Equivalent threshold sound pressure levels for acoustic test signals of short duration

Hearing thresholds were measured for broadband clicks of 100 µs duration and for brief tones (0.500, 1, 2, 4, and 8 kHz). The signal shape of the tone pulses was of type 2-3-2, ie each pulse consisted of two periods of linear rise and fall and three periods with constant amplitude in between. The measurements were performed with two types of headphones, Telephonics TDH-39 and Sennheiser HDA-200.

The sound pressure levels were measured in an IEC 318 ear simulator with Type 1 adapter (a flat plate) and a conical ring. The audiometric methods used in the experiments were the ascending method (ISO 8253-1) and a transformed up/down procedure. Twenty-eight normal hearing test subjects (13 females and 15 males) in the age range from 18 to 26 years participated in the experiments.

The results of this investigation will be used in standardisation (ISO/TC43/WG1).