Sound Principles of HVAC Equipment - WASBO.com

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Sound Principlesof HVAC Equipment

©2015 Modine Manufacturing Company

January 29, 2015Presented by: John Smith

Review by:

Course Objectives – CEU (1 Hour)Course Objectives – CEU (1 Hour)

Overview of Sound Basics• Sound Pressure• Sound Power• Sound Intensity

Review and Application of Sound Standards• OSHA 1910.95• ANSIS12.60• AHRI 575• AHRI 260

Test Methods for Sound Pressure

Test Method for Sound Power

This document contains statements that involve assumptions, risks, and uncertainties, and actual results, performance, or achievements may differ materially from those expressed or implied in these statements. Contents of this document are confidential and must not be used in any way detrimental to Modine's interests.

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What is Sound?What is Sound?

sound1 (sound) n. a) Vibrations transmitted through an elastic solid or a liquid or

gas, with frequencies in the approximate range of 20 to 20,000 hertz, capable of being detected by human organs of hearing.

b) Transmitted vibrations of any frequency.c) The sensation stimulated in the organs of hearing by such

vibrations in the air or other medium.

Sound BasicsSound Basics

Frequency refers to the number of vibrations that an individual particle makes per unit of time

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A wave is made up of many different vibrational frequencies


A sound wave is a pressure disturbance that travels through a medium by particle to particle interaction

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Distance From Source

PerceivedIntensity

1 m 160 units

2 m 40 units

3 m 17.8 units

4 m 10 units

Intensity = or Intensity =Energy

Time * Area

Power

Area

Small amplitudecorresponds to

low energy wave

Large amplitudecorresponds to

high energy wave

Amplitude and Energy


• The typical human ear can detect an intensity of which displaces particles of air by a mere one-billionth of a centimeter

• Since the range of intensities that the human ear can detect is so large, the scale that is frequently used by physicists to measure intensity is a scale based on multiples of 10

• This type of scale is something referred to as a logarithmic scale• The scale for measuring intensity is the decibel scale

W

M21 * 10 ‐12

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Source Intensity Intensity Level# of Times GreaterThan TOH

Threshold of Hearing (TOH) 1*10-12 W/m2 0 dB 100

Rustling Leaves 1*10-11 W/m2 10 dB 101

Whisper 1*10-10 W/m2 20 dB 102

Normal Conversation 1*10-6 W/m2 60 dB 106

Busy Street Traffic 1*10-5 W/m2 70 dB 107

Vacuum Cleaner 1*10-4 W/m2 80 dB 108

Large Orchestra 6.3*10-3 W/m2 98 dB 109.8

Walkman at Maximum Level 1*10-2 W/m2 100 dB 1010

Front Rows of Rock Concert 1*10-1 W/m2 110 dB 1011

Threshold of Pain 1*101 W/m2 130 dB 1013

Military Jet Takeoff 1*102 W/m2 140 dB 1014

Instant Perforation of Eardrum 1*104 W/m2 160 dB 1016

How do Humans Process SoundHow do Humans Process Sound

The ear consists of three basic parts - the outer ear, the middle ear, and the inner ear. Each part of the ear serves a specific purpose in the task of detecting and interpreting sound.

The outer ear serves to collect and channel sound to the middle ear.

The middle ear serves to transform the energy of a sound wave into the internal vibrations of the bone structure of the middle ear and ultimately transform these vibrations into compressional wave in the inner ear.

The inner ear serves to transform the energy of a compressional wave within the inner ear fluid into nerve impulses that can be transmitted to the brain. The three parts of the ear are shown here.

The three parts of the ear are shown here.

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Sound ImportanceSound Importance

• United States Department of Labor -> OSHA 1910.95• Leed Certifications for schools -> ANSI S12.60• AHRI Standards -> 575 & 260• Sound levels in classroom setting• Explanation of Sound in an understandable manner that

can be used for apples to apples comparisons

Basics on Sound StandardsBasics on Sound Standards

• Sound Power Standard for testing using either a reverberation room or to follow ISO 9614 procedure for intensity measurements

• Rationale. Ducted Equipment presents unique challenges when providing sound ratings since their ratings are used to both compare products and to provide the information necessary to predict application sound levels.

• Scope. This standard applies to Ducted Equipment and specifies the method for the determination of the sound power rating of indoor sections of factory-made residential, commercial and industrial air-conditioning and heat pump equipment, which are electrically driven, with mechanical compression and containing fans, using mapped sound data for rating the various Sound Components.

• The true Apples to Apples test that is our end game data

ANSI/AHRI Standard 260 (I-P)

2012 Standard for

Sound Rating of Ducted Air Moving and Conditioning Equipment

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• This document establishes a uniform method of measuring the sound levels produced by air-conditioning and refrigerating machinery installed in mechanical equipment spaces.

• Specifications for sound levels produced by machinery may be written, both for the purpose of supplying information in order to evaluate compliance with noise exposure limits and for the purpose of providing information for adequate building design to meet the acoustical design goals of adjacent occupied spaces.

• Purpose. The purpose of this standard is to establish a uniform method of measuring and recording the Sound Pressure Level of machinery installed in a mechanical equipment space. It is not the intent of this standard to be used for the sound rating of equipment.

• This standard is based upon the procedures established in ANSI Standard S1.13

ANSI/AHRI Standard 575 (Formerly ARI Standard 575)

2008 Standard for

Method of Measuring Machinery Sound Within an Equipment Space


• This standard applies to siting and building-design-dependent sources of intrusive noise in learning spaces in schools, including noise produced by heating, ventilating, and air-conditioning (HVAC) systems; building services; and exterior sound sources such as vehicular traffic and aircraft overflights.

• The one-hour average A-weighted sound levels shall be measured in accordance with ANSI/ASA S12.9 Part 2 and ANSI/ASA 12.9 Part 3, as applicable, and in accordance with ANSI/ASA S1.13.

ANSI/ASA S12.60-2010/Part 1(Revision of ANSI/ASA S12.60-2002)

AMERICAN NATIONAL STANDARD

Acoustical Performance Criteria, Design Requirements, and Guidelines for Schools,Part 1: Permanent Schools

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• This part of ANSI/ASA S12.60 is applicable to relocatable classrooms and other relocatablemodular core learning spaces of small to moderate size.

• The location with the highest A-weighted sound level shall be termed the “key” location. The microphone shall be located at a height of 1.0 to 1.2 m (40 to 28 in.) above the floor; no closer than 1 m (40 in.) from a wall or a fixed object such as HVAC plenum or bookshelves; and no closer than 0.5 m (20 in.) from a readily movable object such as a desk, chair, or table.

ANSI/ASA S12.60-200/Part 2

AMERICAN NATIONAL STANDARD

Acoustical Performance Criteria, Design Requirements, and Guidelines for Schools,Part 2: Relocatable Classroom Factors

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Means of Sound TestingMeans of Sound Testing

Sound Pressure (Pa) – The perceived temperature at any location inside the room. This value is affected by the surroundings/environment the unit is being run.

Sound Power (Watts) – The heaters overall power. In any situation, the heater will always produce the power that it is meant to produce. Regardless of the environment and any other circumstances of the room the unit will always produce the same power.

Sound Intensity (Watts / Area) – The directionality of the heat produced from the unit. If there is a blower discharge in one direction, the intensity will be higher in that direction due to thermal energy discharged. The rest of the room will receive heat, but at a slower rate as the temperature disperses evenly throughout the room.

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What is Sound Pressure?What is Sound Pressure?

Every unit was tested at the shown points and each point was taken 3 times and averaged to ensure an accurate reading

Each point was broken into third octave bands and averaged to ensure accurate readings across the octaves

Logarithmic averaging • Values can not be averaged normally as the

pressures are on a logarithmic scale

• To obtain an A(average) weighted sound pressure , the following formula must be used from ANSI 575 where M refers to the total measurement points

• The same method of averaging is used to average octave bands

Sound Pressure• The force of sound on a surface area• Value Measured in (pressure ~ Pa, inch / water, Bar)

Sound Pressure Level• Value Measured in (dB)• Logarithmic ScaleSound Pressure Level = 10 log( p2 / pref

2 ) = 10 log( p / pref )2 = 20 log ( p / pref )


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Key sound pressure considerations• Sound pressure is the easiest and quickest to test

• This allows it to be used for quick iterative testing for the best implementation of improvement processes

• Sound pressure is different at every point in the room due to the directionality of the sound and the characteristics of the room and every object in the room.

• Pressure ratings are different in a sound chamber than what will be recorded in a school or any other environment.

Purpose of Sound PressurePurpose of Sound Pressure

• Quick method for iterative testing

• Allows for the fastest means to collecting data

• Shows octave breakdowns for sound engineering

• Most understandable form of sound data

• The only form of data that is tailored to your exact circumstances

1. silence;2. audible sound;3. atmospheric pressure;4. sound pressure

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What is Sound Power?What is Sound Power?

Sound Power• Energy rate - the energy of sound per unit of

time• Value Measured in (Power ~ Watts,

Horsepower)

Sound Power Level• Value Measured in (dB)• Logarithmic Scale• Lw = 10 log (N / No)

What Can Sound Power Do For MeWhat Can Sound Power Do For Me

Sound power is an incredibly powerful tool that can be used to solve for the actual sound pressure values, octave values, and the NC Rating just based on the Room characteristics.

Characteristics include the materials used in construction of the room and the geometrical areas of the walls, ceiling, and floor

3.104

4log10

2

Rd

QLL wp

)1/(__

SR

i i

iii SS /_

Q is the directivity factor based on the measurement environment.

Full sphere Q = 1Half sphere Q = 2Quarter sphere Q =4 Eighth sphere Q = 8

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What Can Sound Power Do For MeWhat Can Sound Power Do For Me

Situation and sound source

sound power Pac watts

sound power level LwdB re 10−12 W

Rocket engine 1,000,000 W 180 dB

Turbojet engine 10,000 W 160 dB

Siren 1,000 W 150 dB

Heavy truck engine orloudspeaker rock concert

100 W 140 dB

Machine gun 10 W 130 dB

Jackhammer 1 W 120 dB

Excavator, trumpet 0.3 W 115 dB

Chain saw 0.1 W 110 dB

Helicopter 0.01 W 100 dB

Loud speech,vivid children

0.001 W 90 dB

Usual talking,Typewriter

10−5 W 70 dB

Refrigerator 10−7 W 50 dB

Method of Testing Sound PowerMethod of Testing Sound Power

Sound Power from Pressure Based Array• A hemispherical grid that fully surrounds the

entire unit is required.• Fast and Easy type of sound power test• Many pressure readings are taken at one time• Has error

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Reverberation Room• Reverberation room has to be qualified by test data to be applicable for

sound power• Test makes use of the Comparison Method, using a calibrated sound

source.• The difference between the sound pressure readings of the unit in question

and the calibrated source is the difference in sound power


Sound Power from Intensity• Requires use of an intensity Probe• Very complex and slow testing method• More engineering inside of the result• Best to reduce error

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Sound IntensitySound Intensity

Sound Intensity Testing• This test also requires a grid that surrounds

the entire unit and many data points.• The more data points taken, the better the

analysis of where the sound is coming from on the unit in test

• Intensity is the measurement of the flow of sound and can be used to create a graphical print of every frequency from the third octave. The data can be used to specifically target the problem spots on the unit with the best means of suppressing the frequency that is creating the largest problems

Sound IntensitySound Intensity

Sound Intensity Testing• Each component has a different frequency

profile and the sounds that are emitted from the unit can be different based on the directionality on the sound.

• Sound intensity has no influence from the surrounding environment and is considered the best means of sound power calculating.

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Sample of 500Hz Intensity MeasurementsSample of 500Hz Intensity Measurements

Sound CancellingSound Cancelling

Use: to block transmission noise. Physical Properties: Non-porous, high density and usually non-fibrous. Barriers are generally flexible or damped. The noise is blocked, reflected and re-routed in another direction. Barrier materials are tested and rated for their Sound Transmission Loss capability. The number is stated in dB and the higher number signifies the better barrier.Effectiveness is expressed as STC (Sound Transmission Class).STC: Single number rating derived from decibel loss data at several frequencies.

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Sound absorptionThe process by which the intensity of sound is diminished by the conversion of the energy of the sound wave into heat. The absorption of sound is an important case of sound attenuation. Regardless of the material through which sound passes, its intensity, measured by the average flow of energy in the wave per unit time per unit area perpendicular to the direction of propagation, decreases with distance from the source. This decrease is called attenuation.


The Tuned Resonant AbsorberIn many noise control applications, the objective is to remove or reduce sounds that occur only in a narrow range of frequencies. For such situations, it is possible to design a sound absorption system that is "tuned" to those targeted frequencies in which perforated metal plays a critically active role. This kind of system is called a Tuned Resonant Absorber. By employing such a system, the designer can reduce the thickness of the absorbing layer and save space and cost. This is illustrated in the chart above. It clearly shows that if the target frequency range centered on 2,000 Hz, an absorbing layer of just 1" would remove nearly all of that sound.

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Room CapabilitiesRoom Capabilities

Sound Room• Capable of testing sound pressure,

and sound intensity.• Room Size: (L x W x H) 31ft x 21 ft x 14 ft (9.52m x

6.60m x 4.54m)• Door Size: 8ft x 9ft (2.4m x 2.7m)• Non-conditioned airspace• 2 tons cooling water supply for test unit• Power Supply: 480Vac 3 Phase, 280Vac 3 Phase, 120

VacSingle Phase. (Others available upon request)

• Tachometer: 0 to 30,000 RPM• Room cutoff frequency: 100 Hz• Background noise: 20 dBA• 15dBA above background for full certainty • Data Acquisition: 8 Channels OctoBox+ with two pulse

input channels• Sampling rate: up to 48kHz• Two 1/2" Prepolarized Condenser Microphones with

frequency response: ±2dB from 3.15hz to 20kHz and ±1dB from 12.5Hz to 10kHz and upper limit of dynamic range:

• 146dB re. 20μPa. with 3% distortion

Testing CapabilitiesTesting Capabilities

Sound Pressure• Large Profile for diverse points of interest• Semi-Anachoic sound reduction for

sound localization

Sound Power• Large Profile larger grid sizes for

larger items• Can be calculated through

intensity measurement

Sound Intensity• Provides view of item sound distribution• Allows troubleshooting through analysis of

frequency bands

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QuestionsQuestions

Works CitedWorks Cited

Allain, Rhett. "What Is The Speed of Sound." Wired. Dot Physics, 17 Oct. 2012. Web. 10 Oct. 2013.

ANSI/AHRI Standard 260 (I-P), Sound Rating of Ducted Air Moving and Conditioning Equipment, 2012, Air-Conditioning, Heating, and Refrigeration Institute, 2111 Wilson Boulevard, Suite 500, Arlington, VA 22201, U.S.A.

ANSI/AHRI Standard 575 (Formerly ARI Standard 575), Method of Measuring Machinery Sound Within an Equipment Space, 2008, Air-Conditioning, Heating, and Refrigeration Institute, 2111 Wilson Boulevard, Suite 500, Arlington, VA 22201, U.S.A.

ANSI/ASA Standard S12.60-2009/Part 2, American National Standard Acoustical Performance Criteria, Design Requirements, and Guidelines for Schools, Part 2: Relocatable Classroom Factors, 2009, America National Standards Institute, 25 West 43rd Street, 4th Floor, New York, NY, 10036, U.S.A.

ANSI/ASA Standard S12.60-2010/Part 1 (Revision of ANSI/ASA S12.60-2002), American National Standard Acoustical Performance Criteria, Design Requirements, and Guidelines for Schools, Part 1: Permanent Schools, 2010, America National Standards Institute, 25 West 43rd Street, 4th Floor, New York, NY, 10036, U.S.A.

"Intensity and the Decibel Scale." Intensity and the Decibel Scale. Physics Classroom, n.d. Web. 10 Oct. 2013.

LMS, A Siemens Business. “DPS Acoustic Testing Presentation Milwaukee”. File last modified 15 April 2013. Microsoft Powerpoint file.

"PERF HANDBOOK - How Perforated Metals Are Used in Acoustics." Perforated Handbook Index. IPA Recources, n.d. Web. 15 Oct. 2013.

"Sound." Def. 1. The Free Dictionary. Farlex Inc, n.d. Web. 10 Oct. 2013.

"Sound Absorption." Def. 1. The Free Dictionary. Farlex Inc, n.d. Web. 15 Oct. 2013.

"The Human Ear." The Human Ear. Physics Classroom, n.d. Web. 11 Oct. 2013.

"The Speed of Sound." The Speed of Sound. The Physics Classroom, n.d. Web. 10 Oct. 2013.

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