Constant humming in the kitchen can become a serious irritant, especially in studio apartments or small apartments where the cooking area is combined with the living room. Many owners of household appliances wonder: why does the new unit make sounds and is this a sign of a breakdown? Understanding the physics of the operation of the compressor and refrigerant helps to distinguish normal operation from an incipient malfunction.
Modern production standards require manufacturers to adhere to strict acoustic limits, but absolute silence cannot be achieved. The movement of gases in the tubes, the vibration of the motor and the operation of fans create background sound, which in most cases is within safe limits. It is important to be able to distinguish the nature of this sound so as not to miss the moment when a quiet hum is replaced by an alarming knock.
Physics of sound: why the refrigerator hums
The main source of acoustic vibrations in the refrigeration chamber is compressor. This is the heart of the system, which compresses the refrigerant and forces it to circulate throughout the circuit. Old models used piston units, which produced a characteristic knock with each cycle of switching on and off, while modern inverter motors operate almost silently, only slightly increasing speed.
In addition to the motor, the sound background is created by physical processes occurring inside the system. The expansion and contraction of metal tubes under the influence of temperature changes causes a cracking noise that often frightens inexperienced users. Also, in systems with No Frost a fan is constantly running to circulate cold air, which adds constant low-frequency noise.
Why is an old refrigerator noisier than a new one?
Old models were equipped with compressors with large backlash of parts and less effective sound insulation of the housing. Over time, vibrations break the fastenings, and the oil in the engine thickens, increasing friction and, as a result, the loudness of operation.
Do not forget about the sounds made by the refrigerant itself. When passing through the capillary tube and expansion valve, freon changes its state of aggregation, which is accompanied by gurgling and overflow. These sounds can be heard even after the compressor is turned off, until the pressure in the system is completely equalized.
Noise level standards: decibels and standards
To evaluate the volume of household appliances, a logarithmic unit of measurement is used - decibel (dB). According to current GOSTs and international standards, normal noise level for a refrigerator the range is considered to be from 25 to 45 dB. However, the perception of this parameter is subjective and depends on the frequency characteristics of the sound and the acoustics of the room.
Manufacturers are required to indicate the sound power level in the technical documentation and on the energy-efficient sticker. Typically this value is measured at a distance of one meter from the source. It is worth distinguishing between “sound power” and “sound pressure”, since the first value is always higher than the second by about 10-15 dB, which often misleads buyers.
The table below shows a comparison of various noise levels with familiar everyday situations so that you can better navigate the numbers:
| Noise level (dB) | Sound source | Perception |
|---|---|---|
| 25-30 dB | Whisper, ticking hours | Barely audible, comfortable for sleeping |
| 35-40 dB | Modern refrigerator, quiet conversation | Background noise, does not interfere with rest |
| 45-50 dB | Old refrigerator, office noise | Noticeable, can be distracting in silence |
| 55-60 dB | Loud conversation, running washing machine | Discomfortable, interferes with conversation |
It is important to consider that the 35 dB declared by the manufacturer are ideal laboratory conditions. In actual operation, especially when installed close to a wall or furniture, the noise level may be subjectively felt higher due to resonance.
Types of compressors and their effect on acoustics
The choice of engine type directly determines how quiet your equipment will operate. The market is dominated by two main types of compressors, each of which has its own acoustic characteristics and operating modes.
Linear (conventional) compressors they work on the principle “turned on - cooled - turned off”. At the moment of starting, the motor consumes maximum current and produces a characteristic relay click, followed by a hum. Cyclical operation leads to a periodic increase and decrease in noise, which for many people is more annoying than a monotonous background.
Inverter compressors deprived of this drawback. They turn on once at the first start and then only smoothly regulate the power, maintaining the set temperature. The absence of constant starts and stops makes their operation much quieter, and the service life of such units, as a rule, is longer.
There are also two-compressor systems, where separate motors are responsible for cooling the freezer and refrigeration chambers. On the one hand, this makes it possible not to turn on both engines at the same time, reducing peak noise. On the other hand, the presence of two sources of vibration theoretically doubles the likelihood of sound anomalies, although modern models have learned to work very quietly.
External factors: why a quiet refrigerator began to make noise
Even the most advanced and quiet unit can begin to hum louder than expected due to errors during installation or operation. Often the problem lies not in the technology, but in the conditions of its placement.
The first thing you need to pay attention to is horizontal installation. If the refrigerator is placed on an uneven floor, the body warps, which leads to vibration and beating of the internal parts against the walls. Adjusting the legs is the first action that must be performed after purchase.
⚠️ Attention: Never install the refrigerator close to the wall or sideways to the cabinets without a gap. The minimum distance to the back wall should be 5-7 cm for free air circulation. Violation of this rule leads not only to overheating, but also to increased noise due to resonance.
The second common reason is contact of the case with other objects. Vibration from a running motor is transmitted to the floor and walls. If the refrigerator touches a kitchen unit, pipe or wall, they begin to work as resonators, amplifying the sound many times over. Also check if bottles or cans on the door shelves are vibrating.
The third factor is the condition of the floor. Linoleum or thin laminate may not dampen vibration sufficiently. In some cases, installing special anti-vibration pads made of rubber or thick felt under the legs helps.
When noise becomes a sign of breakdown
Not all sounds are safe. There are acoustic signals that indicate critical wear of parts or a malfunction of the system. Ignoring such symptoms can lead to costly repairs.
If you hear loud metallic knock clunking noises when starting, this may indicate broken compressor bearings or a weakened internal motor mount. In normal condition, the compressor is mounted on springs, and if they burst or stretch, the motor begins to beat against the casing.
☑️ Sound diagnostics
Whistling or hissing the sound often indicates a refrigerant leak. Freon escaping under pressure through a microcrack creates a characteristic whistle. In this case, the refrigerator may stop freezing, and the compressor will work non-stop, trying to compensate for the loss of cold.
A uniform hum that turns into a loud hum that does not stop for hours indicates a malfunction of the thermostat or temperature sensor. The system “does not understand” that the goal has been achieved and causes the motor to wear out.
⚠️ Attention: If you hear a loud gurgling sound accompanied by a complete lack of cold, the capillary tube may be clogged or the compressor has failed. Operation in this mode is prohibited.
Do-it-yourself methods for reducing noise
Before calling a technician or thinking about buying new equipment, try eliminating the noise yourself. Many methods are simple and do not require special tools.
Start with content revisions. Remove glass bottles that may touch each other from shelves. Check that the vegetable drawers are tightly closed and that the shelves are not rattling in the grooves. Sometimes it is enough to place a piece of foam rubber or masking tape under the shelf to eliminate vibration.
If the problem is resonance with the furniture, move the refrigerator a couple of centimeters. Make sure it does not touch any surfaces. If the floor is very slippery and hard (tiles), consider purchasing special rubber mats for the feet that dampen vibration.
In the case of models where the compressor itself is noisy, some craftsmen are trying to install additional sound insulation on the motor casing. However, here you need to be extremely careful: overheating the compressor may be damaged due to insufficient cooling. Any manipulations with the motor insulation should leave free air access.
Is it possible to lubricate the compressor for silence?
Self-lubrication of compressor bearings at home is practically impossible and ineffective. Modern units are sealed, and opening will lead to freon leakage and breakdown.
It is also worth checking the fan in the No Frost system. If there is ice or hair/dust on the blades, it will hum. Cleaning the fan often returns silence.
FAQ: Frequently Asked Questions
Is it normal for the refrigerator to make sounds immediately after turning off?
Yes, this is absolutely normal. After the compressor stops, the pressure in the system equalizes, the refrigerant continues to flow, and the metal tubes cool and contract, making clicking and gurgling noises. This process can last several minutes.
Why is the new refrigerator noisier than the old one?
Modern models often have more powerful compressors for quickly freezing and preserving food when the door is opened. In addition, the thin walls of new buildings may dampen sound worse than the massive metal of old Soviet units. However, their noise level in dB is often lower.
Can the noise level depend on the number of products inside?
Yes, it can. A full refrigerator is quieter, as the products act as additional sound insulation and heat storage, allowing the compressor to turn on less often. An empty refrigerator will “walk” more often and sound louder.
What to do if the refrigerator hums only at night?
At night, the general background noise in the apartment decreases, and the operation of the equipment becomes more noticeable. Also at night, the voltage in the network can stabilize or, conversely, jump, which affects the operation of the motor. If the humming does not turn into knocking, this is normal.