Binaural loudness summation by cochlear implant users.

Abstract

The loudness summation in people with bilateral and unilateral cochlear implants (CIs) was investigated. The stimuli were 1/3‐octave bands of noise centered at frequencies of 0.25, 1, and 4 kHz presented frontally from a loudspeaker in an ascending or random sequence of level. Subjects rated different intensity levels between the threshold of hearing and level of discomfort on scales from 0 to 100. Eight intensity levels were used for normally hearing subjects who served as a control group. For the CI users, results showed difference in loudness between monaural and binaural conditions with substantial amount of binaural loudness summation. The shape of the intensity‐loudness function varied between monaural and binaural conditions, depending on the listener. The power function of control group exhibited an exponent of near 0.5. In binaural condition, stimuli of the same sound pressure level were about 1.8 louder than in monaural condition. For 0.25‐ and 4‐kHz bands of noise, no consistent differences bet...