Build a box around it lined with foam insulation (nothing on top) about 12'' larger than the hvac unit on all sides, and at least a foot or 2 taller. It will dampen much of the noise and still allow air circulation. You can even build it an inch above ground for more air entry.
Insulate the Vent: Use acoustic insulation or foam tape around the edges of the vent cover to dampen sound. This can help reduce vibrations and noise. Adjust the Airflow: If possible, adjust the airflow using dampers. Reducing airflow can sometimes decrease noise levels.
Wall Soundproofing
Flat acoustic foam is one material that can be used for soundproofing and is one of the best to use to muffle noise. You can also use wood or vinyl panels to keep the sound from the HVAC unit contained. It's usually the most cost-effective way to reduce noise.
You can reduce noise from an air conditioner by installing a sound blanket or sound curtain, choosing the location of the unit carefully, surrounding it with a fence, and adding sound absorbing or sound blocking material to the enclosure.
Dust, dirt, and debris around the coil fins, air ducts, and outdoor condenser unit are common causes of noise. Loose or misaligned parts like the fan blades or belt, lack of lubricant, blockage in the drain pipe, copper lines, or vents, and a malfunctioning thermostat can also lead to a noisy air conditioner.
The short answer is yes. The blankets are designed to insulate your compressor and prevent the loss of heat. This can also save you money on your energy bill. The blankets also provide a barrier between a hot compressor and any flammable materials that are nearby it.
Wrap the unit with sound damping materials
If you want to achieve a high level of soundproofing, it's a good idea to wrap the unit itself with sound damping materials. Many HVAC sound dampening materials are very easy to work with, and you most likely won't need to hire anyone to install it if you don't want to.
The duct silencers enable maintaining proper acoustic parameters in the rooms – even reducing noise in the rooms which require a high degree of acoustic comforts, such as e.g. sleeping rooms or reading rooms. The noise can be generated not only by the flow of air through the ducts.
Regularly replacing the air filters, as recommended by the manufacturer or HVAC technician, can significantly reduce fan noise, improve indoor air quality, and enhance overall system efficiency. You can also know your filter needs to be changed by looking at the color.
Fencing: Try putting a fence in front of or around the air conditioner, this creates a barrier for the sound and traps the sound's movement. You can use plywood to fence the air conditioner, or buy an air conditioner fence.
The most ideal solution is to use separate ducts to feed each room and if that is not possible then at least position the ducts as far away from each other as possible. A suitable acoustic foam duct lining material is the fire retardent Duct Foam. It's best not to use fibreglass type materials due to fibre migration.
Use Sound Blankets and Barrier Walls
Products like those offered by Sound Fighter Systems are designed specifically for HVAC noise reduction. These barriers not only mitigate sounds from HVAC units but can also block external noise from highways, railways, and industrial activities.
For example, a smaller duct system could contribute to less air circulating through your home. This means that your new furnace is noisier because the larger size of its components allows you to receive more airflow.
It is best to place the Duct Silencer within 2 - 4 feet of the blower / ventilator for maximum noise reduction.
Vent silencers are mounted after relief valves to reduce noise pollution to a bearable level. Relief valves are commonly used in i.e. power stations, as well as chemical, petrochemical and other similar plants.
Install Acoustic Panels
If your AC is still noisy after all of the basic treatments, consider installing acoustic panels. Acoustic panels are large, soft-furnished panels that absorb sound. You can install acoustic panels around your AC unit or strategically around your home. It may cost a little bit of investment.
Adding density to the closet wall improves the overall soundproofing performance. Installing a second layer of drywall on your existing wall with a damping compound increases density and reduces vibrations. This noise-proofing glue improves sound isolation by dissipating vibrations.
Barriers such as fences and garden walls can be used to screen noise from neighbours. To be effective, any fences or walls must block the line of sight from the neighbour's window to the air conditioner, be of solid construction and contain no gaps or holes.
These jackets, made from high-quality materials, effectively reduce noise levels and improve energy efficiency. In summary, several types of compressor insulation jackets can reduce noise and improve efficiency.