Speech Reception Threshold Estimation via EEG-Based Continuous Speech Envelope Reconstruction.

Previous studies have demonstrated the feasibility of estimating the speech reception threshold (SRT) based on electroencephalography (EEG), termed SRTneuro, in younger normal-hearing (YNH) participants. This method may support speech perception in hearing-aid users through continuous adaptation of noise-reduction algorithms. The prevalence of hearing impairment and thereby hearing-aid use increases with age. The SRTneuro estimation is based on envelope reconstruction accuracy, which has also been shown to increase with age, possibly due to excitatory/inhibitory imbalance or recruitment of additional cortical regions. This could affect the estimated SRTneuro. This study investigated the age-related changes in the temporal response function (TRF) and the feasibility of SRTneuro estimation across age. Twenty YNH and 22 older normal-hearing (ONH) participants listened to audiobook excerpts at various signal-to-noise ratios (SNRs) while EEG was recorded using 66 scalp electrodes and 12 in-ear-EEG electrodes. A linear decoder reconstructed the speech envelope, and the Pearson's correlation was calculated between the reconstructed and speech-stimulus envelopes. A sigmoid function was fitted to the reconstruction-accuracy-versus-SNR data points, and the midpoint was used as the estimated SRTneuro. The results show that the SRTneuro can be estimated with similar precision in both age groups, whether using all scalp electrodes or only those in and around the ear. This consistency across age groups was observed despite physiological differences, with the ONH participants showing higher reconstruction accuracies and greater TRF amplitudes. Overall, these findings demonstrate the robustness of the SRTneuro method in older individuals and highlight its potential for applications in age-related hearing loss and hearing-aid technology.

Purpose:Signal‐to‐noise ratio(SNR) of MR abdominal imaging in diagnostic radiology is maximized by minimizing the coil‐to‐patient distance. However, for radiotherapy applications, customized vacuum‐bag is needed for abdominal immobilization at the cost of the increasing distance to the posterior spine coil. This sub‐optimized coil setting for RT applications may compromise image quality, such as SNR and homogeneity, thus potentially affect tissue delineation. In this study, we quantitatively evaluate the effect of the vertical position change on SNR and image quality change using an ACR MR phantom.Methods:An ACR MR phantom was placed on the flat couch top. Images were acquired using an 18‐channel body array coil and spine coil on a dedicated 1.5T MR‐simulator. The scan was repeated three times with the ACR phantom elevated up to 7.5cm from the couch top, with a step size of 2.5cm. All images were acquired using standard ACR test sequence protocol of 2D spin‐echo T1‐weighted(TR/TE=500/200ms) and T2‐weighted(TR/TE1/TE2=2000/20/80) sequences. For all scans, pre‐scan normalization was turned on, and the distance between the phantom and the anterior 18‐channel body array coil was kept constant. SNR was calculated using the slice with a large water‐only region of the phantom. Percent intensity uniformity(PIU) and low contrast object detectability(LCD) were assessed by following ACR test guidelines.Results:The decrease in image SNR(from 335.8 to 169.3) and LCD(T1: from 31 to 19 spokes, T2: 26 to 16 spokes) were observed with increasing vertical distance. After elevating the phantom by 2.5cm(approximately the thickness of standard vacuum‐bag), SNR change(from 335.8 to 275.5) and LCD(T1: 31 to 26 spokes, T2: 26 to 21 spokes) change were noted. However, similar PIU was obtained for all choices of vertical distance (T1: 94.5%–95.0%, T2: 94.4%–96.8%).Conclusion:After elevating the scan object, reduction in SNR level and contrast detectability but no change in image homogeneity was observed.

Perception of sounds and speech involves structures in the auditory brainstem that rapidly process ongoing auditory stimuli. The role of these structures in speech processing can be investigated by measuring their electrical activity using scalp-mounted electrodes. However, typical analysis methods involve averaging neural responses to many short repetitive stimuli that bear little relevance to daily listening environments. Recently, subcortical responses to more ecologically relevant continuous speech were detected using linear encoding models. These methods estimate the temporal response function (TRF), which is a regression model that minimises the error between the measured neural signal and a predictor derived from the stimulus. Using predictors that model the highly non-linear peripheral auditory system may improve linear TRF estimation accuracy and peak detection. Here, we compare predictors from both simple and complex peripheral auditory models for estimating brainstem TRFs on electroencephalography (EEG) data from 24 participants listening to continuous speech. We also investigate the data length required for estimating subcortical TRFs, and find that around 12 minutes of data is sufficient for clear wave V peaks (>3 dB SNR) to be seen in nearly all participants. Interestingly, predictors derived from simple filterbank-based models of the peripheral auditory system yield TRF wave V peak SNRs that are not significantly different from those estimated using a complex model of the auditory nerve, provided that the nonlinear effects of adaptation in the auditory system are appropriately modelled. Crucially, computing predictors from these simpler models is more than 50 times faster compared to the complex model. This work paves the way for efficient modelling and detection of subcortical processing of continuous speech, which may lead to improved diagnosis metrics for hearing impairment and assistive hearing technology.

This study aimed to characterize horizontal plane sound localization in interfering noise at different signal-to-noise ratios (SNRs) and to compare performance across normal-hearing listeners and users of unilateral and bilateral cochlear implants (CIs). CI users report difficulties with listening in noisy environments. Although their difficulties with speech understanding have been investigated in several studies, the ability to localize sounds in background noise has not extensively been examined, despite the benefits of binaural hearing being greatest in noisy situations. Sound localization is a measure of binaural processing and is thus well suited to assessing the benefit of bilateral implantation. The results will inform clinicians and implant manufacturers how to focus their efforts to improve localization with CIs in noisy situations. Six normal-hearing listeners, four unilateral, and 10 bilateral CI users indicated the perceived location of sound sources using a light pointer method. Target sounds were noise pulses played from one of 11 loudspeakers placed between -80 and +80 degrees in the frontal horizontal plane in the free field. Localization was assessed in quiet and in diffuse background noise at SNRs between +10 and -7 dB. Speech reception thresholds were measured and their relation to the localization results examined. Localization performance declined with decreasing SNR: target sounds were perceived closer to the median plane and the standard deviation of responses increased. Localization performance across groups was compared using a measure of "Spatial Resolvability" (SR). This measure gives the angular separation between two sound sources that would enable an ideal observer to correctly distinguish them 69.1% of the time. For all participants SR increased with decreasing SNR, that is, at low SNRs the spatial separation between sound sources remained distinguishable only when it was larger. Normal-hearing participants performed best, with SR between 1.4 and 5.1 degrees in quiet. Bilateral CI users showed SR between 8.3 and 43.6 degrees in quiet, corresponding approximately to the spatial resolution of normal-hearing listeners at an SNR of -5 dB. Most bilateral CI users had lost the ability to correctly determine which side the sound came from at an SNR of -3 dB. Overall, the SNR had to be at least +7 dB to achieve localization performance near to that in quiet for all bilateral CI users. No significant correlation was found between spatial resolution and speech reception thresholds, but the speech processor sensitivity setting did significantly affect performance. Unilateral CI users showed the most severe localization problems, with only two of four participants being able to correctly determine which side sounds came from in quiet. This study is the first to examine sound localization with CIs at various SNRs and to compare it with normal hearing. The results confirm that localization with CIs is strongly disrupted in noisy situations. Bilateral CIs were shown to be clearly superior over unilateral CIs for localization in quiet and in noisy situations. With bilateral CIs, localization declined at moderately high absolute noise levels (>63 dB SPL), suggesting that an extension of the acoustic-dynamic range to higher levels would be beneficial. The absence of a relation between speech reception thresholds and spatial resolution highlights the need for additional clinical tests to assess the binaural benefit of a second implant.

Objective To explore the detection of cortical responses to continuous speech using a single EEG channel. Particularly, to compare detection rates and times using a cross-correlation approach and parameters extracted from the temporal response function (TRF). Design EEG from 32-channels were recorded whilst presenting 25-min continuous English speech. Detection parameters were cross-correlation between speech and EEG (XCOR), peak value and power of the TRF filter (TRF-peak and TRF-power), and correlation between predicted TRF and true EEG (TRF-COR). A bootstrap analysis was used to determine response statistical significance. Different electrode configurations were compared: Using single channels Cz or Fz, or selecting channels with the highest correlation value. Study sample Seventeen native English-speaking subjects with mild-to-moderate hearing loss. Results Significant cortical responses were detected from all subjects at Fz channel with XCOR and TRF-COR. Lower detection time was seen for XCOR (mean = 4.8 min) over TRF parameters (best TRF-COR, mean = 6.4 min), with significant time differences from XCOR to TRF-peak and TRF-power. Analysing multiple EEG channels and testing channels with the highest correlation between envelope and EEG reduced detection sensitivity compared to Fz alone. Conclusions Cortical responses to continuous speech can be detected from a single channel with recording times that may be suitable for clinical application.

Purpose: While 4DCT provides organ/tumor motion information, it often samples data over 10–20 breathing cycles. For patients presenting with compromised pulmonary function, breathing patterns can change over the acquisition time, potentially leading to tumor delineation discrepancies. This work introduces a novel adaptive velocity-modulated binning (AVB) 4DCT algorithm that modulates the reconstruction based on the respiratory waveform, yielding a patient-specific 4DCT solution. Methods: AVB was implemented in a research reconstruction configuration. After filtering the respiratory waveform, the algorithm examines neighboring data to a phase reconstruction point and the temporal gate is widened until the difference between the reconstruction point and waveform exceeds a threshold value—defined as percent difference between maximum/minimum waveform amplitude. The algorithm only impacts reconstruction if the gate width exceeds a set minimum temporal width required for accurate reconstruction. A sensitivity experiment of threshold values (0.5, 1, 5, 10, and 12%) was conducted to examine the interplay between threshold, signal to noise ratio (SNR), and image sharpness for phantom and several patient 4DCT cases using ten-phase reconstructions. Individual phase reconstructions were examined. Subtraction images and regions of interest were compared to quantify changes in SNR. Results: AVB increased signal in reconstructed 4DCT slices for respiratory waveforms that met the prescribed criteria. For the end-exhale phases, where the respiratory velocity is low, patient data revealed a threshold of 0.5% demonstrated increased SNR in the AVB reconstructions. For intermediate breathing phases, threshold values were required to be >10% to notice appreciable changes in CT intensity with AVB. AVB reconstructions exhibited appreciably higher SNR and reduced noise in regions of interest that were photon deprived such as the liver. Conclusion: We demonstrated that patient-specific velocity-based 4DCT reconstruction is feasible. Image noise was reduced with AVB, suggesting potential applications for low-dose acquisitions and to improve 4DCT reconstruction for irregular breathing patients. The submitting institution holds research agreements with Philips Healthcare.

The auditory brainstem response (ABR) is a measure of subcortical activity in response to auditory stimuli. The wave V peak of the ABR depends on the stimulus intensity level, and has been widely used for clinical hearing assessment. Conventional methods estimate the ABR average electroencephalography (EEG) responses to short unnatural stimuli such as clicks. Recent work has moved toward more ecologically relevant continuous speech stimuli using linear deconvolution models called temporal response functions (TRFs). Investigating whether the TRF waveform changes with stimulus intensity is a crucial step toward the use of natural speech stimuli for hearing assessments involving subcortical responses. Here, we develop methods to estimate level-dependent subcortical TRFs using EEG data collected from 21 participants listening to continuous speech presented at 4 different intensity levels. We find that level-dependent changes can be detected in the wave V peak of the subcortical TRF for almost all participants, and are consistent with level-dependent changes in click-ABR wave V. We also investigate the most suitable peripheral auditory model to generate predictors for level-dependent subcortical TRFs and find that simple gammatone filterbanks perform the best. Additionally, around 6 min of data may be sufficient for detecting level-dependent effects and wave V peaks above the noise floor for speech segments with higher intensity. Finally, we show a proof-of-concept that level-dependent subcortical TRFs can be detected even for the inherent intensity fluctuations in natural continuous speech.

Everyday speech perception often occurs in multimodal environments, requiring listeners to divide attention across sensory modalities to prioritize relevant information. Although this division of attention modestly reduces cortical encoding of natural continuous speech, its impact on subcortical processing remains unclear. To investigate this, we used an audiovisual dual-task paradigm to manipulate bimodal divided attention. Participants completed a primary visual memory task (low or high cognitive load) while simultaneously performing a secondary task of listening to audiobook segments. Sixteen young adults with normal hearing completed these tasks while their EEG signals were recorded. In a third condition, participants performed only the listening task. Subcortical responses to the audiobook segments were analyzed using temporal response functions (TRFs), which predicted EEG responses from speech predictors derived from auditory nerve models. Across all conditions, TRFs displayed a prominent peak at ∼8 ms, resembling the wave V peak of auditory brainstem responses, indicating subcortical origins. No significant differences in latencies or amplitudes of this peak, nor in TRF prediction correlations, were observed between conditions. These findings provide no evidence that bimodal divided attention affects the subcortical processing of continuous speech, indicating that its effects may be restricted to cortical levels.NEW & NOTEWORTHY This study shows that auditory subcortical processing of natural continuous speech remains unaffected when attention is divided across auditory and visual modalities. These findings indicate that the influence of crossmodal attention on the processing of natural continuous speech may be restricted to cortical levels.

For moderate hearing impairment, the speech‐reception threshold (SRT) for sentences in stationary noise is roughly up to 5 dB higher than for normal hearing. However, a fluctuating interfacing sound seems more typical for everyday listening conditions than stationary noise. For a group of young hearing‐impaired listeners, the difference in SRT with normal‐hearing listeners increased from 2.7 dB for stationary noise to 7 dB for 100% sinusoidally intensity‐modulated noise, and even to 10.5 dB for interfering speech. In this experiment, the interfering speech was the time‐reversed voice of the same speaker as the signal, which may have introduced an extra difficulty. In a subsequent experiment, the SRT for sentences from two speakers (one male and one female) was measured with a variety of fluctuating maskers covering the range from stationary noise to interfering speech. The two voices were mutually used as masker, giving a meaningful interference. Meaningless interference was obtained by time reversal of the interfering speech or by modulating noise with the envelope of speech. Two types of modulation were used: one broadband and one in which high‐ and low‐frequency noise (separation frequency 1000 Hz) was modulated with the high‐ and low‐frequency envelope of speech, respectively.

This paper introduces a novel technique for signal-to-noise ratio (SNR) estimation for scenarios where two closely-spaced microphones are available. The proposed technique utilizes the real and imaginary parts of the coherence function between the input signals to estimate the SNR without assuming prior knowledge of the noise statistics. The corresponding dual-microphone speech enhancement algorithm utilizes a Wiener filter as a gain function constructed using the SNR values computed by the coherence function. Since the proposed SNR estimation technique does not require access to noise statistics, it can be applied in situations where interfering speakers are present. An adaptive speech reception threshold (SRT) test was used to assess the intelligibility of speech processed by the proposed algorithm in scenarios where one or two interfering talkers were present in anechoic and reverberant conditions. Intelligibility listening tests were conducted with both normal-hearing (NH) and cochlear implant (CI) listeners. Results revealed significant improvements in intelligibility and quality over a (baseline) fixed directional algorithm and a well-established beamformer algorithm. In a nearly anechoic room with competing talkers, the improvement in SRT obtained relative to the directional microphone ranged from 5-10 dB, while the improvement obtained by the beamformer was about 2 dB. In reverberant environments, the improvement in SRT remained high (4-7 dB) at T60 = 220 ms, and decreased to 1-2 dB at T60 = 465 ms. Overall, the proposed algorithm provided significant benefits in intelligibility in anechoic and mildly reverberant environments making it suitable for hearing aid and cochlear implant applications.

Speech perception in noise is an important aspect of the rehabilitation of children with hearing loss. We aimed to evaluate the feasibility and reliability of the Dutch digits-in-noise (DIN) test in the clinical follow-up of children with hearing aids (HAs) and/or cochlear implants (CIs). A second aim of the study was to gain insight in the speech perception in noise performance of children with different degrees of hearing loss. We retrospectively analyzed DIN test data of Dutch-speaking children with hearing loss (N = 188; 5 to 18 years old). A free-field version of the DIN-test was used. Children with open-set phoneme recognition in quiet of >70% at 65 dB SPL (best aided condition) were included. Ages ranged from 5 to 18 years old. All were experienced HA or CI users and had used their device(s) for at least 1 year before the measurement in the study. The DIN-test was performed in the framework of a clinical rehabilitation program. During testing, children wore their own devices with normal daily programs. The average speech reception threshold (SRT) was -3.6 dB (SD 3.6) for the first list and significantly improved to -4.0 dB (SD 3.1) for the second list. HA users had a 4-dB better SRT compared with CI users. The larger the child's hearing loss, the worse the SRT is. However, 15% of the children who completed a first list of 24 trials were unable to complete a second list. Mean adaptive staircase trajectories across trials suggested that learning occurred throughout the first list, and that loss of sustained attention contributed to response variability during the second list. The DIN test can be used to assess speech perception in noise abilities for children with different degrees of hearing loss and using HAs or CIs. The children with hearing loss required a higher signal-to-noise ratio (SNR) than did normal-hearing children and the required SNR is larger as the hearing loss increases. However, the current measurement procedure should be optimized for use in standard pediatric audiological care, as 15% of the children were unable to conduct a second list after the first list to reach a more stable SNR.

Neural envelope tracking predicts speech intelligibility and hearing aid benefit in children with hearing loss

Leading and following: Noise differently affects semantic and acoustic processing during naturalistic speech comprehension

To prospectively evaluate ultrasmall superparamagnetic iron oxide (USPIO) magnetic resonance (MR) imaging for the depiction of macrophages in infected areas of an experimental rabbit vertebral osteomyelitis model. Lumbar vertebral osteomyelitis was induced in 10 rabbits with intradiscal injection of bacteria in a vertebral disk (test level) versus saline injection in another disk (control level). After a mean interval of 12 days, rabbits were imaged prior to and 24 hours after administration of USPIO. The MR imaging protocol included T1-weighted spin-echo, T2-weighted fast spin-echo, and T2*-weighted gradient-echo sequences. MR findings were compared with histologic findings (macrophage immunostaining and Perls Prussian blue staining). A Wilcoxon signed rank test was used to compare signal-to-noise ratio (SNR) results before and after USPIO administration. T1-weighted MR images of infected vertebral test levels obtained 24 hours after USPIO administration showed a significant increase in SNR (P = .005), whereas T2- and T2*-weighted images showed no significant changes in SNR (P = .14 and P = .87, respectively). Histologic examination results of infected areas demonstrated complete replacement of hematopoietic bone marrow by macrophage infiltration. Perls Prussian blue staining showed that some macrophages were iron loaded. T1- (P = .02), T2- (P = .04), and T2*-weighted (P = .04) images of control vertebrae showed a significant decrease in SNR. Histologic examination results confirmed the persistence of normal hematopoietic bone marrow without macrophage infiltration, which was reflected by more intensive Perls Prussian blue staining compared with that in infected areas. MR imaging can depict USPIO-loaded macrophage infiltration present in infected areas in an experimental rabbit model of vertebral osteomyelitis.

There is evidence from past animal work that the neural signal-to-noise ratio (SNR) is modulated through the action of the medial olivocochlear reflex (MOCR). This is commonly referred to as unmasking. However, evidence of unmasking in humans is limited, perhaps due to the traditional approach of measuring the MOCR using otoacoustic emissions-a preneural metric. The amplitudes and latencies of the late latency response (LLR) are sensitive to changes in SNR and may provide a means to noninvasively evaluate MOCR unmasking at the neural level. The purpose of this study was to investigate MOCR-mediated enhancement of ipsilateral noise in humans using the LLR. Fifty normal-hearing adults were recruited. The LLR was measured for a 60 dB SPL, 1-kHz tone in both ipsilateral quiet and ipsilateral noise, with and without presentation of contralateral noise. For the ipsilateral noise conditions, the noise was presented at three different levels to achieve SNRs of +5 dB, +15 dB, and +25 dB. The contralateral noise was always 60 dB SPL white noise. LLR latencies (P1, N1, and P2) and interpeak amplitudes (P1-N1 and N1-P2) were measured for all conditions. In addition, otoacoustic emissions (OAEs) for a 1-kHz tone burst were measured in ipsilateral quiet both with and without contralateral noise. The same contralateral noise was used for both OAEs and LLRs. For the ipsilateral noise conditions, SNR had a significant effect on LLR latencies and interpeak amplitudes: Latencies decreased, and amplitudes increased as SNR improved. The presentation of contralateral noise had a significant effect on P1 and N1 latencies, both of which decreased. LLR interpeak amplitudes significantly increased upon the presentation of contralateral noise. For the ipsilateral quiet condition, there were no significant effects of contralateral noise on LLR metrics. Though OAE magnitudes were significantly reduced upon presentation of contralateral noise, consistent significant relationships between OAE magnitude changes and changes in the LLR metrics were not found. Findings suggest that the presentation of contralateral noise enhances the neural response to an ipsilateral noise, potentially through MOC efferent feedback. https://doi.org/10.23641/asha.29441903.