ACRYLITE Soundstop Transparent Noise Barrier Panels Review

Overview

Drive under the Governor Mario M. Cuomo Bridge in Tarrytown or along I-5 through San Diego's North Coast Corridor and the noise walls are clear. That is ACRYLITE Soundstop, a specialty acrylic sheet that Röhm first put into a noise barrier in 1980 and that has been going up along American highways since a 1995 pilot in East Brunswick, New Jersey. FHWA's own review names ACRYLITE and Plaskolite as the only two makers approved for transparent barriers in the United States, with ACRYLITE's the most commonly used.

Almost nobody reading this will buy a noise wall. But Soundstop is the largest single use of thick acrylic as an architectural window in the country, and the questions it answers, how acrylic holds up for decades outdoors, how it breaks, how it sounds, how it gets cleaned, are the same questions that apply to any big commercial acrylic panel. We have not specified or installed it. The facts come from the Polyvantis technical data sheets, the NYSDOT specification, the Durisol MASH product guide, FHWA and FDOT policy documents, and a Texas DOT field evaluation of a Soundstop wall in Dallas, all listed at the end.

The three sheets

Soundstop XT is extruded, the economy grade: 15, 18, 20, and 25 mm thick, up to 8 by 19.5 feet, clear or in about seventeen transparent colors from Danish Green to Sapphire. It passes the 45 kg pendulum test of EN 1794-2 (Class 2 in the 2011 edition), which qualifies it for ground-mounted walls.

Soundstop GS CC is cast, and it has polyamide threads embedded in the sheet, black or clear, running across the width or the length. When a GS CC panel is struck hard enough to break, the threads hold the pieces together instead of letting them fall on the road below. It passes the 400 kg pendulum test (EN 1794-2:2011 Class 3), and Polyvantis states that it may be used on bridges without additional restraint structures. That is the sheet on the bridges named above, and it is what New York's standard spec calls for: clear panels with embedded black filaments for shatter resistance and bird deterrence.

Bird Guard is either sheet with stripes formed into the acrylic, black 2 mm stripes at 30 mm spacing or white 20 mm stripes at 100 mm. Polyvantis specifies the pattern must be integral to the panel and disallows applied films, which delaminate and haze.

The panels weigh 3.66 pounds per square foot at 15 mm and 6.10 at 25 mm, half of glass at the same thickness. They can be cold-curved to a radius of 330 times the thickness, about 22 feet for 20 mm sheet.

Sound

Soundstop is a reflective barrier. It stops noise by mass and stiffness, not by absorbing it. Per ASTM E90, the sound transmission class is 32 at 15 mm, 34 at 20 mm, and 36 at 25 mm, the same numbers for XT and GS CC. The European figures put 15 mm sheet at a weighted sound reduction index of 30 dB and 25 mm at 33 dB, in the highest airborne class, B3. New York's spec requires only STC 27.

For context, FHWA cites transmission-loss ranges of 34 to 40 dB for concrete and 18 to 27 for metal barriers, and notes that whatever the panel does, a barrier's real-world insertion loss is usually limited to 5 to 10 dBA by sound going over and around the ends. A 20 mm acrylic panel is, acoustically, in concrete's class. If a job needs absorption, the SilentView frame tilts the Soundstop sheet 30 degrees and bounces incoming noise up into a horizontal absorptive element; it can retrofit existing posts.

Thirty years of clarity

This is the reason acrylic won the transparent-barrier market. Polyvantis guarantees Soundstop for 30 years against yellowing and for light transmission: 90 percent minimum on delivery, 88 percent minimum after 30 years outdoors. The data behind that: 92 percent light transmission new and 92 percent after ten years of Arizona exposure, haze from 1 percent to under 5 percent, yellowness index from under 1 to under 3. FHWA's review puts it plainly: acrylic barriers are the most common because some other plastics turn yellow.

The comparison is polycarbonate. Polyvantis also sells LEXAN polycarbonate barrier sheet, which reaches the same acoustic numbers at roughly half the thickness with far higher impact strength, and warrants it for ten years against breakage and loss of light transmission. Thirty years against ten is the whole argument; our acrylic vs polycarbonate guide covers the chemistry behind it.

Impact on the acrylic side is respectable, not heroic: 11 times glass, the EN 1794-1 stone-impact test, and a pass on the ASTM E1996 large-missile hurricane test above 15 mm. Fire class is CC2, with a burning rate of 0.70 to 0.78 inches per minute and a brushfire rating of Class 2; the sheet is combustible and lives below 160°F (XT) or 180°F (GS CC).

The crash test and the paperwork

Noise walls on the edge of a roadway are a roadside hardware item, and Soundstop has the certificates. The current Durisol system was crash-tested to AASHTO MASH Test Level 4 (tests 4-10, 4-11, and 4-12) at 17 feet tall with 10-foot post spacing, and FHWA issued eligibility letter B-352 for Federal-aid reimbursement in December 2020. The earlier generation passed NCHRP 350 in 2005 at the University of Nebraska's Midwest Roadside Safety Facility and went into over a hundred installations. NYSDOT carries a dedicated pay item, 643.92000007, measured per square foot on one face, naming Ekho Infrastructure Solutions of Honey Brook, Pennsylvania as the supplier. Design rules in the specs: under design wind load, deflection under 3 inches and stress under 3,000 psi; at a 1.5 load factor, no buckling, cracking, or detachment; restraint systems to a safety factor of 4.

Installations run from the Van Wyck Expressway and the Verrazzano Bridge in New York to the Scudder Falls Bridge, I-75 in Dayton and Toledo, I-71 in Columbus, I-40 in Knoxville, US-169 in Edina, Highway 407 in Toronto, and about 30,000 square feet on the I-64 Hampton Roads Express Lanes.

What the field says

The best independent evidence is a Texas DOT study of a 10-foot, 15 mm Soundstop wall added on top of an 8-foot concrete wall on the I-30 bridge in Dallas in October 2013, with before-and-after noise monitoring and nine months of inspection.

Three findings matter for anyone specifying it. First, the acrylic itself was fine. Second, the gaskets were not: about 80 percent of the horizontal rubber gaskets were broken, sagging, or out of place within a year, many wrongly placed at installation, and weeds grew through the gaps; the authors note the openings significantly reduce the wall's transmission loss. Buy the gasket detail and the installer's attention as carefully as the sheet. Third, graffiti: ten panels were tagged within weeks. Cleaning cost $4,167, of which the graffiti remover was $73.50 and a steam cleaner $200; the remaining $3,893 was traffic control. The acrylic came clean; the concrete below did not. Polyvantis names two commercial graffiti removers as safe and says rain normally does the rest.

The Texas neighbors liked the wall, both for the sound and for still seeing the sky, and Ohio DOT, which had eleven transparent barriers and more than any other state, told the researchers it was very satisfied structurally and acoustically, with no major maintenance problems and panels that are for the most part self-cleaning. The drawback it named was cost. FHWA design guidance adds the general cautions for any plastic barrier: it can haze, damaged panels are replaced rather than repaired, and clear sheet invites knives and lighters as well as paint.

Birds are the other real cost of transparency. A Tuscan highway study logged 114 fatal strikes across 26 species on clear barriers, and a Korean national estimate covered 1,400 km of them. Polyvantis' spec language claims the Bird Guard pattern prevents more than 90 percent of impacts but publishes no test and defers to the American Bird Conservancy. Treat the stripes as mandatory near trees or water and the 90 percent as a claim.

Price

There is no list price. Polyvantis, Emco Plastics, Port Plastics, and Professional Plastics all quote it cut to size, and the MASH system comes through Durisol or Ekho. The only public anchors are agency figures: FHWA's national inventory priced barriers in the "other materials" category, where transparent panels land, at about $34 per square foot in 2010 dollars against $21 to $32 for concrete, block, wood, and metal; Ohio DOT told Texas researchers a transparent wall runs roughly twice an equivalent concrete one; FHWA's design guidance says the cost can be as much as 20 times that of concrete or steel panels. Those last two figures contradict each other, and we could not find a bid tabulation to settle it; Florida caps any noise barrier it will fund at $40 per square foot. For a sense of what thick acrylic costs at retail, see our acrylic window cost guide.

Who should specify it

Transportation agencies, bridge designers, and rail authorities where a wall must not block a view or shade the homes behind it, and architects who want a proven 30-year outdoor acrylic for a wind screen or balustrade. Choose GS CC on any structure, Bird Guard near habitat, and a gasket system with a track record. If nobody needs to see through the wall, concrete does the same acoustic job for half the money, and Plaskolite's OPTIX NB is the one domestic alternative in clear acrylic; our acrylic vs glass guide explains why laminated glass rarely competes at this size.

Material	Acrylic (PMMA); XT extruded or GS cast; GS CC cast with embedded polyamide filaments
Thickness	XT: 15, 18, 20, 25 mm; GS CC: 12, 15, 20, 25 mm
Sheet size	XT up to 8 ft × 19.5 ft; GS CC 2000 × 3000 to 2000 × 5000 mm and 2380 × 3300 mm
Weight	3.66 lb/sq ft at 15 mm; 4.86 at 20 mm; 6.10 at 25 mm
Sound transmission class	STC 32 (15 mm), 34 (20 mm), 36 (25 mm) per ASTM E90
Light transmission	90% minimum on delivery, 88% minimum guaranteed after 30 years
Weathering	92% transmission and haze under 5% after ten years in Arizona (ASTM D1003)
Impact	11× glass; passes EN 1794-1 stone impact and ASTM E1996 large missile above 15 mm
Fracture safety	XT: EN 1794-2 Class 2 (45 kg pendulum); GS CC: EN 1794-2:2011 Class 3 (400 kg pendulum)
Fire	CC2; brushfire EN 1794-2 Annex A Class 2; self-ignition 860–878°F
Crash test	MASH TL-4 (tests 4-10, 4-11, 4-12) at 17 ft height, 10 ft post spacing
Colors	Clear plus 17 transparent tints, frosted, grey, and white; Bird Guard stripes black 2 mm at 30 mm or white 20 mm at 100 mm
Warranty	30 years no yellowing and light transmission
Maker	POLYVANTIS Sanford LLC, Sanford, Maine (ACRYLITE); sold as PLEXIGLAS Soundstop outside the Americas

ACRYLITE Soundstop Transparent Noise Barrier Panels

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Specifications

Our Verdict