Source: https://guthlabs.ai/docs/instruments/reverb-time-rt60-sabine-formula/implementation/

instrument implementation / implementation-contract

# Reverb Time RT60 (Sabine Formula) implementation

A source-bound implementation contract for Reverb Time RT60 (Sabine Formula); deployment and executable qualification remain separate.

Status: **VERIFIED_CLEAN**Lifecycle: **implementation-contract**

## Binding contract

This record describes what an executable surface must bind and validate. It does not claim that a public calculator, package, or production route is deployed.

**Record owner**: Guth Instruments

**Lifecycle**: verified-clean

**Evidence ID**: t7-010

**Effect**: Computation or source lookup only

## Input and validation requirements

The zero-absorption case produces division by zero and must be rejected or represented as undefined/infinite. The specification also provides no defined branch behavior for absorption coefficients outside the conventional table range or for Sabine-model validity limits.

## Required corrections

No binding erratum is attached to this unique-name record. Implementers must still preserve the declared units, domain, and failure behavior.

## Inspectable interface fixture

The sample below is evidence for interface and validation tests, not a production implementation.

````
{
  "inputs": {
    "volume_m3": 180,
    "frequency_band_hz": "500 octave band",
    "surfaces": [
      {
        "material": "carpet on floor",
        "area_m2": 60,
        "absorption_coefficient": 0.3
      },
      {
        "material": "acoustic ceiling tile",
        "area_m2": 60,
        "absorption_coefficient": 0.6
      },
      {
        "material": "painted drywall walls",
        "area_m2": 120,
        "absorption_coefficient": 0.1
      }
    ]
  },
  "expected_outputs": {
    "equivalent_absorption_A_m2": 66,
    "RT60_s": 0.4390909091
  },
  "reference_data": {
    "carpet_on_floor_500Hz": {
      "absorption_coefficient": 0.3,
      "source_convention": "widely tabulated standard value in architectural-acoustics octave-band coefficient tables"
    },
    "acoustic_ceiling_tile_500Hz": {
      "absorption_coefficient": 0.6,
      "source_convention": "widely tabulated standard value in architectural-acoustics octave-band coefficient tables"
    },
    "painted_drywall_500Hz": {
      "absorption_coefficient": 0.1,
      "source_convention": "widely tabulated standard value in architectural-acoustics octave-band coefficient tables"
    }
  },
  "working": "A=(60*0.30)+(60*0.60)+(120*0.10)=18+36+12=66 m^2. Numerator=0.161*180=28.98. RT60=28.98/66=0.4390909091 s."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/reverb-time-rt60-sabine-formula/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/reverb-time-rt60-sabine-formula/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/reverb-time-rt60-sabine-formula/qualification/>)

## Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

- `VERIFIED_LEDGER.json`

- `evidence-tranche7/tranche7-results.json`