Frequency Sweep Test: Online 20 Hz to 20 kHz Sine Sweep
Overview
Frequency Sweep Test. Set a start and end frequency, pick a sweep duration and direction, then click Start Sweep to run the Frequency Sweep Test from 20Hz up to 20kHz across your speakers or headphones. Watch the live spectrum and the current-frequency readout for gaps, distortion, or drop-offs that flag a frequency response problem. To find a hum, a whistle or a resonance peak, use the live microphone frequency spectrum analyzer and watch the frequency spectrum update in real time.
Press play on this frequency sweep test and one sine tone glides from 20 Hz up to 20,000 Hz while you listen for where the sound dips, swells or rattles. It runs on HTML5 in your browser, nothing to install, and tells you more about your speakers, room and ears than a spec sheet, whether you are an audiophile chasing a better listening experience or checking new headphones.
What a Frequency Sweep Test Reveals About Speakers and Room Acoustics
A frequency sweep plays one tone at constant amplitude while its pitch moves through the band. Because the signal never changes level, a good audio system should play it at the same volume throughout. Where the volume suddenly increases or decreases, something is wrong at that frequency in Hz: a cabinet or room resonances peak, a cancellation dip from a wall, or a speaker that can't reproduce it. Level matching and hotkeys keep bias out, which is why the abx blind test player suits double-blind comparison of codecs.
That makes it a quick way to spot flaws in room acoustics and loudspeakers. Note the problem frequencies, move a speaker a few centimetres and play it again to fine-tune your listening space. It also shows how low your system goes, often the first question audio engineering answers.
Linear vs Exponential Sweep Scale
The sweep scale sets how the tone climbs. A linear sweep adds the same number of hertz every second. An exponential (logarithmic) sweep multiplies frequency by the same factor every second, so each octave gets equal time, matching how you hear pitch. A slow log sweep at one octave per 5 seconds covers the full frequency range in under a minute. The sweeping sine tone follows: Mask traffic and noisy neighbors by playing steady white, pink or brown noise from the free noise generator while you work or sleep.
$$f(t) = f_0 \times \left(\frac{f_1}{f_0}\right)^{t/T}$$
where \(f_0\) is the start, \(f_1\) the end and \(T\) the total time of the sine wave.
Worked Example: 30 Hz Start Frequency to 16 kHz End Frequency
Set a start frequency of 30 Hz, an end frequency of 16 kHz and a duration of 18 seconds. That spans \(\log_2(16000 / 30) = 9.06\) octaves, so the exponential sweep spends 1.99 seconds per octave, roughly doubling every 2 seconds:
| Time (s) | Exponential sweep | Linear sweep |
|---|---|---|
| 0 | 30 Hz | 30 Hz |
| 4 | 121 Hz | 3,579 Hz |
| 8 | 489 Hz | 7,128 Hz |
| 10 | 982 Hz | 8,902 Hz |
| 14 | 3,964 Hz | 12,451 Hz |
| 18 | 16 kHz | 16 kHz |
The exponential version spends 10.05 seconds below 1 kHz, where most music lives. The linear one crosses that region in 1.1 seconds and spends 12.4 seconds above 5 kHz, a poor choice for hunting bass problems.
Setting the Level in dBFS and the Duration
The level is set in dBFS, decibels below digital full scale. Start well below 0 and keep your audio levels low: a steady tone sounds deceptively quiet, and loud sounds held for minutes cause ear damage. Adjust these parameters with the sliders until each octave lasts long enough to judge.
Low and High Sweep Checks for Subwoofers and Hearing
Test each end of the band on its own, whether for a subwoofer, a headphone, an earbud or your hearing.
Low Frequency Test for Bass and Subwoofer Extension
A low frequency test sweeps only the bottom octaves. Where the tone fades out is your frequency extension. Small speakers struggle with low frequencies, so a subwoofer audio test often reveals rattles or a drop near 30Hz that music hides.
- Low frequency response: where the bass fades or booms
- Crossover: where the sub hands off to the mains
High Frequency Test and the Upper Limit of Your Hearing
A high frequency test plays a descending tone and asks when you first hear the high pitch tone. High frequencies are easy for cheap drivers, so your ears are usually the weakest components. Hearing rolloff with age stops many adults at 14-16 kHz; anything above 10 kHz is a bonus. A voice over (spoken voiceover) naming the frequency helps you find the boundary.
- Extended high frequency response: 8 kHz to 22 kHz, the highest frequencies
- Hearing test or audiogram: only up to 8 kHz
- Mosquito tone: above 17 kHz
If the top sounds dull on every device, a hearing loss check beats another frequency response test.
Chasing a Bedroom Bass Boom With a Slow Sweep
The question on the table is simple: should the subwoofer in a 4.03 m by 3.37 m bedroom studio move, or does it need an EQ cut? Kick drums sound fat on one note and thin on the next, and the answer turns out to be a room mode at about 85 Hz, caused by the room's length rather than the sub.
I set the sweep to 25 Hz start, 250 Hz end, 40 seconds, exponential, at -18 dBFS, and sit in the mixing chair with a phone stopwatch running. Forty seconds over 3.32 octaves gives 12.04 seconds per octave, slow enough to judge each note. The tone is even until it swells hard at 21.3 seconds, then drops back. Plugging that into the exponential formula: \(25 \times 10^{21.3/40} = 85.2\) Hz.
The cross-check is the axial room-mode formula, \(f = n \times 343 / (2L)\), with sound at 343 m/s. For the 4.03 m length, the second mode lands at 85.1 Hz, within 0.1 Hz of what the frequency sweep found. The 3.37 m width gives 50.9 Hz and 101.8 Hz, and neither swelled, so the length is the culprit.
| Sweep length | Seconds per octave | Error from a 0.5 s late reaction at 85 Hz |
|---|---|---|
| 40 s | 12.0 | +2.5 Hz |
| 20 s | 6.0 | +5.0 Hz |
That rerun matters more than it looks. On a rising sweep you always hear the swell a moment after it starts, so your reading lands high, and halving the length doubles the error. A peak read off a fast sweep can point an EQ filter at 90 Hz when the problem sits at 85 Hz, and a narrow cut in the wrong place does nothing. The number I'd trust least is the one you get from a single fast pass.
The next step is specific: slide the sub 0.5 m along the long wall, rerun the identical 40-second sweep, and only if the swell at 85 Hz is still there, add a narrow parametric cut at 85 Hz. Moving the speaker changes how it drives the mode for the whole room; an EQ cut only fixes the one seat you measured from.
Sweep Pitfalls: Aliasing, Sample Rate and Sound Card Distortion
A cheap sound card can create aliasing: ghost frequencies folded into the audible range, so instead of a continuously descending sweep you hear warbling. A 44.1 kHz file on a soundcard running at 48 kHz goes through resampling, which adds similar artefacts. Distortion shows up as harmonics above the real tone, and harmonic distortion is easiest to hear in bass. Background noise hides quiet dips.
Why a Frequency Sweep WAV File Beats an MP3
The .wav format is uncompressed; an MP3 or other compressed format adds artefacts that mask the tone. If your browser struggles, download the file and run the freq sweep test from a desktop audio application.
Making Your Own Test Tones in Audacity
Free editor Audacity generates test tones and sweeps through its Chirp generator or a Nyquist plug-in, then exports a test tone for any device.
Test Tones for Driver Break-In, Then a Sweep to Check It
A sweep per se isn't how you break in new drivers. Builders use a fixed frequency tone near resonance, such as 30Hz at around 10 volts for a sub driver. Sweep before and after: any break-in change shows up in the bottom octave.
Other Audio Checks to Pair With a Sweep
Frequency response tests are only part of an audio test session. Add:
- Stereo imaging and left/right checks
- Speaker polarity
- Dynamic range and noise floor
Frequently Asked Questions
- What is a frequency sweep test?
- It plays a single tone at constant amplitude whose pitch moves steadily from a start frequency to an end frequency. Because the level never changes, any part of the sweep that sounds louder or quieter points to a speaker, headphone or room problem at that frequency.
- Should I use a linear or logarithmic sweep?
- Use logarithmic for most listening tests. It gives every octave the same time, which matches how you hear pitch, while a linear sweep rushes through the bass and spends most of its time on high frequencies.
- How do I test my speakers with a sweep?
- Sit in your normal listening spot, set a moderate volume and play a full range sweep. Note the times or frequencies where the tone swells, fades or rattles, change one thing such as speaker position, and run the identical sweep again.
- What sweep duration should I use?
- Short sweeps of around 10 seconds are fine for a quick check. For finding a specific peak or dip, use a longer, slower sweep so each octave lasts several seconds and your reaction time causes less error.
- Can I use a sweep for room acoustics?
- Yes. Low frequency sweeps are a simple way to hear room modes: a bass note that booms or vanishes at one spot in the room usually comes from the room's dimensions rather than the speaker.
- Is 32 Hz low bass?
- Yes. 32 Hz is in the deep bass that many small speakers cannot reproduce at all, so it is a good point to listen for in a subwoofer sweep.
- Why does the sweep sound distorted or warbly at high frequencies?
- A cheap sound card or poor resampling can cause aliasing, which creates ghost tones in the audible range. Try playing an uncompressed WAV file from a desktop audio player, or match the sample rate of your device.