The Decibel Scale Hearing Threshold Discomfort Conversation Pain Threshold How Do We Quantify Noise?
The Decibel Scale Conversation Train Chain Saw Increasing the Decibel Level by 10 Doubles the Sound Intensity
75 Decibels The individual is exposed to a combined total 78 Decibels
The Decibel Scale A reduction of 3 dB(A) is like doubling the distance from the noise. 67 dB(A) 50 ft
The Decibel Scale A reduction of 3 dB(A) is like doubling the distance from the noise. 67 dB(A) 100 ft - 3 dB(A) = 64 dB(A)
A 3dB(A) reduction corresponds to: doubling the distance reducing traffic volume by 50% reducing traffic speed by 25%
FHWA - Noise Abatement Criteria 67 dB(A) “this is not an absolute value or design standard, only a level where noise mitigation must be considered” For new construction or reconstruction (ISO 11819-1)
Side-Line Measurements Statistical By- pass Method (ISO 11819-1)
Walls –top 10 States in 1998 spent over $1.3M per mile –do nothing to eliminate the noise at the source Earth Berms –require a lot of land if very high Vegetation –takes a long time to develop –200’ thick would only achieve a 10 dB reduction Noise Barrier Effectiveness Must Justify Expense
“Pavement / tire noise has been studied for well over 30 years and several large databases have been compiled in the last decade. NCHRP Synthesis 268 is a summary of the research findings of this extensively studied topic.”
Conclusions: “In general, when dense-graded asphalt and PCC pavements are compared, the dense-graded is quieter by 2 to 3 dB(A)” A 3dB(A) reduction corresponds to: - doubling the distance - reducing traffic volume by 50% - reducing traffic speed by 25%
Conclusions: “Open-graded asphalt shows the greatest potential for noise reduction for passby noise. Reduction when compared to dense- graded asphalt ranged from 1 to 9 dB(A).” A 9dB(A) reduction corresponds to: - a reduction in traffic noise by almost 50%!
I-64 Noise Study in Louisville By Local Engineering FirmBy Local Engineering Firm Readings taken before and after B/S OverlayReadings taken before and after B/S Overlay A 4-6 decibel reduction between old PCC and new asphaltA 4-6 decibel reduction between old PCC and new asphalt
I-74 in Ohio Driving on Dense HMA onto OGFC then back onto Dense HMA
Texas Highway Driving on Dense Graded Mix then onto OGFC
Is It Cost Effective? A decrease of 2 dB means a reduction of five feet in wall height or for a mile of pavement a reduction of $528,000 (Average of $20/sf)
OGFC is the quietest surface type. (Wayson, NCHRP Synthesis 268) SMA has also proven to be a quiet surface. (Wisconsin DOT, 1993) Dense graded HMA surfaces are quieter than PCC pavements. (Hibbs and Larson, Report FHWA-SA-96- 068, May 1996) Summary: Effect of Pavement Surface
Arizona DOT Uses ARFC to Provide Quiet Pavements ADOT is Spending $34M to Overlay PCCP in the Phoenix MetropolitanADOT is Spending $34M to Overlay PCCP in the Phoenix Metropolitan The ARFC is Minus 9.5mm & 9-9.5% BinderThe ARFC is Minus 9.5mm & 9-9.5% Binder 12.5 mm Thick When Used on Flexible Pavement12.5 mm Thick When Used on Flexible Pavement 25 mm Thick When Used on PCCP25 mm Thick When Used on PCCP ADOT Uses Pavement Type (ARFC) as a Noise Mitigation Strategy (4 dBA)ADOT Uses Pavement Type (ARFC) as a Noise Mitigation Strategy (4 dBA)
–Highway noise very important to public –Small changes in dB(A) level very noticeable reduction of 3dB(A) like doubling distance or halving trafficreduction of 3dB(A) like doubling distance or halving traffic –Sound barriers expensive and not very effective –Controlling Noise at the Source is Best Option Dense HMA 2-4dB(A) quieter than PCCDense HMA 2-4dB(A) quieter than PCC OGFCs 1-9dB(A) quieter than Dense HMAOGFCs 1-9dB(A) quieter than Dense HMA Summary
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