Read the guide: Vibration frequency explained
How to measure vibration frequency
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Step 1: Place your phone flat, screen up, on a hard, flat part of the thing you want to measure, away from moving parts. Tape it down if the surface is smooth or sloped.
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Step 2: If you can, switch the source off. Tap Start (on iPhone, tap Allow) and keep still for the 2-second "Hold still" step.
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Step 3: Switch the source on. The analyzer records for 60 seconds by default. Pick no limit if the vibration comes and goes.
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Step 4: Read the top 3 peaks. Each one shows its frequency in Hz and the matching speed in RPM.
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Step 5: Use the axis toggle to see whether each peak is mostly up-down, side-to-side or front-back.
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Step 6: Check the highest measurable frequency in the details. Treat any peak close to it with care (see the aliasing section below).
What your result means
Your result lands on one of four levels. This page uses the machines and appliances scale, which is based on RMS velocity in millimeters per second (mm/s).
| Level | Range (RMS velocity) | What to do |
|---|---|---|
| Smooth | Under 0.71 mm/s under 0.028 in/s | Very little shaking. Peaks this small can still reveal a rhythm, but there is nothing to fix. |
| Normal | 0.71 to 1.8 mm/s 0.028 to 0.071 in/s | Normal for most small machines. Note the main peak so you can compare it later. |
| Rough, check it | 1.8 to 4.5 mm/s 0.071 to 0.177 in/s | Worth checking. Match the main peak to a running speed to find which part is causing it. |
| Too much vibration | 4.5 mm/s or more 0.177 in/s or more | Strong shaking. Find the part whose speed matches the main peak and fix it before long running. |
How to read the vibration frequency analyzer
The vibration frequency analyzer spreads the shaking out by frequency in its spectrum chart. The horizontal axis runs from slow rhythms on the left to fast ones on the right. The height of each bar shows how much shaking happens at that frequency. The main peak is marked. Here is what common patterns mean:
- One sharp peak. One steady source, such as a motor or a spinning drum.
- A peak plus peaks at 2× and 3× its frequency. These are harmonics of one source. The lowest one is usually the running speed.
- Peaks that aren’t multiples of each other. Two or more sources turning at different speeds.
- A broad hump with no clear peak. Random shaking, like footsteps or wind, or a structure ringing at its own natural frequency.
The axis toggle helps too. With the phone flat, “front-back” is the direction its top edge points. Point the top edge along a machine’s shaft, and front-back becomes the shaft direction. Shake mostly across the shaft often points to imbalance. Strong shake along the shaft is a common sign of misalignment.
Common vibration frequencies
To measure vibration frequency well, it helps to know what to expect. RPM = Hz × 60, and the Hz to RPM converter does the math for any value.
| Source | Typical frequency | Speed |
|---|---|---|
| Ceiling fan on low | about 1 to 1.7 Hz | 60 to 100 RPM |
| Dryer drum | under 1 Hz (too slow to read well) | 45 to 60 RPM |
| Top-load washer spin | often 10 to 15 Hz | 600 to 900 RPM |
| Front-load washer spin | about 17 to 23 Hz | 1,000 to 1,400 RPM |
| Car wheel at 60 mph (225/65R17 tire) | about 11.8 Hz | about 707 RPM |
| Engine idling at 750 RPM | 12.5 Hz | 750 RPM |
| 4-cylinder firing at 750 RPM | 25 Hz | 1,500 per minute |
| Electric motor, 1,750 RPM | about 29 Hz | 1,750 RPM |
| Fixed-speed fridge compressor | 50 to 60 Hz (too fast) | 3,000 to 3,600 RPM |
| Bouncy wooden floor | often 4 to 8 Hz | not a rotation |
Why the analyzer tops out near 30 Hz
Phones deliver about 60 samples per second. To see a rhythm, you need at least two samples per cycle, so the highest frequency a phone can measure is half its sample rate: about 30 Hz. The exact limit for your phone is shown in the details.
Faster vibration doesn’t simply vanish. It can fold back and show up as a false, lower peak. This is called aliasing. For example, a 50 Hz hum sampled 60 times a second can look like a 10 Hz peak. When the tool suspects this, it says “The main vibration may be faster than your phone can measure.” Other clues: the peak jumps between runs, or it doesn’t match any speed you know. Check the known speed of the machine first. If it’s above the limit, don’t trust a low peak.
Common causes and fixes
Once you know the main peak, match it to a cause:
- Peak at a machine’s running speed. Usually imbalance. Clean fans and rotors, replace damaged blades, or have the part balanced.
- Peak at twice the running speed. Often misalignment or loose mounts. Tighten bolts and check that shafts line up.
- Peak at your wheel speed, measured by a passenger. Usually a tire or wheel issue. Never measure while you drive. The car vibration test does this match for you.
- Steady low peak that no machine explains. Often a floor or frame ringing at its own frequency. Move the source, put it on rubber isolation feet, or stiffen the structure.
- Many evenly spaced peaks. Something knocks once per turn, such as a loose part or a rub. Stop the machine and look for it.
What this tool can’t measure
- Anything above about 30 Hz directly, including bearings, gears, sound and electrical hum.
- Anything below 1 Hz. The tool ignores these very slow rhythms.
- Exact peak strength. Heights are approximate, and different phones read a little differently.
- Certified results. This is a good guide, not a certified measurement. The guide to vibration frequency explains the basics in more depth.
Frequently asked questions
What's the difference between Hz and RPM?
Both count the same thing: how many times something repeats. Hz counts per second and RPM counts per minute, so RPM = Hz × 60. A 12.5 Hz shake is 750 RPM.
Can I use this as a vibration frequency meter for a tuning fork or speaker?
Only for rhythms below about 30 Hz. A tuning fork at 440 Hz, and most speaker sound, is far too fast for a phone's motion sensor. For bass, see the subwoofer vibration test.
Why do I see peaks when nothing is running?
Buildings are never perfectly still. Footsteps, a fridge, heating and cooling, traffic and wind all add small peaks, and the phone's own sensor adds some noise. Run a test with the source off and compare it with a run with the source on.
Why does my main peak change between runs?
The source may change speed, as with inverter motors and variable-speed fans. Two sources at almost the same speed can also take turns being the strongest. A peak that jumps around a lot can also be a false peak from vibration faster than your phone can measure.
Why does the analyzer run for 60 seconds?
It splits the recording into overlapping windows and averages them. More windows smooth out random noise, so the peaks come out steadier and easier to trust.
Last updated .