Acoustic & Vibration Fundamentals

ACOUSTICS AND UMM… VIBRATION FUNDAMENTALS

JEFF BOLDT | 2019-09-09 Introduction

PRESENTATION INCLUDES • Physics of Sound • Understanding Decibels • Psychoacoustics • Acoustic Scales • Sound Power and Pressure PRESENTER Jeff Boldt, PE, FASHRAE, LEED® AP, HBDP, FPE

Managing Principal – Director of Innovation & Quality at IMEG Corp. (>1,200 staff) Chair ASHRAE SSPC-90.1 MSC Former Chair ASHRAE 189.1 Acoustics Discussion Group Author AEDG Small Healthcare Facilities & AEDG Large Hospitals Member WHEA Code Committee Member SSPC 3.6, TC2.6, 5.2, 8.6 Search for “Jeff Boldt Engineering Nerd” Acoustical Background

Two years graduate study through Heriot-Watt University in Acoustics, Vibration, and Noise Control Emphasis in building systems and noise control HVAC noise, generator enclosures, property line noise, Architectural Acoustics Has read many acoustical texts PHYSICS OF SOUND Physics of Sound Compression - Rarefraction Speed & Wave Equation

Speed in air ~ 1100 fps ~ 750 mph Speed depends on • Material - mostly density (e.g. faster in metals) • Temperature V=f*L Velocity = frequency*wave length Frequency

Audible Range ~ 16 Hz – 20 kHz (20,000 Hz) Audible Length ~ 68 ft – 5/8” 1,000 Hz ~ 1.1 feet Speech ~ 500 – 5,000 Hz • 2 to 0.2 feet Middle C = 262 Hz Grand Piano 28 – 4,186 Hz How People Describe Sounds Voice Frequencies

Please put this into Excel and reprint the charts. Please only show the “normal” curves and include both in one graph. Volume Range

HUMAN EAR HEARS OVER A VOLUME RANGE OF: • 140 dB (120 starts pain region) • 10^14 to 1 • 100 trillion to 1 • Accuracy of ~ +/- 5 dB • Comparable to a scale that weighs small ants (1 milligram) and the largest (110,000 ton) aircraft carriers, with reasonable USS Gerald Ford on the James River accuracy Reflection

Specular = follows mirror rule Diffuse = random reflections Reflection is specular if surface irregularities are much smaller than the wave length Dissipative Absorption

Friction converts noise to heat Typically fibrous materials Should be ~1/4 wavelength deep or held away from rigid surfaces May need covering for: • Cleanliness • Durability • Vapor barrier Reactive Absorption

Tuned frequencies Very narrow band if not dampened Best for narrow frequencies Vehicle mufflers Perforated panels – small holes Can’t equal absorptive performance Gypsum board - Transformers Reactive Absorption

Mufflers Dissipative (“packed” muffler)

Reactive muffler Active Absorption

Active • Measure and counter noise • Needs to be a controlled situation • Digisonix was the last manufacturer I know of • Works best at low frequencies • Absorptive silencers were cheaper, except maybe at very low frequencies DECIBELS Decibels

Used to handle large ranges Decibel is a ratio, not a quantity Alexander Graham Bell invented the Bel Notation is dB, dBA, etc. Sound Power & Pressure

Lw = SwL = Sound Power = energy • Lw = 10*log(watts/10^-12W) dB • Lw = 10*log(watts) + 120 dB • Like Lumens Lp = SpL = Sound Pressure • Lp = 10*log(p^2/Pref^2) dB • Lp = 20*log(p/Pref) dB • Like Footcandles At 1 kHz 0 dB is audible (youngsters) At 1 kHz 120 dB is painful More Decibels

Original energy = Original dB 1 Double energy = +3 dB 2 4X energy = +6 dB 4 10X energy = +10 dB 10 100X energy = +20 dB 100 Etc. Adding each 10 dB adds a zero • 120 dB is 1 followed by 12 zeros • Them zeros ain’t nothing • Jethro Bodine understood… Adding Decibels

Divide each number by 10 Take the anti-log (10^X) of each number Add the numbers Take the 10-log of the sum Multiply by 10 Spreadsheet has this feature Create in Excel so we own © to this

Decibel Addition Graph Sound Pressure

Sound Pressure Level Sound Source (Decibels, A-weighted) Saturn Rocket 194 Ram Jet 160 Propeller Aircraft 140 Threshold of Pain 135 Riveter 120 Heavy Truck 100 Noisy Office 80 Heavy Traffic 80 Conversational Speech 60 Private Office 50 Quite Resident 40 Recording Studio 30 Leaves Rustling 20 Hearing threshold good ears at frequency of maximum sensitivity 10 Hearing threshold excellent ears at frequency of maximum response 0 PSYCHOACOUSTICS Psychoacoustics

Octave = double frequency Preferred center frequencies • 31.5 Hz • 63 Hz • 125 Hz • 250 Hz • 500 Hz • 1K, 2K, 4K, 8K • 16K Psychoacoustics

Hyperacusis = poor ability to accommodate large volume ranges • Most common in elderly and young Sense of direction is mostly from phase effects, but also from shadowing • Concert hall design • Vertical symmetry – Dolby Psychoacoustics

Hearing loss is either: • Conductivity – mechanical failure • All solvable • Can you make a graphic of a ME ruling the Universe? • Sensory-Neuro – electrical failure • Sensory-Neuro is more common • Sensory-Neuro is irreparable • Can you make a graphic of a despondent EE? Psychoacoustics

Hearing loss is either: • Conductivity – mechanical failure • All can be repaired • Sensory-Neuro – electrical failure • Sensory-Neuro is more common • Sensory-Neuro is irreparable Psychoacoustics

60 yrs 4,000 Hz -15 dB Hearing Loss – Men

60 yrs 4,000 Hz -32 dB Honey I can barely hear you Voice Frequencies

Recreate graph Information

Most information is in consonants Consonants are high frequency Vowels add volume and tone Honey I can hear you – but all I get is WA-WA- ACOUSTIC SCALES Acoustic Scales

Everybody’s got one • Beranek has the most… Phons

Phons = equal loudness contours Single number is 1K perceived loudness Decibel scale Phons and Sones

Sensitivity much flatter for loud noise Most people consider +10 dB double volume 1 Sone = 40 Phons 2 Sones = 50 Phons Etc. Wikipedia = best Sone definition Pink and White Noise

Pink noise has equal power per octave White noise has equal power per Hertz

80 70 60 Pink Noise 50 White Noise 40 dB 30 20 10 0 63 125 250 500 1000 2000 4000 8000 Hz Weighing Scales

dB(A) is the most common one-number acoustic value • dBA resembles 40 Phon contour • OSHA uses dBA dB(B) is for louder sounds • Resembles the 80 Phon contour • Never used dB(C) is for even louder sounds • dBC is nearly unweighted • C and “flat” are often the same on meters dBA, B, and C Weighting

Flat weights all frequencies equally

dBC slightly filters high and low frequencies to simulate the sensitivity of the (young) human ear at high vlolumes. dB(B) is between A&C, but is seldom used. It simulates the human ear at moderate volumes.

dBA filters high and especially low frequencies to simulate the sensitivity of the (young) human ear at low volumes. dBA Sensitivity Curve

20 dBA Curve

-5 63 125 250 500 1000 2000 4000 8000 RTA App NC (Noise Criteria)

Another one-number index Proposed by Beranek Based on the worst octave Emphasizes annoying high frequencies Used by AMCA for noise ratings of grilles, registers, and diffusers Used by AHRI to rate VAV boxes NC Curves

Worst case determines rating PNC & NCB Criteria

PNC = Preferred NC • Improvement over NC • Very seldom used NCB • Lowered 4K & 8K limits • Added 32 and 63 Hz criteria • Proposed by Beranek in 1989 NCB Curves RC (Room Criteria)

Developed by ASHRAE Not as common as dBA or NC Gives information about character of sound • RC-35R = Rumble • RC-35H = Hiss RC Curves RC Mark II

Latest ASHRAE noise index Improves on RC, but is more complex Very strict criteria for “Normal” frequency distribution E.g. RC-35 (N) Spreadsheet Capabilities

Calculates the following: • Unweighted dB • dBA • NC • RC Mark II • Outdoor property line noise – very fast Spreadsheet Example 1

SOUND CALCULATIONS Octave Center Frequency (Hertz) 6 2 1 2 5 2 5 0 5 0 0 1 K 2 K 4 K 8 K

Sound Pressure at Chosen Location (Lp) 69.0 46.0 46.0 4 4.0 40.0 37.0 30.0 20.0 Total dB at Selected Location 69.1 dB dBA Calculations A-W eighting Conversion -2 6 .2 -1 6 .1 - 8 .6 - 3 .2 0 . 0 1 .2 1 . 0 - 1 . 1 A-W eighted Sound Pressure (LpA) 4 2 .8 2 9 .9 3 7 .4 4 0 .8 4 0 .0 3 8 .2 3 1 .0 1 8 .9

dBA at Chosen Location (Perceived Volum e) 47.4 dBA

RC M ark II Calculations Conversion to RC Contour -20 -15 -10 -5 0 5 10 15 O ctave Band RC Ratings 49 31 36 39 40 42 40 15 D eviation from R C R ating 9 -9 -4 -1 0 2 0 -25 Spectral Deviation factor ranges LF MF HF Spectral D eviations 8 .7 -3.9 0.4 Q AI (Q uality Assessm ent Index) 1 2 .6 Q AI > 10 is likely to cause com plaints at m arginal noise Descriptions of RC abbreviations: 49.0 (N) denotes Neutral character sound, which is pr eferred. Q AI <5 is considered neutral. (LF) denotes that the sound is dom inated by Low Frequency Rum ble. (M F) denotes that the sound is dom inated by M id- Frequency Roar. (HF) denotes that the sound is dom inated by High -Frequency Hiss. LFB denotes likely m oderate but perceptible soun d-induced ceiling/wall vibration. LFA denotes likely noticeable sound-induced ceiling/w all vibration.

RC M ark II Rating (per ASHRAE 2003 Applications - 47.28) RC 40 LF LFB

Noise Criteria (NC) Calculations Peak NC curve each octave band is below 50 30 40 40 40 40 35 25

NC is not an appropriate rating scale for values ov er N C 50. N oise C riteria R ating = NC 50 OUTDOOR NOISE Temperature Refraction

Make better graphic Directivity Directivity

Directivity = Q • Q - Multiplier Application • 1 +0 dB Spherical • 2 +3 dB Ground (normal) • 4 +6 dB One wall • 8 +9 dB Two walls • 12 +12 dB roof also = megaphone

Outdoor Shadowing Outdoor Barrier Effect

Barriers • Noise reduction depends on extra distance divided by wavelength • NR = 10*log(3+20* DL*freq/1100) Title 35 Emergency Generator Other Outdoor Effects

Humidity – low RH attenuates (slightly) Foliage – negligible Ground absorption Wind and temperature Humidity vs. Absorption

Make new graphic Acoustic Home Office

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ACOUSTICS IN BUILDINGS

JEFF BOLDT | 2019-09-08 Introduction

PRESENTATION INCLUDES • Physics of Sound • Understanding Decibels • Psychoacoustics • Acoustic Scales • Sound Power and Pressure PRESENTER Jeff Boldt, PE, FASHRAE, LEED® AP, HBDP, FPE

Managing Principal – Director of Innovation & Quality at IMEG Corp. (>1,200 staff) Chair ASHRAE SSPC-90.1 MSC Former Chair ASHRAE 189.1 Acoustics Discussion Group Author AEDG Small Healthcare & AEDG Large Hospitals Member WHEA Code Committee Member SSPC 3.6, TC2.6, 5.2, 8.6 Search for “Jeff Boldt Engineering Nerd” Acoustical Background

Two years graduate study through Heriot-Watt University in Acoustics, Vibration, and Noise Control Emphasis in building systems and noise control HVAC noise, generator enclosures, property line noise, Architectural Acoustics ROOM ACOUSTICS Sound Buildup and Decay Reverberation Time (RT60)

Measures rate of noise decay Used for auditoriums, classrooms Initial decay rate measured in seconds for a 60 dB reductions Actual tests measure only the initial decay rate Longer = reverberant = organ music Shorter = high speech intelligibility RT60 Churches

Desirable RT60

Create new graphic RT60 Churches

Create new graphic Acoustic Home Office

Questions Indoor Lw to Lp – Classical Room Effect Methods Laws

OSHA for employees • 80 dBA = have a plan • 85 dBA for 8 hours limit • 90 dBA for 4 hours, etc. Illinois Title 35 • By octaves, not dBA, Need special meter • Measured at property line • Varies with land use combinations • Very restrictive ~ 35 dBA equivalent for Class A land at night State or local noise ordinances • Madison = 65 dBA to residential Standards

Office goals • Usually NC-35 or RC-35 No hearing loss below 75 dBA Almost none below 80 dBA High speech intelligibility ANSI 12.60 for Classrooms (New) • Very strict • Discuss costs with client FGI-2010 and 2014 Guidelines for Healthcare ANSI/ASA S12.60-2002

Acoustical Performance Criteria, Design Requirements and Guidelines for Schools • Minimum STC-50 for walls between classrooms • Maximum 35dBA (~NC or RC27). All non-people sources • Maximum reverberation time (RT60) for classrooms under 10,000 cubic feet (~1,100 SF) of 0.6 seconds • Maximum reverberation time (RT60) for classrooms between 10,000 and 20,000 cubic feet (~1,100 to 2,000 SF) of 0.6 seconds Noise Control Methods

Source Noise • Quiet equipment • Reduce HP • Muffle or box equipment Path • Barrier, box, distance Receiver • Box, hearing protection Noise Control Methods

Absorb sound at source or Need a graphic receiver Higher STC barrier Break vibration path • Resilient gypsum board clips or adhesive • Floating floors • Separated studs Shift to less audible frequency Adjust background noise Barrier Theory

Noise reduction through barriers is complex Heavier is better, but resonance and coincidence limit results Separating layers resiliently increases resistance to sound Mass Law Example Isotropic vs. Orthotropic Walls, Ceilings, Floors

STC – Sound Transmission Class • 125 – 4,000 Hz attenuation • Compare noise reduction to standard curves • Allows 32 dB total deficiency • Allows 8 dB max in any octave Single vs. Multiple Layers Insulation Thickness Flanking Paths and Gaps

Back to back receptacles Door undercuts An STC-20 door in a STC60 wall will result in a total STC of around 25 - a common mechanical room problem A STC-60 wall with 1% gaps is really STC-20 Leakage Area vs. STC Door Seals Sample Wall STC Values

34 – 2x1/2” gyp, 2.5” metal studs 42 – Same with R-8 fiberglass 39 - 2x5/8” gyp, 3.5” metal studs 47 – same with fiberglass fill 50 – 3x0.5” gyp, 2.5” stud, fiberglass 50 – 8” solid concrete 50 – 12” lightweight painted block 54 - 4x.5” gyp, 2.5” stud, fiberglass STC and Insulation Density Concrete Block Options Impact Insulation Class (IIC)

Measures resistance of floors to high heels, door slamming, dropping weights, etc. Need to reduce impact and resist sound transmission Soft surface + heavy floor is best Ceiling Ratings

Absorption • NRC = absorption in speech range • AC = Articulation Class. Stop overhearing conversations. • ~120 for gypsum board ceilings • ~150 with NRC=0.55 • >170 preferred • Max possible ~225 Transmission Resistance • STC – raw transmission resistance • CSTC – noise to adjacent room through plenum. Compare to wall • CAC – 1995 replacement for CSTC Glass STC

Thicker is better (Mass Law) More panes increase STC Large gaps increase STC SF6 fill gas increases STC, but adds 200 Hz resonance – so better for speech than equipment Other fill gasses do not help STC Laminating increases STC Glass Spacing Effect Acoustic Glass IIC and Carpet Transformer Noise Fan Noise – Generic

SOUND CALCULATIONS Octave Center Frequency (Hertz) 62 125 250 500 1K 2K 4K 8K Estimated Discharge Sound Power Levels 45 45 43 39 34 28 24 19 for BIAF Fan at 1 cfm and 1" Static Pressure (dB) Conversion to 1,000 cfm: 10*log(cfm) 30.0 30.0 30.0 30.0 30.0 30.0 30.0 30.0 Conversion to 5” Static Pressure: 20*log(SP) 14.0 14.0 14.0 14.0 14.0 14.0 14.0 14.0 Blade Frequency Interval Correction 3 0 0 0 0 0 Correction Factor for Off-Peak Operation (0- 15dB). Fan Noise – Generic Figure Fan Surge Air Outlet Velocities Diffuser Connections Duct Breakout Noise Duct Breakout Below RTU Part 2

Room Modes Early and late reflections Speech Intelligibility Rooms are sound system components Spreadsheet Capabilities mech library – design tools - Acoustic tables.xlsx Fan noise through duct system Breakout at any location Noise in room with noise source RT60 for room Noise in adjacent room Plenum attenuation dB addition Outdoor noise (condensing units) STC & NRC data is growing Sample Outdoor Calc – Mech library - design tools

Octave Center Frequency (Hz) OUTDOOR SOUND CALCULATIONS 62 125 250 500 1000 2000 4000 8 000

Distance to Selected Location (feet) 140 140 140 140 140 140 140 140 Sound Power of Equipment (dB). Based on RTAC 225STD. 88 97 99 97 92 90 81 79 Conversion to Sound Pressure at Selected Location based on spherical divergance (- 20logR+0.6) -43.5 -43.5 -43.5 -43.5 -43.5 -43.5 -43.5 -43.5 Amplification due to Q=0(spherical), 3dB(hemispherical), 6dB(2 planes), 9dB(quadrant) 6 6 6 6 6 6 6 6 Attenuation of Air at 68F&0%RH 0 0.0 0.0 -0.1 -0.2 -0.4 -1.0 -1.0 Attenuation due to Foliage, ground, wind, and temperature (long distances only) Barrier delta-L (feet) 0.21 0.21 0.21 0.21 0.21 0.21 0.21 0.21 Attenuation due to Barriers N=2dL/wave length; A=10log(3+10N)-Aground; or zero if no delta-L -5.1 -5.4 -5.9 -6.9 -8.3 -10.2 -12.5 -15.2 Sound Pressure at Selected Location 45.4 54.1 55.5 52.5 46.0 41.9 30.0 25.3 Illinois Ordinance for Class B to Class B Property During Daytime Hours 78.0 72.0 64.0 58.0 52.0 46.0 41.0 39.0 Excess Predicted Noise per IL Code -32.6 -17.9 -8.5 -5.5 -6.0 -4.1 -11.0 -13.7 Total Sound Pressure (dB) 59.4

A-Weighting Conversion -26.2 -16.1 -8.6 -3.2 0 1.2 1 1 Sound Pressure Selected Location (A- W eighted) 19.2 38.0 46.9 49.3 46.0 43.1 31.0 26.3 dBA at Selected Location (Perceived Volume) 53.0dBA Acoustic Home Office

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