Relationships among word familiarity, volume unit level, root-mean-square power, and word difficulty

Abstract

Due to time constraints, 10-25 item NU-6 word lists that are rank-ordered by word difficulty (W-D) are often used for audiological speech intelligibility testing rather than full 50-item lists (Hurley and Sell, 2003). The factors contributing to W-D are not well delineated. Although word familiarity is well established as an important contributor to W-D (Savin, 1963), the contributions of acoustical factors such as peak VU level (VU) and root-mean-square (RMS) power are less known. A better understanding of relationships among factors associated with W-D may prove useful in compiling word lists. This study investigated the relationships among word familiarity, VU, RMS power, and W-D for four 50-item NU-6 word lists. VU and RMS measures for each word were obtained with SoundForge. The standard frequency index (SFI) provided a measure of word familiarity (Carroll et al, 1971). An unexpected positive significant (p<.05) correlation was found between W-D and VU level for one list and weak positive correlations for three lists. Positive correlations are in the opposite direction hypothesized for this variable. No significant correlations were found between W-D and RMS power. Significant negative correlations were found between W-D and SFI for three NU-6 lists. Expected and unexpected findings will be addressed.