A computational modelling framework for assessing information transmission with cochlear implants.

Computational models are useful tools to investigate scientific questions that would be complicated to address using an experimental approach. In the context of cochlear-implants (CIs), being able to simulate the neural activity evoked by these devices could help in understanding their limitations to provide natural hearing. Here, we present a computational modelling framework to quantify the transmission of information from sound to spikes in the auditory nerve of a CI user.

Modeling temporal information encoding by the population of fibers in the healthy and synaptopathic auditory nerve.

We report a theoretical study aimed at investigating the impact of cochlear synapse loss (synaptopathy) on the encoding of the envelope (ENV) and temporal fine structure (TFS) of sounds by the population of auditory nerve fibers. A computational model was used to simulate auditory-nerve spike trains evoked by sinusoidally amplitude-modulated (AM) tones at 10 Hz with various carrier frequencies and levels. The model included 16 cochlear channels with characteristic frequencies (CFs) from 250 Hz to 8 kHz.

On the externalization of sound sources with headphones without reference to a real source.

Sounds presented over headphones are generally perceived as internalized, i.e., originating from a source inside the head.

The intelligibility of speech in a harmonic masker varying in fundamental frequency contour, broadband temporal envelope, and spatial location.

Differences in fundamental frequency (F0), modulations in the masker envelope, and differences in spatial location between a speech target and a masker can improve speech intelligibility in cocktail-party situations. These cues have been thoroughly investigated independently and associated with unmasking mechanisms: F0 segregation, temporal dip listening and spatial unmasking, respectively. Two experiments were conducted to examine whether F0 segregation interacts with spatial unmasking (experiment 1) or temporal modulations in the masker envelope (experiment 2) by measuring speech reception thresholds for a monotonized or an intonated voice against eight types of harmonic complex masker.

Speech Intelligibility for Target and Masker with Different Spectra.

The speech intelligibility index (SII) calculation is based on the assumption that the effective range of signal-to-noise ratio (SNR) regarding speech intelligibility is [- 15 dB; +15 dB]. In a specific frequency band, speech intelligibility would remain constant by varying the SNRs above + 15 dB or below - 15 dB. These assumptions were tested in four experiments measuring speech reception thresholds (SRTs) with a speech target and speech-spectrum noise, while attenuating target or noise above or below 1400 Hz, with different levels of attenuation in order to test different SNRs in the two bands.

Speech intelligibility prediction in reverberation: Towards an integrated model of speech transmission, spatial unmasking, and binaural de-reverberation.

Room acoustic indicators of intelligibility have focused on the effects of temporal smearing of speech by reverberation and masking by diffuse ambient noise. In the presence of a discrete noise source, these indicators neglect the binaural listener's ability to separate target speech from noise. Lavandier and Culling [(2010).