Airborne Survey Results.pdf

NCE REPORT 2022-038

Okeanos Explorer, Airborne Noise Survey Report

Revision 0

Ben Bonnice

Ben Kirschmeier

6/02/2022

Prepared for:

NOAA

151 Watt Ave

Pascagoula, MA 39567

Attention: Mr. Justin Kusterer

Prepared by:

Noise Control Engineering, LLC

85 Rangeway Rd.

Building 2, Floor 2

Billerica, MA 01862

978-670-5339

978-667-7047 (fax) noise-control.com

Report 2022-038, Rev 0 Okeanos Explorer Noise Control Engineering, LLC Airborne Noise Survey i

REVISION HISTORY

Rev Date Summary of Changes

0 6/2/2022 Original Issue ii

TABLE OF CONTENTS

0.0 EXECUTIVE SUMMARY

1.0 INSTRUMENTATION AND SETUP

1.1 Instrumentation

1.2 Calibration

1.3 Measurement Parameters

2.0 RESULTS

2.1 Aft Working Deck

2.2 ROV Garage

2.3 1-28-2-L Stateroom

2.4 1-66-2-L Stateroom

3.0 RECOMMODATIONS

3.1 Aft Working Deck

3.2 ROV Garage

3.3 1-28-2-L Stateroom

APPENDIX A: SILENCER PRUDUCT SHEETS ................................................................ A-1 iii

LIST OF TABLES

Table 1. Aft Working Deck Fan Noise Levels Table 2. Aft Working Deck Fan Noise Levels

LIST OF FIGURES

Figure 1. Aft Working Deck Fan Locations

0.0 EXECUTIVE SUMMARY

Noise Control Engineering, LLC (NCE) conducted an airborne noise survey aboard the Okeanos

Explorer. Testing was performed on May 5th 2022 while the vessel was docked in Newport, RI, to determine the controlling noise sources of the Aft Working Deck and the ROV garage. While onsite NCE also investigated if two staterooms with high noise levels while underway could be controlled by HVAC and ventilation systems.

The noise levels on the Aft Working Deck were measured to be as high as 97 dB(A). The noise for significant parts of the deck were controlled by the Stern Thruster Supply Fan but contributions were also seen from the following 3 fans:

• Stern Thruster Exhaust

• Winch Room Supply

• Tween Deck Fan

NCE estimates that the noise on the Aft Working Deck can be reduced by 15 to 18 dB if those 4 fans are treated with IAC D-Duct Diffuser Silencers.

The ROV garage was measured to be as high as 86 dB(A) and was controlled by the supply and exhaust fans. NCE is recommending an IAC Conic Flow Silencer Model 12FCS for the supply fan and an IAC D-Duct Diffuser Silencer for the exhaust fan.

Staterooms 1-28-2-L and 1-66-2-L were measured to be 71 and 58 dB(A) respectively. NCE would need to go underway to confirm but expects that both staterooms are controlled by machinery noise while underway. Stateroom 1-28-2-L noise levels while dockside are still loud and NCE would recommend NOAA consider additional efforts to reduce the HVAC and ventilation noise.

NCE would recommend that the AHU fan be reviewed for maintenance as the noise and vibration measured around it indicates it may be damaged. NCE is not currently recommending specific silencers for the HVAC as the limited space in the fan room likely will require a silencer be custom made. NCE can work with NOAA to get silencers produced if NOAA desires.

INTRODUCTION

Noise Control Engineering, LLC (NCE) conducted an airborne noise survey aboard the Okeanos

Explorer. Testing was performed on May 5th 2022 while the vessel was docked in Newport, RI, to determine the controlling noise sources of the Aft Working Deck and the ROV garage. While onsite NCE also investigated if two staterooms with high noise levels while underway could be controlled by HVAC and ventilation systems.

1.0 INSTRUMENTATION AND SETUP

1.1 Instrumentation

All sound pressure level measurements were performed using a PCB Model 377B20 microphone with a 426E01 preamp. Data was collected using a National Instruments 9234 data acquisition hardware card with custom LabView software written for collection of noise data. This setup conforms to the requirements of a Type 1 averaging sound level meter as specified in IEC

61672-1. A windscreen was used for all measurements.

1.2 Calibration

The microphone was field calibrated prior to the survey with a Larson Davis Cal 200 portable microphone calibrator. This calibrator produces a tone at 1000 Hz at a level of 114 dB.

All instrumentation was laboratory calibrated traceable to NIST standards within the previous 12 months.

1.3 Measurement Parameters

The sound level meter was configured to measure overall A-weighted sound pressure levels between 31.5 and 8000 Hz. Octave band and narrowband sound pressure levels were recorded for diagnostic purposes. An averaging time of 15 seconds was used with RMS averaging.

2.0 RESULTS

2.1 Aft Working Deck

Based on NOAA guidance, the Aft Working Deck was one of the main locations of interest for noise mitigation. This area has had several complaints due to high noise levels. NCE measured the ventilation fans located on the Aft Working Deck for the thruster room, winch room and tween deck. In NCE’s experience these fans are going to control the Aft Working Deck. This allows NCE to perform the testing dockside.

Measurements were taken at various locations around the Aft Working Deck with different fan configurations to determine the controlling fans and determine the magnitude of the noise level.

The four fans that most effected the noise on the working deck are shown in Table 1

Table 1. Aft Working Deck Fan Noise Levels

Fan Maximum Level dB(A)

Stern Thruster Supply Fan 97

Stern Thruster Exhaust Fan 90

Winch Room Supply Fan 85

Tween Deck Ventilation Fan 80

The Locations of these fans are shown below in Figure 1. The Thruster Room Supply Fan location is indicated by the red circle as it was not shown on this GA.

Figure 1. Aft Working Deck Fan Locations

The Stern Thruster Supply Fan was the loudest ventilation fan on the Aft Working Deck. This fan was measured to be 97 dB(A) near the fan and causes significant parts of the deck to be above 85 dB(A). This is important because personnel should be required to were hearing protection to prevent hearing damage. Levels this high are also uncomfortable and make communication difficult. This fan should be the priority to be addressed.

The Stern Thruster Exhaust Fan, although quieter than the supply fan, still caused the area around and in the ROV garage to exceed 85 dB(A). Being the second loudest fan and the proximity to the ROV garage makes this the second priority for the aft working deck.

The Winch Room Supply Fan and the Tween Deck Fans do not cause levels above 85 dB(A) on the aft working deck. Based purely on crew safety these fans do not need to be treated. NCE would still recommend treating these fans to reduce the noise further and improve audibility at the Crane Controls (Winch Room Fan) and ROV Bay (Tween Deck Fan)

Since the design of the ventilation system is similar for all 4 fans, the same model silencer has been recommended. Details of the silencer are in section 2.13.1. NCE estimates that these silencers should drop the noise levels by 15-18 dB on the Aft Working Deck.

2.2 ROV Garage

The ROV Garage was the other main location that was requested for noise mitigation. Measured noise levels were between 84 and 86 dB(A) with the Supply and Exhaust Fans operating. With the fans secured the ROV garage was measured to be 61 dB(A). Clearly showing that the ventilation fans are controlling the noise in the space. Recommendations include inline silencers as described in 3.2

2.3 1-28-2-L Stateroom

Based on a previous noise survey, stateroom 1-28-2-L was noted to be particularly loud at 76 dB(A) while underway. Since the stateroom was located directly forward of the Fan room(1-34-

1-Q), NCE took the opportunity to investigate if the noise could be controlled by HVAC or ventilation fans.

The fan room contained an AHU and a return air ventilation fan. The AHU supplied conditioned air to the stateroom. While the ventilation fan simply had ducting passing through the stateroom.

The noise in the stateroom while dockside with all HVAC and ventilation operating was measured to be 71 dB(A). The noise measured in the stateroom from the ventilation fan and

AHU individually can be seen in Table 2

Table 2. Aft Working Deck Fan Noise Levels

Fan Maximum Level dB(A)

AHU 69

Ventilation Fan 67

Based on the 5 dB difference in measured noise levels between the underway and dockside noise surveys, it seems likely that the Generator Sets are controlling the noise in the room while underway. NCE would need to go underway to confirm that. Still 71 dB(A) while dockside is loud for a stateroom and NCE would recommend that the HVAC be addressed.

The AHU does control the noise in the stateroom dockside and would need to be addressed before any significant attenuation would be seen. It should be noted that the fan for this AHU does not seem to be operating correctly based on noise and vibration measurements on and around the fan. A significant blade pass tone was noted, and the unit had high vibration. NCE would recommend that the fan be replaced before performing significant mitigation efforts. If more attenuation is desired, it is possible an elbow silencer could be installed as there is limited space to install a traditional silencer. If desired NCE could work with NOAA and venders to produce a silencer that would fit in the space.

The ventilation fan did contribute to the noise in the compartment via “breakout” noise. This is the noise that is transmitted through the duct wall into the compartment. In order to treat this, we would need to either:

• Reduce the fan noise level with a silencer

• Add insulation to the duct in the compartment to reduce the breakout noise

Due to the limited space in the overhead of the stateroom a silencer in the fan room would likely be the best option. It would have to be an elbow silencer due to the limited space to install a traditional silencer. If desired NCE could work with NOAA and venders to produce a silencer that would fit in the space.

2.4 1-66-2-L Stateroom

Based on the previous noise survey, Stateroom 1-66-2-L was also noted to be particularly loud at

79 dB(A) while underway. Due to the proximity of machinery space ventilation trunks, NCE investigated if HVAC and ventilation could control the noise in this space. NCE measured the stateroom to be 58 dB(A) with all HVAC and ventilation systems operating. The noise level measured during underway is likely due to the propulsion motor. NCE can investigate this further if desired.

3.0 RECOMMODATIONS

3.1 Aft Working Deck

NCE is recommending an IAC D-Duct Diffuser Silencer for the following fans:

• Stern Thruster Supply

• Stern Thruster Exhaust

• Winch Room Supply

• Tween Deck Fan

These silencers will provide between 15 and 18 dB of reduction in a compact designed that can be installed between the fan and the weather outlet/inlet. The silencers are between 20 and 30 inches long. NCE will work with NOAA to ensure that the correct silencer model is selected but the primary selection factor is based on the duct diameter. A product cut sheet is attached in xxx

3.2 ROV Garage

For the ROV Garage NCE would recommend an IAC Conic Flow Silencers Model 12FCS. This is a tubular silencer that would require an adapter to convert the square duct to round duct. A square silencer can be specified if that is preferred.

NCE is recommending an IAC D-Duct Diffuser Silencer for the ROV Garage Exhaust Fan.

3.3 1-28-2-L Stateroom

NCE would recommend that the AHU fan be reviewed for maintenance as it appears to be damaged. NCE is not currently recommending specific silencers for the HVAC. Due to the limited space in the fan room a silencer would likely need to be custom made. NCE can work with NOAA to get silencers produced if NOAA desires.

A-1

APPENDIX A:

SILENCER PRODUCT SHEETS

D-Duct Diffuser / Silencer Section 15000 Specifications

1.01 General

A. Furnish and install “D-Duct” acoustic diffuser silencers of the types and sizes shown on the plans and/or listed in the schedule. Silencers shall be the product of IAC Acoustics. Any specification change must be submitted in writing and approved by the Architect/Engineer, in writing, at least 10 days prior to the bid due-date.

2.01 Materials

A. Outer casings of tubular silencers shall be made of type #G-90 lock-former-quality galvanized steel in the following gauges based on th smallest diameter of the internal diffuser cone:

B. Diffuser silencers shall include an internal core of consistent diameter along the entire length in the direction of airflow. The core diameter shall be selected based on the adjacent hub diameter or, in the case of C-frame mounted motors, the motor frame size for the respective fan system on which the diffuser silencer is installed.

C. The internal core shall be constructed from lock-former-quality type G-90 galvanized perforated steel in the same gauge as the internal diffuser cone. The core shall be supported by a minimum of three (3) welded radial attachment brackets installed at 120 degree angles to each other to provide uniform support.

D. Combustion ratings for the silencer acoustic fill shall be not greater than the following when tested to ASTM E 84, NFPA Standard 255, or UL No. 723:

Flamespread Classification Smoke Development Rating

3.01 Construction

A. Four inch long, 11 gauge, sleeved end connections shall be provided as standard. When noted, rolled angle flanges shall be factory welded to the sleeve.

B. For units where the minimum diffuser cone diameter is 36” or greater, an additional support rod shall be welded between the radial bracket and the sleeve to prevent a twist from being exerted on the internal core by the fan’s air flow.

C. All welds shall be touched-up with zinc-rich paint after fabrication by the manufacturer.

D. The internal core and the rectangular outer jacket of the Diffuser Silencers shall be filled with glass fiber of a density sufficient to obtain the specified acoustic performance. The fill shall be packed under not less than 5% compression to eliminate voids due to vibration or settling. The fill material shall be inert, vermin- and moisture-proof.

4.01 Acoustic Performance

A. All silencer ratings shall be determined in a duct-to-reverberant room test facility which provides for airflow in both directions through the test silencer in accordance with ASTM Specification E477-99. The test facility shall be NVLAP accredited for the ASTM E477-99 test standard. Data from a non-accredited laboratory will not be acceptable. The test set-up and procedure shall be such that all effects due to end reflection, directivity, flanking transmission, standing waves and test chamber sound absorption are eliminated.

Acoustic ratings shall include Dynamic Insertion Loss (DIL) and Self-Noise (SN) Power Levels both for FORWARD FLOW (air and noise in same direction) and REVERSE FLOW (air and noise in opposite directions) with airflow of at least 2000 fpm entering face velocity.

5.01 Aerodynamic Performance

A. Diffuser Silencers shall function as pressure regain devices to minimize system pressure losses at the fan.

Fan selections are based on the regain performance of the Diffuser Silencer configurations specified. Any deviations in configuration which adversely affect the fan performance efficiency will not be accepted.

B. Silencers shall not fail structurally when exposed to a differential air pressure of 8 inches water gauge inside to outside the casing.

6.01 Certification

A. With submittals, the manufacturer shall supply certified test data on Dynamic Insertion Loss, Self-Noise Power Levels, and Aerodynamic Performance for Reverse and Forward Flow test conditions. Test data shall be for a standard product. All rating tests shall be conducted in the same facility, shall utilize the same silencer, and shall be open to inspection upon request from the Architect/Engineer.

7.01 Duct Transitions

A. When transitions are required to adapt silencer dimensions to connecting duct work they shall be furnished by the installing contractor.

Cone Diameter, In.

Up to 35.5

Metal Gauge

Cone Diameter, In.

Up to 35.5

Metal Gauge

>36 18 38-60 18

D-Duct Diffuser / Silencer Type: DDS

Forward & Reverse Flow Ratings

The IAC D-Duct (DDS) Diffuser / Silencer is designed for installation at the outlet of a vane axial fans. Available in sizes matched directly to manufacturer’s fan sizes, it has excellent acoustic performance.

At the same time it reduces system pressure drop and can be used as an effective inlet cone and silencer. The combined interior diffuser cone and exterior square jacket casing makes these units excellent when requiring aerodynamic-regain devices as well as silencers.

Overall, the IAC D-Duct Diffusers / Silencers have been completely engineered to provide noise attenuation directly at the source, improving fan aerodynamic performance for the inlet and discharge.

All D-Duct Diffusers / Silencers have been rated with procedures certified in strict accordance with ASTM E477-99 in a NVLAP Accredited Acoustical Laboratory.

(+) Forward Flow / (-) Reverse Flow. Aero-acoustic performance data based on NVLAP accredited laboratory tests conducted in strict accordance with ASTM E477-99. Contact IAC if attenuation in excess of 50 dB is required.

FRONT VIEW

4” INLET

SLEEVE

SECTION VIEW

4” INLET

SLEEVE

Physical Data Dynamic Insertion Loss (DIL) Ratings (dB):

IAC

Model

Octave Band 1 2 3 4 5 6 7 8

Hz 63 125 250 500 1K 2K 4K 8K

18-A - 3 13 22 27 23 17 13 20-A - 2 12 20 26 22 16 12 24-A 1 4 14 20 24 20 15 12 24-B 1 5 15 20 25 21 15 12 30-A 1 7 15 19 21 17 14 12 30-B 1 8 15 19 21 17 14 12 30-B 2 8 15 19 21 18 14 12 36-A 2 8 15 18 17 13 12 11 36-B 2 9 15 18 17 13 11 10 36-C 2 9 15 18 18 14 11 10 36-D 2 9 16 18 19 14 11 10 42-A 3 10 16 17 16 12 10 9 42-B 3 10 16 17 16 12 11 10 42-C 3 10 16 18 16 13 11 10 48-A 3 11 17 18 16 12 10 10 48-B 3 11 17 18 16 12 11 10 48-C 3 11 18 19 17 13 12 10 54-A 3 11 17 18 16 12 10 10 54-B 3 11 17 18 16 12 11 10 54-C 3 11 17 19 17 12 12 10 60-A 4 12 18 19 14 10 10 10 60-B 4 12 18 20 16 12 11 10 66-A 4 12 18 19 14 10 10 10 66-B 4 12 18 20 16 12 11 10 70-A 4 12 17 16 12 10 10 10

70-B 4 12 18 18 15 10 10 10

IAC

Model

I Inlet

Diameter (in)

O Outlet

Diameter (in)

S (in)

L (in)

Weight (lb)

18-A 18.5 24 28 20.0 125 20-A 20.5 28 32 20.0 140 24-A 24.5 30 34 24.0 165 24-B 24.5 30 34 24.0 180 30-A 30.5 40 44 30.0 225

30-B 30.5 40 44 30.0 240 30-C 30.5 40 44 30.0 260 36-A 36.5 46 50 37.75 290 36-B 36.5 46 50 37.75 300 36-C 36.5 46 50 37.75 310

36-D 36.5 46 50 37.75 325 42-A 42.5 52 56 36.0 400 42-B 42.5 52 56 36.0 410 42-C 42.5 52 56 36.0 430 48-A 48.5 60 64 43.5 550

48-B 48.5 60 64 43.5 580 48-C 48.5 60 64 43.5 610 54-A 55.25 68 72 48.0 700 54-B 55.25 68 72 48.0 750 54-C 55.25 68 72 48.0 790

60-A 61.0 74 78 52.75 750 60-B 61.0 74 78 52.75 790 66-A 67.0 82 86 58.5 1190 66-B 67.0 82 86 58.5 1250 70-A 73.0 90 94 68.0 1400 70-B 73.0 90 94 68.0 1500

Custom sizes are available. Please contact IAC Acoustics representative for details.

Ducted Discharge

Discharge Into Low Velocity Plenums

Free Discharge

To ta l P re ss ur e Lo ss , i

.w .g

0.5

1.0

1.5

2.0

Fan Discharge Velocity, fpm

3000 4000 5000 6000

2000 fpm IN DUCT

Fan + DDS Silencer

Fan Only

AIR

FLOW

Fan Duct

FLOW

Fan Duct

AIR

FLOW

Fan

Plenum

AIR

FLOW

Fan

Plenum

AIR

FLOW

Fan

AIR

FLOW

Fan

AIR

FAN PLUS DDS SILENCER

AIR

FLOW

Fan Duct

FLOW

Fan Duct

AIR

FLOW

Fan

Plenum

AIR

FLOW

Fan

Plenum

AIR

FLOW

Fan

AIR

FLOW

Fan

AIR

FAN PLUS 45° (OR GREATER)

TRANSITION, NO DIFFUSER

To ta l P re ss ur e Lo ss , i

.w .g

0.5

1.0

1.5

2.0

Fan Discharge Velocity, fpm

3000 4000 5000 6000

500 fpm IN DUCT

Fan + DDS Silencer

Fan Only

AIR

FLOW

Fan Duct

FLOW

Fan Duct

AIR

FLOW

Fan

Plenum

AIR

FLOW

Fan

Plenum

AIR

FLOW

Fan

AIR

FLOW

Fan

AIR

FAN PLUS 45° (OR GREATER)

TRANSITION, NO DIFFUSER

AIR

FLOW

Fan Duct

FLOW

Fan Duct

AIR

FLOW

Fan

Plenum

AIR

FLOW

Fan

Plenum

AIR

FLOW

Fan

AIR

FLOW

Fan

AIR

FAN PLUS DDS SILENCER

AT PLENUM ENTRANCE

To ta l P re ss ur e Lo ss , i

.w .g

0.5

1.0

1.5

2.0

Fan Discharge Velocity, fpm

3000 4000 5000 6000

<100 fpm DOWNSTREAM

Fan + DDS Silencer

Fan Only

AIR

FLOW

Fan Duct

FLOW

Fan Duct

AIR

FLOW

Fan

Plenum

AIR

FLOW

Fan

Plenum

AIR

FLOW

Fan

AIR

FLOW

Fan

AIR

FAN PLUS DDS SILENCER

AIR

FLOW

Fan Duct

FLOW

Fan Duct

AIR

FLOW

Fan

Plenum

AIR

FLOW

Fan

Plenum

AIR

FLOW

Fan

AIR

FLOW

Fan

AIR

FAN DISCHARGE,

NO DIFFUSER

(+) Forward Flow / (-) Reverse Flow. Aero-acoustic performance data based on NVLAP accredited laboratory tests conducted in strict accordance with ASTM E477-99. Contact IAC if attenuation in excess of 50 dB is required. 108

Quiet-Duct Conic-Flow® Silencers Section 15000 Specifications

1.01 General

A. Furnish and install “Conic-Flow” (tubular) silencers of the types and sizes shown on the plans and/or listed in the schedule. Silencers shall be the product of IAC Acoustics. Any specification change must be submitted in writing and approved by the Architect/Engineer, in writing, at least 10 days prior to the bid due-date.

2.01 Materials

A. Outer casings of tubular silencers shall be made of type #G-90 lock-former-quality galvanized steel in the following gauges:

B. Interior construction of tubular silencers shall be compatible with the respective outside casing.

C. Filler material shall be inorganic glass fiber of a proper density to obtain the specified acoustic performance and be packed under not less than 5% compression to eliminate voids due to vibration and settling. Material shall be inert, vermin- and moisture-proof.

D. Combustion ratings for the silencer acoustic fill shall be not greater than the following when tested to ASTM E 84, NFPA Standard 255, or UL No. 723:

Flamespread Classification Smoke Development Rating

3.01 Construction

A. Units shall be constructed in accordance with the

ASHRAE Guide recommendations for high pressure duct work. Seams shall be lock formed and mastic filled.

Rectangular casing seams shall be in the corners of the silencer shell to provide maximum unit strength and rigidity. Interior partitions shall be fabricated from single-piece, margin-perforated sheets and shall have die-formed entrance and exit shapes so as to provide the maximum aerodynamic efficiency and minimum self-noise characteristics in the sound attenuator. Blunt noses or squared off partitions will not be accepted.

B. Interior partitions for tubular silencers shall be secured with galvanized steel radial mounting brackets welded to the partition and the outer casing. The radial brackets shall be installed full length and at 120 degree angles to each other to assure uniform spacing for consistent aerodynamic and acoustic performance.

C. Sound attenuating units shall not fail structurally when subjected to a differential air pressure of 8 inches water gauge from inside to outside the casing. Airtight construction shall be provided by use of a duct sealing compound on the job-site material and labor furnished by the contractor.

4.01 Acoustic Performance

A. All silencer ratings shall be determined in a duct-to-reverberant room test facility which provides for airflow in both directions through the test silencer in accordance with ASTM Specification E477-99. The test facility shall be NVLAP accredited for the ASTM E477-99 test standard. Data from a non-accredited laboratory will not be acceptable. The test set-up and procedure shall be such that all effects due to end reflection, directivity, flanking transmission, standing waves and test chamber sound absorption are eliminated.

Acoustic ratings shall include Dynamic Insertion Loss (DIL) and Self-Noise (SN) Power Levels both for FORWARD FLOW (air and noise in same direction) and REVERSE FLOW (air and noise in opposite directions) with airflow of at least 2000 fpm entering face velocity.

Data for rectangular and tubular type silencers shall be presented for tests conducted using silencers no smaller than the following cross-sections:

Rectangular, inch: 24 x 24, 24 x 30, or 24 x 36 Tubular, inch: 12, 24, 36 and 48

5.01 Aerodynamic Performance

A. Static pressure loss of silencers shall not exceed those listed in the silencer schedule as the airflow indicates.

Airflow measurements shall be made in accordance with ASTM specification E477-99 and applicable portions of ASME, AMCA, and ADC airflow test codes.

Tests shall be reported on the identical units for which acoustic data is presented.

6.01 Certification

A. With submittals, the manufacturer shall supply certified test data on Dynamic Insertion Loss, Self-Noise Power Levels, and Aerodynamic Performance for Reverse and Forward Flow test conditions. Test data shall be for a standard product. All rating tests shall be conducted in the same facility, shall utilize the same silencer, and shall be open to inspection upon request from the Architect/Engineer.

7.01 Duct Transitions

A. When transitions are required to adapt silencer dimensions to connecting duct work they shall be furnished by the installing contractor.

Outside Diamer, In. Metal Gauge Outside

Diameter, In. Metal Gauge

12-36 22 38-60 18

Low Frequency Conic-Flow® Silencers Type: FCS

Forward & Reverse Flow Ratings

The IAC Type FCS Conic-Flow Silencers have been rated with procedures certified in accordance with applicable portions of ASTM E477. All Dynamic Insertion Loss and Self-Noise Acoustic Performance Data were obtained in a NVLAP accredited Aero-Acoustic Laboratory using the duct-to-room reverberant test facility with air flowing through the silencers.

(+) Forward Flow / (-) Reverse Flow. Aero-acoustic performance data based on NVLAP accredited laboratory tests conducted in strict accordance with ASTM E477-99. Contact IAC if attenuation in excess of 50 dB is required.

Table I: Dynamic Insertion Loss (DIL) Ratings: Forward (+) / Reverse (-) Flow

IAC Model Octave Band 1 2 3 4 5 6 7 8

Hz 63 125 250 500 1K 2K 4K 8K Face Velocity, fpm Dynamic Insertion Loss, dB

12FCS

-4000 10 18 29 42 40 35 31 21 -2000 10 17 27 39 38 35 32 26

0 10 16 26 36 36 36 33 26 2000 9 14 24 33 34 37 34 27 4000 8 12 22 29 33 39 35 27

24FCS

-4000 10 18 31 41 42 35 21 15 -2000 10 16 29 38 40 35 22 17

0 9 15 27 36 38 36 22 18 2000 8 13 25 32 37 35 23 19 4000 7 12 23 29 35 35 23 20

36FCS

-4000 12 21 35 41 40 27 19 14 -2000 11 20 33 38 39 27 21 14

0 10 18 31 37 38 27 22 15 2000 9 16 29 35 36 28 23 16 4000 8 14 27 33 34 28 24 17

48FCS

-4000 15 25 39 41 37 23 15 11 -2000 13 22 37 39 36 23 17 12

0 12 20 35 37 36 24 19 16 2000 10 18 33 35 35 24 20 16 4000 9 16 30 34 35 25 21 17 -4000 18 30 43 41 35 16 12 10 -2000 16 27 41 40 34 17 13 11

60FCS 0 14 25 39 39 33 19 15 13

2000 12 22 37 37 33 20 16 15 4000 10 20 34 35 33 22 18 16

L D

Designating Silencers

Model: 12 FCS 36 Type: FCS Diameter: 12” Length: 36”

Table II: Weights & Measures

Model Duct Diameter, Inches 12 14 16 18 20 22 24 26

Silencer Length, Inches 36 36 36 36 40 44 48 52

FCS Weight, lb. 99 111 132 149 168 188 208 234

Model Duct Diameter, Inches 28 30 32 36 40 44 48 60

Silencer Length, Inches 56 60 64 72 80 88 96 120

FCS Weight, lb. 255 374 495 600 746 951 1140 1873

Table III: Aerodynamic Performance

IAC Model L/Ft

FCS All Sizes 0.04 0.06 0.07 0.10 0.12 0.15 0.19 0.22 0.26 0.30 0.34 0.39 0.44 0.50 0.55 0.61

Silencer Face Velocity, fpm 1000 1200 1400 1600 1800 2000 2200 2400 2600 2800 3000 3200 3400 3600 3800 4000

Static Pressure Drop, i.w.g.

Table IV: Self-Noise Power Levels, dB re: 10-12 Watts

IAC Model Octave Band 1 2 3 4 5 6 7 8

Hz 63 125 250 500 1K 2K 4K 8K Silencer Face Velocity, fpm

FCS

(all sizes)

-3000 57 58 58 57 56 57 56 52 -2000 50 49 51 49 46 47 45 39 -1000 38 34 39 35 29 30 26 20

1000 44 43 37 37 38 38 20 20

2000 56 54 50 50 50 50 41 31

3000 63 60 57 57 57 57 53 47

(+) Forward Flow / (-) Reverse Flow. Aero-acoustic performance data based on NVLAP accredited laboratory tests conducted in strict accordance with ASTM E477-99.

TAKE NOTE!

• Silencer Face Area is the cross-sectional area at the silencer entrance

• Face Velocity is the CFM of airflow divided by the Face Area (in sq. ft.)

• Pressure Drop for any velocity can be calculated from this equation:

PD = (Actual FV/Catalog FV)2 x (Catalog PD)

• Self Noise values shown are for a four-square-foot face area silencer

• For each doubling of the face area add 3 dB to the self-noise values listed

• For each halving of the face area subtract 3 dB from the self-noise values listed

• Weights and measures are listed for limited number of available sizes