Speech Encoding Research Articles

An appropriate system for securing real-time voice communication based on ADPCM coding and chaotic maps

This paper presents a very simple and efficient encryption scheme based on controlled chaotic maps and ADPCM (Adaptive Differential Pulse Code Modulation) coding, in order to secure the real-time voice communication for operating at 16, 24, 32 or 40 kbps. This encryption algorithm adopts three main operations one to generate chaotic values using two chaotic logistic maps starting from independent initial conditions, the second to transform them into binary words using random encoding tables and the third to execute some basic operations and substitutions. It has important properties of randomness that can pass NIST batteries of tests. The evaluation and simulation analysis indicate that our proposal possesses an excellent statistical and cryptographic properties; it provides low correlation between adjacent samples in encryption speech, extremely sensitive encryption keys and has a large key space which is sufficient to protect against brute-force attack. As an illustrative example, an application on a commonly-encoder type used in communications, standard ITU-T G.726, is presented.

Brainstem Encoding of Aided Speech in Hearing Aid Users with Cochlear Dead Region(s).

Introduction Neural encoding of speech begins with the analysis of the signal as a whole broken down into its sinusoidal components in the cochlea, which has to be conserved up to the higher auditory centers. Some of these components target the dead regions of the cochlea causing little or no excitation. Measuring aided speech-evoked auditory brainstem response elicited by speech stimuli with different spectral maxima can give insight into the brainstem encoding of aided speech with spectral maxima at these dead regions.Objective This research aims to study the impact of dead regions of the cochlea on speech processing at the brainstem level after a long period of hearing aid use.Methods This study comprised 30 ears without dead regions and 46 ears with dead regions at low, mid, or high frequencies. For all ears, we measured the aided speech-evoked auditory brainstem response using speech stimuli of low, mid, and high spectral maxima.Results Aided speech-evoked auditory brainstem response was producible in all subjects. Responses evoked by stimuli with spectral maxima at dead regions had longer latencies and smaller amplitudes when compared with the control group or the responses of other stimuli.Conclusion The presence of cochlear dead regions affects brainstem encoding of speech with spectral maxima perpendicular to these regions. Brainstem neuroplasticity and the extrinsic redundancy of speech can minimize the impact of dead regions in chronic hearing aid users.

A Novel Approach for Speech Encryption: Zaslavsky Map as Pseudo Random Number Generator

Recently emerged interest in the transfer of information, whether speech or image or text information. To maintain the confidentiality of such information we need to encrypt it. This paper proposes a new cryptography technique for speech to increases the security of the data meant to be transferred on an insecure medium. The proposed scheme for speech encryption is based on Zaslavsky map and Cat map transform. In this work, the original speech signal is first compressed by discrete cosine transform (DCT) to reduce the residual intelligibility and then the plain data is hidden using random numbers generated using Zaslavsky map. The output data is then processed by Cat map to perplex the data samples so as to make the information unable to understand by an intruder. These two lower dimensional chaotic maps act together to make encryption in higher dimensional space which expands the key space and consequently enhances the security against brute force attack. The resulting system gives more complex dynamical properties proofed with good randomness and unpredictability. Various analyses such as signal to noise ratio (SNR), key space, correlation and brute force attack have been carried out. The analysis shows that the proposed algorithm is computationally simple and efficient compared to conventional higher dimensional chaotic maps. The signal obtained in the proposed technique after decryption at the recipient end is a replica of the original signal which was meant for encryption.

Robust Encoding in the Human Auditory Brainstem: Use It or Lose It?

The human auditory brainstem faithfully represents the acoustic structure of sounds (Galbraith et al., 1995). In musicians, presumably because music training and exposure places high demands on the auditory system, brainstem encoding of both speech and musical sounds is more robust than in non-musicians. It is believed that the corticofugal system, a vast network of efferent connections within the auditory neuroaxis, drives top-down plastic changes underlying the enhancements in brainstem encoding in musicians and other populations with fine-tuned auditory abilities (Wong et al., 2007). Could these same mechanisms lead to impoverished brainstem encoding in those individuals whose musical skill proficiency is below average? Two recent studies on brainstem encoding in amusia, a congenital music disorder, shed a complementary light on this issue (Lehmann et al., 2015; Liu et al., 2015). Together they suggest that a subcortical deficit in auditory processing, which varies as a function of the degree of musical (dis)ability, can emerge as a consequence of limited meaningful interactions with music. We discuss how this notion of auditory detuning fits with the emerging view on top-down induced subcortical plasticity in auditory processing and address its implications for auditory rehabilitation.

Lorenz and Rossler Chaotic System for Speech Signal Encryption

this paper an algorithm for speech encryption based on three dimension chaotic maps is proposed. The proposed algorithm consists of three main units: generation of keys, samples substitution and samples permutation process. In order to maximize the benefits of the substitution process, it is performed in two stages with cipher feedback, for the system. Moreover bit-level permutation for sample is introduced as substitution mechanism in the permutation stage. The Lorenz and Rossler chaotic system are employed as generation of keystream used for substitution and permutation process respectively. From the experimental results, it is concluded that the proposed algorithm has the advantages of very low residual intelligibility, key sensitivity and high quality recovered signal, and moreover the proposed algorithm can resist known- plaintext attacks and supports large key space make brute-force attacks infeasible.

Incorporating data hiding into G.729 speech codec

The rapid development of speech communication technology has made it possible for low bit-rate speech to become appropriate steganographic cover media. To incorporate data hiding into the low bit-rate speech codec, a novel steganography algorithm is proposed in this paper. By analyzing the encoding rule of fixed codebook vector, the way of transposing encoding locations of adjacent pulses is found to be suitable for data embedding with good imperceptibility. Based on encoding location transposition of adjacent pulses, the relationship between adjacent pulse locations is used to embed secret data while the fixed codebook search is being conducted during the encoding process of G.729 codec, which can maintain synchronization between data embedding and speech encoding. The experimental results demonstrate that the proposed steganography algorithm performs well in imperceptibility with a hiding capacity of 550 bits/s. Furthermore, the real-time and anti-detection performances are also satisfactory.

Modelling the Noise-Robustness of Infants' Word Representations: The Impact of Previous Experience.

During language acquisition, infants frequently encounter ambient noise. We present a computational model to address whether specific acoustic processing abilities are necessary to detect known words in moderate noise—an ability attested experimentally in infants. The model implements a general purpose speech encoding and word detection procedure. Importantly, the model contains no dedicated processes for removing or cancelling out ambient noise, and it can replicate the patterns of results obtained in several infant experiments. In addition to noise, we also addressed the role of previous experience with particular target words: does the frequency of a word matter, and does it play a role whether that word has been spoken by one or multiple speakers? The simulation results show that both factors affect noise robustness. We also investigated how robust word detection is to changes in speaker identity by comparing words spoken by known versus unknown speakers during the simulated test. This factor interacted with both noise level and past experience, showing that an increase in exposure is only helpful when a familiar speaker provides the test material. Added variability proved helpful only when encountering an unknown speaker. Finally, we addressed whether infants need to recognise specific words, or whether a more parsimonious explanation of infant behaviour, which we refer to as matching, is sufficient. Recognition involves a focus of attention on a specific target word, while matching only requires finding the best correspondence of acoustic input to a known pattern in the memory. Attending to a specific target word proves to be more noise robust, but a general word matching procedure can be sufficient to simulate experimental data stemming from young infants. A change from acoustic matching to targeted recognition provides an explanation of the improvements observed in infants around their first birthday. In summary, we present a computational model incorporating only the processes infants might employ when hearing words in noise. Our findings show that a parsimonious interpretation of behaviour is sufficient and we offer a formal account of emerging abilities.

P76. Transient suppression of speech comprehension by continuous theta-burst magnetic stimulation of the pre-SMA

The pre-supplementary motor area (pre-SMA) may be engaged in speech comprehension under difficult circumstances such as poor acoustic signal quality, cognitive load, or time-critical conditions. For instance, it has been assumed that comprehension of time-compressed speech involves mesial frontal brain structures including SMA-proper and pre-SMA, which buffer phonological materials ( Vagharchakian et al., 2012 ). In line with this notion, left pre-SMA was strongly activated when subjects were trained to understand ultra-fast speech at high syllable rates, likely by providing a prosodic interface for the time-critical encoding of speech with respect to its syllabic structure ( Dietrich et al., 2013 ). Here, we tested the functional role of the pre-SMA for ultra-fast speech comprehension by inducing a transient ‘virtual lesion’ using continuous theta burst magnetic stimulation (cTBS; 3 stimuli at 50 Hz, repeated every 200 ms, 600 pulses in total, stimulation intensity equaling 120% of resting motor threshold for the right abductor pollicis brevis muscle). Pre-SMA as defined individually by functional MRI was targeted using a frameless neuro-navigation system. Nineteen healthy subjects performed a sentence repetition task comprising of sentence utterances synthesized at five distinct syllable rates (8, 10, 12, 14, 16 syl/s) prior to stimulation (pre-stimulation baseline), 10 min after stimulation (assumed maximum of the TMS effect), and 60 min after cTBS procedure (post-stimulation baseline), respectively. Speech comprehension was quantified by the percentage of correctly reproduced words. Compared to baseline speech comprehension was decreased at high speech rates of 12 syl/s or faster at 10 min, but not at 60 min after stimulation. This transient impairment of speech comprehension following cTBS suggests that pre-SMA, indeed, contributes to time-critical encoding of phonetic-linguistic information. Our results further lend support to the notion that TBS can be used as a tool for transient interference with pre-SMA cognitive function ( Fig. 1 ).

Brainstem encoding of speech in normal-hearing individuals with absent acoustic reflex

The acoustic reflex test is an important tool for identifying auditory disorder from the middle ear to the superior olivary complex. Absence of acoustic reflexes is the early sign of many auditory disorders. Absence of acoustic reflex with normal hearing sensitivity may be an early sign of auditory neuropathy with poor encoding of speech at initial stage. Speech auditory brainstem response was recorded with /da/ (40 ms) stimuli in two groups of patients. The control group contained normal-hearing participants with presence of acoustic reflex, whereas the experimental group contained normal-hearing participants with absent acoustic reflexes. The peak latency, amplitude, and F0 and F1 mean amplitude were analyzed in both groups. MANOVA showed no significant difference in any parameter between the control and experimental group. Results of the current study showed that absence of acoustic reflexes in normal-hearing patients without auditory complaint is not sufficient by itself to diagnose the existence of auditory neuropathy. This study also highlighted that normal-hearing patients with absence of acoustic reflex have similar brainstem encoding of speech as that of patients with acoustic reflex.

Differential oscillatory encoding of foreign speech

Neuronal oscillations play a key role in auditory perception of verbal input, with the oscillatory rhythms of the brain showing synchronization with specific frequencies of speech. Here we investigated the neural oscillatory patterns associated with perceiving native, foreign, and unknown speech. Spectral power and phase synchronization were compared to those of a silent context. Power synchronization to native speech was found in frequency ranges corresponding to the theta band, while no synchronization patterns were found for the foreign speech context and the unknown language context. For phase synchrony, the native and unknown languages showed higher synchronization in the theta-band than the foreign language when compared to the silent condition. These results suggest that neural synchronization patterns are markedly different for native and foreign languages.

Speech encoding by coupled cortical theta and gamma oscillations.

Many environmental stimuli present a quasi-rhythmic structure at different timescales that the brain needs to decompose and integrate. Cortical oscillations have been proposed as instruments of sensory de-multiplexing, i.e., the parallel processing of different frequency streams in sensory signals. Yet their causal role in such a process has never been demonstrated. Here, we used a neural microcircuit model to address whether coupled theta-gamma oscillations, as observed in human auditory cortex, could underpin the multiscale sensory analysis of speech. We show that, in continuous speech, theta oscillations can flexibly track the syllabic rhythm and temporally organize the phoneme-level response of gamma neurons into a code that enables syllable identification. The tracking of slow speech fluctuations by theta oscillations, and its coupling to gamma-spiking activity both appeared as critical features for accurate speech encoding. These results demonstrate that cortical oscillations can be a key instrument of speech de-multiplexing, parsing, and encoding.

The impact of musicianship on the cortical mechanisms related to separating speech from background noise.

Musicians have enhanced auditory processing abilities. In some studies, these abilities are paralleled by an improved understanding of speech in noisy environments, partially due to more robust encoding of speech signals in noise at the level of the brainstem. Little is known about the impact of musicianship on attention-dependent cortical activity related to lexical access during a speech-in-noise task. To address this issue, we presented musicians and nonmusicians with single words mixed with three levels of background noise, across two conditions, while monitoring electrical brain activity. In the active condition, listeners repeated the words aloud, and in the passive condition, they ignored the words and watched a silent film. When background noise was most intense, musicians repeated more words correctly compared with nonmusicians. Auditory evoked responses were attenuated and delayed with the addition of background noise. In musicians, P1 amplitude was marginally enhanced during active listening and was related to task performance in the most difficult listening condition. By comparing ERPs from the active and passive conditions, we isolated an N400 related to lexical access. The amplitude of the N400 was not influenced by the level of background noise in musicians, whereas N400 amplitude increased with the level of background noise in nonmusicians. In nonmusicians, the increase in N400 amplitude was related to a reduction in task performance. In musicians only, there was a rightward shift of the sources contributing to the N400 as the level of background noise increased. This pattern of results supports the hypothesis that encoding of speech in noise is more robust in musicians and suggests that this facilitates lexical access. Moreover, the shift in sources suggests that musicians, to a greater extent than nonmusicians, may increasingly rely on acoustic cues to understand speech in noise.

Speech Auditory Brainstem Response through hearing aid stimulation

Millions of people across the world are hearing impaired, and rely on hearing aids to improve their everyday life. Objective audiometry could optimize hearing aid fitting, and is of particular interest for non-communicative patients. Speech Auditory Brainstem Response (speech ABR), a fine electrophysiological marker of speech encoding, is presently seen as a promising candidate for implementing objective audiometry; yet, unlike lower-frequency auditory-evoked potentials (AEPs) such as cortical AEPs or auditory steady-state responses (ASSRs), aided-speech ABRs (i.e. speech ABRs through hearing aid stimulation) have almost never been recorded. This may be due to their high-frequency components requesting a high temporal precision of the stimulation. We assess here a new approach to record high-quality and artifact-free speech ABR while stimulating directly through hearing aids. In 4 normal-hearing adults, we recorded speech ABR evoked by a /ba/ syllable binaurally delivered through insert earphones for quality control or through hearing aids. To assess the presence of a potential stimulus artifact, recordings were also done in mute conditions with the exact same potential sources of stimulus artifacts as in the main runs. Hearing aid stimulation led to artifact-free speech ABR in each participant, with the same quality as when using insert earphones, as shown with signal-to-noise (SNR) measurements. Our new approach consisting in directly transmitting speech stimuli through hearing aids allowed for a perfect temporal precision mandatory in speech ABR recordings, and could thus constitute a decisive step in hearing impairment investigation and in hearing aid fitting improvement.

Interdependent processing and encoding of speech and concurrent background noise.

Speech processing can often take place in adverse listening conditions that involve the mixing of speech and background noise. In this study, we investigated processing dependencies between background noise and indexical speech features, using a speeded classification paradigm (Garner, 1974; Exp. 1), and whether background noise is encoded and represented in memory for spoken words in a continuous recognition memory paradigm (Exp. 2). Whether or not the noise spectrally overlapped with the speech signal was also manipulated. The results of Experiment 1 indicated that background noise and indexical features of speech (gender, talker identity) cannot be completely segregated during processing, even when the two auditory streams are spectrally nonoverlapping. Perceptual interference was asymmetric, whereby irrelevant indexical feature variation in the speech signal slowed noise classification to a greater extent than irrelevant noise variation slowed speech classification. This asymmetry may stem from the fact that speech features have greater functional relevance to listeners, and are thus more difficult to selectively ignore than background noise. Experiment 2 revealed that a recognition cost for words embedded in different types of background noise on the first and second occurrences only emerged when the noise and the speech signal were spectrally overlapping. Together, these data suggest integral processing of speech and background noise, modulated by the level of processing and the spectral separation of the speech and noise.

Subcortical processing of speech in individuals with type 2 diabetes mellitus

The study was done to compare speech-evoked auditory brainstem response (ABR) in normal-hearing individuals without diabetes mellitus and normal-hearing individuals with type 2 diabetes mellitus (T2DM). A case-control study design was used to carry out the study. A total of 50 individuals were recruited in the study, divided into two groups. One group consisted of 25 individuals with type 2 diabetes mellitus with normal-hearing and the other group consisted of 25 individuals without diabetes with normal hearing as a control group. The results indicated that the mean latencies and amplitudes was significantly different in the type 2 diabetes mellitus group in comparison to the control group. The amplitude of the F0, F1, higher formants, and RMS values were higher in the control group when compared to the T2DM group. The present study concluded that there is problem in the encoding of speech at the brainstem level despite normal hearing in individuals with type 2 diabetes mellitus.

Brainstem encoding of speech and musical stimuli in congenital amusia: evidence from Cantonese speakers.

Congenital amusia is a neurodevelopmental disorder of musical processing that also impacts subtle aspects of speech processing. It remains debated at what stage(s) of auditory processing deficits in amusia arise. In this study, we investigated whether amusia originates from impaired subcortical encoding of speech (in quiet and noise) and musical sounds in the brainstem. Fourteen Cantonese-speaking amusics and 14 matched controls passively listened to six Cantonese lexical tones in quiet, two Cantonese tones in noise (signal-to-noise ratios at 0 and 20 dB), and two cello tones in quiet while their frequency-following responses (FFRs) to these tones were recorded. All participants also completed a behavioral lexical tone identification task. The results indicated normal brainstem encoding of pitch in speech (in quiet and noise) and musical stimuli in amusics relative to controls, as measured by FFR pitch strength, pitch error, and stimulus-to-response correlation. There was also no group difference in neural conduction time or FFR amplitudes. Both groups demonstrated better FFRs to speech (in quiet and noise) than to musical stimuli. However, a significant group difference was observed for tone identification, with amusics showing significantly lower accuracy than controls. Analysis of the tone confusion matrices suggested that amusics were more likely than controls to confuse between tones that shared similar acoustic features. Interestingly, this deficit in lexical tone identification was not coupled with brainstem abnormality for either speech or musical stimuli. Together, our results suggest that the amusic brainstem is not functioning abnormally, although higher-order linguistic pitch processing is impaired in amusia. This finding has significant implications for theories of central auditory processing, requiring further investigations into how different stages of auditory processing interact in the human brain.

Auditory envelope following responses in the mature and developing human brain

Event Abstract Back to Event Auditory envelope following responses in the mature and developing human brain Huizhen Tang1*, Jon Brock1, Stephen Crain2 and Blake Johnson1 1 Macquarie University , Cognitive Science , Australia 2 Macquarie University , Linguistics , Australia Recent theories of speech perception propose that the speech envelope (the overall waveform of the speech signal) plays a crucial role in speech perception by aligning brain excitability patterns with the intensity fluctuations of the speech sounds. We tested two main hypotheses derived from these theories: (1) That the sound envelope provides crucial cues for encoding of temporal information in sounds; (2) that temporal encoding is not fully mature in preschool-aged children (3 to 5 years old). The acoustic stimulus was a broadband noise amplitude-modulated in a continuous sweep of frequencies from 1 to 80 Hz. Brain responses were measured with magnetoencephalography. The adult temporal modulation transfer function showed precise and continuous phase tracking throughout the frequency range, while children showed significantly worse tracking at both high and low modulation frequencies. Adult and child transfer functions also differed significantly in their preferred modulation frequencies, and hemispheric asymmetries. These results are the first to describe the auditory temporal modulation transfer function in preschool children. They show that the immature brain differs markedly from the adult brain in its capacity to encode temporal information in sounds. These results must be accounted for by neurolinguistic theories that emphasize the role of specific temporal modulation frequencies for the neural encoding of speech. Keywords: Auditory Perception, Brain Mapping, Language, Magnetoencephalography, Brain Development Conference: XII International Conference on Cognitive Neuroscience (ICON-XII), Brisbane, Queensland, Australia, 27 Jul - 31 Jul, 2014. Presentation Type: Poster Topic: Language Citation: Tang H, Brock J, Crain S and Johnson B (2015). Auditory envelope following responses in the mature and developing human brain. Conference Abstract: XII International Conference on Cognitive Neuroscience (ICON-XII). doi: 10.3389/conf.fnhum.2015.217.00363 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 19 Feb 2015; Published Online: 24 Apr 2015. * Correspondence: Ms. Huizhen Tang, Macquarie University, Cognitive Science, North Ryde, Australia, joann.tang@mq.edu.au Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Huizhen Tang Jon Brock Stephen Crain Blake Johnson Google Huizhen Tang Jon Brock Stephen Crain Blake Johnson Google Scholar Huizhen Tang Jon Brock Stephen Crain Blake Johnson PubMed Huizhen Tang Jon Brock Stephen Crain Blake Johnson Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Engagement in community music classes sparks neuroplasticity and language development in children from disadvantaged backgrounds.

Children from disadvantaged backgrounds often face impoverished auditory environments, such as greater exposure to ambient noise and fewer opportunities to participate in complex language interactions during development. These circumstances increase their risk for academic failure and dropout. Given the academic and neural benefits associated with musicianship, music training may be one method for providing auditory enrichment to children from disadvantaged backgrounds. We followed a group of primary-school students from gang reduction zones in Los Angeles, CA, USA for 2 years as they participated in Harmony Project. By providing free community music instruction for disadvantaged children, Harmony Project promotes the healthy development of children as learners, the development of children as ambassadors of peace and understanding, and the development of stronger communities. Children who were more engaged in the music program—as defined by better attendance and classroom participation—developed stronger brain encoding of speech after 2 years than their less-engaged peers in the program. Additionally, children who were more engaged in the program showed increases in reading scores, while those less engaged did not show improvements. The neural gains accompanying music engagement were seen in the very measures of neural speech processing that are weaker in children from disadvantaged backgrounds. Our results suggest that community music programs such as Harmony Project provide a form of auditory enrichment that counteracts some of the biological adversities of growing up in poverty, and can further support community-based interventions aimed at improving child health and wellness.

Why do I hear but not understand? Stochastic undersampling as a model of degraded neural encoding of speech.

Hearing impairment is a serious disease with increasing prevalence. It is defined based on increased audiometric thresholds but increased thresholds are only partly responsible for the greater difficulty understanding speech in noisy environments experienced by some older listeners or by hearing-impaired listeners. Identifying the additional factors and mechanisms that impair intelligibility is fundamental to understanding hearing impairment but these factors remain uncertain. Traditionally, these additional factors have been sought in the way the speech spectrum is encoded in the pattern of impaired mechanical cochlear responses. Recent studies, however, are steering the focus toward impaired encoding of the speech waveform in the auditory nerve. In our recent work, we gave evidence that a significant factor might be the loss of afferent auditory nerve fibers, a pathology that comes with aging or noise overexposure. Our approach was based on a signal-processing analogy whereby the auditory nerve may be regarded as a stochastic sampler of the sound waveform and deafferentation may be described in terms of waveform undersampling. We showed that stochastic undersampling simultaneously degrades the encoding of soft and rapid waveform features, and that this degrades speech intelligibility in noise more than in quiet without significant increases in audiometric thresholds. Here, we review our recent work in a broader context and argue that the stochastic undersampling analogy may be extended to study the perceptual consequences of various different hearing pathologies and their treatment.

Topographic recordings of auditory evoked potentials to speech: subcortical and cortical responses.

Topographies of speech auditory brainstem response (speech ABR), a fine electrophysiological marker of speech encoding, have never been described. Yet, they could provide useful information to assess speech ABR generators and better characterize populations of interest (e.g., musicians, dyslexics). We present here a novel methodology of topographic speech ABR recording, using a 32-channel low sampling rate (5 kHz) EEG system. Quality of speech ABRs obtained with this conventional multichannel EEG system were compared to that of signals simultaneously recorded with a high sampling rate (13.3 kHz) EEG system. Correlations between speech ABRs recorded with the two systems revealed highly similar signals, without any significant difference between their signal-to-noise ratios (SNRs). Moreover, an advanced denoising method for multichannel data (denoising source separation) significantly improved SNR and allowed topography of speech ABR to be recovered.