Sound Rating of Ducted Air Moving and Conditioning Equipment

4301 NORTH FAIRFAX DRIVE  ARLINGTON, VIRGINIA 22203

2001

STANDARD for

Standard 260

SOUND RATING OF DUCTED AIR MOVING AND CONDITIONING EQUIPMENT

Printed in U.S.A.Registered United States Patent and Trademark Office

IMPORTANT
SAFETY RECOMMENDATIONS
It is strongly recommended that the product be designed, constructed, assembled and installed in accordance with nationally recognized safety requirements appropriate for products covered by this standard.
ARI, as a manufacturers' trade association, uses its best efforts to develop standards employing state-of-the-art and accepted industry practices. However, ARI does not certify or guarantee safety of any products or systems designed, tested, rated, installed or operated in accordance with these standards or that any tests conducted under its standards will be non-hazardous or free from risk.

Note:

This is a new standard.

Foreword:

Ducted Equipment must be sound rated in relation to its various individual Sound Components to describe it acoustically and to provide the necessary information for predicting application sound levels. This standard addresses the sound rating of these various Sound Components. Ducted air-conditioning equipment can have ducted discharge, ducted inlet, free inlet (or free discharge) combined with casing radiated, or casing radiated Sound Components depending on its specific manufactured configuration.

All Sound Components are acoustically described/rated by utilizing a "Mapped" Sound Rating approach that is typically referenced to the product's supply fan operating map. The supply fan is contained in the Base Unit of the product. In addition, this standard defines an approach to account for and add the acoustical effects of product Appurtenances (such as modulation devices or inlet/discharge plenums) and Other Sound Sources (such as the refrigeration circuit, exhaust fans, etc.) to the Base Unit Mapped Sound Rating. Thus, Mapped Sound Ratings can be developed for a given product configuration and each of its various Sound Components.

All ducted product Sound Components are rated utilizing a Reverberation Room Technique, modeled after AMCA Standard 300. Reverberation room tests are conducted using a Comparison Method and a Reference Sound Source calibrated in accordance with ARI Standard 250.

Sound ratings are in the form of Octave Band Sound Power Levels (dB) from 125 to 8,000 Hz derived from One-Third Octave Band (dB) measurements for the various product Sound Components. Sound ratings may be provided for the 63 Hz Octave Band if the reverberation room has been qualified in accordance with ARI Standard 280.

A listing of current ARI Sound Standards is located in Appendix C.

TABLE OF CONTENTS

SECTIONPAGE

Section 1.Purpose...... 1

Section 2.Scope...... 1

Section 3.Definitions...... 1

Section 4.Requirements for Acquiring Mapped Sound Data...... 3

Section 5.Sound Power Level Calculations and Ratings...... 7

Section 6.Minimum Data Requirements for Published Sound Ratings...... 9

Section 7.Conformance Conditions...... 10

FIGURES

Figure 1.Typical Ducted Discharge Test Setup ...... 5

Figure 2.Typical Ducted Inlet Test Setup ...... 5

Figure 3.Typical Free Inlet Combined with Casing Radiated Test Setup...... 5

Figure 4.Typical Casing Radiated Test Setup...... 6

Figure 5.Typical Free Inlet Test Setup...... 6

APPENDICES

Appendix A.References - Normative...... 11

Appendix B.References - Informative...... 12

Appendix C.ARI Standards on Sound - Informative...... 13

Appendix D.Atkins Sound Attenuation Adjustments for Acoustic Test Duct

Elbows - Normative...... 14

Appendix E.Effects of Other Sources - Normative...... 15

Appendix F.Supply Fan Modulation Device Effects - Normative...... 16

Appendix G.Method of Processing Acquired Data - Normative...... 17

TABLES FOR APPENDICES

Table C1.ARI Standards on Sound - Informative...... 13

ARI STANDARD 260-2001

SOUND RATING OF DUCTED AIR MOVING AND CONDITIONING EQUIPMENT

ARI STANDARD 260-2001

Section 1. Purpose

1.1Purpose. The purpose of this standard is to establish a method of sound rating the indoor portions of ducted air moving and conditioning equipment and to provide definitions; requirements for acquiring mapped sound data; Sound Power Level calculations and ratings; minimum data requirements for published sound ratings; and conformance conditions.

1.1.1Intent. This standard is intended for the guidance of the industry, including manufacturers, engineers, installers, contractors and users.

1.1.2Review and Amendment. This standard is subject to review and amendment as technology advances.

Section 2. Scope

2.1Scope. This standard applies to all ducted air moving and conditioning equipment containing fans as defined in Section 3 of this standard.

Examples of such equipment when ducted are:

Unitary Air-Conditioners, as defined in ARI Standard 210/240and ARI Standard 340/360
ARI-Source Unitary Heat Pumps, as defined in ARI Standard 340/360
Water-Source Heat Pumps, as defined in ISO 13256-1
Fan-Coil Air-Conditioners, as defined in ARI Standard 440
Central-Station Air-Handling Units, as defined in ARI Standard 430

2.2Exclusions. This standard does not apply to:

Air Control and Distribution Devices, which are covered by ARI Standard 880
Packaged Terminal Air-Conditioners, which are covered by ANSI/ARI Standard 300
Outdoor sound from outdoor portions of Ducted Equipment that would be covered under ARI Standards 270 and 370
The sound radiated from ductwork attached to the fan and/or equipment when such ductwork is not offered by the manufacturer as a standard part of the equipment
The casing (base pan) radiated sound component for rooftop or down draft products

Section 3. Definitions

All terms in this document shall follow the standard industry definitions established in the current edition of ASHRAE Terminology of Heating, Ventilation, Air-Conditioning and Refrigeration, unless otherwise defined in this section.

3.1AcousticTest Duct. The duct used to convey the sound of the unit configuration under test to the reverberation room during a ducted discharge or the ducted inlet sound component test. A Duct End Correction (E) must be added to the sound data measured in the reverberation room to account for the presence of an open-ended duct terminating in the reverberation room.

3.2AcousticTest Duct Elbow. An elbow added to the Acoustic Test Duct during a reverberation room test to facilitate testing. An adjustment must be made (in addition to the Duct End Correction) to the sound data to account for the presence of the Acoustic Test Duct Elbow. Appendix D of this standard defines the Atkins sound attenuation adjustments.

3.3Base Unit. A factory-made encased assembly consisting of one or more fans meant to be connected to a duct and other necessary equipment to perform one or more of the functions of circulating, cleaning, heating, cooling, humidifying, and mixing of air, but which does not always include a source of heating or cooling.

3.3.1Appurtenance. An addition to a Base Unit

for purposes of control, isolation, safety, static pressure regain, wear etc.

Examples of Appurtenances include:

Coil(s)

1.Cooling coil

Cooling and dehumidifying coil
Water spray (wetted coil)
Heating coil

Electric heater(s)
Air filter

Dampers

Moisture eliminator

Fan-motor drive

Gas heat exchangers
Inlet or discharge plenums
Modulating devices in the fan inlet/discharge
Application duct geometries (such

as duct elbow configurations)

3.4Comparison Method. A method of determining Sound Power Level of a source under test in a reverberation room by comparing the average Sound Pressure Level of that source to the average Sound Pressure Level of a Reference Sound Source of known Sound Power Level output. The difference in Sound Power Level is equal to the difference in Sound Pressure Level when conditions in the room are the same for both sets of measurements.

3.5Duct End Correction, E. Accounts for the acoustic energy in an Acoustic Test Duct that is reflected back towards the source. A method for computing E is defined in 5.2.1 of this standard.

3.6Ducted Equipment. Heating, ventilating and air-conditioning equipment having one or more supply fans. The equipment may be configured with either:

Free inlet(s) with ducted discharge(s)
Ducted inlet(s) with free discharge(s)
Ducted inlet(s) and ducted discharge(s)

This equipment may be ducted in various configurations horizontally and vertically, and may incorporate multiple inlets and outlets.

3.7Effective Diameter, D. Diameter of an Acoustic Test Duct and is equal to either the diameter, ft [m], of a circular duct or the Effective Diameter, ft [m], of a rectangular duct.

D is given by the following expression:

(1)

where:

AREA = Cross-sectional area of the duct, ft2 [m2]

3.8Hertz (Hz). A unit of frequency equal to one cycle per second.

3.9Low Frequency Data. Data in the 63 Hz Octave Band (50, 63 and 80 Hz One-Third Octave Bands).

3.10Mapped Sound Rating. A rating based upon tests performed across the range of operating conditions typically defined for the product supply fan map, in the Base Unit, and as defined by the product manufacturer. These products include:

Belt-driven products with or without variable

frequency drives

Direct-drive products with variable frequency

drives

Direct-drive products with discrete speed taps

Note: Special case –when a supply fan is used in conjunction with a return fan in the Base Unit (See Appendix E of this standard).

3.11Octave Band. A band of sound covering a range of frequencies such that the highest is twice the lowest. The Octave Bands used in this standard are those defined in ANSI Standard S1.11.

3.12One-Third Octave Band. A band of sound covering a range of frequencies such that the highest frequency is the cube root of two times the lowest. The One-Third Octave Bands used in this standard are those defined in ANSI Standard S1.11.

3.13Reference Sound Source (RSS). A portable, aerodynamic sound source that produces a known stable broad band sound power output.

3.14Reverberation Room Technique. A technique used to derive the Sound Power Level of Ducted Equipment Sound Components. The technique utilizes an Acoustic Test Duct coupled to a reverberation room to measure the ducted inlet or ducted discharge sound. Other setup configurations allow the testing of the casing radiated or free inlet (or free discharge) combined with the casing radiated Sound Components. This technique is incorporated in AMCA Standard 300.

3.15"Shall" or "Should". "Shall" or "should" shall be interpreted as follows:

3.15.1Shall. Where "shall" or "shall not" is used for a provision specified, that provision is mandatory if compliance with the standard is claimed.

3.15.2Should. "Should" is used to indicate provisions which are not mandatory but which are desirable as good practice.

3.16Sound Components. The various Sound Sources emanating from the product that need to be independently defined to adequately describe a product’s acoustic effect on a typical application.

Depending on the configuration of the equipment the Sound Components that need to be defined consist of several or all the following:

Ducted discharge
Free inlet (or free discharge) combined with

casing radiated

Casing radiated
Ducted inlet
Free inlet (and/or free discharge)

3.17Sound Power Level, Lw. This is ten times the logarithm to the base ten of the ratio of the sound power radiated by the source to a reference sound power, expressed in decibels (dB). The reference sound power used in this standard is 1 picowatt (pW)

Lw = (dB)

Reference power = 10-12 watt. Following convenient form is obtained when the reference sound power is introduced in to the above equation

Lw = 10log10W + 120 (dB)

Where the power, W, is measured in watts.

3.18Sound Pressure Level,Lp. This is twenty times the logarithm to the base ten of the ratio of a given sound pressure to a reference sound pressure of 20 Pa, expressed in decibels (dB).

Lp = = (dB)

The reference pressure Pref = 2X10-5 Pa or 20 µPa

When reference pressure Pref is introduced, following convenient form is obtained.

Lw = 20log10Prms + 94 (dB)

3.19Sound Sources.

Base Unit. Sound generated by the supply fan(s) in the Base Unit.
Appurtenance. Sound generated or attenuated due to the Appurtenance having supply fan airflow through it.
Other. Sound generated by an element that is not dependent on the supply fan airflow of the product. The refrigerant circuit, airborne noise from a variable frequency drive (VFD) ventilation fan, motor noise due to a VFD, gas burner combustion noise, and exhaust fans are examples of Other Sound Sources.

Section 4. Requirements for Acquiring Mapped Sound Data

4.1General Overview. This standard incorporates a Reverberation Room Technique utilizing AMCA Standard 300 to obtain the Sound Power Levels of the various Sound Components for ducted air-moving and air-conditioning equipment. It goes beyond AMCA Standard 300 which is for rating fans, by adding the effects of Appurtenances and Other Sound Sources to the Base Unit to obtain the Mapped Sound Rating of a given product configuration. Sound Power Levels shall be obtained utilizing the Comparison Method and a Reference Sound Source calibrated per ARI Standard 250. The One-Third Octave Band Sound Pressure Levels of Sound Components can be measured to obtain the Sound Power Levels required to rate each sound component of the equipment.

Products having multiple ducted inlets or multiple ducted discharges on a common face that are meant by the manufacturer to join into a common duct shall be ducted into the reverberation room and tested at the same time. A Duct End Correction of only one of the ducts shall be made. However, if products have multiple ducted inlets or discharges on a common face or different faces, and are not joined into a common duct, each shall be ducted into the reverberation room and tested separately. Duct End Corrections shall be made for each of the ducts.

The three Ducted Equipment configurations addressed by this standard are equipment with:

Free inlet(s) with ducted discharge(s)
Ducted inlet(s) with free discharge(s)
Ducted inlet(s) and ducted discharge(s)

The three equipment configurations have the following Sound Components:

4.1.1Equipment with Free Inlet(s) and Ducted

Discharge(s). The following Sound Power Levels

shall be determined for this configuration:

a.Free inlet combined with casing radiated

Ducted discharge
Free inlet

Note: The free inlet combined with casing radiated sound power component shall not be derived from separate free inlet and casing radiated sound tests.

4.1.2Equipment with Ducted Inlet(s) and Free Discharge(s). The following Sound Power Levels can be determined for this configuration:

Ducted inlet
Casing radiated combined with free discharge
Free discharge

Note: The free discharge combined with casing radiated sound power component shall not be derived from separate free discharge and casing radiated sound tests.

4.1.3Equipment with Ducted Inlet(s) and Ducted Discharge(s). The following Sound Power Levels can be determined for this configuration:

Ducted inlet
Casing radiated
Ducted discharge

4.2Testing Considerations. All Ducted Equipment is acoustically described by conducting Mapped Sound Rating tests. Mapped Sound Ratings for each Sound Component of a product are obtained by first mapping the supply fan in the Base Unit. The Appurtenance and Other Sound Sources are added as necessary to a supply fan sound map of the Base Unit.

4.2.1Base Unit. A sufficient number of speed curves and test points along each speed curve shall be evaluated to ensure that the difference between adjacent test points does not exceed 5 dB for any given One-Third Octave Band. At a minimum, Base Units shall be tested along the highest and lowest speed curves across the full operational map as

specified by the manufacturer.

4.2.2Appurtenances. A sufficient number of test data points shall be evaluated to ensure that the acoustical effect of the Appurtenance on the Base Unit is understood. The objective of the test is to determine if the Appurtenance can be represented by an averaged acoustical effect or if it must be described as a function of airflow velocity.

4.2.2.1Mechanical Airflow Control Device. The effects of a mechanical airflow control device (excluding variable frequency drives) shall be defined as outlined in AMCA Standard 300 (Appendix G).

4.2.3Other Sources. A sufficient number of operating conditions shall be evaluated to ensure that the acoustical effects of the Other Sound Sources on the Base Units are understood.

4.2.3.1Refrigerant Circuit Sources. Refrigerant circuit related sources are identified and defined only in reference to the ARI thermal rating standard operation point for a given product (see Appendix E).

4.2.3.2Exhaust and Return Fans. The effects of the exhaust and return fan Sound Source shall be evaluated at a nominal static pressure and airflow specified by the manufacturer (see Appendix E).

4.2.3.3Burners. The effects of the burner Sound Source shall be evaluated at the input rate and gas type specified on the nameplate.

4.3Method of Test. All sound tests shall be conducted

utilizing a Reverberation Room Technique modeled after AMCA Standard 300. However, the specific test setup will depend on the product Sound Components being tested.

4.3.1Ducted Sound Components. For ducted inlet and ducted discharge components tested in accordance with AMCA Standard 300 (Section 5), the Duct End Correction (E) must be added to each One-Third Octave Band for all products. The addition of the Duct End Correction (E) provides the user with the sound power that would be transmitted into a non-reflecting duct system.

Although a straight Acoustic Test Duct is preferred for ducted component tests, an Acoustic Test Duct Elbow may be used to accommodate test facility issues. If an Acoustic Test Duct Elbow is employed, adjustments shall be added to the sound data to account for attenuation of the Acoustic Test Duct Elbow using the Atkins adjustments as given in Appendix D.

4.3.1.1Orifice End Plate. The orifice end plate, as described in AMCA Standard 300 (Appendix C, Section C2), shall not be used to control the Acoustic Test Duct airflow in this standard.

4.3.2Casing Radiated Combined with a Free Inlet or Free Discharge. All casing radiated with free inlet or free discharge Sound Components shall be tested per AMCA Standard 300 (Section 5).