ARI575 - Measuring Machinary Sound

4301 NORTH FAIRFAX DRIVE ! ARLINGTON, VIRGINIA 22203

Standard 575

1994STANDARD for

METHOD OFMEASURINGMACHINERYSOUNDWITHIN ANEQUIPMENTSPACE

Price $15.00 (M) $30.00 (NM) ©Copyright 1994, by Air-Conditioning and Refrigeration InstitutePrinted 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 withnationally 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 andaccepted industry practices. However, ARI does not certify or guarantee safety of any products, components orsystems designed, tested, rated, installed or operated in accordance with these standards or that any tests conductedunder its standards will be non-hazardous or free from risk.

FOREWORD

This document establishes a uniform method of measuring the sound levels produced by air-conditioning andrefrigerating machinery installed in mechanical equipment spaces. However, it should be emphasized that thisstandard was developed for use where the test conditions usually cannot be controlled, e.g., ambient temperature;equipment loading; physical attributes of the space; background sound sources, etc. Since the results obtained mayvary substantially, a tolerance on these results cannot be specified.

Uniform practices in making sound level measurements are necessary for effective communication between the owner,the architect, the acoustician, the consulting engineer, the contractor and the equipment manufacturer.

Specification for sound levels produced by machinery may be written, both for the purpose of supplying informationin order to evaluate compliance with noise exposure limits and for the purpose of providing information for adequatebuilding design to meet the acoustical design goals of adjacent occupied spaces. In view of the geometrical andacoustical properties of large equipment, both purposes can best be served by sound data expressed in terms of soundpressure level measured close to the equipment. Sound pressure measurements close to the equipment are least affectedby the environment in which the machines are installed.

This standard is based upon the procedures established in American National Standard S1.13-1971 (R1986).

Note:

This standard supersedes ARI Standard 575-87.

TABLE OF CONTENTS

SECTION PAGE

Section 1. Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Section 2. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Section 3. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Section 4. Instruments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Section 5. Sound Measurements and Calculation Procedures . . . . . . . . . . . . . . . . . . . . 2

Section 6. Machinery Sound Spedifications and Data Presentation . . . . . . . . . . . . . . . . 4

Section 7. System Operating Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Section 8. Voluntary Conformance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

FIGURES

Figure 1. Test Unit Measurement Points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

APPENDICES

Appendix A. Operating Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Appendix B. Sound Level Recording Format Per ARI Standard 575 . . . . . . . . . . . . . . . . . 9

Appendix C. References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

ARI STANDARD 575-94

1

METHOD OF MEASURING MACHINERY SOUNDWITHIN AN EQUIPMENT SPACE

Section 1. Purpose

1.1 Purpose. The purpose of this standard is to establish base 10 of the ratio of a given pressure to a referencea uniform method of measuring and recording the sound pressure. The reference pressure (P ) used in this standardpressure level of machinery installed in a mechanical is 20 micropascals.equipment space. It is not the intent of this standard to beused for the sound rating of equipment. L = 20 log (p/P )

Section 2. Scope pressure, in Pa.

2.1 Scope. This standard applies to water chilling 3.6 Uncertain and Valid Measurements.systems, pumps and similar operating machines and partsthereof, which for reasons of size or operating characteristicsare more practically evaluated in situ.

Section 3. Definitions

3.1 "A" -Weighted Sound Pressure Level. The measuredvalue obtained with a sound level meter using its "A"weighting network.

3.2 Octave Band. An octave band is a band of soundcovering a range of frequencies such that the highest is twicethe lowest. The octave bands used in this standard are thosedefined in American National Standard Institute StandardS1.11-1986.

3.3 Operating Conditions. Operating conditions are thoseconditions specified for the particular installation. Ingeneral, they are those parameters listed in the jobspecification sheets for the particular equipment. Examplesof parameters to be recorded are found on data sheets inAppendix A.

3.4 "Shall," "Should," "Recommended" or "It IsRecommended." "Shall," "should," "recommended" or "it isrecommended" shall be interpreted as follows:

3.4.1 Shall. Where "shall" or "shall not" is used for addition, an electrical calibration of the instrumentationa provision specified, that provision is mandatory if system over the entire frequency range of interest shall becompliance with the standard is claimed. performed periodically as recommended by the

3.4.2 Should, Recommended or It Is Recommended."Should," "recommended" or "it is recommended" isused to indicate provisions which are not mandatory butwhich are desirable as good practice.

3.5 Sound Pressure Level. The sound pressure level (L ),p

in decibels (dB), of a sound is 20 times the logarithm to the

o

p 10 o

where p is the measured RMS (root mean square) sound

3.6.1 An uncertain measurement is at a point wheresound energy of other sources causes the observed valueto be above its true value.

3.6.2 A valid measurement is at a point where otherequipment or adjacent surfaces do not significantlyaffect the value observed.

Section 4. Instruments

4.1 Sound Level Meter. A meter meeting the requirementsof the Type 1 meter described in American NationalStandards Institute Standard S1.4-1983 is to be used.

4.2 Frequency Analyzer. An octave or third-octave bandfilter set meeting the requirements for Class II or III filtersrespectively, of American National Standards InstituteStandard S1.11-1986 is to be used.

4.3 Calibration. During each series of measurements, anacoustical calibrator with an accuracy of ±0.5 dB shall beapplied to the microphone for checking the calibration of theentire measuring system at one or more frequencies over thefrequency range of interest. The calibrator shall be checkedat the manufacturer's recommended intervals or at least onceevery year to verify that its output has not changed. In

manufacturer, but at intervals of not more than two years.

Section 5. Sound Measurements and

ARI STANDARD 575-94

2

Calculation Procedures the measured values. If the "A" weighted sound

5.1 Measurements.

5.1.1 Measurement Points. The points wheremeasurements are to be taken are determined relative toa reference parallelopiped, which is the smallestimaginary rectangular parallelopiped that will enclosethe machine (see Figure 1). Minor projections from themachine are disregarded in determining the size of thereference parallelopiped.

The measurement points shall be positioned on the Noise. Any "A"-weighted or octave band soundsurface of a measurement parallelopiped whose planes pressure level taken with test unit operating must be atare 1 meter out from the vertical sides of the reference least 6 dB above the corresponding level with the testparallelopiped. Key measurement points are located at unit off and other equipment operating. Any levelthe center of each vertical plane of the measurement which does not meet this criterion shall be markedparallelopiped. The remaining measurement points are uncertain by the use of an asterisk (*). The number ofat 1 meter intervals on the measurement planes starting uncertain measurement points is N .from the key points. All measurement points are at aheight of 1.5 meters from the floor. If the shortestdistance between two measurement points at a corner ofthe measurement parallelopiped is less than 1 meter, thepoint nearest to the corner shall be eliminated. Thetotal number of points on the measurementparallelopiped is N.

5.1.2 Operation of Sound Level Meter. The soundlevel meter shall be used in the slow response position.The instrument manufacturer's recommendations shallbe followed in using the meter and in determining thecorrect microphone orientation for the flattest frequencyresponse.

5.1.3 Data to be Taken. "A" weighted soundpressure level measurements shall be taken at allmeasurement points. Octave band measurements (63through 8000 Hz octave bands) shall be made at thefour key measurement points.

A full set of measurements shall be taken with the testunit operating. A second full set of data shall beobtained with the test unit off and all other equipmentin the area operating as before to establish thebackground sound levels.

5.1.4 Valid Measurement Points. A validmeasurement point cannot be closer than 1 meter to awall or other plane surface larger than 1 square meter.A measurement shall not be recorded at anymeasurement point that does not meet this criterion.The number of invalid measurement points is N .1

5.1.5 Pure Tones. When pure tones are generated bythe operating machine, interference patterns may affect

pressure level or any octave band sound pressure levelvaries 6 dB or more within an area of 0.5 meter radiusof the measuring point and on the surface of themeasurement parallelopiped, the highest and lowestvalues observed within this area shall be recorded. Ifvariations are less than 6 dB the value obtained at thespecified measurement point shall be recorded.

5.2 Calculation Procedures.

5.2.1 Uncertain Measurements Due to Background

U

5.2.2 Pure Tones. Where the highest and lowestvalues were recorded for a measurement point asspecified in 5.1.5 the value used in the calculations forthis point shall be the highest value minus 3 dB.

5.2.3 Representative "A"-Weighted Sound PressureLevel. If half or more of the measurement pointsremain (that is, if N - N - N $ N/2) after applying theU 1

limitations of 5.1.4 and 5.2.1, the representative "A"-Weighted Sound Pressure Level (A ) shall be calculatedR

using Equation 1. However, if less than half remain,the Representative High Limit Sound Pressure levelshall be calculated per 5.2.5.

5.2.4 Representative Octave Band Sound PressureLevels. If two or more key measuring points remainafter applying the limitations of 5.1.4 and 5.2.1, theRepresentative Octave Band Sound Pressure Levels(OB ) shall be calculated using Equation 1. However,R

if less than two remain the Representative High LimitOctave Band Sound Pressure Level shall be calculatedper 5.2.6.

ARI STANDARD 575-94

3

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ARI STANDARD 575-94

4

5.2.5 Representative High Limit "A"-Weighted Sound 6.2 Data Presentation. When a sound test is conducted inPressure Levels. If half or more of the measurement accordance with this standard, a report shall be supplied andpoints can be obtained by adding the uncertain to the it shall include the information in 6.2.1; 6.2.2 and 6.2.3. Invalid measurement points (that is, if N - N $ N/2), then addition, the data defined in 6.2.4 should be provided when1

a Representative High Limit "A"-Weighted Sound specified by the user.Pressure Level (A ) can be calculated using Equation 1H

with N = O. If this criteria cannot be met neither aU

Representative or Representative High Limit "A"-Weighted Sound Pressure Level can be obtained.

5.2.6 Representative High Limit Octave Band Level.If two or more key measurement points can be obtainedby adding the uncertain points to the valid measurementpoints a Representative High Limit Octave Band SoundPressure Level (OB ) can be calculated usingH

Equation 1. If this criteria cannot be met neitherRepresentative nor Representative High Limit OctaveBand Sound Pressure Levels can be obtained.

5.2.7 Sound Pressure Level Averaging Equation.

L = 10 log - 10 log n (1)10 10

Where: L = Representative or High Limit SoundPressure Level Logarithmic averagerounded off to the nearest 0.5 dB)

L = Sound pressure level at the measuredn

pointsn = Number of points to be averaged =

(N - N - N )U 1

Section 6. Machinery Sound Specificationsand Data Presentation

6.1 Sound Level Specifications. Information required forspecifying machinery sound levels should include thefollowing:

a. Machine description.

b. Desired Representative "A"-Weighted SoundPressure Level (A ).R

c. If desired, optional Representative Octave BandSound Pressure Level (OB ).R

d. Operating conditions at which (A ) and (OB ) areR R

specified (see Section 7).

6.2.1 Statement that the test was conducted inaccordance with ARI Standard 575.

6.2.2 Description of the machine, the operatingconditions and a sketch showing the test layout andmicrophone locations (see Appendix B for Form andsample calculation).

6.2.3 Representative "A"-Weighted Sound PressureLevel (A ) or Representative High Limit SoundR

Pressure Level (A ) as calculated per 5.2. A will beH H

reported only if the data for computing A cannot beR

obtained. If the latter course is followed, the reasonsthat the A cannot be obtained shall be submitted to theR

user.

6.2.4 Representative Octave Band Sound PressureLevels at (OB ) or Representative High Limit OctaveR

Band Sound Pressure Levels (OB ), in the 63 HzH

through 8000 Hz bands, inclusive, as calculated highlimit. OB levels, calculated per 5.2, shall only beH

reported in the case that OB levels cannot be obtained.R

If the latter course is followed, the reasons that thelower value OB cannot be obtained shall be submittedR

to the user.

Section 7. System Operating Conditions

7.1 Operating Conditions for Test. Sound tests shall bemade with the machine operating at design operatingconditions. If this operating point cannot be obtained, thesound test may be made at some other steady state conditionmutually agreed upon by the parties concerned. Thiscondition shall clearly be described in the test report. SeeAppendix A for examples of typical report forms.

Section 8. Voluntary Conformance

8.1 Conformance. While conformance with this standardis voluntary, conformance shall not be claimed or impliedfor products or equipment within its Purpose (Section 1) andScope (Section 2) unless such claims meet all of therequirements of the standard.

ARI STANDARD 575-94

5

APPENDIX A

Operating Conditions

The following data forms shown in this appendix are intended as a guide to ensure that adequate data are recorded. Becauseof the wide range of machinery which can be expected to be installed in building machinery spaces, a universal data form is notpractical. If the attached forms are not adequate, one should be tailored to meet individual requirements.

CENTRIFUGAL CHILLER OPERATIONAL DATA RECORDING FORMPER ARI STANDARD 575

MACHINE SPECIFICATIONS:

Model: Manufacturer: Serial:

Rated Compressor Speed: Capacity:

Rated Load Amperage: Volts:

Type of Driver: Refrigerant:

Auxiliaries, such as Gears:

Comments:

TEST CONDITIONS:

Suction Temperature/Pressure EF [EC]/ psig [kPa]

Chilled Water Temperature In/Out EF [EC]/ EF [EC]

Chilled Water Pressure In/Out psig [kPa]/ psig [kPa]

Discharge Temperature/Pressure EF [EC]/ psig [kPa]

Condenser Water Temperature In/Out EF [EC]/ EF [EC]

Condenser Water Pressure In/Out psig [kPa]/ psig [kPa]

Interstage(s) Temperature/Pressure EF [EC]/ psig [kPa]

EF [EC]/ psig [kPa]

Compressor Speed rpm

Compressor Capacity Control Position

Driver Speed rpm

Electric Motor amps volts

Steam Turbine Pressures:Before Control Valve psig [kPa]

Steam Chest psig [kPa]

Condenser psig [kPa]

ARI STANDARD 575-94

6

RECIPROCATING CHILLER OPERATIONAL DATA RECORDING FORMPER ARI STANDARD 575



Rated Compressor Speed: Capacity:

Rated Load Amperage: Volts:

Type of Driver: Refrigerant:


Comments:

TEST CONDITIONS:





Condenser Water Temperature In/Out EF [EC]/ EF [EC]

Condenser Water Pressure In/Out psig [kPa]/ psig [kPa]

Number of Compressors

Number of Compressors Running

Compressor Speed rpm

Electric Motor—Compressor 1 amps volts

2 amps volts

3 amps volts

4 amps volts

ARI STANDARD 575-94

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ABSORPTION CHILLER OPERATIONAL DATA RECORDING FORMPER ARI STANDARD 575



Capacity: Pump Speed:

Heat Source: Steam: Hot Water:

Rated Steam Pressure: Rated Hot Water Temperature:

Type and Location of Steam (Hot Water) Control Valve:

Comments:

TEST CONDITIONS:



Condenser Water Temperature—Absorber In/Out EF [EC]/ EF [EC]

Condenser Water Pressure—Absorber In/Out psig [kPa]/ psig [kPa]

Condenser Water Temperature—Condenser In/Out EF [EC]/ EF [EC]

Condenser Water Pressure—Condenser In/Out psig [kPa]/ psig [kPa]

Capacity Control Valve Position

Steam (Hot Water) Pressure at Control ValveUpstream/Downstream psig [kPa]/ psig [kPa]

Steam (Hot Water) Temperature at Control ValveUpstream/Downstream EF [EC]/ EF [EC]

ARI STANDARD 575-94

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PUMP OPERATIONAL DATA RECORDING FORMPER ARI STANDARD 575



Rated Pump Speed: Capacity:

Rated Load Amperage: Voltage:

Type of Driver: Type of Pump:


Comments:

TEST CONDITIONS:

Fluid Being Pumped



Pump Speed rpm

Driver Speed rpm

Electric Motor amps volts

ARI STANDARD 575-94

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APPENDIX B. SOUND LEVEL RECORDING FORMATPER ARI STANDARD 575

Unit Type

Model Number

Serial Number

Measurement 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26Position

db(A) TestUnit ON

db(A) TestUnit Off

A-Weighted Sound Pressure Level dbA AR ______________ or AH ____________

Hz

Octave Band Sound Pressure Levels at Key Measurement Points

Key Location ( ) Key Location ( ) Key Location ( ) Key Location ( )

Test Test Test Test Test Test Test Test AverageUnit Unit Unit Unit Unit Unit Unit Unit Octave BandON Off ON OFF ON OFF ON OFF Level

63

125

250

500

1000

2000

4000

8000

*Indicates uncertain measurements (See 5.2.1 of standard)

Sketch Showing Microphone Locations, Orientation of Test Unit,Key Measurement Points, and Surroundings

Tested By: Reported By: Date:

ARI STANDARD 575-94

10

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ARI STANDARD 575-94

11

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antilog108910

% antilog108810

% antilog108710

% antilog108910

% antilog109110

% antilog109010

% antilog109010

% antilog109010

% antilog109010

% antilog108810

% antilog108710

% antilog108810

% antilog108710

antilog1077(10

% antilog1081(10

antilog108310

% antilog108410

antilog1087 & 3

10% antilog10

77(10

ARI STANDARD 575-94

12

SAMPLE CALCULATIONS

Sample calculation for a water chiller where the measurement procedure is complicated by

1) the close proximity of a wall,2) the close proximity of a water tank,3) a pure tone generated in the gear box at 2,000 Hz,4) a pure tone generated by an adjacent pump at 4,000 Hz,5) high background level in the 63 Hz band.

To obtain the Representative "A" Weighted Sound Pressure Level

(Note D)

A = 10 logR 10

- 10 log 1310

A = 100.1 - 11.1R

= 89.0 dB (Note E)

To obtain the Representative Octave Band Sound Pressure at 1 Meter

For the 63 Hz Band:

(Note C)

OB = 10 log - 10 log 2H 10 10

OB = 79.4 dB; use 79.5 dBH

For the 125 Hz Band:

OB = 10 log - 10 log 2R 10 10

OB = 83.4 dB; use 83.5 dBR

For the 2000 Hz Band:

(Note B)

OB = 10 log - 10 log 2H 10 10

OB = 81.7 dB; use 81.5 dBH

ARI STANDARD 575-94

13

NOTE A: No measurements can be taken at these points because they are less than 1 meter from large surfaces (see 5.1.4).

NOTE B: Two values are recorded because of the pure tones present (see 5.1.5). The value used in the calculations shall be3 dB below the highest value (see 5.2.2).

NOTE C: A valid measurement must be 6 dB above the ambient (see 5.2.1). Final results using these values less than 6 dBabove background result in Representative High Limit Values.

NOTE D: The level of the ambient here is 84 - 3 = 81 dB. This is 7 dB below the measured value and is an acceptablemeasurement.

NOTE E: Thirteen valid measurements exist out of a possible 24 measurements. This is greater than half, and a value of AR

can be obtained. See the last statement of 5.2.3.

ARI STANDARD 575-94

14

APPENDIX C. REFERENCESListed here are all standards, handbooks, and otherpublications essential to the formation and implementationof the standard. All references in this appendix areconsidered as part of this standard.

ASHRAE Terminology of Heating, Ventilation, Air-Conditioning and Refrigeration, American Society ofHeating, Refrigerating, and Air-Conditioning Engineers,Inc., 1991.

ANSI Standard S1.11-1986, Specifications for Octave,Half-Octave, and Third-Octave Band Filter Sets, AmericanNational Standards Institute.

Documents

ARI575 - Measuring Machinary Sound