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Objective: In a cochlear implant (CI) speech processor, noise reduction (NR) is a critical component for enabling CI users to attain improved speech perception under noisy conditions. Identifying an effective NR approach has long been a key topic in CI research. Method: Recently, a deep denoising autoencoder (DDAE) based NR approach was proposed and shown to be effective in restoring clean speech...
This paper put forward a new method of observing tongue movement in ultrasound images by calculating the accelerations of tongue points during speech production. By applying this method, the current study further compared the tongue movements in producing Mandarin mid-vowel [τ], the so-called transitional vowel with those of two steady monophthongs [i] and [a] in Mandarin Chinese. The results revealed...
This study compares the perceptual performance of Mandarin basic vowels “e” (/ɤ/) and “u” (/u/) in different contexts (independent & contextual). Results indicate that perception of the target vowel is influenced by the adjacent vowel context in a contrastive manner in both identification and discrimination tests. Moreover, in a context of higher F1 and F2, listeners found it more difficult to...
In order to explore the effects of tone categories on the perception of Mandarin vowels, the present study investigated the perceptual performance of vowel continua, which contained three Mandarin vowels /a, ɤ, u/ under four different tone conditions (i.e. high-level, mid-rising, falling-rising, and high-falling tones). The results showed that there was a shift in the categorical boundaries of /a/-/ɤ/...
It has always been challenging to non-intrusively predict speech intelligibility without the access of clean reference speech signal. This is extremely so in the scenario when predicting the intelligibility of noise-suppressed speech because of the non-linear distortion introduced by noise-suppression algorithms. The purpose of this study was to assess the segmental contribution to the non-intrusive...
It is necessary to identify speech segments carrying important information for speech intelligibility, particularly in noise. Earlier work based on a relative rootmean-square (RMS) level based segmentation suggested that middle-level (ranging from the overall RMS level to 10 dB below) segments contained more vowel-consonant boundaries wherein the spectral change was often most prominent, and perhaps...
The narrow dynamic range for speech perception partially accounts for the poor speech understanding abilities of hearing-impaired patients fitted with cochlear implants, particularly in challenging listening conditions, e.g., in reverberation. Wide dynamic range compression is designed to compress speech signal into the usable hearing dynamic range of implanted patients; however, it normally uses...
In this paper, we assess the perceptual contributions of vowel versus consonant information to speech perception by unilateral and bilateral cochlear implant (CI) listeners. Consistent with the earlier results reported for normal hearing and hearing impaired listeners, vowels play a significantly more important role compared to consonants in the sentence perception by cochlear implant listeners. In...
Most existing intelligibility indices require access to the input (clean) reference signal to predict speech intelligibility in noise. In some real-world applications, however, only the noise-masked speech is available, rendering existing indices of little use. The present study assessed the performance of an intelligibility measure that could be used to predict non-intrusively (i.e., with no access...
Noisy listening conditions remain challenging for most cochlear implant patients. The present study simulated the effects of decay rates of excitation spread in cochlear implants on the intelligibility of Mandarin speech in noise. Mandarin sentence and tone stimuli were processed by noise-vocoder, and presented to normal-hearing listeners for identification. The decay rates of excitation spread were...
This paper introduces a new speech enhancement approach based on the design of a frequency-specific composite gain function for Wiener filtering. Motivated by the recently established finding that the acoustic cues at low frequencies can improve speech recognition in noise by the combined electric and acoustic stimulation technique, a less aggressive gain function is applied to replace the Wiener...
Cochlear implant (CI) devices employ electrical pulsatile stimulation of the auditory nerves (AN) to restore partial hearing to a profoundly deafened person. In order to improve the speech perception for CI users speaking tonal language, such as Mandarin, the pulse-rate has been suggested to be modulated according to the Mandarin tonal patterns to convey the Mandarin tonal information. However, recent...
Cochlear implant (CI) devices employ electrical pulsatile stimulation of the auditory nerves (AN) to restore partial hearing to a profoundly deafened person. In order to improve the speech perception for CI users speaking tonal language, such as Mandarin, the pulse-rate has been suggested to be modulated according to the Mandarin tonal patterns to convey the Mandarin tonal information. However, recent...
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