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BS EN ISO 389-8:2004 – Reference Equivalent Threshold Sound Pressure

Audiometry Standards

  • Specifies reference equivalent threshold sound pressure levels (RETSPLs) for circumaural earphones

  • Defines "audiometric zero" — the quietest sound a normal-hearing person can detect

  • All hearing test results are measured relative to these reference values

  • H4TLT headsets have RETSPLs defined by in-house testing to this standard

What this standard covers


BS EN ISO 389-8:2004 defines the Reference Equivalent Threshold Sound Pressure Levels (RETSPLs) used for the calibration of circumaural earphones in audiometry.


In practice, it provides the reference “audiometric zero” values needed to ensure hearing threshold measurements are consistent.


Why it matters If reference levels are wrong, results can drift and comparisons become unreliable. Using recognised RETSPL reference values supports accurate, repeatable audiometry across different systems and equipment setups.


H4TLT alignmentH4TLT’s headset reference levels (RETSPLs) are supported by documented measurement work aligned to the principles of ISO 389-8. Supporting evidence is held within the technical file.

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