12 Specs to Lock Before You Sign
Lock these twelve specifications into the tender and you remove the ambiguity that lets a non-compliant acoustic barrier reach the site — acoustic ratings, coating, posts, foundations and acceptance, all tied to JT/T 646-2025.
Before signing, the tender must pin down both acoustic figures — Rw ≥ 26 dB and NRC ≥ 0.60 to JT/T 646-2025 — plus panel construction, coating/galvanizing, H-section post spacing 2.0–4.0 m, wind- and soil-sized foundations, and clear acceptance clauses with test reports. Ambiguity on any one of these twelve is where sub-standard noise barrier deliveries hide.
Write them in; don't leave them to interpretation.
A highway sound barrier tender fails most often not on price but on missing detail. When the acoustic figure, coating or foundation load is left open, the lowest bidder fills the gap with the cheapest compliant-on-paper option. The fix is to enumerate the specifications so every bidder prices the same thing and any shortfall is provable at acceptance.
The twelve items below cover acoustics, construction, protection, structure and verification. Use them as a tender schedule; each maps to a number or a named standard you can enforce. For the underlying panel data, see the noise barrier specifications page.
Each row is a clause worth pasting into the tender.
| # | Specification | What to write |
|---|---|---|
| 1 | Transmission rating | Rw ≥ 26 dB (non-transparent) per JT/T 646-2025; name report + lab |
| 2 | Absorption rating | NRC ≥ 0.60 (absorptive) per JT/T 646-2025; state test basis |
| 3 | Panel construction | Louvered / micro-perforated / transparent / full-metal; core type |
| 4 | Material | Galvanized steel, aluminium, or stainless for corrosive sites |
| 5 | Sheet thickness | 0.8 / 1.0 / 1.2 / 1.5 mm as designed |
| 6 | Coating / galvanizing | Hot-dip galvanized + powder coat, RAL colour, thickness & test |
| 7 | Height & module length | 1.0–6.0 m height; 1.96 / 2.46 / 3.0 m lengths |
| 8 | Post system | H-section steel, 2.0–4.0 m spacing |
| 9 | Foundation loads | Cast-in-place concrete sized from wind zone & soil |
| 10 | Standards reference | JT/T 646-2025; GB/T 51335; HJ/T 90 |
| 11 | Documentation | Test reports, mill certs, shop drawings supplied |
| 12 | Acceptance clause | Visual + dimensional + contracted acoustic verification |
Zhaobang standard panels are specified to meet or exceed these thresholds, with typical NRC 0.80–0.95 and STC 25–35 dB depending on construction.
These two clauses decide whether the wall works at all.
Specify the transmission figure and the absorption figure as a pair. For Chinese highway projects, that means Rw ≥ 26 dB for non-transparent panels and NRC ≥ 0.60 for absorptive panels under JT/T 646-2025, with the test report number and issuing laboratory named in the contract. For other markets, state the Rw or STC target from the acoustic design report.
The trap is specifying only one. A panel can meet a transmission number yet reflect noise back across the road if its absorption is unstated; conversely a high-NRC face with too little mass transmits low-frequency rumble. Require both, on the same rating basis, so bidders cannot switch standards to look stronger. If you need a refresher on the figures, read our Rw, STC and NRC explained guide.
The clauses that decide service life and stability.
Coating is the most overlooked long-life factor. Require hot-dip galvanizing to a named standard plus electrostatic powder coat in a RAL colour, with coating thickness and a salt-spray or adhesion test — stricter still for coastal or corrosive sites where stainless is the right call. Structurally, fix the H-section post system at 2.0–4.0 m spacing and require cast-in-place concrete foundations sized from the site wind zone and soil conditions, with loads documented in the supplier's drawings. Leaving foundation sizing open is how post movement and wind failure enter the project.
The enforcement spine of the whole tender.
Name the standards explicitly — JT/T 646-2025 for the panels, GB/T 51335 for barrier structures, HJ/T 90 for acoustic design and measurement — and require the supplier's quality-management certificate (such as ISO 9001) with the issuing body stated, so compliance is auditable. Require the supplier to deliver test reports tied to the exact panel construction, mill certificates for the steel, and shop drawings covering posts and foundations.
Finally, write the acceptance clause: visual and dimensional checks at delivery, plus contracted acoustic verification where the project demands it, performed by an agreed party. State that Zhaobang Metal supplies material and drawings while the local contractor or EPC handles foundations and erection — closing the responsibility gap before signing.
For supply envelope, MOQ and lead times, see the noise barrier product page.
For Chinese highway projects, lock Rw of at least 26 dB for non-transparent panels and NRC of at least 0.60 for absorptive panels, referencing JT/T 646-2025, and name the test report and issuing laboratory. For other markets, state the STC or Rw target from the acoustic design report. Always require both a transmission figure and an absorption figure so the panel is judged on the full acoustic job, not just one number.
Coating decides service life, yet tenders often leave it vague. Specify hot-dip galvanizing to a named standard plus powder coat in a RAL colour, with coating thickness and a salt-spray or adhesion test, especially for coastal or corrosive sites where stainless may be required. Zhaobang offers hot-dip galvanized and electrostatic powder-coated finishes in any RAL colour, with stainless as an option for aggressive environments.
Require third-party or supplier test reports tied to the exact panel construction, mill certificates for steel, shop drawings for posts and foundations, and a site acceptance method (visual, dimensional and, where contracted, acoustic verification). State who performs installation and that foundations are sized from the site wind zone and soil. Without these clauses, a non-compliant panel can still be delivered and hard to reject.
Both belong in the tender. Fix H-section post spacing at 2.0-4.0 m and require foundations to be cast-in-place concrete sized from the project wind zone and soil conditions, with the loads documented in the supplier's drawings. Leaving this open invites under-specification that shows up as post movement or failure under wind load, which a panel rating alone cannot prevent.