ISO 389-8:2004规定了125 Hz至8 kHz频率范围内纯音的参考等效阈值声压级（RETSPL），适用于配备特定型号环绕式耳机（森海塞尔HDA 200）的空气传导听力计的校准。 附录A和参考文献中给出了用于确定推荐参考水平的推导和试验条件的一些注释和参考。 附件B中给出了耳机的声音衰减。对于A-E和B-E型语音听力计，免费提供耳机的校正数字- 附件C中给出了现场等效输出。

ISO 389-8:2004 specifies reference equivalent threshold sound pressure levels (RETSPLs) for pure tones in the frequency range from 125 Hz to 8 kHz, applicable to the calibration of air conduction audiometers equipped with a particular model of circumaural earphones (SENNHEISER HDA 200). Some notes and references on the derivation and the test conditions used to determine the recommended reference levels are given in Annex A and the Bibliography. The sound attenuation of the earphone is given in Annex B. For speech audiometers of types A-E and B-E, the correction figures of the earphone for a free-field equivalent output are given in Annex C.