305 s. main street 640 east industrial drive phase 2 construction … packet2... · 2020. 9....

3815 Plaza Drive

Ann Arbor, Michigan 48108

734.995.0200

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R:\20089\DATA\2020-06-29-Midwestern - Hardwood third review.docx

June 29, 2020 City of Chelsea 305 S. Main Street Chelsea, Michigan 48118 Attn: Ms. Julia Upfal

Community Development Director Re: Hardwood Solutions, Inc. 640 East Industrial Drive Phase 2 Construction

Combined Preliminary and Final Site Plan Third Review

Revised Plan Date: June 22, 2020 Dear Ms. Upfal:

Pursuant to your request, we have prepared a third review of the Combined Preliminary and Final Site Plan submittal for conformance to the Chelsea Zoning Ordinance for the reference project. The project includes parcel tax ID number 06-06-12-249-025 (2.676 acres) located in the City of Chelsea, Section 12 of Sylvan Township. The parcel is zoned I-2, Light Industrial. The revised plan set dated June 22, 2020, consists of 5 plan sheets and 5 architectural plan sheets. This project includes the expansion of the existing warehouse building, construction of a new bathroom adjacent to the existing one, new parking and loading area. A response letter was included.

The applicant has revised the plans and provided the information requested in our previous review. We have no further comments for the Planning Commission to consider at this time.

If there are any questions regarding this review, please call or email. Thank you.

Sincerely, MIDWESTERN CONSULTING, LLC

Susan C. Dickinson, P. E.

Soundscape Engineering LLC 3711 N. Ravenswood Ave., Ste. 104 • Chicago, IL 60613 • (312) 436-0032

729 W. Ann Arbor Trl., Ste. 150 • Plymouth, MI 48170 • (734) 418-8663 www.SoundscapeEngineering.com

September 17, 2020 Julia Upfal, AICP Community Development Director Office: (734) 475-1771, Ext 210 [email protected] City of Chelsea 305 S. Main St., Suite 100 Chelsea, MI 48118 Subject: Hardwood Solutions Sound Mitigation Plan Review Dear Julia: Soundscape Engineering has reviewed the previously submitted Acoustical Study/Report by eNoise Control, dated 8/13/2020, and the subsequent report from Hardwood Solutions, Inc., dated 9/9/2020. Our review is a high level overview of the source sounds, predicted sound levels, and sound mitigation proposal. We have not made calculations to verify the accuracy of the predictions nor contacted the fan manufacturer to verify the sound source levels. We offer the following comments on the 9/9/2020 report with references to the 8/13/2020 report as appropriate.

• Item 3: The 84 dBA is based on measured data from a similar system collected by eNoise Control. It seems to be a reasonable sound level to use in the analysis.

• Item 4.a: We agree that the primary source of sound generation is the 200 HP fan.

• Item 4.b: Duct breakout noise, which is due to fan and/or airflow energy in the duct, radiates

through the duct walls both upstream and downstream of fans. We presume that the breakout noise downstream of the large fan was considered since it is being wrapped with the acoustical jacket. The fan inlet sound power is similar in amplitude to the outlet sound power, but the upstream ductwork is not being treated. We suggest obtaining a statement from either eNoise Control or Hardwood Solutions that the predicted breakout noise from the ductwork upstream of the large fan was also considered. See the bullet addressing Item 6 for comments on breakout noise predictions.

• Item 4.c: We agree with the implication that predicting the sound radiation from the tower collection tank is not practical.

• The other secondary source as listed in the eNoise Control report is the 15 HP fan. At this time, we understand that no noise mitigation effort will be undertaken for this fan. This may be appropriate depending on its radiated sound level.

Peer Review of Hardwood Solutions September 17, 2020 SE Project No. 1861 Page 2 of 3



• Item 5: We concur with the full acoustical enclosure for the fan mitigation strategy and the STC and NRC performance of the enclosure panels.

• Item 5.e: Manufacturers, products and product performance of the acoustic chamber dampers and acoustic louvers are not specified. We suggest obtaining assurance from either eNoise Control or Hardwood Solutions that the predicted sound level at the property line includes the presence and performance of the dampers and louvers in the enclosure walls. This includes which sides of the enclosure these openings are located. This is of interest because dampers and louvers will not attenuate as much sound as the STC 35 enclosure panels. They are necessary for airflow and are a relatively small when the entire enclosure surface is considered, but their acoustical performance must be considered. The Hardwood Solutions statement that the dampers and louvers allow “heat to escape, but not sound” is not accurate. They attenuate the sound that passes through them, but do not eliminate it.

• Item 6: We agree that breakout noise is likely to be a secondary source. While we agree that breakout noise and other secondary sources are either not easy to or essentially impossible to measure in the presence of a separate dominant source, this does not mean that breakout noise cannot be predicted. Refer to the ASHRAE Handbook: HVAC Applications, Chapter 49 Noise and Vibration Control for the well-established breakout noise calculation procedure. After the sound radiation from the fan with enclosure is predicted, it can be compared to the predicted breakout sound on both the fan inlet and outlet ductwork to see where duct jacketing may need to be installed. While the analysis does not need to be submitted, it is not explicitly stated that breakout noise from the fan inlet and outlet ducts was or was not a significant contributor to the sound level at the property line.

• Item 7: It appears that the HF37 Rectangular Vibration Isolator is what is commonly referred to as a flexible duct connection. These are used at connections to air moving equipment, such as fans and air handling units. The neoprene in the connection is acoustically much weaker than sheet metal, meaning sound can pass through its walls more easily. It is useful as a vibration break at the fan as shown in Exhibit 3, and it would be beneficial to locate it within the enclosure to prevent vibration transmission to the enclosure walls. However, we recommend eliminating it at the duct connection to the bag house because it is more important to contain the sound within the duct at this point in the system than to reduce vibration. We agree that the high velocity airflow can induce vibration in the ductwork, but it seems that this would be a lesser source. If the applicant or their consultant disagree, we welcome a more detailed explanation as to why it is needed at the bag house connection.

• Item 8: The predicted level seems to reference page 8 of the eNoise Control report since the predicted level is identical at the east property line. These predicted property line sound levels seem reasonable for the proposed noise mitigation materials and methods.

Final Note Should the installation not meet the noise ordinance, the contributing sound sources should be evaluated and mitigation steps taken. Additional jacketing/blankets or silencers may be necessary. Our comments are an expert review of the submission. We have not performed an analysis to verify any predictions, only a cursory examination to determine whether the reported sound levels seem reasonable

Peer Review of Hardwood Solutions September 17, 2020 SE Project No. 1861 Page 3 of 3



given the sound source and acoustical treatment proposal. We cannot comment on such things as local codes, life safety requirements or any other non-acoustical issues. This concludes our assessment. Thank you for the opportunity to assist you with this project. Please contact us if you have any questions. Sincerely,

Soundscape Engineering LLC Per:

Mandy Kachur, PE, INCE.Bd.Cert. Principal Consultant [email protected] direct: (734) 494-0322

680 East Industrial Drive Chelsea, Michigan 48118 Phone: 734-475-0144 Fax: 734-475-0457

Item 4.b: Duct breakout noise, which is due to fan and/or airflow energy in the duct, radiates through

the duct walls both upstream and downstream of fans. We presume that the breakout noise

downstream of the large fan was considered since it is being wrapped with the acoustical jacket. The

fan inlet sound power is similar in amplitude to the outlet sound power, but the upstream ductwork is

not being treated. We suggest obtaining a statement from either eNoise Control or Hardwood Solutions

that the predicted breakout noise from the ductwork upstream of the large fan was also considered.

See the bullet addressing Item 6 for comments on breakout noise predictions

Breakout noise from the upstream ductwork was considered. Statement form John Jones

Honeyville Metal Inc, Manufacturer “We believe that sound wrap on the suction line, from

building to fan inlet, would not be needed. The suction line is under vacuum and would not be

subject to the same type of sound pressure that is in the blow line, from fan to filter.”

Item 5.e: Manufacturers, products and product performance of the acoustic chamber dampers and

acoustic louvers are not specified. We suggest obtaining assurance from either eNoise Control or

Hardwood Solutions that the predicted sound level at the property line includes the presence and

performance of the dampers and louvers in the enclosure walls. This includes which sides of the

enclosure these openings are located. This is of interest because dampers and louvers will not

attenuate as much sound as the STC 35 enclosure panels. They are necessary for airflow and are a

relatively small when the entire enclosure surface is considered, but their acoustical performance must

be considered. The Hardwood Solutions statement that the dampers and louvers allow “heat to escape,

but not sound” is not accurate. They attenuate the sound that passes through them, but do not

eliminate it.

We concur that any acoustic louver or silencer does not “eliminate sound” but lower sound

levels. At this point we have not submitted a detailed approval CAD shop drawing of the sound

enclosure or potential acoustic louver/silencer integration into the enclosure. eNoise will design

and submit an appropriately designed (aggressive transmission loss) acoustic louvers and/or

silencers for airflow and noise reduction – Jeff Unger eNoise Control

Item 7: It appears that the HF37 Rectangular Vibration Isolator is what is commonly referred to as a

flexible duct connection. These are used at connections to air moving equipment, such as fans and air

handling units. The neoprene in the connection is acoustically much weaker than sheet metal, meaning

sound can pass through its walls more easily. It is useful as a vibration break at the fan as shown in

Exhibit 3, and it would be beneficial to locate it within the enclosure to prevent vibration transmission to

the enclosure walls. However, we recommend eliminating it at the duct connection to the bag house

because it is more important to contain the sound within the duct at this point in the system than to

reduce vibration. We agree that the high velocity airflow can induce vibration in the ductwork, but it

seems that this would be a lesser source. If the applicant or their consultant disagree, we welcome a

more detailed explanation as to why it is needed at the bag house connection.

The vibration brake will be placed at the fan and captured in the sound enclosure.

Hardwood Solutions – Acoustic Report

Page 1 of 16 eNoise Control Confidential

Acoustical Study/Report

For: Hardwood Solutions

Report #9425-R4

Submitted by:

eNoise Control 129 Penn Street

Westfield, IN 46074 P: 317.774.1900

August 13, 2020

Specializing in Acoustics, Noise & Vibration Control

129 Penn Street Westfield, IN 46074

Phone: 317.774.1900 Fax: 317.774.1911

www.eNoiseControl.com



INTRODUCTION: Hardwood Solutions has contracted eNoise Control to offer acoustic modeling and feasibility options for reducing decibel levels at the property line based on a proposed new dust collection system.



INSTRUMENTATION:

Instrument A Precision 1/3 Octave Band Analyzer

Larson- Davis 824 & 831

Type 1 Sound Level Meter per ANSI S1.4



The first step in developing practical and economical noise control solutions is to use one or all of the following basic techniques:

1. Source Treatment – direct treatment to the equipment 2. Transmission path barriers – direct and indirect acoustical path

treatment 3. Receiver isolation – isolate the receiver from the noise

Please refer below for conceptual information on the above. eNoise will consider Source Treatment & Transmission path barrier options

Reprint from BRD catalog



SUMMARY & CONCLUSIONS

1. Hardwood Solutions has contracted with eNoise Control to evaluate a proposed new dust collection system and model property line decibel levels along offer feasible engineering noise reducing options.

2. Hardwood Solutions is proposing installation of new dust collection system within 12’ to the property line.

3. The goal is to be at or below 71 dBA at the property line while the equipment is running.

4. Noise contributing sources of the dust collection system include: large 200HP fan, break-out noise from discharge duct, break out noise from intake duct, metal duct vibration/radiated noise, one smaller 15 HP fan, tower collection tank (bag house) vibration/radiated noise and support structure.

5. eNoise is able to model the large 200HP fan with given sound power data. We also modeled using field data from a similar installation in Ohio. Those two results are below in this study and show property line values without any noise control treatment at 76 and 84 dBA respectively. We are skeptical of the 76 dBA model due to past evaluations by eNoise Control. We feel more confident with the field readings giving us 84 dBA modeling at the property line with no noise control treatment.

6. The difficulty of this project for analysis is noise being generated by ductwork and collection tank at high elevations. It is very difficult to model the contributing decibel levels because the sound data presented is from the noise source (fans) and not the 2nd tier vibration/radiated noise of the duct down stream and the collection tank downstream.

7. Noise control strategies include: full building enclosure, fan sound enclosures, sound control walls, silencers and duct wrap. Some or all these strategies can be implemented to lower noise levels. See point #8 below where we model the large blower fan only.

8. We conclude noise levels to be around 84 dBA at the property line, with most of the noise being contributed by and near the large 200HP fan. Noise goal of 71 dBA would mean “in design” a 13 dBA (or greater) reduction goal. We also conclude associated duct and collection tank contributing in the mid 70’s of dBA, thus reduction goals of 5 to 10 dBA from those 2nd tier noise sources. Our modeling only takes into account noise control treatment of the large blower: sound wall (15’ high) modeling 70.7 dBA at property line and a full sound enclosure (around blower only) modeling 66.5 dBA at the property line. eNoise Control has not modeled any other secondary noise sources (i.e. duct work, collection tank, secondary blower, etc.) which we deem contributors of noise to the property line.

9. Localized efforts would reduce noise: i.e. fan enclosure, ~ 15’ high sound wall, duct/pipe wrapping, etc. There is no real full proof way to measure/guarantee results of all the components (i.e. pipe, duct, tank, angle support, etc.) which will generate vibration/noise.



ANALYSIS AND ENGINEERING RECOMMENDATION

Modeling at 84 dBA with no treatment

12’ distance

88’ distance

245’ distance

213’ distance

600’ distance



Modeling at 70.7 dBA with 15’ high sound wall {no treatment above the 15’ high level} {large fan source modeled only}



Modeling at 66.5 dBA with full 4-sided with roof fan sound enclosure {no sound control treatment in any other area of collection system} {large fan source modeled only} Feasibility Noise Control Options: 1. Full building with minimum STC-35 rating and NRC-0.75 rating. Full sealed doors, penetrations, etc. This can take the form of concrete, block, metal outer skin with insulation lined interior. {i.e. Butler Building, tilt up concrete, etc.}. {sound reduction up to 20 dBA} Price locally. 2. Full localized sound enclosure with minimum STC-35 rating and NRC-0.75 rating. Modular acoustic steel panels (see brochure). {sound reduction up to 20 dBA} Pricing $60 / SF. 3. Acoustic steel sound barrier wall minimum STC-35 rating and NRC-0.75 rating. Modular acoustic steel panels or concrete, block, etc. lined with sound absorption. {sound reduction 10 to 15 dBA} Pricing $50 / SF. 4. Pipe / duct acoustic lagging. {sound reduction 3 to 6 dBA}. Pricing $7 / SF. 5. Silencers for exhaust noise from fan. {sound reduction up to 10 dBA}. Pricing $8,000.00 per silencer



Representative noise sources (arrow) and height of sound wall that can “block/capture” these noise sources depending on height.



A sound wall will at minimum need to block “line of sight” to lower noise levels

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Full acoustic steel enclosure {mainly for fans/blowers}



Example of acoustic steel barrier wall

305 s. main street 640 east industrial drive phase 2 construction … packet2... · 2020. 9....

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