HVAC Noise Reduction Methods and Techniques for Duct Systems

Cabinet air conditioner design that reduces noise by buffering the airflow out of the heat exchanger before it enters the ducts. The air conditioner has a shell with an air inlet in the rear and an air outlet in the front. The airflow path is split into two sections. The heat exchanger is between the cross-flow fan and rear shell. The air outlet of the heat exchanger is not opposite the air inlet of the through-flow duct. This causes the air to turn or shift as it leaves the heat exchanger before entering the ducts. This buffering reduces the peak air speeds and noise at the outlet.

Reducing noise in devices with compressors that generate airflow by using a cavity adjacent to the airflow duct to create a noise-damping resonator. An acoustic resistive screen is held in tension over an aperture in the wall separating the duct and cavity. The screen is configured to resist airflow between the duct and cavity, forming a resonator with the cavity. The screen properties are optimized for the device geometry to maximize noise attenuation.

Airflow regulation structure for air ducts in air conditioners to prevent unbalanced airflow and surging noise at the outlet. The structure allows adjustment of the airflow direction inside the duct. It consists of a rotatable adjustment part that can be fixed in place using positioning features. The adjustment part has a rotating shaft that can be turned to change the duct airflow path. Limiting grooves and protrusions prevent the shaft from rotating too far and ensure stable adjustment. This prevents unbalanced airflow and surging noise at the duct outlet.

A fan and air conditioner design with improved airflow and reduced noise compared to conventional designs. The fan has a two-section volute tongue that steps in height. The first section extends along the air duct opening and the second section extends from the end of the first section. This smooths the airflow transition and reduces vortex formation compared to a single tongue. The air conditioner has a matching stepped volute tongue in the duct cover and seat. This joint configuration improves airflow in the duct and reduces noise compared to conventional ducts.

Fan module for reducing backflow and losses in compact ventilation systems like air ducts. The module has a fan with a backflow prevention body on the pressure side. The body has a shape that prevents air from flowing back towards the fan in the central region near the axis. This prevents toroidal vortices and losses that can occur with freewheeling fans in narrow ducts. The backflow prevention body can be removably attached to the fan's existing mounting. Placing multiple modules close together in ducts without significant flow loss.

Air passage silencer with improved low frequency attenuation and reduced wind noise compared to conventional expansion type silencers. The silencer has a tapered opening structure at the expansion to outlet connection, surrounded by a rear space. A porous material is added in the rear space opening to absorb sound. This provides resonance in the tapered space for low frequency attenuation, without backflow turbulence. The tapered opening reduces wind noise compared to a sudden expansion. The expansion size, tapered shape, and rear space dimensions are optimized for performance.

Silencer for reducing noise in ducts like HVAC systems. The silencer has a sound absorbing damping element that extends along the duct length. It also has a holding device that secures the damping element in sections. This allows the silencer to be installed in ducts like flat ducts. The holding device has a fastening mechanism to secure the silencer in the duct.

Fresh air module for air conditioners that reduces noise compared to conventional modules. The module has a housing with an inlet and outlet, a fan assembly with a motor and wind wheel, and a partition between the motor and fresh air duct. The motor is outside the duct in a separate compartment. This isolates the motor noise from the airflow, preventing amplification and reducing overall noise.

Air port device and air conditioning unit with reduced noise. The air port device has a silencing cover inside the air duct between the inlet and outlet. The cover has holes for airflow and disperses it to reduce turbulence. It also has a cone to guide air uniformly. This reduces noise by scattering and refracting sound, lowering flow velocity, and absorbing noise with cotton.

Air duct design for air conditioners that reduces vortex wind phenomenon, noise, and improves user experience compared to conventional spiral case air ducts. The duct has detachable volute covers and seats that form extendable tongues to gradually expand airflow from the inner duct to the outer duct. This reduces vortices and noise compared to sudden expansion in conventional ducts. The outer tongue extends further than the inner tongue and the outer duct opening is smaller. The tongues' lengths and angles are balanced to further reduce noise.

An air duct design for a wall-mounted air conditioner indoor unit that improves airflow and reduces noise. The duct has components like an evaporator, wind wheel, volute, front and rear tongues, and air deflector arranged from the inlet to outlet. The key difference is that the air outlet frame extends from the front and rear tongues and has a greater horizontal distance between the impeller and the front plate compared to traditional designs. This modified outlet geometry improves airflow and reduces noise compared to conventional duct configurations.

Muffling noise in ducts using resonating membranes without openings to prevent wind noise. The membranes are integrated into the duct walls and vibrate in response to sound. They form closed resonant spaces that suppress duct end noise when excited by nearby sources. The membranes are designed to have higher order vibration modes for better absorption. The membrane positions are optimized for interference cancellation. This allows muffling specific frequencies without amplifying others. It avoids the drawbacks of open resonators like Helmholtz resonators that generate wind noise.

A silencing system for ventilation ducts that provides both high ventilation and soundproofing performance. The system uses silencers inside ducts instead of external resonators. The silencers have specific properties to prevent resonance amplification and noise generation. The silencers have a standardized elasticity modulus range of 0 < Re[Bn] < 1 and Im[Bn] > 0 inside the duct. This prevents resonance and amplification while still allowing airflow. The silencer geometry and materials also prevent wind noise generation compared to external resonators.

A silencing system to prevent negative pressure buildup in enclosed spaces while still allowing ventilation. The system uses silencers installed in ventilation ducts that have specific geometry to balance sound insulation and airflow. The silencers have a cavity connected to the duct and a porous material inside. This configuration allows sound absorption without restricting airflow. It satisfies a specific relationship between opening area and transmission loss to prevent negative pressure issues.

Indoor unit for air conditioners that improves airflow performance and reduces noise. The indoor unit has a duct with opposing walls and a fan inside. The fan diameter, duct outlet length, and width have specific relationships. This limits fan size based on outlet dimensions. It allows optimizing fan size for duct dimensions to improve airflow and reduce noise compared to arbitrary fan sizes. The relationships are: d = a*L2 - b*L2 = 2 - c (fan diameter vs outlet length) and d = a1 - e*a1^3 + f = 2 + g (fan diameter vs outlet width) with a=2.85-2.95, b=1.51e-3-1.61e-3, c=1241.3-1261.3, e=6.05-6.

Air conditioner duct damping device to reduce vibration and noise in air conditioning systems. The device consists of an external mechanism, an internal collection mechanism, and a bottom sedimentation mechanism. The external mechanism stabilizes the device during operation and counteracts vibration. The internal collection mechanism has a rotating main board and outer board that absorb vibrations. The bottom sedimentation mechanism collects dust and uses water to form cakes that prevent dust spreading. The device is installed in air conditioner ducts to dampen vibrations and reduce noise.

Universal duct liner insulation for curvilinear ducts like oval ducts in HVAC systems that provides a smooth and consistent airstream surface with improved airflow efficiency compared to traditional insulation. The insulation is a compressible layer sandwiched between an inner insulation layer and an outer elastically deformable layer. The compressible layer conforms to the curved duct shape when compressed by the outer layer, preventing drooping and sagging. This ensures uniform insulation thickness around the duct interior, reducing inconsistencies compared to loose insulation.

Air conditioner indoor unit and air conditioner with reduced noise at low airflow rates. The indoor unit has a volute with a pivoting section that can rotate to decrease the width of the airflow duct. This forces removal of the return flow area and prevents airflow discontinuities and drafts at low speeds. The pivoting duct section reduces noise by eliminating turbulent areas and airflow separation at low flow rates.

Compact noise reduction using resonant structures in ducts and tubes. The soundproof structure body has a resonant structure inside a duct or tube that absorbs sound. The resonant structure is positioned and sized to optimize absorption by offsetting the phase difference between reflected waves from the resonator and duct opening. This requires the resonant frequency and duct opening reflections to have a phase difference within π/3.

PET composite folding plate type periodic structure noise reduction air duct for automotive air conditioners that provides improved low frequency noise reduction compared to conventional PET piping. The duct uses a folded plate acoustic crystal structure inside the duct to suppress sound transmission in the low frequency range. The structure consists of a folded PET plate with resonance units that vibrate in response to sound waves. When the plate frequency matches the resonance units, energy is localized in the resonators and the plate vibration is restrained. This forms a band gap where sound waves are suppressed. The folded plate structure is embedded in the duct using injection molding.