Sound insulation test reports are among the most scrutinised documents in construction disputes. When a hotel guest complains about hearing their neighbour's television, or a tenant claims their office is not compliant with the building's acoustic specification, the field test report becomes the primary evidence. A poorly structured report — missing measurement positions, absent calibration records, incorrect referencing of the calculation method — can invalidate months of fieldwork and leave the tester exposed to professional liability.
The report template described here follows the mandatory reporting requirements of ISO 16283-1:2014 (Airborne sound insulation in buildings) and ASTM E336-19 (Measurement of Airborne Sound Attenuation Between Rooms in Buildings). Both standards require the same core information, structured differently. The template handles both in a combined format with a standard selection at the front page.
What the Two Standards Require
ISO 16283-1:2014 (used in the UK, Europe, and much of the world) reports the Apparent Sound Reduction Index R'T,w (the single-number rating of the measured field performance, using the actual reverberation time of the receiving room to normalise the results) and the Level Difference DnT,w (normalised to a reference T = 0.5 s reverberation time).
ASTM E336-19 (used in the US and Canada) reports FSTC (Field Sound Transmission Class), calculated from the Noise Isolation Class (NIC), and optionally FIIC (Field Impact Insulation Class) for floor/ceiling assemblies. ASTM E336 uses the same 1/3-octave band data as ISO 16283 but applies a different single-number rating procedure.
A test report should state which standard was used and reference the specific edition (ISO 16283-1:2014 or ASTM E336-19, not a generic "per ISO/ASTM").
Report Template — Section by Section
Cover Page
| Field | Example |
|---|---|
| Report title | "Airborne Sound Insulation Field Test Report" |
| Report reference | "AP-ST-2026-0112" |
| Project name | "Harbour View Apartments, Block C" |
| Client | "Oceanic Developments Ltd" |
| Test date | "2026-03-15" |
| Report date | "2026-03-18" |
| Test standard | "ISO 16283-1:2014 + ASTM E336-19" |
| Test organisation | "AcousPlan Acoustics Ltd" |
| Tester name | "K. Okafor, BEng (Hons), MIOA" |
| Tester signature | _________________ |
| Page count | "22 pages + 3 appendices" |
Section 1 — Test Summary
A half-page executive summary stating the test pair (e.g., "Living Room Flat 4A / Living Room Flat 3A"), the measured result (R'T,w = 51 dB, or FSTC = 49), the applicable specification (e.g., Approved Document E requirement: R'T,w ≥ 43 dB, or IBC 2021 §1207.3: STC ≥ 50), and the compliance outcome (PASS or FAIL).
This section is what the client reads. Everything below it is the technical substantiation.
Section 2 — Test Configuration
| Field | Source Room | Receiving Room |
|---|---|---|
| Room ID | Flat 4A — Living Room | Flat 3A — Living Room |
| Floor area | 18.4 m² | 17.9 m² |
| Volume | 46.0 m³ | 44.7 m³ |
| Height | 2.5 m | 2.5 m |
| Floor finish | Engineered timber | Carpet on underlay |
| Wall finishes | Painted plasterboard | Painted plasterboard |
| Ceiling finish | Plasterboard + plaster skim | Plasterboard + plaster skim |
| Separating construction | 100 mm dense concrete block, 13 mm plaster both sides | (same) |
| Flanking elements | Concrete floor slab continuous, masonry perimeter walls | (same) |
A scaled plan drawing of the test pair showing source/receiver room geometry and loudspeaker and microphone positions is mandatory under both ISO 16283-1 §6.2 and ASTM E336 §7.5. The drawing can be a hand sketch of acceptable quality, provided measurement positions are dimensioned.
Section 3 — Equipment List
| Equipment | Manufacturer/Model | Serial No. | Calibration Ref | Calibration Date |
|---|---|---|---|---|
| Integrating SLM | Norsonic Nor150 | 1502834 | NOR-2025-1847 | 2025-11-20 |
| Dodecahedral loudspeaker | 01dB DO 12 | 0012984 | — | — |
| Power amplifier | Crown XLS 1502 | 5820341 | — | — |
| Pink noise generator | Norsonic Nor150 (internal) | — | — | — |
| Pistonphone calibrator | Brüel & Kjær 4231 | 3120847 | BK-2025-2198 | 2025-10-14 |
ISO 16283-1 requires that the sound level meter meets IEC 61672-1 Class 1. ASTM E336-19 §6.1 requires Class 1. Do not use Class 2 instruments for test reports intended to demonstrate regulatory compliance.
Section 4 — Measurement Positions
ISO 16283-1 uses a loudspeaker scanning method. The template records:
- Source positions: minimum 2, dimensioned on the floor plan
- Receive positions: minimum 5 fixed or continuous path scan description
- Microphone height: standard is 1.2–1.8 m above floor
Section 5 — 1/3-Octave Band Data Table
This is the core measurement data. One row per 1/3-octave band, columns for source room level, receiving room level, level difference, receiving room reverberation time, and normalised level difference DnT.
| Freq (Hz) | Ls (dB) | Lr (dB) | D = Ls − Lr | T (s) | DnT = D + 10 log(T/0.5) |
|---|---|---|---|---|---|
| 100 | 88.2 | 63.1 | 25.1 | 0.61 | 25.9 |
| 125 | 87.4 | 59.8 | 27.6 | 0.58 | 28.3 |
| 160 | 86.9 | 56.2 | 30.7 | 0.55 | 31.1 |
| 200 | 85.8 | 54.1 | 31.7 | 0.52 | 31.9 |
| 250 | 84.3 | 51.4 | 32.9 | 0.49 | 32.7 |
| 315 | 83.7 | 50.2 | 33.5 | 0.47 | 33.1 |
| 400 | 82.1 | 47.8 | 34.3 | 0.45 | 33.8 |
| 500 | 81.4 | 46.3 | 35.1 | 0.44 | 34.5 |
| 630 | 80.6 | 44.9 | 35.7 | 0.43 | 35.0 |
| 800 | 79.8 | 43.2 | 36.6 | 0.43 | 35.9 |
| 1000 | 78.9 | 41.8 | 37.1 | 0.42 | 36.3 |
| 1250 | 78.1 | 40.6 | 37.5 | 0.41 | 36.6 |
| 1600 | 77.3 | 39.4 | 37.9 | 0.41 | 37.0 |
| 2000 | 76.5 | 38.9 | 37.6 | 0.40 | 36.6 |
| 2500 | 75.8 | 38.3 | 37.5 | 0.40 | 36.5 |
| 3150 | 74.9 | 38.0 | 36.9 | 0.39 | 35.8 |
The single-number rating DnT,w is calculated by fitting the measured DnT curve to the reference curve (ISO 717-1:2013) using the standard curve-fitting procedure. The template includes a calculation worksheet implementing this procedure.
Single-Number Rating Calculation
The ISO 717-1 procedure: adjust the reference curve up or down in 1 dB steps until the sum of unfavourable deviations (measured value more than 2 dB below reference) is ≤ 32 dB across the 16 1/3-octave bands from 100–3150 Hz. The reference curve value at 500 Hz is the single-number rating.
The ASTM E336 STC procedure: the reference contour is adjusted downward from the 500 Hz value until the sum of deficiencies (measured value below reference) does not exceed 32 dB over 16 bands (125–4000 Hz), and no single deficiency exceeds 8 dB. The contour value at 500 Hz is the STC or FSTC rating.
Both methods produce a single-number rating that can be compared against code requirements.
Section 6 — Reverberation Time of Receiving Room
The reverberation time T measured in the receiving room is used to normalise the level difference. It must be measured in the receiving room with no source in the test pair (separate measurement session, or extracted from the decay curves of the interrupted noise measurements).
| Freq (Hz) | T20 (s) | T30 (s) | Selected T |
|---|---|---|---|
| 125 | 0.59 | 0.57 | 0.58 |
| 250 | 0.50 | 0.48 | 0.49 |
| 500 | 0.45 | 0.44 | 0.44 |
| 1000 | 0.43 | 0.42 | 0.42 |
| 2000 | 0.41 | 0.40 | 0.40 |
| 4000 | 0.38 | 0.38 | 0.38 |
| Average 500–2000 | — | — | 0.42 s |
ISO 16283-1 §4.3 permits using a measured T or calculating it from the room volume and assumed absorption. The template uses measured T for accuracy.
Section 7 — Conformity Statement
This section provides the formal statement of compliance or non-compliance:
"The airborne sound insulation of the separating construction between Flat 4A Living Room and Flat 3A Living Room, measured in accordance with ISO 16283-1:2014, is DnT,w = 51 dB (Ctr = −3 dB, C = −1 dB). The applicable standard for this building type is Approved Document E (2003 edition, incorporating 2004 and 2010 amendments), which requires DnT,w + Ctr ≥ 43 dB. The measured result satisfies this requirement with a margin of 8 dB."
The Ctr spectrum adaptation term is relevant for low-frequency-heavy sources (urban traffic, home cinema, bass music). If the building is exposed to these sources or the specification refers to R'T,w(Ctr), the adapted result DnT,w + Ctr must be compared against the limit.
Adapting the Template for Impact Insulation (FIIC/L'nT,w)
For floor/ceiling assemblies, append a second data section for impact insulation measurements per ISO 16283-2 (using the standardised tapping machine) or ASTM E1007 (FIIC). The measurement columns change to: tapping machine position, receiving room level at each 1/3-octave band, normalised impact sound pressure level Ln', and the single-number rating L'n,w (ISO) or FIIC (ASTM).
IBC 2021 §1207.3 requires FIIC ≥ 50 (50 STC + FIIC minimum) for floor/ceiling assemblies between occupancies. UK Approved Document E requires L'nT,w ≤ 62 dB for between floors in dwellings.
Using AcousPlan for Pre-Test Prediction
Before conducting field tests, the Sound Insulation Calculator predicts R'T,w and STC for the partition assembly, including an estimate of flanking reduction based on the construction type. This is useful for:
- Confirming that the specified assembly is likely to achieve the required rating before scheduling a test
- Identifying the most likely flanking paths that will reduce field performance below laboratory ratings
- Generating a specification change recommendation if the predicted FSTC is below the target
Related Resources
- Sound Insulation Calculator — predict STC, Rw, and FSTC for partition assemblies
- Flanking Transmission Guide — why field STC is always lower than lab STC, and what to do about it
- Understanding STC and Rw — explaining the difference between US and European rating systems
- Absorption Coefficient Testing — understanding what test data means and how to verify it