HVAC Silencers
J.A. Brown installs professional grade HVAC Silencers designed for noise reduction.

HVAC Silencers
IAC Acoustics rectangular and cylindrical duct attenuators provide effective, predictable noise reduction at substantial savings over other noise reduction methods because IAC products are laboratory-developed and tested under controlled conditions. Moreover, we manufacture duct silencers to specific metal tolerances and with controlled acoustic infill flow resistances to achieve consistent results.
Should none of our standard range of silencers meet your requirements we will develop one for you. If you have a special requirement, please contact us and our specialist team will be able to provide you with a bespoke solution.
Applications
- Quiet-Vent® Silencers solve a common problem in air handling the passage of noise from one space to another through vents provided for air passage. These modern low-cost units are easy to install, permit circulation of air in either direction, yet effectively stop noise in both directions.
- Quiet-Duct® Rectangular Silencers are suitable for conventional applications including low-frequency silencers having acoustic performance specifically engineered for the 63 Hz, 125 Hz and 250 Hz octave bands.
- Clean-Flow Rectangular Silencers are ideal for systems requiring a higher degree of cleanliness and hygiene such as hospitals or clean room applications. Linings on the fill material guard against erosion of particulate matter into the airstream. Specific internal construction features protect the lining against chaffing or premature failure and are necessary to maintain the rated aero-acoustic performance.
- Conic-Flow® Tubular Silencers are available for silencer applications including low-frequency silencers having acoustic performance specifically engineered for the 63 Hz, 125 Hz and 250 Hz octave bands.
- D-Duct Acoustic Diffuser Silencers are appropriate for use on axial fan systems. The combined interior diffuser cone and exterior square jacket casing make these units aerodynamic regain devices as well as silencers.
- Rectangular Packless Silencers are the ultimate solution for ultra-clean environments and corrosive / flammable environments. The complete absence of fill, combined with ease of cleaning and draining makes Packless silencers well suited for engine test cells, chemical plants, refineries and facilities that handle or process hazardous materials.
- Tubular Packless Silencers are excellent for small diameter circular duct systems such as fume hoods. The Packless design of these units makes them equally suitable to the types of systems mentioned for the Rectangular Packless silencers.
- IAC’s Green Duct Attenuator range is the first British made ‘green’ silencer range for air handling applications. With acoustic infill material made from specially developed post-industrial organic fibre, IAC's range of green Duct Attenuators offers a solution to the ever-increasing requirements for eco-friendly HVAC systems.
Cross Section Through Typical IAC Quiet-Duct Silencer
Die-formed single-piece splitter constructed throughout Shell-noise radiation minimized by double-skin or splitter construction in most models Acoustic splitters designed for maximum attenuation at low frequencies, the toughest job of all Straight-through air passages designed for maximum pressure drop Solid, rounded noses that increase noise reduction Bell-mouth entrance and exit to minimize turbulence, pressure drop and Self-Noise No protruding fastener heads to case turbulence or Self-Noise Solid air-impingement surfaces and self-cleaning air passages to minimize dirt entrapment Acoustic fill protected against erosion by perforated metal containments.
Duct Attenuator Design
All of the duct attenuators manufactured by IAC Acoustics are of the passive design because they do not require mechanical or electrical means to function. They do their job very simply by providing a trouble free static means for the dissipation of sound energy by converting it into very minute quantities of heat. Many of the original air conditioning attenuators developed by IAC in 1950 are still in use today.
Active duct attenuators operate electronically by means of microprocessors, loudspeakers and microphones. They cancel sound by feeding back an additional noise source that is 180 degrees out of phase with the original noise. In theory, noise reduction is effective for low frequencies, usually below 300, Hz. Initial research to develop a commercial product was particularly strong in Great Britain but, today, research goes on throughout the world. HVAC noise control requirements are rarely confined to a narrow low frequency range. The broad band low and high frequency attenuation capabilities of typical passive attenuators are practically always required.
Forward and Reverse Flow
In 1972, IAC developed silencer Dynamic Insertion Loss and Self-Noise ratings both under FORWARD FLOW (+) and REVERSE FLOW (-) conditions for Rectangular and Cylindrical Duct Attenuators. Since attenuation values are generally higher in the first five octave bands in the Reverse Flow (-) mode compared to the Forward Flow (+) mode, more economical silencer selections can often be made on return air systems. These phenomena are illustrated below.
Product Resources
Have questions about HVAC Silencers? Contact a J.A.Brown specialist today!
Brochure & Catalog
HVAC Silencer Specifications
- Quiet-Duct Ultra/Low Full Section
- Quiet-Duct Ultra/Low Type ULL1
- Quiet-Duct Ultra/Low Type ULL2
- Quiet-Duct Ultra/Low Type ULL3
- Quiet-Duct Ultra/Low Type ULM1
- Quiet-Duct Ultra/Low Type ULM2
- Quiet-Duct Ultra/Low Type ULM3
- Quiet-Duct Ultra/Low Type ULS1
- Quiet-Duct Ultra/Low Type ULS2
- Quiet-Duct Ultra/Low Type ULS3
- Quiet-Duct Ultra/ZAPD Full Section
- Quiet-Duct Ultra/ZAPD Type Z12A
- Quiet-Duct Ultra/ZAPD Type Z12B
- Quiet-Duct Ultra/ZAPD Type Z12C
- Quiet-Duct Ultra/ZAPD Type Z12D
- Quiet-Duct Ultra/ZAPD Type Z6A
- Quiet-Duct Ultra/ZAPD Type Z6B
- Quiet-Duct Ultra/ZAPD Type Z6C
- Quiet-Duct Ultra/ZAPD Type Z6D
- Quiet-Duct Ultra/ZAPD Type Z6E
- Quiet-Duct Ultra/ZAPD Type Z9A
- Quiet-Duct Ultra/ZAPD Type Z9B
- Quiet-Duct Ultra/ZAPD Type Z9C
- Quiet-Duct Ultra/ZAPD Type Z9D
- Quiet-Duct Ultra/ZAPD Type Z9E
- Quiet-Duct Commercial Series Full Section
- Quiet-Duct Commercial Series Type ES
- Quiet-Duct Commercial Series Type L
- Quiet-Duct Commercial Series Type LFL
- Quiet-Duct Commercial Series Type LFM
- Quiet-Duct Commercial Series Type LFS
- Quiet-Duct Commercial Series Type ML
- Quiet-Duct Commercial Series Type MS
- Quiet-Duct Commercial Series Type S
Ready To Reduce Noise?
J.A. Brown company expertly serving Pennsylvania from Pittsburgh to Philadelphia, Delaware, and Southern New Jersey for nearly 70 years!
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Why Choose J.A. Brown?
With decades of experience, a commitment to delivering tailored solutions, and a proven track record across diverse industries, J.A. Brown stands out as your trusted partner.
We understand the unique challenges of noise and vibration control, whether in manufacturing, healthcare, or commercial settings. When precision, reliability, and expertise matter, J.A. Brown delivers results that meet regulatory standards and exceed client expectations.
Decades of Expertise
With nearly 70 years in business, J.A. Brown brings unmatched knowledge and experience to tackle even the most challenging noise and vibration isolation issues.
Premier Partnerships
We use industry-leading products, from IAC Acoustics, Kinetics Noise Control, and Catalyst Acoustics Group to deliver unmatched performance and durability.
Tailored Solutions
We provide custom noise and vibration control solutions designed to meet the unique demands of your industry, ensuring precision and lasting performance.
Proven Results
We have a proven track record of successfully implementing noise and vibration control systems that meet regulatory standards and enhance operational environments.
What to Expect When Working with J.A. Brown
When you partner with J.A. Brown for your noise and vibration control needs, you can expect a seamless, comprehensive process from initial evaluation to project completion.
We take pride in providing clear communication, technical expertise, and hands-on support at every stage of the project to ensure your goals are met with precision and reliability.

Initial Consultation and Assessment
We begin with a detailed consultation to understand your specific noise and vibration control needs. We identify problem areas and assess the unique requirements of your facility. This involves potentially introducing you to an industry expert Acoustic Consultant from our expansive network.
Customized Solution Design
Based on this assessment, our team develops a customized solution tailored to your environment. This includes selecting the appropriate materials and products to address your specific needs.
Comprehensive Proposal
We provide a clear, detailed proposal that outlines the scope of work, project timeline, and costs, ensuring you have a full understanding of the process and expectations before moving forward.
Professional Installation
Our experienced technicians handle the installation, working efficiently to minimize disruption to your operations. We ensure products are installed to the highest standards for best performance.
Compliance and Final Testing
We can facilitate rigorous testing to ensure all solutions meet industry standards, providing you with peace of mind that your project is fully completed.
Ongoing Support and Follow-Up
We offer follow-up services to ensure the system is functioning as expected. We provide ongoing support and maintenance to ensure long-term effectiveness.

Get In Touch
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