ISTIQ Noise Control Weblog

DUCT SILENCER

Whenever ventilation is required in the enclosed compartment and at the same time noise is to be controlled, installing duct silencers or attenuator are the best way to solve the problem. The silencers permit air to flow through while reduce the noise by absorbing it.

In selecting a silencer, a balance between noise attenuations and pressure drop need to be considered carefully. By using internally developed software, ISTIQ Noise Control can help to make the right choice quickly and most importantly, accurately.

Introduction

ISTIQ Duct Silencers are designed to efficiently reduce noise by generator sets, air handling systems, compressor, blower system and all situations requiring air intake and outlet for these equipments to operate.

A duct silencer should always positioned in the plant room and if possible as close to the noise source as possible. Normally for a single equipment, two units of duct silencers - intake and discharge is required to effectively reduce the noise to a desired level.

Construction

ISTIQ Duct Silencers consist of a galvanised sheet metal case containing two side panels and one or more splitters. Normal low pressure silencers uses Pittsburgh  seams with attached angle frames step welded to the case. Duct sealer is then used to seal to ensure that the silencer is airtight. For high pressure system, the silencer has fully welded seams. The angle frame are protected by a paint finish.

Inside the splitters, rockwool or fibre glass is used as sound absorptive infill and is held in the splitters inside a perforated galvanised steel skin. Different  acoustic infill is used depending on the application to ensure excellent performance and its effectiveness.

For heavier industrial or marine application, enhanced construction and corrosion resistance are required.  ISTIQ Engineers will be glad to discuss and advice your specific needs regarding the design of the structural, aerodynamic and corrosion protection requirement.

Features

ISTIQ Duct Silencers are available in two different models, which basically have two different thicknesses of splitters - 200 mm and 300 mm. The thicker the splitter the better performance at lower frequencies. Each of the models have six length sizes from  900 to 3000 mm. The cross sectional  area has no limited size. The performance or the insertion loss of each model is shown in the table 1.

ISTIQ Duct Silencers will be supplied in sections whenever the silencer dimension exceeded 2100W x 2100H x 2100mmL. This will make the transportation and installation easier. The assembly of sectionalized silencers to be done at site.

SELECTION GUIDELINES

The right selection of silencer should gives the essential attenuation at a permissible amount of pressure drop of a given air requirement. The selection method therefore can be simplified as follows :-

• Establish the noise target. Noise target could be in noise overall value or in NC criteria as recommended in Table 1.
• Obtain the noise level of the source,
• Calculate the difference of the level between the noise target and the noise source. Should there is any distance involve or any condition which noise will reduce naturally, it should be considered.
• Match up the difference of the level with the insertion loss of ISTIQ silencer and select the model as shown in Table 2.
• The silencer can be sized up by knowing the airflow requirement and the allowable pressure drop across the silencer by using the formulae below :

                Pressure Drop   = kv²

                where v                = Air Flow in m³/s

                                                   Width x Height in m²

              

                And k as listed in Table 3.

For detailed procedures of calculating the required attenuation, ISTIQ Engineers will be glad to help.

This entry was posted on Tuesday, March 4th, 2008 at 4:03 pm and is filed under OUR PRODUCTS. You can follow any responses to this entry through the RSS 2.0 feed. Responses are currently closed, but you can trackback from your own site.