# Motor Noise (Rotation Sound) Inspection: Judging Quality by Sound

Canonical URL: https://deeplyinc.com/cases/motor-noise-inspection
Language: en
Solution: industrial
Published: 2026-09-23
Last verified: 2026-09-23

Replace the noise judgment skilled inspectors made by ear with automatic judgment based on rotation-sound data. One consistent standard instead of one per inspector, inspected in-line without an anechoic room

## Classification

- Industry: Automotive parts
- Process: Post-assembly inspection
- Inspection target: Motors & actuators
- Target sound: Motor noise

## Overview

Listen AI learns the sound a motor makes when it spins after assembly and judges noise and defects automatically. When operators judge noise by ear, the standard differs from person to person, and judgment know-how can leave with a skilled inspector who retires. Deeply has deployed motor noise inspection at four sites

## Customer Tasks

- Move from operators' listening judgment to automatic rotation-sound judgment
- Unify inspector-by-inspector standards into one data-defined standard
- Inspect in-line without building an anechoic room or inspection booth
- Preserve skilled inspectors' judgment know-how as data

## Field Challenges

- Repetitive listening inspection brought fatigue and inconsistent judgment. Inspectors had to hear similar motor sounds without missing any in a short time, and the longer the shift, the harder it was to keep the same standard
- Defect judgments tended to come up relatively more often at night and early morning — a pattern common in shift work
- It took a long time to pass skilled inspectors' judgment criteria on to new inspectors
- Building an anechoic room to replace listening inspection would cost around KRW 100–200 million, and the room would have to be rebuilt every time the line moved

## Site Conditions and Constraints

- Production line running in shifts
- In-line inspection position that allows only simple sound insulation, no anechoic room
- Internal motor defects that are hard to judge by vision because the part rotates
- Defects reflected more in the high-frequency band of sound than in low-frequency vibration

## Deployment and System Setup

- Microphone-based rotation-sound analysis
- Direct integration with the production-line PLC
- Redundant servers so inspection continues if one server fails
- Judgment from the rotation sound after power is applied to the motor

## Outcomes

Key metric
- 82%: Reduction in motor defect rate (Definition: Reduction in motor defect rate compared with before automatic rotation-sound judgment)
- 82%: Reduction in motor defect rate (Definition: Reduction in motor defect rate compared with before automatic rotation-sound judgment)
- 4: Motor noise inspection deployments (Definition: Sites where motor noise inspection has been deployed)
- 100%: Higher inspection throughput (Definition: Twice the inspections in the same time as before)

## Measurement Conditions and Limitations

- Measurement conditions: The vibration-versus-sound comparison was made on an automotive parts maker's motor cases. Judgment criteria were set by cross-validating decibel (dB) measurements with the on-site laboratory
- Limitations: Judgment accuracy depends on motor type, rotation conditions, and line noise. Each site is confirmed with a PoC first, and judgment criteria are agreed afterwards

## Related Pages

- [Listen AI Industrial](https://deeplyinc.com/solution/industrial)
- [Inquiry](https://deeplyinc.com/inquiry)

## Machine-Readable References

- [llms.txt](https://deeplyinc.com/llms.txt)
- [llms-full.txt](https://deeplyinc.com/llms-full.txt)