distances on the slider correspond to equal musical intervals rather than equal hertz.
Waveforms and harmonics
- Sine: a pure single frequency with no harmonics. Ideal for calibration and threshold testing.
- Square: contains only odd harmonics with rapidly decreasing amplitude, producing a hollow, buzzy tone.
- Triangle: also contains odd harmonics but falls off faster, giving a softer sound than a square wave.
- Sawtooth: contains both odd and even harmonics and sounds bright and buzzy, similar to a string or brass instrument.
A pure sine is the safest choice for level calibration because its peak and RMS values have a known relationship. Complex waveforms have higher peak levels for the same perceived loudness, so reduce the volume when switching from sine to square or sawtooth.
Duration and continuous mode
A timed tone is useful for measurements that need a known start and end. Continuous mode is better for tuning, finding feedback frequencies, or comparing drivers. The generator fades in and out over a few milliseconds to avoid clicks. Sudden starts and stops create broadband transients that can damage tweeters and contaminate measurements, so the short ramp is intentional. Always start with the volume low and increase gradually.
Understanding the level display
The meter shows the root-mean-square level of the generated signal relative to digital full scale. A sine wave at full scale has a peak of 0 dBFS and an RMS level of about −3 dBFS. The level depends on both the volume setting and the waveform, so use the meter to avoid clipping and to compare settings. The oscilloscope shows the actual waveform shape; a clean sine should appear smooth, while a clipped or distorted signal will show flattened peaks.
Frequently asked questions
Can this generator produce frequencies above 20 kHz?
The interface limits the range to 20 Hz–20 kHz because that covers human hearing and the safe operating range of most playback systems. Some audio interfaces support higher sample rates, but ultrasonic tones are inaudible and can stress speakers.
Why does the tone sound different on my phone speaker?
Small speakers cannot reproduce low frequencies efficiently and often add resonance in the midrange. Use headphones or a full-range system for accurate listening, and avoid high volumes.
Is a sine wave the best test signal?
For frequency response and level calibration, yes. For testing harmonic distortion or speaker behaviour, square and sawtooth waves reveal different characteristics. Use the simplest signal that answers your question.