Frequency Sweep Generator — Free

This sweep generator plays a sine tone that glides between two frequencies from 20 Hz to 20 kHz in linear, logarithmic or percussive mode, with an adjustable duration, a direction switch and WAV export. It runs through the Web Audio API in your browser, and nothing is uploaded or recorded.

How to use it

1. Set both ends of the sweep with the start and end dials. They default to 20 Hz and 20 kHz, cover the same 20 Hz to 20 kHz range on a logarithmic scale, and accept typed values as well as dragging.
2. Choose a duration from 0.2 to 20 seconds with the slider; the default of 5 seconds suits a full-band listen.
3. Choose the sweep mode. Linear, Logarithmic and Percussive are the three options, and Logarithmic is selected at the start.
4. Choose the direction. Up travels from the start dial to the end dial; Down reverses it, and the hint line spells out the actual travel, for example 20.00 kHz to 20.0 Hz.
5. Press Play Sweep and watch the frequency readout, which refreshes about every 100 ms while the sweep runs. Stop ends it early.
6. Press Download WAV to render the current sweep offline. The export is clamped to between 0.5 and 20 seconds and saves a mono WAV file.

Linear versus logarithmic sweeps

A linear sweep holds the rate of change in hertz per second constant, while a logarithmic sweep holds the ratio constant, and that single difference changes both the sound and the measurement.

Mode	Frequency law	20 Hz to 20 kHz over 5 seconds	Time per octave
Linear	Constant hertz per second	3,996 Hz per second	Uneven: about 20 ms for 20 to 100 Hz, about 250 ms for the last kilohertz
Logarithmic	Constant ratio per second	About 4× per second, or two octaves per second	Even: about 0.5 s per octave
Percussive	Repeated short chirps	One chirp every 0.28 s, each lasting 0.03 to 0.14 s	Same law as the log sweep inside each chirp

Pitch perception is logarithmic: every octave doubles the frequency, so equal time per octave is what sounds like an even glide. A linear sweep spends almost all of its time in the top two octaves, which is why it sounds like it races through the bass and then lingers up high. Use linear when the measurement is defined in hertz, for example when checking the response of a fixed-bandwidth device, and logarithmic when you are listening across the audible range.

Why a log sweep is the standard room-measurement stimulus

A logarithmic sine sweep played through a loudspeaker and recorded with a microphone is the usual way to measure a room, because deconvolving the recording with the known sweep recovers the impulse response in one pass. From that impulse response you can derive the frequency response, the decay behavior and the arrival times of reflections in a way that is easy to window and analyse.

Two properties make the log sweep attractive. First, every octave receives an equal share of the sweep’s duration, so the recorded level and the signal-to-noise ratio stay even from 20 Hz to 20 kHz; broadband noise needs many averaged frames to reach the same confidence. Second, the loudspeaker’s own harmonic distortion lands at different times in the deconvolved result. For a sweep of duration T running from f1 to f2, the k-th harmonic appears ahead of the linear impulse response by roughly T × ln(k) / ln(f2 / f1): for a 5-second 20 Hz to 20 kHz sweep, the second-harmonic residue sits about 0.5 s before the main arrival, where it can be windowed out of the measurement. That separation is why log sweep plus deconvolution is the preferred stimulus, and the same sweep makes a good listening test for rattles, buzzes and drivers that roll off early.

Percussive mode chops the glide into repeated chirps: one every 0.28 s, each between 0.03 and 0.14 s long, so a 5-second run contains about 18 of them. The gaps give your ears a reference between repeats, which suits quick audibility checks and demonstrations where you want each sweep to be clearly delimited.

Accuracy, limits and troubleshooting

• Range and clamping. The dials cover 20 Hz to 20 kHz while the engine clamps at 1 Hz and 20 kHz, so nothing outside the audio band can be scheduled.
• Scheduling is exact, rendering is not. Both sweeps are scheduled on the audio clock with oscillator ramps, so page load or scrolling cannot disturb the frequency trajectory. The visual readout is display only.
• The readout can freeze in a background tab. It updates through animation frames at roughly 10 Hz while visible; a hidden tab stops refreshing the display while the audio continues normally.
• Very short sweeps are hard to judge. At 0.2 s a full-range sweep is a chirp, which is useful as a stimulus but difficult to evaluate by ear. Use 3 to 10 seconds for listening tests.
• Percussive runs need duration. With one chirp every 0.28 s, a 1-second run contains only a few repeats; lengthen the duration for a full sequence.
• Bluetooth and device DSP. Codec latency can delay the start and some codecs band-limit the top octave, so judge high-frequency behavior on wired headphones or speakers. Windows audio enhancements and macOS voice isolation can also alter playback.
• Speaker limits, not sweep faults. Phone and laptop speakers cannot reproduce 20 Hz, and hard low-frequency sweeps at high level mostly produce mechanical rattle. Reduce the level and repeat.
• Level is relative. Sweeps play at a fixed internal gain with a 20 ms fade-in and 80 ms fade-out, and levels are reported in dBFS, not SPL.
• Hearing care. Start low, keep the level fixed, and stop if a frequency becomes uncomfortable. Turning the level up to chase a tone you cannot hear clearly is the wrong move; work at a comfortable setting instead.

Related tools

• Tone Generator: stop on a single frequency when you have found the one that misbehaves.
• Noise Generator: feed pink or white noise through the same system for a broadband comparison.
• Perceptual Sine Sweep: an alternative sweep presentation designed around perceived pitch.
• Room Acoustic Test: check decay times and resonances with a swept stimulus.