• ISR Rectangular Silencers
• ISC Circular Silencers

Type ISC-BN Full Flow Silencers
Unrestricted air flow with interior waits of the silencer acoustically packed to the necessary thickness. Good for low and mid band attenuation of noise.

Type ISC-BC Center Bullet Silencers
Supplied with acoustically packed center bullet tor increased attenuation in the higher frequencies.

Type ISC-BF Combined Treatment Silencers
Includes both an acoustically packed center bullet and interior walls for the highest attenuation possible with a circular silencer.

Media Protection
Acoustical media is covered with galvanized mild steel perforated plate. When internal silencer velocities become excessive, fiberglass cloth is added to prevent leaching of media into the air stream. If even higher velocities or high temperatures exist, an additional layer of stainless steel mesh is also added for increased protection. In applications where air moisture or bacteria is a problem, mylar is used to prevent mildew growth and bacteria contamination. When any of the above protective coatings are used, acoustical values are adjusted to reflect the change in silencer performance.

Casings
Silencer casings are fabricated from heavy gauge mild steel and are continuously welded to provide an airtight unit. Thick walls reduce transmitted noise to a minimum. All silencers are given an external coat of paint before shipment. When high temperatures or corrosive/abrasive gases are present, special materials and paints are used.

Connections
Silencer connections are always sized and drilled to match application requirements. A wide range of inlet and outlet connection types are available including; angle flanges and slip fit connections on all silencer types and ASA flanges, weld necks, and NPT connections on ISC silencers. Special transitions, elbow connections, flow straighteners, etc. are also available.

Customized to Fit
All ISRand ISC silencers are customized to fit the requirements of the job with mounting feet or heavy duty suspension gussets supplied to match the supporting structure. A wide range of arrangements and accessories are available making J.P. industrial silencers suitable for many applications not possible with other standard designs. Some of the more often requested arrangements and accessories:

• Side inlet boxes (integral with silencer) for centrifugal fan applications
• Inlet and exhaust filters (integral with silencer)
• Filter boxes (for attachment to silencers)
• Weatherhoods (with and without filters)
• Inlet and outlet screens

Choosing the Right Silencer
Type ISR and ISC silencers can be used to solve a large variety of industrial noise problems. Choosing the correct one will depend on the requirements of the specific application. Your J.P. representative has the tools necessary to help you determine these requirements and will, if you choose, carry out the whole procedure with the selection of the appropriate silencer to within +/- 3 dB (instrumentation measurement tolerance). On projects where sound is critical, even tighter tolerances can be applied. The following formulas and tables can be used to make the job of defining silencer requirements easier.

DISTANCE CORRECTIONS
Octave Band Distance Correction = - 20 Log r + 2.5 dB
where r is the distance from noise source in ft. for free field, hemispherical radiation.

LOGARITHMIC ADDING RULE
Resultant SPL - Higher of SPL1 or SPL2 + FACTOR
where SPL is sound pressure level in dB or dBA and FACTOR is equal to:
3 when the difference between SPL1 & SPL2 is 0 or 1,
2 when the difference between SPL1 & SPL2 is 2 or 3,
1 when the difference between SPL1 & SPL2 is from 4 to 9,
0 when the difference between SPL1 & SPL2 is 10 or more.

Directive Correction Chart