HVAC Noise Solutions

What is HVAC?

HVAC stands for Heating, Ventilation, and Air Conditioning. Each component in a home may be separate, such as a radiant system combined with window air conditioning units. However, it’s more common for combined systems such as central heating and AC systems that use a single blower to circulate air using internal ducts, or with a ductless system for different rooms in the house.

The purpose of an HVAC system is more than an adjustment to temperature. HVACs improve indoor air quality and provide comfort for everyone inside a building. Natural ventilation is present in most homes and refers to the way air typically moves windows, doors, vents, and other openings. This exchange of air is necessary to replenish oxygen, and to remove odors, carbon dioxide, unpleasant odors, and excessive moisture.

Mechanical ventilation uses a mechanical system, the V in HVAC, to move the air around. Once the air is brought in, it is drawn into an air handling unit where the work begins. Here, air is drawn through filters to remove dirt, dust, allergens, and other particles. Then, air is either sent to be heated or sent to be cooled and have excess humidity removed and is directed into the home.

What Kind of Sound Issues are Caused by HVAC Systems and How Can They Be Acoustically Treated?

Problem 1: Mechanical Noise

This noise is from the fan itself. Rotating the movement of bulk air can cause large whooshing sounds that become undesirable background noises.

Solution: To reduce this mechanical noise, the fan itself or the room that it is in must be insulated. A plywood box around the fan, lined with a sound-absorbing material like ATS Acoustics Fiberglass Board, but allowing ample room for air to flow into the fan (if applicable) can lessen the fan noise in the room it’s in. This won’t prevent sound from the fan from traveling through the ducts it’s connected to. Sound absorbing duct liners may be the best solution in that case.

Problem 2: Air Flow Noise

Air Flow noises usually come from distortions in the ducting system, such as bends and bottlenecks. These distortions due to bad duct design or high speeds inside the ducts can cause the airflow to become turbulent. When turbulent, the air molecules spin around the duct, causing air flow noises.

Solution: To keep air from becoming turbulent, redesigning the ducting system can mitigate the resistance. For example, instead of having a 90° bend in the ducts, try having an angle bend. By making sure that the bends are as curved as possible, air is less likely to collide with the sides of the ducts, reducing the air flow noise.

Another option is to place a sound damper before and after the bend. By dividing the dampers into different sections, the air is forced into layers and causes the streamline of air to become constant and less turbulent. Unwanted sound passing through duct walls can also be reduced or eliminated by wrapping the outside of the duct with an acoustic barrier/absorber material, known as lagging. We, at ATS, can recommend using a viscoelastic sound dampening product, such as our QuietCoat 113, which can easily be applied with a sprayer, brush, or roller. QuietCoat can be applied to metal in multiple coats. Using this product, noise is typically reduced from 6dB to 20dB.

If air flow noise in the room is coming from ducts above a drop ceiling, replacing standard ceiling tiles with higher-rated acoustical ceiling tiles may help. We recommend our ATS Acoustic Ceiling Panels. These panels fit easily in standard 24” x 48” and 24” x 24” ceiling grid systems and absorb much more sound than standard drop ceiling panels. As an added benefit, our Ceiling Panels come in a variety of colors that can offer a unique and customized look to your space. Simply just lay the panel in your existing suspended t-bar grid system.

Problem 3: Vibrational Noise

This source of noise comes from vibrations of moving parts in the system. Because of the fast speeds of the rotating fan, the pressure between the air intake and outlet begins to fluctuate. This causes vibrations to travel through the flow that it stands on and through the ducts. If the HVAC system is next to a wall, vibrations can also transfer through the wall into adjacent rooms.

Solution: To begin, make sure that the fan box is not connected to anything except the floor. This includes no contact with bulkheads, walls, or anything else. If you put the fan on vibration dampers, this reduces the movement transferred to the floor and reduces noise from the rooms below. Finally, make sure that the connection to the ducting system is flexible.This lets the fan move freely without letting vibrations move to the floor, bulkhead, or ducting system. As a reminder, be sure to not cut any air supply to or from the HVAC unit!

Problem 4: The Room or Space

Your space might be contributing to the noise problems coming from the HVAC system. If you have a large, open area with high ceilings, and a lot of hard, smooth surfaces like metal and glass, sound is more likely to bounce around the room.

Solution: ATS Acoustic panels are designed to reduce overall echo and reverb in rooms. They absorb sound and cause it to die away more quickly. This means it travels less throughout the space. If HVAC noise is resonating or “hanging in the air” in a large space, acoustic panels may help.

If you have the chance to redesign your room, or you are thinking about choosing a new space to reside in, consider these room specs: drop ceilings, carpet, and wall coverings. By utilizing these designs, noise is more likely to be muffled and less reflective. Other options include added a white noise machine to the space. We recommend the peaceful, non-looping white noise sound machine by SNOOZ.

If your HVAC system is outside, noisy components can be treated with acoustical blanket wraps. These are great for compressors, compressor piping, and oil separators. Other solutions can include modular steel sound barrier walls or outdoor noise curtains (which blocks the line of sight as well as noise).
General Tips: Make sure that you are cleaning your HVAC systems regularly according to its manual. This can include inspections, repairs, dust cleaning, and refilling fluids.