Frequency Sweep Test

Ever wondered why your subwoofer rattles at one note but goes dead silent at another, or why your headphones seem to colour certain frequencies in ways a spec sheet never warned you about? A frequency sweep test answers those questions by moving a pure tone continuously through the entire audible range — revealing every peak, dip, resonance, and rolloff point your system hides. Whether you are a home-studio engineer chasing a flat response, an audiophile hunting speaker defects, or someone trying to match a tinnitus pitch, the sweep signal you generate here puts precise, actionable data in your hands.

What Is a Sweep Test and How Does Audio Scanning Work

A frequency sweep test is a method of acoustic measurement in which a single sine wave — or another chosen tone shape — moves progressively from a start frequency to an end frequency across the complete audible band. Unlike pink noise or white noise, which play all audible pitches simultaneously, a sweep plays one pitch at a time. This concentration of the full available dynamic range into a single pitch gives the probe output a far higher energy per band compared to broadband noise sources, making it far more immune to room ambience and background interference. The result is cleaner readings and sharper identification of resonant pitches. The measure audio round trip delay is free to use with no sign-up, and works on both desktop and mobile browsers.

The sweep is sometimes called a chirp or chirp signal in signal-processing literature, and the terms glide and glidesweep appear in professional engineering contexts. Professional analyzers also refer to it as a swept sine excitation when characterising an electromechanical system or transducer. The standard covered band is 20 Hz to 20 kHz — the full range of audible pitches for a healthy human ear — though this free online frequency sweep generator also supports ultra-low bass sweeps starting from 1 Hz and extends to higher sample rates for pro-audio use. Sound testing with a sweep rather than broadband noise offers superior resolution for calibration and perception studies alike.

Linear Sweep vs. Logarithmic Sweep and Frequency Response Behaviour

The most important choice you make before running any sweep test is the pitch scale: linear or logarithmic. In a linear sweep, the pitch advances by equal step sizes over equal time intervals — for example, sweeping from 20 Hz to 40 Hz takes exactly the same wall-clock time as sweeping from 10,000 Hz to 10,020 Hz. On a linear time scale, that upper segment covers only a tiny 3-cent pitch interval — far less than a musical semitone — so the bass region receives proportionally far less test time than the treble. A linear sweep produces a white-like spectrum and is best paired with a linear FFT analyzer or a linear FFT for accurate acoustic evaluation.

A logarithmic sweep — also written as a log sweep or exponential sweep — allocates equal time to each musical interval. Sweeping from 20 Hz to 40 Hz (one octave) takes exactly the same duration as sweeping from 10 kHz to 20 kHz (also one octave), which matches the way human perception and psychoacoustics process musical pitch. The logarithmic version produces a pink-like spectrum and is the correct stimulus when using a log-frequency-scaled spectrum tool. Professional electroacoustics engineers strongly prefer the log sweep because it dedicates proportionally more output duration to the bass octaves where standing waves and resonance problems are most common. A logarithmic scaling approach also naturally matches the logarithmic time scale used by most professional analyzers, so a perfectly linear system exhibits a genuinely even response to the logarithmically swept stimulus.

When you use a linear scaling approach, be sure to select the corresponding linear version in the analyzer software, otherwise the displayed curve will appear to slope incorrectly. In both cases, you can optionally apply sliding curve averaging or use the peak hold function on your spectrum tool to capture the full pitch range in a single pass.

How the Logarithmic Ear Perceives the Audio Spectrum — the Fletcher-Munson Effect

Human perception of sound is not flat. Our ears are most sensitive roughly between 2 kHz and 5 kHz, and significantly less sensitive at the low end and very high range. This non-linearity is captured by the well-known Fletcher-Munson effect and its more rigorously measured successor, the ISO equal loudness contours. When you run a constant-amplitude sweep, the upper medium pitches — roughly 2 kHz–5 kHz — will be perceived as louder than they measure in dBSPL, even though the probe output has an equal-amplitude profile throughout.

Important: Do not use perceived volume level alone to judge even output during a sweep. Focus instead on strong, localised dips and peaks rather than the gradual rise and fall caused by the equal loudness contours. The equal-loudness curve creates an illusion of unevenness even in a perfectly calibrated system.

This psychoacoustic reality is why audiometry and formal audiometric check protocols always compensate for equal-loudness curves, and why a perceptual sine sweep — a sweep that adjusts amplitude weighting across the band — can be more representative of subjective listening experience than a simple constant-level sweep. When evaluating systems by ear, always use the logarithmic sweep mode, since your ears are themselves working on a roughly logarithmic scale.

Full Spectrum Applications: What You Can Use a Frequency Sweep Test For

The answer to "what can I use this tone generator for?" is remarkably broad. Any situation where you need to understand how a system responds to a variable input of changing pitch — whether that system is a driver cabinet, a pair of headphones, a room, or a human auditory system — is a candidate for sweep-based evaluation. Below are the most important application areas.

Acoustic Component Measurements, Speaker Testing, and Room Acoustics

Sweep-based acoustic component evaluation covers everything from small enclosures to large concert-hall room acoustics. When you play a log sweep through a transducer system and capture the output with a measurement microphone, you can extract the amplitude response, phase response, and even the impulse response via post-processing — all from a single short sweep file. This is the basis of modern electroacoustics software such as Room EQ Wizard.

• Resonant pitches and standing waves appear as sharp peaks or dips in the measured curve, making them immediately actionable for room treatment or equalization.
• A midrange driver or full-range transducer can be verified for an even, uniform output across its intended operating band.
• The impedance profile of a driver — including its resonance pitch — is measurable with a sweep output plus a series resistor, confirming design compliance without specialist instrumentation.
• Acoustic amplitude response in non-free-field environments (rooms) versus open conditions can be compared directly using the same sweep file.
• Room ambience effects such as reflections, ripples, and colourations are all captured in a single pass, enabling informed decisions about acoustic treatment and driver placement.

For evaluations involving a mixing console, power amp, or microphone input, the sweep can be injected at the analog input or digital input of the device under test, and the output captured by an analysis tool. This closed-loop approach — sometimes called closed signal path measurement — fully characterises the output profile, consistency, and phase response of the complete chain including input stages, gain stages, and output transformers.

Playback Device Evaluation, Distortion Analysis, and Frequency Response Measurement

Sweep-based evaluation of reproduction devices — including headphones, earphones, power stages, DACs, and built-in transducers in mobile phones, tablet computers, and smart devices — is one of the most common applications of this tool. Because the sweep plays one pitch at a time, any colouration product generated by the device appears at a different pitch from the probe tone, making it easy to separate total harmonic distortion and intermodulation artefacts from the fundamental.

A spectrum tool watching the output while you play a sweep will show burst-like spikes of harmonic energy each time the fundamental passes through a pitch where the device is non-linear. You can assess pitch resolution, response coverage, output bandwidth, and consistency all at once. For smartphones and devices with automatic gain control, note that the AGC may attempt to compensate for the changing content — use a stepped sweep with sufficient dwell time per step in that case, or disable it before evaluation. A pre-tone or short pre-loaded output at a fixed level can be used as an audible trigger to synchronise the generator with the capture window of your analysis tool.

When evaluating hi-fi or stereo systems, look for: consistent amplitude response across the audible band; the absence of unexpected peaks at crossover points; smooth pitch transitions through the evaluation bandwidth; and low impulse-response ringing that indicates good time-domain behaviour. Professional engineers also check impedance profile and phase response simultaneously using swept-sine analysis, particularly for drivers wired through passive crossovers where impedance swings can stress the power amp.

Tinnitus Frequency Matching, Hearing Assessment, and Audiology Applications

One of the most personally meaningful uses of a pitch sweeper is tinnitus pitch matching. If you experience pure-tone tinnitus — a constant, single-pitched ringing — sweeping through narrow pitch ranges with this online tone generator allows you to isolate the precise pitch of your tinnitus. Knowing your tinnitus pitch enables you to better target masking sounds, personalise sound therapy, and engage in structured pitch-differentiation training with an audiologist.

For a rigorous match, always check pitches one octave higher (pitch × 2) and one step lower (pitch × ½) after you find a candidate — tones that are an octave apart are easy to confuse, and your ringing pitch could sit at any higher or lower position within the audible range. The process is a form of informal audiometry and should be complemented by a formal audiology check with a licensed specialist if results are clinically relevant. Audiology clinics use calibrated pure-tone audiometers for this purpose, but this tool can give you a useful preliminary picture.

General auditory evaluation use cases also include: checking the highest pitch you can detect (typically declining with age, often below 10000 Hz by middle age); verifying whether you can detect at the same level in both ears; and identifying pitches that are audible in one ear but not the other. Because people cannot detect tones below about 20 Hz or above around 10 kHz very well, you can damage your hearing or your drivers if you play tones at extreme levels while attempting to compensate for poor sensitivity. For additional neuroscience context, researchers at MIT have investigated whether repeated exposure to 40 Hz tones might reduce some of the molecular changes associated with Alzheimer's disease. Studies on transgenic mice produced encouraging results, and early human trials are ongoing — though this tool is emphatically not a medical device and makes no therapeutic claims. Separately, pitch-differentiation training using swept tones has shown promise in auditory rehabilitation contexts, and gamma entrainment research at around 40 Hz continues to develop as an area of active neuroscience inquiry.

Safety warning: You can damage your hearing or your drivers if you play tones at extreme levels. Set your system to a comfortable listening level using a mid-range reference tone (e.g. 1000 Hz at a level you can listen to without discomfort). Do not increase the output beyond this reference — especially in the upper register above 8 kHz, where auditory sensitivity is most fragile. Damage from harmful sound levels is permanent. Similarly, very low pitches at high output can over-excite a woofer cone and cause mechanical damage; always start with the output low and raise it gradually during any low-frequency driver check.

Worked Examples: Three Practical Frequency Sweep Test Scenarios

Example 1 — Using a 20-80Hz Log Sweep to Find a Subwoofer Enclosure Resonance

Suppose you have just built a ported low-frequency enclosure and want to confirm that the port is tuned to its design resonance pitch. Place a measurement microphone about 1 metre in front of the driver on-axis. Route the low-frequency driver check file (20–80 Hz, log sweep, ascending) through your power amp at a moderate output level — low enough not to over-excite the driver, but high enough for the microphone to register a clean output.

1. Open your spectrum analysis tool and set it to display on a log-pitch scale covering 15 Hz to 120 Hz, with the retained-peak function enabled.
2. Play the 20–80 Hz log sweep file. Watch the spectrum plot build up as the sweep moves through the bass band.
3. Identify the impedance dip region: The port tuning pitch typically appears as a notch or localised dip in the near-field pressure response measured at the port mouth, and a peak in the cone response just below tuning. If you see a sharp dip near your design target (e.g. around 40 Hz), the port is tuned correctly.
4. Compare ascending and descending sweeps: Run the 80–20 Hz descending file and overlay the result. Asymmetry between the two curves in the low-frequency driver region suggests mechanical non-linearity or a settling condition issue with the port mass.
5. Interpret results: A smooth output profile peaking naturally around 50–80 Hz and rolling off below 20 Hz at the expected rate confirms enclosure integrity. Unexpected peaks elsewhere point to panel resonances or a structural problem requiring attention before the enclosure is finalised.

Example 2 — Running a 1Hz-20kHz Linear Sweep Through Headphones to Locate Audible Distortion

You want to know at what pitch your hi-fi headphones begin to exhibit audible colouration. Connect your headphones to a calibrated interface and use the full-range linear sweep long test sound at a modest input level (around −12 dBFS to protect the drivers).

1. Set a safe output level: Play a 1000 Hz reference tone and set your system to a comfortable listening level. Lock the output setting here.
2. Start the linear sweep reproduction while monitoring both by ear and through a linear FFT analyzer capturing the headphone output via a dummy head or in-ear microphone.
3. Listen for roughness or buzzing: Note the approximate pitch at which you first hear non-linear artefacts — this is often in the upper bass or lower midrange for dynamic drivers. Record the value in Hz.
4. Confirm with the analyzer: On the linear FFT analyzer display, look for harmonic sidebands appearing at integer multiples of the sweep pitch — e.g. a second harmonic at twice the probe tone pitch. This confirms total harmonic distortion rather than a coincidental room resonance.
5. Evaluate the output profile: A good pair of headphones should show a broadly smooth output from around 20 Hz to around 20 kHz, with no sudden dips greater than 6 dB at any single pitch (though a gradual high-pitch rolloff above 10 kHz is normal and expected).

Example 3 — Performing Tinnitus Frequency Matching with a Narrow-Range Sweep

Tinnitus frequency matching is one of the most delicate applications of an online frequency generator. The goal is to find the single pitch that most closely resembles the perceived tone of your tinnitus, enabling better-targeted relief sounds and pitch-differentiation training.

1. Start broad: Use the full-range log sweep (1 Hz–20 kHz) at a very low, comfortable level — well below your normal listening level. Listen for the moment during the sweep when the external tone seems to overlap with or resemble your internal tinnitus pitch.
2. Note the approximate pitch: If your tinnitus seems loudest or most similar to the sweep around the high-pitched region (common for noise-induced cases), it may fall anywhere between 1000 Hz and 12 kHz. Note the rough position in the sweep.
3. Narrow the range: Switch to a constant-tone mode and use fine-pitch adjustment (e.g. steps of 1 Hz, 0.01 Hz, or 0.001 Hz) to home in on the precise match. This precision level of pitch change is only achievable with an interactive frequency generator, not pre-rendered sweep files.
4. Check octave neighbours: Once you find a candidate match, double the pitch (go one step higher) and then halve it (go one step lower) to confirm you have the correct octave. Tones that are one octave apart sound similar in quality and are easily confused — a careful interval check is essential.
5. Document and share: Record the matched pitch in Hz and share it with your audiologist. This information can guide targeted notched-music therapy or relief sounds calibrated to your pure-tone tinnitus pitch.

This tool is also useful for tuning instruments, conducting classroom science experiments (finding the resonance pitch of a wineglass or cavity), evaluating the input sensitivity of a mixing console, verifying equalization curves applied by DSP processors, and checking output gear for production quality assurance. Whether you download a WAV file or MP3 file for offline use, play a tone directly from this online interface, or use the interactive oscillator mode to adjust pitch in real time, the underlying principle of signal processing remains the same: isolate any pitch in the audible range, concentrate the available output energy there, and let the system under test reveal exactly what it can and cannot do.

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