Field sound insulation testing — STC, DnT,w and impact sound measured in the finished building
A catalogue STC says what a panel did in a laboratory. It does not say what the wall that was built in your project actually stops. Geonoise measures the sound insulation of walls, floors, doors and façades as installed, to ISO 16283-1/-2/-3 and ASTM E336, and reports the DnT,w, R'w, ASTC or L'nT,w that your contract, brand standard or reviewer asks for — with an interpretation of pass or fail and, when it fails, of where the sound is getting through.
We keep field work and laboratory work clearly apart. STC and Rw tests on products to ASTM E90 and ISO 10140-2 are the work of the ALT laboratory. Geonoise works on site, with Class 1 instruments calibrated by an ISO/IEC 17025 accredited laboratory, and we sell none of the walls, doors, seals or measures we recommend — so the number in the report is the number the wall delivers, not the number anyone would like it to be. For the rating itself, read what STC is and how it is tested.
When you need a field sound insulation test
- Condominium or housing handover before transfer, when the contract or specification states an insulation value between units
- Hotel brand-standard verification before opening — many brands require sample guest rooms to be measured on site and do not accept a product certificate
- Acceptance of office, meeting-room and executive fit-outs where speech confidentiality is specified
- Schools, hospitals and clinics that need privacy between rooms
- A complaint or dispute: residents can hear their neighbours and someone has to establish whether the wall meets the specification, and who is responsible
- Before and after remedial work, to prove how many decibels the money bought
- Façades and windows of buildings on a main road, a railway or near an airport, to ISO 16283-3
What we measure
- Airborne sound insulation between rooms — walls and floors — to ISO 16283-1, reported as DnT,w and R'w (ISO 717-1), and to ASTM E336, reported as ASTC or NIC (ASTM E413) where the specification is American
- Impact sound insulation of floors to ISO 16283-2 with a standard tapping machine, reported as L'nT,w (ISO 717-2) or AIIC (ASTM E1007 / E989)
- Façade and window insulation to ISO 16283-3 with a loudspeaker or real traffic noise, reported as D2m,nT,w
- Flanking transmission to ISO 10848-2, and a scan with the 128-microphone acoustic camera, when the result is below expectation and the path has to be found
- Doors and door sets, both as installed and as part of a composite wall
- Reverberation time of the receiving room to ISO 3382-2, which is part of every measurement and is what standardises the result
How the test is done on site
One room pair takes about 45–90 minutes, depending on the number of positions the standard requires, and can be done in an empty building or an occupied one if extraneous noise can be controlled during the measurement.
- A dodecahedron loudspeaker with power amplifier generates pink noise in the source room from at least two loudspeaker positions
- Average sound pressure levels are measured in the source and receiving rooms with Class 1 sound level meters to IEC 61672-1, at fixed positions or by scanning, in one-third-octave bands from 50 to 5000 Hz
- Background noise in the receiving room is measured and corrected for as the standard requires
- Reverberation time of the receiving room is measured, to standardise the level difference (DnT) or derive the apparent sound reduction index (R')
- For floors, the standard tapping machine is operated at a minimum of four positions on the floor above and measured in the room below
- The single-number rating is calculated to ISO 717-1/-2 or ASTM E413/E989, with spectrum adaptation terms (C, Ctr) where the specification calls for them
- Field calibration before and after every measurement; temperature, room dimensions and the condition of the separating element are recorded with photographs
Laboratory STC versus the field result
The value measured on site is normally 5–10 points below the product's STC or Rw, because the field result includes every path the sound can take — flanking through the floor and the ceiling void, gaps at the head and base tracks, socket boxes, pipe penetrations, the door, and the quality of the installation. This is not a measurement error; it is the building. It is also why a contract should name the field value (DnT,w or ASTC) as the acceptance criterion, not the laboratory one. When a result falls short of the specification, we find the path with flanking measurements to ISO 10848-2 and the acoustic camera, and establish whether the product, the installation or the design is responsible, before anyone repairs or claims.
What you receive
- A measurement report in Thai or English stating the standard, method, positions, room dimensions, element condition and instruments, complete to what ISO 16283 or ASTM E336 requires
- The single-number rating (DnT,w, R'w, L'nT,w, ASTC, AIIC) with the per-band curve and reference contour, compared against the contractual or standard value
- A pass/fail statement and, on a fail, a diagnosis of the path and Good / Better / Best remedial options tied to no supplier
- The calibration certificate of every instrument used, appended to the report
- Raw data in a form that can be re-examined when the other party or the reviewer asks for it
- Signed by a named consultant, for use in handover, contractual claims and legal proceedings
Typical targets
Thai building law sets no general insulation requirement between rooms; the criterion comes from the project specification and from brand standards. Values we see most often: condominium units DnT,w 50 or better, or ASTC 45–50; hotel guest rooms STC 50–55 (laboratory), roughly DnT,w 45–50 in the field; meeting rooms DnT,w 40–45; residential floors L'nT,w no higher than 55–60 dB. These are orientation values — the acceptance value is the one in your contract, and we can review that clause before it is signed.
Standards & method
ISO 16283-1 (airborne) · ISO 16283-2 (impact) · ISO 16283-3 (façade) · ISO 717-1/-2 (single-number ratings) · ASTM E336 / E413 (ASTC, NIC) · ASTM E1007 / E989 (AIIC) · ISO 10848-2 (flanking) · ISO 3382-2 (reverberation time) · IEC 61672-1 Class 1 · instruments calibrated by an ISO/IEC 17025 accredited laboratory · laboratory testing to ASTM E90 / ISO 10140-2 by the ALT laboratory
FAQ
Can you measure STC on site?
STC is a laboratory value to ASTM E90. What can be measured on site is its field equivalent: ASTC or NIC to ASTM E336, and DnT,w or R'w to ISO 16283-1. We report the value your specification names and explain how it relates to the product's STC.
How is this different from the STC on the product certificate?
The certificate describes the panel in a test chamber. The field value describes the wall as built in your building, including flanking, gaps, doors and workmanship, and is usually 5–10 points lower. Only a field measurement confirms what was actually delivered.
Do the rooms have to be empty or fully finished?
The walls, floors, doors and the services that penetrate them must be complete and sealed, because whatever is unfinished is where the sound will go. Furniture is fine. Measurement in an occupied building is possible if extraneous noise can be controlled during the test, and we can work outside office hours.
How long does it take, and how many room pairs?
About 45–90 minutes per room pair for airborne insulation and about 30 minutes more for impact sound. The number of pairs is set by the specification or the brand standard, typically sample rooms for each wall and floor type. The report follows within 5–10 working days.
What happens if the result fails the specification?
We find the path first, with flanking measurements to ISO 10848-2 and the acoustic camera, and establish whether the product, the installation or the design is responsible. Then we propose supplier-independent remedial options and re-measure after the work to close the item. We do not sell the measures we recommend.
Does Geonoise also test in the laboratory?
No. STC and Rw tests on products to ASTM E90 and ISO 10140-2 are done by the ALT laboratory in Bangkok. Where a project needs both a product test and on-site verification, we coordinate both through one point of contact.