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Vibration Frequency Analyzer

This free vibration frequency analyzer lets you point your device at a running motor, pump, fan or gearbox and see the live FFT spectrum of the sound it radiates. The analyzer auto-detects the dominant frequencies, overlays 1X–5X order lines from a shaft speed you type (1X = RPM ÷ 60 Hz), lets you switch between spectrum and time-domain waveform, smooths the trace with spectral averaging, and exports the data as CSV or a PNG chart.

⚠ This reads airborne SOUND, not accelerometer vibration. A device microphone captures the sound your machine radiates into the air, so it reveals the frequency content — which is genuinely useful for matching peaks against your calculated bearing, gear-mesh, imbalance and blade-pass frequencies. It is not a calibrated vibration measurement: it does not give amplitude in mm/s velocity or g acceleration, and it cannot be used for ISO 10816 / ISO 2372 severity, which requires a calibrated accelerometer mounted on the machine. For real condition monitoring, use an accelerometer + analyzer. Auto-gain, noise suppression and echo cancellation are requested off. Nothing is recorded or uploaded.

Microphone

Idle — press Start to allow your microphone and see the live machine spectrum.

View

Frequency axis

FFT size

Averaging

Peak labels

Shaft speed (RPM, optional)

Show 1X–5X order lines

Enter the shaft speed to overlay 1X–5X order lines (1X = RPM ÷ 60).

Overlay on — type an RPM above to draw the order lines.

Vertical axis = relative level (dBFS, uncalibrated) — not mm/s or g. Horizontal axis = frequency. Dashed cyan = RPM order lines; amber dots = detected peaks.

Dominant frequencies

The strongest peaks above the noise. When you enter an RPM, the Order column shows how many times running speed each peak sits at — match these against the frequencies from a bearing, gear-mesh or imbalance calculator. Frequencies are reliable; the order match is a diagnostic convention, not a diagnosis.

#	Frequency	Rel. level	Order (×RPM)
Start the analyzer to detect dominant frequencies.

Capture details

Frequency resolution improves with a larger FFT size (narrower bins) at the cost of a slower update. A larger FFT helps separate close orders such as 1X imbalance from a nearby bearing tone.

Sample rate —

Frequency resolution —

Export gives you a local download only: CSV = frequency vs relative dBFS per bin (with a header noting it is not calibrated amplitude); PNG = the chart as drawn. Nothing leaves your device.

How It Works

Acting as a browser-based FFT spectrum analyzer, the tool streams audio from your microphone and runs a Fast Fourier Transform (FFT) on each short window, splitting the sound into hundreds or thousands of frequency bins. The result is plotted as a spectrum — on a logarithmic axis (so a 30 Hz shaft tone and a 6 kHz gear whine both get readable space) or a linear axis (so evenly-spaced harmonics line up at a constant pitch). A waveform view shows the raw time-domain signal instead, which is handy for spotting impulsive knocks and modulation at a glance.

Every frame the tool looks for local maxima that stand clearly above their neighbours, ranks them by level, removes near-duplicates, and lists the strongest. Spectral averaging blends each new frame into a running exponential average (EMA) so random fluctuations settle down and the persistent machine tones stand out — Heavy averaging gives the most stable reading, Off shows the instantaneous spectrum. When you see a cluster of peaks spaced evenly either side of a central tone, those are sidebands — a sign of amplitude or frequency modulation typically caused by shaft speed variation, eccentricity, or gear-tooth wear.

The real power is the RPM order overlay. Type a shaft speed and the tool draws dashed lines at 1X, 2X, 3X, 4X and 5X of running speed, where 1X = RPM ÷ 60 in hertz. Rotating-machinery faults concentrate energy at specific multiples (orders) of running speed, so when a measured peak lands on an order line it gives you a frequency to investigate. This is calibration-independent: the frequency of a peak comes straight from the FFT and does not depend on how loud the mic thinks it is. For fans and impellers, the blade-pass frequency (BPF) appears at the number of blades multiplied by shaft Hz; similarly, the gear mesh frequency (GMF) of a gearbox appears at the number of gear teeth multiplied by shaft Hz — enter either product into the RPM-to-Hz converter to confirm the expected value before comparing it against what you see in the spectrum.

Common order & frequency conventions

These are widely-used conventions in rotating-machinery diagnostics, not guarantees. A peak at an order does not by itself prove a fault — confirm with the actual bearing geometry, gear tooth counts and a calibrated instrument. Use the bearing fault frequency calculator to compute BPFO, BPFI, BSF and FTF from your bearing's geometry, then compare those calculated values against the peaks you see in the spectrum.

Typical frequency signatures to match against your measured peaks (orders relative to running speed f_r = RPM ÷ 60).
Frequency	Often associated with
1X (f_r)	Mass unbalance — usually the dominant 1X peak.
2X	Misalignment, looseness, bent shaft (strong 2X, sometimes 3X).
Sub-1X (~0.4–0.5X)	Oil whirl, rub, or some bearing-cage motion.
Bearing tones (BPFO/BPFI/BSF/FTF)	Non-synchronous, set by bearing geometry — use a bearing-fault calculator with Nb, ball & pitch diameter and contact angle.
Gear mesh (GMF = teeth × shaft Hz)	Gear wear/eccentricity, often with shaft-speed sidebands either side of GMF.
Blade pass (BPF = blades × RPM ÷ 60)	Fans, pumps and impellers; aerodynamic/hydraulic excitation.

What is trustworthy and what is not

Because this tool listens to airborne sound through an uncalibrated microphone, the vertical axis is relative dBFS, not a vibration amplitude. You cannot read mm/s velocity or g acceleration from it, and you cannot judge ISO 10816 severity zones — that needs a calibrated accelerometer mounted on the machine. If you do have an RMS velocity reading from a calibrated instrument, use the vibration severity checker to classify it against the ISO 2372 A/B/C/D zones. What survives the lack of calibration is genuinely useful: this acoustic view of the machine vibration spectrum faithfully shows which frequencies are present, how they line up with your RPM orders and calculated fault frequencies, and how the spectrum changes before vs after a repair when you keep the same mic, distance and gain. Consumer mics also roll off at the extremes, so deep sub-bass and any true low-frequency structural motion may read low or vanish. For HVAC diagnostics, placing the device 15–30 cm from a fan housing and using Heavy averaging reliably reveals blade-pass and motor-frequency peaks even on a smartphone mic. For best results with any machine, position the mic on the quietest axis relative to background noise, hold it steady, and capture at least 10 seconds of Heavy-averaged spectrum before exporting.

Frequently Asked Questions

Is this a real vibration meter?

No. It captures the airborne sound your machine radiates through the device microphone, not true vibration from an accelerometer mounted on the machine. That makes the frequency content meaningful and useful for matching against calculated bearing, gear and imbalance frequencies, but it is not a calibrated vibration measurement — it gives no amplitude in mm/s velocity or g acceleration. For genuine condition monitoring you need an accelerometer and a vibration analyzer.

Can I use this to check ISO 10816 severity?

No. ISO 10816 and ISO 2372 severity zones (Good / Acceptable / Unsatisfactory / Unacceptable) are defined in terms of vibration velocity in mm/s RMS measured with a calibrated accelerometer at the right location. A browser microphone gives only relative dBFS sound levels, which cannot be converted to mm/s. Use the frequency content here to locate suspect tones, then measure severity with a proper calibrated instrument.

How do the 1X–5X order lines work?

Enter the shaft speed in RPM and the tool draws dashed lines at multiples of running speed, where 1X equals RPM divided by 60 in hertz. For example, 1750 RPM gives 1X ≈ 29.2 Hz, 2X ≈ 58.3 Hz, and so on. Many rotating-machinery faults concentrate energy at specific orders — 1X for unbalance, often 2X for misalignment — so a measured peak that lands on an order line is a lead to investigate, not a diagnosis on its own.

How accurate are the detected frequencies?

The frequency of each peak is reliable because it comes straight from the FFT and does not depend on calibration. Resolution is set by the FFT size and sample rate — a larger FFT gives narrower bins (shown as Hz per bin in Capture details) and separates close peaks better, at the cost of a slower update. Averaging stabilises the trace so persistent machine tones stand out from random noise.

Why must auto-gain and noise suppression be off?

The tool requests the raw microphone signal with automatic gain control, noise suppression and echo cancellation switched off, because those features actively reshape the spectrum — pumping levels and carving out frequencies — which would corrupt the readings. We request them off, but a browser or OS may still apply processing it does not expose, so if the spectrum looks artificially clean, disable microphone enhancements in your system settings.

Is my audio recorded or uploaded?

No. The microphone signal is analysed in real time entirely in your browser to compute the spectrum, then discarded — nothing is recorded, saved, or transmitted. The CSV and PNG exports are local downloads you trigger yourself. The microphone is released the moment you press Stop or close the tab.

Which FFT size should I choose for motor or bearing analysis?

Use 8192 or 16384 for most rotating-machinery work. A larger FFT gives finer frequency bins — at 44100 Hz sample rate, an 8192-point FFT yields about 5.4 Hz per bin, while 16384 halves that to roughly 2.7 Hz — which helps separate a 1X imbalance peak from a nearby bearing tone or an electrical-line frequency harmonic. The trade-off is a slower screen update, which you can offset with Heavy averaging to keep the trace stable. Use 32768 only if you need to resolve very closely spaced spectral lines on a slow, steady machine.

What do sidebands around a peak indicate?

When you see equally spaced peaks flanking a central tone, those are sidebands caused by amplitude or frequency modulation. In rotating machinery, sidebands spaced at shaft frequency (1X) around a gear-mesh frequency (GMF) typically indicate gear eccentricity or worn teeth. Sidebands around a bearing defect frequency spaced at the cage frequency (FTF) can signal cage damage or wear. The sideband spacing is the modulating frequency — compare it against the RPM order lines or values from the bearing-fault calculator to narrow down the source.

Can I use this tool for HVAC fan or pump diagnostics?

Yes, with the caveats stated above. For fans and centrifugal pumps, the most useful signatures are the blade-pass frequency (number of blades × shaft Hz), its harmonics, and the motor electrical line frequency (typically 50 or 60 Hz and its 2× harmonic at 100/120 Hz). Place the device 15–30 cm from the fan housing or pump casing, use Heavy averaging, and enter the shaft RPM to overlay order lines. You can track whether a dominant peak shifts over weeks using the CSV export — useful for trending purposes even without a calibrated amplitude.

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