Noise Barrier Material Evaluation & Selection Mia Waters Washington State Department of Transportation TRB ADC40, Transportation Related Noise & Vibration Williamsburg, VA July 11, 2006

Moving past the State of traditional concrete…  Why?  Cost of keeping traditions  A new world of materials in development  Ability to have choices / provisional options  What?  plastic – metal – composite – wood - transparent – translucent – absorptive – canted – recycled – easily replaced – lower cost – light weight - and more…  Where?  Vertical and horizontal  How?  Use the process & criteria that fit your organization…

Rating Criteria?  Transmission Loss (TL)  Sound Transmission Class (STC)  Other?  Cost  Foundation needs  Ease of installation  Ease of replacement  Graffiti resistance / clean-ability  Absorption  Aging – longevity - durability  Aesthetic characteristics  Weight  Crash test worthiness  Approved by others? Who?

 As you mentioned, the weakness in the STC is that it does not anticipate fully the low frequency content of the traffic noise. Thus, a barrier with an STC 20 rating could produce less than a 20 dBA direct reduction of typical traffic sound passing through it.  Ideally, what you want to do is to create a standardized traffic spectrum, compute the overall A-weighted level of that spectrum, the subtract the TL's of the barrier from that spectrum at each frequency, compute the overall A-weighted level of the resulting spectrum, and then take the difference between the two overall A- weighted levels. (Ref. N Stewart)

Selection criteria options  Europe  Japan  Canada  Various US states  A recommended US national criteria?

European selection criteria  EN1793 (5)   1. “Road traffic noise reducing devices — Test method for determining the acoustic performance — Part 1: Intrinsic characteristics of   sound absorption”, EN (1997).   2. “Road traffic noise reducing devices — Test method for determining the acoustic performance — Part 1: Intrinsic characteristics of   airborne sound insulation”, EN (1997).   3. “Road traffic noise reducing devices — Test method for determining the acoustic performance — Part 1: Normalized traffic noise   spectrum”, EN (1997).   4. “Road traffic noise reducing devices — Test method for determining the acoustic performance — Part 5: Intrinsic characteristics - In   situ values of sound reflection and airborne sound insulation”, ENV (2002).   5. “Road traffic noise reducing devices — Test method for determining the acoustic performance — Part 4: Intrinsic characteristics - In   situ values of sound diffraction”, prENV (2002).  EN1794 (2)   1. “Road traffic noise reducing devices — Non-acoustic performance — Part 1: Mechanical performances and stability requirements”,   EN (1998).   2. “Road traffic noise reducing devices — Non-acoustic performance — Part 2: General safety and environmental requirements”,   EN (1998).  EN14388 (1)   “Road traffic noise reducing devices — Specifications”, prEN (2002).  EN14389 (2)   1. “Road traffic noise reducing devices — Long term performance or road traffic noise reducing devices — Part 1: Acoustical   parameters”, prEN (2002).   2. “Road traffic noise reducing devices — Long term performance or road traffic noise reducing devices — Part 1: Non-acoustical   parameters”, prEN (not published).  EN14990 draft  Precast concrete barriers  Where to find discussions of the standards:     Courtesy of Ulf Sandberg & Jean-Pierre Clairbois

Japan  ISO (1997)  Recent interest, noise reducing devices on top of barriers, interested in a modified version of EN  Reference Kohei Yamamoto

Canada  Canadian Standards Association (CSA) Z107.9 Focus on material and design… Takes the noise barrier height into consideration when determining required TL Note that the Canadian maximum wall height is 5 M (about 16 feet).

United States  Nevada (Sound Wall Eval. Manual, STC of 25 dB)  Virginia (has approved list, how were products chosen?)  Florida (temp. design bulletin C03-04 – identifies specific criteria related and unrelated to noise when evaluating materials. FDOT requires an STC of 20 dB)  Wisconsin (TL 20 dB, all frequencies)

What did WSDOT want?  Simplicity  Ease of finding the data in the application/literature  Protection of residents (reduce complaints of less protection when using alternative materials)

Challenges  FHWA guidance recommends transmissions loss in dBA (but some note that TL doesn’t exist in dBA)  Independent laboratory testing is in dB  Sound Transmission Class of 25 dB representative enough? It only uses a few frequencies to calculate it…

Debate…choices  US and other countries decide on an ISO standard?  US National list of approved materials?  Low tech - if a product can meet the structural requirements of the AASHTO Guide for the Structural Design of Sound Barriers AND is light tight (the flashlight test) then it will have enough mass to meet low frequency TL requirements and with no gaps in the wall, will meet high frequency TL requirements (ref. Figallo)  ANSI 12.8 (1987) Methods for Determination of Insertion Loss of Outdoor Noise Barriers  ISO In-situ determination of insertion loss of outdoor noise barriers of all types  CSA Z107.9 – in discussion for adoption by ANSI  DIN (EN) 1793 – test method for determining acoustical performance  ASTM E1332. The difference is that the spectrum specified in E 1332 is a generalized transportation noise spectrum averaging in some aircraft and rail noise rather than just traffic noise. This rating was developed for exterior walls of buildings subjected to transportation noise. E 1332 requires TL data down to 80 Hz for the rating. Labs do not always report results below 100 or 125 Hz.

Thanks for input from…  Larry Finegold  Ulf Sandberg  Jean-Pierre Clairbois  Shawn Gilbertson  Jim Laughlin  Soren Pedersen  Tim Kelsall  Chris Menge  Mariano Berrios  Areg Gharabegian  Roger Wayson  Amy Costello  Noral Stewart  Gary Figallo  Bill Bowlby  Ken Polcak  Rich Peppin  Bob Mero  Win Lindeman  Jay Waldschmidt  Patrick Harrison  Dave Goodwin  David Freudenrich  Jim Chambers  Gary Ehrlich  Micah Downing

What did WSDOT finally choose…for now?  Unconditional approval from acoustics group of Transmission Loss (TL) of 20 dB for all measured frequencies  Conditional approval – limited use for TL for product with any measured frequency at less than 20 dB, e.g.,  Temporary barriers  Low truck volume roadways Flexibility for other parameter depending on project needs, safety, cost, and aesthetic choice.

 To understand the breadth and interest of replies, all messages and advice received by WSDOT on this topic will be put onto the WSDOT website by July 20 th at:  vironmental/aae/default.htm