91/55445 DC被替代
Amendment No.1 To Bs 2497: Part 5: 1988 Standard Reference Zero For The Calibration Of Pure Tone Air Conduction Audiometers. Part 5: Specification For A Standard Reference Zero Using An Acoustic Coupler Complying With Bs 4668 (iso 389: 1985/dam 1)
出版：British Standards Institution
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