Introduction
For applications where quiet operation is critical — electric motors for HVAC, office equipment, medical devices, and household appliances — bearing noise is a key selection parameter. But “quiet” isn’t a specification — you need to specify the right noise grade and vibration class according to recognized standards. This guide explains the ABEC, JIS, and DIN noise grade systems, how they compare, and which grade to specify for your noise-sensitive application.
What Are Noise Grades? Z, V, ZV Systems
Bearing noise grades are a manufacturer classification — not an ISO or ABMA standard — that classify bearings by their vibration (and hence noise) level during production testing. The most common systems are:
- Z, Z1, Z2, Z3, Z4 — Chinese GB/T 32333 standard (widely adopted across Asia). Higher Z number = lower vibration = quieter bearing. Z3 is the standard for “low noise” electric motor bearings; Z4 is premium ultra-quiet.
- V, V1, V2, V3, V4 — velocity-based vibration grades used alongside Z grades. V grades measure RMS velocity (mm/s); Z grades measure RMS acceleration or displacement depending on frequency band.
- ZV1, ZV2, ZV3 — combined Z (acceleration/displacement) and V (velocity) rating. ZV3 is the most common specification for high-quality motor bearings.
- EMQ (Electric Motor Quality) — a general designation (not a formal standard) indicating the bearing meets low-noise requirements for small electric motors, roughly equating to Z2-Z3 or V2-V3 levels.
ABEC Precision Grades and Their Relationship to Noise
ABEC (Annular Bearing Engineers Committee) grades define dimensional tolerances and running accuracy — not noise directly. However, higher ABEC grades generally produce lower noise because tighter tolerances mean less geometric imperfection to generate vibration:
| ABEC Grade | ISO Equivalent | Typical Bore Tolerance | Typical Radial Runout | Typical Noise Level |
|---|---|---|---|---|
| ABEC-1 | Normal (P0) | ±10 µm (for 30mm bore) | 15 µm | Standard — acceptable for general industrial |
| ABEC-3 | Class 6 (P6) | ±8 µm | 10 µm | Moderate — electric motors, fans |
| ABEC-5 | Class 5 (P5) | ±5 µm | 5 µm | Low — precision motors, machine tools |
| ABEC-7 | Class 4 (P4) | ±4 µm | 3 µm | Very low — aerospace gyros, dental drills |
| ABEC-9 | Class 2 (P2) | ±2.5 µm | 1.5 µm | Ultra-low — semiconductor, super-precision |
JIS B 1517 Noise Standards (Japan)
The Japanese Industrial Standard JIS B 1517 defines vibration levels for rolling bearings in three frequency bands (low, medium, high). Compliance is indicated by a vibration level number (higher = tighter = lower vibration):
- JIS Level 1 — equivalent to ABEC-1, general industrial use
- JIS Level 2 — equivalent to ABEC-3, motor quality
- JIS Level 3-4 — equivalent to ABEC-5 to ABEC-7, precision applications
DIN 620 Noise Testing (Germany)
DIN 620 (and the related DIN 5426 for bearing noise measurement) defines test methods rather than noise grades. The standard specifies:
- Measurement setup: bearing mounted on a precision mandrel, outer ring loaded axially
- Speed: 1,800 RPM (standard) or application-specific
- Frequency bands: 50-300 Hz (low), 300-1,800 Hz (medium), 1,800-10,000 Hz (high)
- Measurement parameter: RMS vibration velocity (mm/s) in each frequency band
How to Choose the Right Noise Grade
| Application | Recommended Noise Grade | Approximate Standard |
|---|---|---|
| Conveyor roller, agricultural | Z1 / V1 | ABEC-1 |
| Standard industrial motor | Z2 / V2 (EMQ) | ABEC-3 |
| HVAC fan, office equipment, power tools | Z3 / V3 / ZV3 | ABEC-3 to ABEC-5 |
| Medical device, dental handpiece | Z3-Z4 | ABEC-5 |
| Hard disk drive spindle, semiconductor wafer handling | Z4+ | ABEC-7 to ABEC-9 |
Conclusion
For most noise-sensitive industrial applications (electric motors, fans, pumps), specifying ZV3 or EMQ grade is sufficient and cost-effective. Only go to ABEC-5 or higher when dimensional precision (runout, bore tolerance) matters as much as noise. Boret supplies deep groove ball bearings from Z1 through Z4 vibration grades — contact our application team with your noise requirements and we’ll recommend the right grade for your application.