A study was conducted to examine the effect of multiplicity of frequency components on the audibility of tone presented against interfering noise. The measurement method was essentially identical to that of an earlier study, but triangle-wave tones were used instead as an example of complex tones. The background noise and the target tones were reproduced by a personal computer. They were amplified using a power amplifier and presented to the listener through a loudspeaker in a soundproof room. The listener's chair was set at a distance of 2.5m from the loudspeaker, while the frequency characteristic of the sound reproduction system was corrected to be substantially flat at the listener's position using an equalizer. All the listeners performed pure-tone audiometry and tympanometry and completed a questionnaire concerning hearing difficulties before participating in the experiment to confirm that they had normal hearing for their age.
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