Spectral maxima sound coding algorithms, for example n-ofm strategies, used in commercial cochlear implant devices rely on selecting channels with the highest energy in each frequency band. This technique works well i...
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ISBN:
(纸本)9781479928934
Spectral maxima sound coding algorithms, for example n-ofm strategies, used in commercial cochlear implant devices rely on selecting channels with the highest energy in each frequency band. This technique works well in quiet, but is inherently problematic in noisy conditions when noise dominates the target, and noise-dominant channels are mistakenly selected for stimulation. A new channel selection criterion is proposed to addresses this shortcoming which adaptively assigns weights to each time-frequency unit based on the formant location of speech and instantaneous signal to noise ratio. The performance of the proposed technique is evaluated acutely with three cochlear implant users in different noise scenarios. Results indicate that the proposed technique improves speech intelligibility and perception quality, particularly at low signal-to-noise ratio. Significance of the proposed technique lies in its ability to be integrated with the existing sound coding framework employed within commercial cochlear implant processors, making it easier to adapt for resource-limited and time critical devices.
Speech and audio coding standards al-E defined in international organizations having wide range of activities, only part of them dealing with bit rate compression of speech and audio. The UIT (international Telecommun...
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Speech and audio coding standards al-E defined in international organizations having wide range of activities, only part of them dealing with bit rate compression of speech and audio. The UIT (international Telecommunication Union) deals with interactive communication standards, the ETSI (European Telecommunications Standards Institute) with mobile communication standards in Europe while multimedia communication standard's are under the responsability of the ISO (International Organization Sor Standardization). After a brief description of the standardization mechanism, we will review the features of speech and audio compression schemes (bit rates, quality complexity and delay) and the main applications of these standards. A list of these compression standards, already;adopted or in the course of definition, will be provided for each normalization organization. Finally: this payer gives the orientations or trends which are emerging in the field of audio compression standardization.
The MPEG-2 Advanced Audio Coder is the latest issue of the MPEG audio encoders/decoders family whose most popular version is known as MP3. It gathers many of the latest highly efficient sound compression techniques in...
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The MPEG-2 Advanced Audio Coder is the latest issue of the MPEG audio encoders/decoders family whose most popular version is known as MP3. It gathers many of the latest highly efficient sound compression techniques in a quite classically structured coder. The main part is based or a Discrete Cosine Transform with variable resolution. The output from this filterbank is compressed by the combination of an adaptive bit allocation module, according to frequency subbands, and a set of noiseless Huffman codebooks. Bit allocation is controlled by a psychoacoustic model which determines an audibility threshold far signal distortion in the frequency domain. This article intends to explain the ISO standard without replacing it, and also to be a general introduction to perceptual audio coding.
A low delay coder for speech and music signals sampled at 32 kHz is described. Its algorithmic delay does not exceed 25 ms which enables audio conferencing applications without echo cancellation. Its bot rate is scala...
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A low delay coder for speech and music signals sampled at 32 kHz is described. Its algorithmic delay does not exceed 25 ms which enables audio conferencing applications without echo cancellation. Its bot rate is scalable between 64 and 32 kbits/s by steps of 8 kbits/s. The transmitter issues the binary code at 64 kbits/s with lower bit rate codes embedded in it. The receiver may operate at lower bit rates with gradual loss of quality. The proposed coder is based on a mixed scheme: the adopted solution contains elements from the CELP speech coder and frequency domain where bit allocation is calculated and transform coefficients are quantized. A first solution based on the DFT is discussed, then a second solution based on a MDCT with small overlap is applied. The quantization of these coefficients is done in the following way. First, a prediction of the whole spectrum is applied. Then, a mean-removed gain-shape split VQ is used for amplitude spectrum quantization and a hierarchical 2-dimensional VQ is used for phase spectrum quantization stage, each codeword describing the selected vector index is split into parts corresponding to different bit rates. Due to the hierarchical codebook structure, truncated indices may be used, without much affecting the signal quality. Simulation results are presented and the robustness of the proposed coder is examined.
This paper presents a scalable three bit-rates (8, 14.1 and 24 il kbit/s) coder: For the two embedded lowest ones, operating in the telephone bandwidth, CELP coding techniques are used. For the highest rate, that both...
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This paper presents a scalable three bit-rates (8, 14.1 and 24 il kbit/s) coder: For the two embedded lowest ones, operating in the telephone bandwidth, CELP coding techniques are used. For the highest rate, that both improves narrowband quality and extends the band to [50-7000Hz], transform coding techniques are used. The main applications deal with transmission over network,with no guaranteed QoS.
Frontal areas of the mammalian cortex are thought to be important for cognitive control and complex behaviour. These areas have been studied mostly in humans, non-human primates and rodents. In this article, we presen...
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Frontal areas of the mammalian cortex are thought to be important for cognitive control and complex behaviour. These areas have been studied mostly in humans, non-human primates and rodents. In this article, we present a quantitative characterization of response properties of a frontal auditory area responsive to sound in the brain of Carollia perspicillata, the frontal auditory field (FAF). Bats are highly vocal animals, and they constitute an important experimental model for studying the auditory system. We combined electrophysiology experiments and computational simulations to compare the response properties of auditory neurons found in the bat FAF and auditory cortex (AC) to simple sounds (pure tones). Anatomical studies have shown that the latter provides feedforward inputs to the former. Our results show that bat FAF neurons are responsive to sounds, and however, when compared to AC neurons, they presented sparser, less precise spiking and longer-lasting responses. Based on the results of an integrate-and-fire neuronal model, we suggest that slow, subthreshold, synaptic dynamics can account for the activity pattern of neurons in the FAF. These properties reflect the general function of the frontal cortex and likely result from its connections with multiple brain regions, including cortico-cortical projections from the AC to the FAF.
Neuronal diversity in the cochlea is largely determined by ion channels. Among voltage-gated channels, hyperpolarization-activated cyclic nucleotide-gated (HCN) channels open with hyperpolarization and depolarize the ...
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Neuronal diversity in the cochlea is largely determined by ion channels. Among voltage-gated channels, hyperpolarization-activated cyclic nucleotide-gated (HCN) channels open with hyperpolarization and depolarize the cell until the resting membrane potential. The functions for hearing are not well elucidated and knowledge about localization is controversial. We created a detailed map of subcellular location and co-expression of all four HCN subunits across different mammalian species including CBA/J, C57Bl/6N, Ly5.1 mice, guinea pigs, cats, and human subjects. We correlated age-related hearing deterioration in CBA/J and C57Bl/6N with expression levels of HCN1, -2, and -4 in individual auditory neurons from the same cohort. Spatiotemporal expression during murine postnatal development exposed HCN2 and HCN4 involvement in a critical phase of hair cell innervation. The huge diversity of subunit composition, but lack of relevant heteromeric pairing along the perisomatic membrane and axon initial segments, highlighted an active role for auditory neurons. Neuron clusters were found to be the hot spots of HCN1, -2, and -4 immunostaining. HCN channels were also located in afferent and efferent fibers of the sensory epithelium. Age-related changes on HCN subtype expression were not uniform among mice and could not be directly correlated with audiometric data. The oldest mice groups revealed HCN channel up- or downregulation, depending on the mouse strain. The unexpected involvement of HCN channels in outer hair cell function where HCN3 overlaps prestin location emphasized the importance for auditory function. A better understanding may open up new possibilities to tune neuronal responses evoked through electrical stimulation by cochlear implants.
Three sound signal compression methods are being offered allowing (depending on the application aim) finding the best trade-off between the compression efficiency and the realization complexity. The testing of the met...
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ISBN:
(纸本)9531840547
Three sound signal compression methods are being offered allowing (depending on the application aim) finding the best trade-off between the compression efficiency and the realization complexity. The testing of the methods proposed was done on a half-nature simulation system including personal computers 10 Mbit/sec Ethernet LAN and the sound signal input/output means.
Binaural hearing benefits with bilateral cochlear implants (CI) are usually smaller than with normal hearing (NH) in the same tasks. This gap in performance has typically been attributed to a lack of coordinated stimu...
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Multi-channel cochlear implants (CI) leverage frequency based cochlear tonotopic mapping to map acoustic information to the cochlear place of stimulation which is primarily determined by electrode locations. Despite t...
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