On a boiling summer day, the best place is a cool, air-conditioned room. However, the comfort fades when your AC unit is making a loud noise. Those humming, hissing, and even worse, rattling noises quickly turn ase into a nuisance, especially during work or rest. 

Loud noises from your AC are not just annoying. They often signal deeper issues you can’t ignore. In this guide, we’ll walk you through the common noise types and how to fix them. We’ll also introduce some quiet AC options if it’s time for an upgrade.

Where Is the AC Noise Coming From?

When your AC starts making unusual noises, the source is usually either the indoor or outdoor unit. These sounds often signal that maintenance is needed.

Inside the AC Unit Making Noise

If your indoor AC unit is being unusually loud, here are a few things to check:

Dirty air filters: Clogged filters may block the airflow, making the unit strain and causing loud blowing sounds.

Loose fan blades: When the blades are unstable, they may rattle or knock during operation.

Poor installation: A poorly mounted unit can vibrate against the wall or ceiling, creating a loud noise.

Outside AC Unit Making Noise

Outdoor units are more likely to produce noise since they’re exposed to the environment, but not always. Check for potential reasons:

Leaves or debris: Leaves, twigs, or small objects can get caught and slap against the spinning fan.

Compressor vibrations: Worn or ageing compressors may rattle or vibrate during startup and operation.

Unlevel bases: If the unit isn’t sitting flat, it may shake or rock slightly, causing knocking sounds.

Strange noises from your AC, no matter inside or outside units, usually mean something needs attention. Some problems are simple to fix, like a clogged filter or loose debris. Others, like compressor issues or poor mounting, may require expert help. 

AC Unit Making Loud Noise? Here’s What Each Sound Means

AC units can make different types of noises, each pointing to a specific issue. Identifying the noise type can help you decide whether it needs a quick fix or professional repair.

1. AC Unit Making Humming Noise

When your AC  makes a humming sound, it may indicate a more serious issue because it suggests an electrical problem. The most common reason is the relay or contactor issue, causing the outdoor unit to buzz but not start. It could also be the ageing of compressors or capacitors.

2. AC Unit Making Hissing Noise

Don’t ignore the hissing sound, which involves the tightness and safety of your AC’s core components. It may be caused by a refrigerant leak, a hissing sound coming from the pipe, and you may feel a drop in its cooling performance. It may also be due to abnormal pressure, with a brief hissing sound when starting up or shutting down. 

3. AC Unit Making Rattling Noise

You may notice a rattling noise from your AC. Here are some common reasons. If the fan blades and panel screws become loose, or leaves and small stones fall into the fan area and collide, they will cause a rattling or clicking noise. In such cases, tighten the loose parts or clean the foreign objects. If it is an internal issue, such as a loose compressor component, it requires professional handling.

4.AC Unit Making Screeching Noise

The sharp and shrill sound from the AC is very annoying and may also indicate a serious issue. If the noise varies with the wind speed, the fan or blower motor is likely worn out and aged. If your AC is an old-style one,  a slipping or ageing belt could be the cause. Repair or replace the components as soon as possible to avoid further damage.

5 Ways to Reduce AC Noise You Can Try

If your AC noise is getting out of hand, don’t rush to replace the unit just yet. There are a few simple fixes you can try first that often make a noticeable difference. Here are five practical steps to help quiet things down and improve performance.

1. Tighten loose screws or outer panels

Loose panels or screws can cause rattling or vibrating sounds as the AC runs. A quick check with a screwdriver might solve the issue.

2. Clean or change dirty air filters

Clogged filters make the system work harder, which can lead to humming or whistling noises. Clean or replace them regularly for smoother airflow.

3. Balance or oil the fan blades

Wobbly or dry fan blades often create knocking or buzzing sounds. Balancing or applying a little lubricant can restore quiet operation.

4. Use rubber pads or sound insulation under the unit

Placing soft material beneath your AC helps absorb vibrations and reduce noise transfer to the floor or walls.

5. Inspect the motor or blower for signs of wear

A worn motor or blower may grind, squeal, or whine. If you hear these sounds, the component may need repair or replacement.

Try These Quiet AC Units without Loud Noise Issues

Loud noises from air conditioners can ruin your everyday comfort. Tired of buzzing, rattling, or constant humming noise? Maybe it’s time for an upgrade. We’ve carefully selected different kinds of ultra-quiet AC, offering powerful cooling with whisper-silent operation.

Quiet Mini-Split AC: DELLA JA Series 12,000 BTU

The DELLA JA Series mini-split AC  is designed for small to medium-sized spaces, up to 550 sq. ft., running at a whisper-quiet 29 decibels. With smart features and a durable inverter system, it’s built to deliver long-term comfort.

Key Features:

• Ultra-Quiet Operation: Runs as low as 29 dB, quieter than a library. A great choice for quiet spaces where even small noises can be disruptive.
• Stable and Durable Design: Inverter compressor minimises wear and tear, reducing the risk of mechanical noise over time.
• Energy Efficient: High SEER2 rating of 20, helping to cut down power usage. You’ll stay cool without running up your electricity bill.
• Smart WiFi Control: Adjust settings from your phone easily. You can control the temperature no matter if you’re home or away. A remote is also provided.
• Compact and Ductless: Suit limited space like RVs or small rooms. Easy installation with no bulky ductwork. You can even install it yourself.

Quiet Portable AC Unit: DELLA Velocity Series 14,000 BTU

The DELLA Velocity Series 14,000 BTU Portable AC is powerful and flexible for a quiet and portable option. This unit is designed for low-noise operation, a great choice for bedrooms and offices. It’s also built with heat mode, a dehumidifier, and smart app control, giving you year-round comfort.

Key Features:

• Low-Noise Operation: Operates at only 49 decibels, right for sleeping, working, or just simply relaxing.
• Portable Design: Built-in wheels and a compact form. You can easily move between rooms.
• Year-Round Use: 4-In-1 design. Functions as a heater and air conditioner, with additional fan and dry modes for multi-season comfort.
• Smart & App Control: Adjust temperature, mode, and timers from anywhere using your smartphone, or just use the remote.
• Cools up to 400 Sq. Ft.: Ideal for medium-sized rooms, apartments, or living areas that need quick, effective cooling.

Quiet Window AC: DELLA Fenestra Series 8,000 BTU

Need a window AC that won’t keep you up at night? The DELLA Fenestra Series 8,000 BTU runs quietly, a great fit for bedrooms, small apartments, or home offices. It cools up to 350 sq. ft. and keeps a low noise, no hum, no vibration, just steady comfort. It offers a practical solution for anyone who wants peace and performance in one unit.

Key Features:

• Ultra-Quiet Operation: Low-noise level to maintain a calm and peaceful atmosphere, providing quiet environments for sleepers.
• 3-in-1 Functionality: Offers cooling, dry, and fan modes for year-round comfort.
• Smart App & Remote Control: It’s a smart window AC. You can change the temperature or mode right from your phone or remote, conveniently during late nights or in quiet spaces like the bedroom.
• Energy Efficient Design: Built to deliver strong cooling while keeping electricity bills down.
• Compact and Stylish: Fits easily into most standard windows with a modern look that blends into any space.

Tired of AC noise getting in the way? These DELLA units offer quiet, reliable cooling for bedrooms, offices, and small living spaces. No matter if you prefer a mini-split AC, portable, or window model, each one is built for comfort without the constant noise. Cool your space, keep the peace.

Conclusion

If your AC unit is making loud noises, don’t ignore it. The sound could be a warning sign of a failing part, poor installation, or blocked airflow. Small problems can turn into big repairs if left unchecked.

Regular maintenance and cleaning can prevent most noise issues. If your unit is too old or too loud, consider switching to a quiet AC that gives you comfort without the background racket.

FAQ

What’s considered a quiet AC unit in decibels?
Anything below 50 dB is usually considered quiet. The lower, the better, especially for bedrooms or offices.

Should I fix my AC noise myself or call a technician?
You can try simple fixes like cleaning and tightening. For electrical or compressor issues, it’s safer to call a professional.

What’s the return policy for mini split AC units?
100-day full refund if bought from dellahome.com. Must be in original condition. DELLA covers parts and shipping if there’s a defect.

What about portable or window ACs and tower fans?
30-day full refund. Must be in original condition. Return shipping is paid by the customer.

How do I track my order?
You’ll get a notification email once your order ships. If you have an account, you can also log in to view order details and tracking info.

Related reading:

How Does A Mini Split Air Conditioner Work

Best Mini Split AC Systems for Your Home in 2025

The Quietest Window Air Conditioners in 2025