Vibration Frequency Analyzer
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.
Idle — press Start to allow your microphone and see the live machine spectrum.
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.
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
The analyzer 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.
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.
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.
| Frequency | Often associated with |
|---|---|
| 1X (fr) | 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. What survives the lack of calibration is genuinely useful: 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.