The sounds produced by home appliances during operation that differ from normal ones due to internal faults are called abnormal sounds. The occurrence of abnormal sounds usually indicates the presence of faults. Therefore, abnormal sound detection can help manufacturing enterprises identify faulty products, enabling timely handling of these products and ensuring the qualification rate of products leaving the factory. Abnormal sound detection has become an important part of enterprises' product quality control.

I. Abnormal Sound Detection Workstation

From the actual situation of home appliance enterprises, on the production lines of complete machines such as refrigerators, washing machines, air conditioners, and range hoods, as well as core components like compressors and motors, there are dedicated abnormal sound detection (also known as acoustic detection) workstations. These workstations realize the judgment of abnormal sounds in home appliances through manual methods or instrument-assisted methods.

Below is a comparison of the abnormal sound detection conditions for various products from three aspects: detection environment, equipment, and methods.

II. Differences and Similarities in Acoustic Detection Methods

It can be seen from the above table that the acoustic detection workstations for various products are all equipped with soundproof rooms, which are used to isolate the noisy background noise in the workshop. Only in a relatively quiet environment can professional technicians make accurate judgments by listening to sounds.

The detection methods are roughly the same: all require professional technicians to make judgments by listening to sounds. These technicians have received specialized training and can determine whether a product has abnormal sounds based on their experience.

From the perspective of detection equipment requirements: For the abnormal sound detection of products such as refrigerators, air conditioners, range hoods, and motors, acoustic detection technicians directly make judgments by listening to sounds—they complete the identification of abnormal sounds through the human ear and the auditory center of the brain, and no special detection equipment is needed. However, since the compressor itself produces very low sound, its abnormal sound detection requires acceleration sensors and audio amplification & playback equipment. These devices convert the shell vibration signals into sound, which is then played in the soundproof room. After that, professional technicians make judgments by listening to the played sound.

III. Implementation of Abnormal Sound Detection

Direct Sound Listening Judgment (for Refrigerators, Air Conditioners, Range Hoods, and Motors)

After the assembly of home appliance products is completed, the products are moved into a soundproof room and powered on to operate. Technicians stay inside the soundproof room, bring their ears close to the main noise sources of the home appliances, and listen to determine whether there are abnormal sounds.

Indirect Sound Listening Judgment (for Compressors)

Since the operating sound of the compressor itself is extremely low, direct sound listening judgment is almost impossible. Therefore, acceleration sensors are used to convert and amplify the vibration of the compressor’s shell. The vibration signal is then played back in the form of audio, allowing technicians to listen and make judgments on abnormal sounds.

IV. System Composition

The traditional manual abnormal sound detection system is composed of both technicians and equipment, and generally requires the following components:

Soundproof Room

A soundproof room can significantly reduce the noise in the production line workshop, thereby creating a quiet environment that facilitates technicians to make judgments by listening to sounds.

Abnormal Sound Detection Equipment

For home appliance products that cannot be judged by direct sound listening, auxiliary equipment is required to amplify and convert signals into audio signals, after which professional technicians listen to the sounds to make judgments.

• To amplify sound signals, sound sensors (microphones) and audio amplification equipment are needed.

• To convert vibration signals into sound signals, acceleration sensors, charge amplifiers, and audio amplification equipment are required.

Professional Technicians

Abnormal sounds are usually caused by various types of faults, with a wide range of types and distinct characteristics. Only after receiving professional training can technicians accurately determine whether a home appliance product has faults based on the sounds.

V. Limitations

The method of determining abnormal sounds by technicians has the following limitations:

• Poor judgment stability: Technicians’ judgment results may change due to psychological or physical changes.

• Ununified judgment standards: Different technicians may not have exactly the same auditory perception of the same type of fault, and inconsistent judgment results may occasionally occur.

• Low detection efficiency: The response speed of technicians’ sound-listening judgment directly affects the detection efficienc