The International Tinnitus Journal

Evidence for cognitive involvement in discriminating speech in babble

Speech in Background babble Discrimination (SIBD) is a recognized challenge. Stochastic Resonance (SR) is offered as the cognitive mechanism for speech discrimination. Objective: We hypothesize that SIBD has the hallmarks of SR processing because it is a non-linear transformation that includes frequency spreading and allows for brain processing without a priori knowledge of the incoming signal. Materials and Methods: To test the hypothesis we created two sets of HINT based, Hagerman style vocabulary, tests. The stochastic signal used is a recording of speech induced emission noise. The first set determines the SR transformation settings using a multi-dimensional optimum search. The second set measures the actual improvement in speech recognition for normally hearing and hearing impaired subjects. Results: The tests show an improvement of approximately 2 to 3 dB SNR of speech intelligibility. The improvement is much more significant for Hearing Impaired (HI) subjects. Conclusion: SR lowers the detection threshold of auditory signals by an order of magnitude. We show that these results, using emissions noise, show higher discrimination rate than reported results using non-matched noise. SR processing is a cognitive process as demonstrated by the sample sentences. OAE is suggested as the brain’s mechanism of SR processing