Loudness discomfort level: selected methods and stimuli

Two investigations were conducted (i) to determine a reliable procedure for obtaining loudness discomfort levels (LDL) and (ii) to observe the effects of frequency on the LDL. Three psychophysical methods were compared in the measurement of the LDL—a programmed method of constant stimuli, the method of adjustment, and a tracking method. The method of constants provided the most reliable judgments over six trials for a 1000-Hz stimulus. The LDL was then measured utilizing the method of constants for pure tones at octave frequencies from 125 to 4000 Hz, and for a wide and narrow band of noise. The LDLs (in dB SPL) were highest at low frequencies (through 500 Hz) and relatively constant for 1000, 2000, 4000 Hz, and the wide-band noise. The relatively high LDLs in the low frequencies are explained on the basis of difference in the intensity level for low frequencies measured in a conventional 6 cm3 coupler and that observed in the ear canal when a supra-aural earphone is fitted on the head. When a correction is made for this difference the LDL results across frequency compared closely with results from loudness-contour studies.