Overview
ISO 11957:1996 - "Acoustics - Determination of sound insulation performance of cabins - Laboratory and in situ measurements" specifies methods to measure how effectively sound‑protecting cabins reduce sound pressure level or sound power. The standard covers both a laboratory method (reverberation room) and in situ methods (external sound field) and applies to complete cabins with a leak ratio ≤ 2 %. It defines quantities such as sound pressure insulation (Dp), apparent insulation (Dpa) and weighted single‑number values (Dpw / Dp,A) and includes guidance on instrumentation, test environment and reporting.
Key topics and requirements
- Scope and applicability: Measurements apply to complete cabins only (not individual components such as doors or windows) and to cabins with a leak ratio smaller than 2%.
- Test environments:
- Laboratory: reverberation room conforming to ISO 3741 (clause 6).
- In situ: external sound field generated in the actual room (clause 7).
- Measurement quantities:
- One‑third‑octave or octave band Dp (difference between room and cabin levels).
- Apparent insulation (Dpa) for in situ conditions.
- Weighted single‑number values (Dpw / Dp,A) per ISO 717‑1 methods.
- Internal noise level (Lp,int) from integrated cabin sources (fans, valves).
- Estimated cabin noise insulation for a specific noise spectrum (Annex A).
- Instrumentation:
- Use type/class 1 instruments (IEC 651 / IEC 804); class 2 acceptable for some in situ measurements.
- Calibration verification with a class‑1 acoustical calibrator (IEC 942).
- Integrating‑averaging sound level meters are preferred.
- Test procedure essentials:
- Cabin installed and operated per manufacturer instructions; doors/windows closed, internal noise sources off for insulation tests (unless measuring internal noise).
- Microphone positions and loudspeaker arrangements defined; measurements averaged on a mean‑square basis.
- Frequency coverage guidance (typical range cited: 50 Hz to 10 000 Hz, with placement/distance recommendations).
- Reporting and uncertainty: Clauses detail required recorded information (test object, conditions, instrumentation, acoustical data) and uncertainty estimation.
Applications and users
- Acoustic test laboratories performing certification or comparative testing of sound‑protecting cabins.
- Manufacturers of control rooms, machine operator cabins, vehicle cabins and other enclosed workspaces seeking validated sound insulation data.
- Acoustic consultants, product developers and compliance engineers using measured Dp / Dpw values to predict in‑service cabin noise reduction and to compare designs.
- Procurement and standards teams specifying acoustic performance for cabins in industrial, transportation or medical contexts.
Related standards
- ISO 3741 (reverberation room requirements), ISO 717‑1 (single‑number rating methods)
- ISO 11546‑1 / ISO 11546‑2 (noise attenuation of enclosures - laboratory and in situ)
- IEC references for instrumentation: IEC 651, IEC 804, IEC 942, IEC 1260
Keywords: ISO 11957:1996, acoustics, sound insulation, cabins, laboratory measurements, in situ measurements, leak ratio, reverberation room, Dp, Dpw, internal noise level.
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