Loudness and timbre of broad-band noise mixed with frequecy-modulated sounds

A series of experiments was conducted concerning the loudness and timbre of broadband noise mixed with frequency-modulated sounds. The results suggested the followings: (1) FM sounds overlapped on broad-band noise can be just detectable when S/N is around zero (S: the level of FM sound, N: the 1/3 octave band level of broad-band noise with center frequency corresponding to carrier frequency of FM sound). (2) FM sounds overlapped on broad-band noise can be detected at S/N of -10 dB or less when it is interrupted. (3) The loudness of broad-band noise shows good correspondence with L_eq. However, when a prominent frequency component, such as FM sounds, is included, loudness level based on ISO 532B (LLz) shows better correspondence than L_eq. (4) The timbre becomes deteriorated when the level of specific frequency component increases or when its frequency becomes high. These effects were found even when the overall values of L_eq were kept constant. Neither L_eq nor LLz is sufficient for evaluating these effects. The method for calculating sharpness proposed by von Bismarck is.an appropriate method for evaluating the metallic aspect of the timbre.