Ear level recordings of the long-term average spectrum of speech

The long-term average speech spectrum (LTASS) was measured at two different recording positions: 30 cm directly in front of the talker (reference position), and at the tragus of the talker's ear (ear-level position), for three groups of subjects: adult males, adult females, and children. Results indicated significant differences in the overall level and frequency spectra between the LTASS obtained at each microphone location. For all three groups of subjects the LTASS measured at the ear-level position consisted of more low frequency energy (i.e., below 1000 Hz) and less high frequency energy (i.e., above 2500 Hz) than did the LTASS measured at the reference microphone position. The findings suggest that the algorithms currently used to prescribe hearing aid gain may underestimate the sensation level of a hearing-impaired individual's own amplified speech productions at frequencies below 1000 Hz and overestimate the sensation level of a talker's own speech above 2500 Hz. The implications of these findings concerning selection of the electroacoustic characteristics of an amplification system for hearing-impaired individuals are discussed.