Equal-loudness level contours below 1 kHz

Abstract

Binaural equal-loudness level contours and the threshold of hearing have been measured on 25 otological normal-hearing subjects. In the frequency range from 50 Hz to 1 kHz the measurements were made in the free field for frontal sound incidence. From 20 to 100 Hz the experiments were made in a pressure field chamber with an inner volume for the test subjects of approximately 1 m3. The experiment is made with pure tones at each of the third octave frequencies in the frequency range. Loudness levels between 20 and 100 phon are measured. The data are going to be used for the standardization work in the Working Group ISO/TC43/WG1 for a revision of the international standard ISO 226.

On the Low Frequency Noise Assessment Method

“…The three parameters k L = 1.5 dB, s L = 11.1 dB, and D 0 = 7 dB which appear in eqn (3) were best fitted to the data. Threshold levels were taken from [5] above 20 Hz, and [6] below. The resulting synergistic correction factor was computed as K TS = g f x g L .…”

“…Finally, it may be of interest to consider that the shape of (single-tone) equal loudness curves at low frequency [5] would argue in favour of W J being more flat than W A and henceforth located "above" the latter. The location of W J "below" W A resulting from this study is a totally unexpected result.…”