Search

[ES] Este docuemnto es un resumen en el cual se explica la metodoligia que vamos a seguir para la realización del experimento que pretende evaluar como afecta el de radio de la cabeza en la percepción y localización de los sonidos. Por lo tanto nuestro trabajo consistirá en evaluar la percepción del sonido por parte del ser humano e intentar mejorarla mediante una serie de experimentos que tienen como referencia la Función de Transferencia Relativa a la Cabeza (HRTF)., [EN] In the present article the methodology followed for the realization of the experimental is defined, which aims to evaluate how the head radio affects the perception and location of sounds. It has been tried to evaluate the perception of the sound on the part of the human being and to try to improve it by means of a series of experiments that have as reference the Relative Function to the Head (HRTF).

Binaural Ambisonic rendering is widely used in immersive applications such as virtual reality due to its sound field rotation capabilities. Binaural Ambisonic reproduction can theoretically replicate the original sound field exactly for frequencies up to what is commonly referred to as the `spatial aliasing frequency', $f_{alias}$. At frequencies above $f_{alias}$ however, reproduction can become inaccurate due to the limited spatial accuracy of reproducing a physical sound field with a finite number of transducers, which in practice causes localisation blur, reduced lateralisation and comb filtering spectral artefacts. The standard approach to improving Ambisonic reproduction is to increase the order of Ambisonics, which allows for exact sound field reproduction up to a higher $f_{alias}$, though at the expense of more channels for storage, more microphone capsules for recording, and more convolutions in binaural reproduction. It is therefore highly desirable to explore alternative methods of improving low-order Ambisonic rendering. One common practice is to employ a dual-band decoder with basic Ambisonic decoding at low frequencies and Max $r_E$ channel weighting above $f_{alias}$, which improves spectral, localisation and lateralisation reproduction. Virtual loudspeaker binaural Ambisonic decoders can be made by multiplying each loudspeaker's head-related impulse responses (HRIRs) with the decode matrix coefficients and summing the resulting spherical harmonic (SH) channels. This approach allows for dual-band decoding and loudspeaker configurations with more loudspeakers than SH channels whilst minimising the required number of convolutions. Binaural Ambisonic reproduction using the virtual loudspeaker approach is then achieved by a summation of direct convolution of each SH channel of the encoded signal with the corresponding SH channel of the binaural decoder. This paper presents the method and results of a perceptual comparison of state-of-the-art pre-processing techniques for virtual loudspeaker binaural Ambisonic rendering. By implementing these pre-processing techniques in the HRTFs used in the virtual loudspeaker binaural rendering stage, improvements can be made to the rendering. All pre-processing techniques are implemented offline, such that the resulting binaural decoders are of the same size and require the same number of real-time convolutions.The three pre-processing techniques investigated in this study are:\begin{itemize} \item Diffuse-field Equalisation (DFE) \item Ambisonic Interaural Level Difference Optimisation (AIO) \item Time Alignment (TA) \end{itemize}DFE is the removal of direction-independent spectral artefacts in the Ambisonic diffuse-field. AIO augments the gains of the left and right virtual loudspeaker HRTF signals above $f_{alias}$ such that Ambisonic renders produce more accurate interaural level differences (ILDs). TA is the removal of interaural time differences (ITDs) between the HRTFs above $f_{alias}$ to reduce high frequency comb filtering effects.The test follows the multiple stimulus with hidden reference and anchors (MUSHRA) paradigm, ITU-R BS.1534-3. Tests are conducted in a quiet listening room using a single set of Sennheiser HD~650 circum-aural headphones and an Apple Macbook Pro with a Fireface UCX audio interface, which has software controlled input and output levels. Headphones are equalised from the RMS average of 11 impulse response measurements, with 1 octave band smoothing in the inverse filter. All audio is 24-bit depth and 48~kHz sample rate. Listening tests are conducted using first, third and fifth order Ambisonics, with respective loudspeaker configurations comprising 6, 26 and 50 loudspeakers, arranged in Lebedev grids. The different test conditions are made up of various combinations of the three pre-processing techniques. The test conditions are as follows:\begin{enumerate} \item HRTF convolution (reference) \item Standard Ambisonic (dual band) \item Ambisonic with DFE (dual band) \item Ambisonic with AIO (dual band) \item Ambisonic with AIO \ DFE (dual band) \item Ambisonic with TA \ DFE (basic) \item Ambisonic with TA \ AIO \ DFE (basic) \item Ambisonic with TA \ AIO \ DFE (dual band)\end{enumerate}The stimuli are synthesised complex acoustic scenes, defined in this paper as an acoustic scene with multiple sources. The synthesised complex scene used in this paper is composed from 24 freely available stems of an orchestra. Instruments are isolated and empirically matched in loudness. The orchestral stems are panned to the vertices of a 24 pt. T-design arrangement, to ensure minimal overlap between virtual loudspeaker positions in the binaural decoders and the sound sources in the complex scene. Synthesising complex scenes in this way allows for an explicit target reference stimulus - in this case a direct HRTF convolved render. If the Ambisonic stimuli are perfectly reconstructed, they will be equivalent to the reference stimulus. Results are analysed using non-parametric statistics and discussed in the full manuscript. The conclusion suggests the perceptually preferred pre-processing algorithms for virtual loudspeaker binaural Ambisonic rendering./latex

Listening tests are the most used method for evaluation of human preferences and perception of sound. This paper presents an overview of main tools and standards for the design of listening tests. Several key standards for ITU- T and ITU-R recommendations are covered, such as ITU-R BS.1116-1 and BS.1534-1 and ITU-T P.800. The list of modern listening test tools for effective design of listening tests is presented as well, showing which standardized listening tests each of the tools covers, along with the associated development software or programming language used for building each tool. Furthermore, the paper gives an overview of the main aspects of Ambisonics and binaural systems as the most commonly used platforms for spatial sound reproduction, and discusses their advantages and disadvantages for specific use in listening tests. Ideas for further study of the influence of different reproduction systems on listening tests are presented as well.

International audience; The purpose of this study is to examine whether brain imagery could provide new insights into the assessment of the listening experience of spatial audio content. Conventional methods of assessing sound reproduction are based on either quality or localization judgments. Their main disadvantage is that the subject is aware of his(her) rating task. In addition, dimensions such as emotions or cognitive load are generally not taken into account. Therefore, our objective is to explore cognitive processes involved when listening to spatial audio content by electroencephalography (EEG) measurement. Descriptors of the listening experience (e.g. immersion, realism) are sought in the electrical activity of the brain.The experiment is based on a reversed implementation of the oddball paradigm. The participant is presented a sequence of visual stimuli (320), which is composed of standard (265) and deviant (55) stimuli. These latter are introduced to cause a surprise effect, that will induce an event-related potential (ERP), known as the « P300 » in the brain. The participant is asked to click whenever he(she) detects a deviant stimulus. Audio stimuli are used to interfere with the detection task. The objective is to observe the effect of such distractors on the P300 response as a function of the type of sound spatialization. Binaural and stereophonic reproductions are compared. It is expected that the distracting effect of binaural reproduction is stronger than that of stereophony. Evidence of this will be sought in both behavioral data (i.e. the performances in detecting deviant stimuli) and EEG measurements. During the experiment, an EEG net of 256 electrodes was placed on the participant’s head to record his(her) brain activity. In addition, a headphone (Sennheiser HD650) was arranged over it to reproduce sound scenes that have been previously recorded in the experimental room. The pretext for justifying the use of a headphone was a listening session as a further step in the experiment. The participant was thus not aware that virtual sounds were going to be played by headphones, and that his(her) listening experience was under study, which was one novelty of this study. Besides, at no time was he(she) asked direct questions about the quality of sound reproduction.The sound scenes contained ambient noise in combination with isolated sounds potentially emanating from the experimenter (e.g. falling keys, running water from a tap, leafing through a book, …), but they were totally free from speech and music signals. The listening level was adjusted to 60 dBA. The oddball experiment was repeated twice: once with the binaural recording (by a dummy head Neumann KU 100) and the other time with the stereophonic recording (by a XY pair). The presentation order was randomized. Intensity stereophony was chosen to provide the highest contrast with binaural spatialization which uses both interaural differences of time and level, as well as spectral cues. The binaural and stereophonic scenes were similar but not identical to prevent any habituation effect.At the beginning of the experiment, the participant was undergoing a training phase for the visual detection task. At the end, he(she) had to complete a questionnaire about the task difficulty, the level of immersion. It was also checked whether he(she) realized that sounds were coming from the headphone. 19 subjects took part into the experiment. EEG measurements were first pre-processed (elimination of electrodes with anomalies, denoising). Only 124 electrodes were retained. The data set consisted of 6080 trials, 1045 of which were deviants. The cortical electrical activity was reconstructed from surface signals. Event-Related Potentials (ERP) were averaged per electrode and per subject for each condition. The differential response between standard and deviant stimuli was examined as a function of the audio distractor (binaural or stereophonic). Cluster of adjacent electrodes with similar differential responses were then clustered. Two Regions Of Interest (ROI) were identified in the frontal and the parietal areas. It was observed that the P300 amplitude was significantly higher in presence of the binaural distractor than for the stereophonic one, suggesting a stronger effect of surprise possibly caused by a more immersive reproduction. This was confirmed by behavioral results which showed a longer response time for binaural distractors (566 ms) than for stereophonic ones (550 ms). However, the detection error rate was not significantly different between the two conditions.

Este trabajo consiste en la realización de un relato sonoro, utilizando técnicas de mezcla binaural, con el fin de conseguir un producto que al ser escuchado con auriculares produzca la sensación de espacialización tridimensional de las acciones y escenas descritas en él. Se realizará todo el proceso, desde la pre-producción en la que se elaborará el guión, pasando por la grabación del material sonoro que se usará en la última fase, la postproducción binaural, que será hecha mediante el software Logic Pro X de Apple., This essay describes a sound story¿s realization, by using binaural mixing techniques, in order to achieve a product that, when listened using headphones, produces a three-dimensional sensation of the actions and scenes described in it. The whole process will be done, from the pre-production, elaborating the script, through the recording of the sound material that will be used in the last phase: the binaural post-production, made with the Apple¿s software Logic Pro X.

Desenvolveu-se um protótipo de um sistema de audio-guiding que permite associar fontes sonoras virtuais aos pontos focais de cada rota de visita e aplicar, na reprodução estereofónica através de auscultadores, um efeito de espacialização controlado em tempo real pela pose (posição e orientação da cabeça) do utilizador relativamente a esses pontos. É assim criado um efeito de realidade aumentada, com os conteúdos áudio (virtuais) a parecerem provir de pontos (reais) especificados. Foi desenvolvido um programa de gestão de rotas para especificar previamente os pontos focais (através de coordenadas GPS), o conteúdo áudio (ficheiro monofónico) pretendido para cada e o ponto do trajeto em que deve ser iniciada a reprodução. Para detetar posição, usou-se um recetor GPS ligado à plataforma de computação transportada pelo utilizador; para monitorizar continuamente os movimentos da sua cabeça (head-tracking), recorreu-se a um sensor inercial (InertiaCube) acoplado aos auscultadores. A aplicação principal, desenvolvida em linguagem C++, recorre a buffers circulares implementados em software para realizar, com a mínima latência possível, o streaming áudio a partir dos ficheiros de entrada. O processamento baseia-se numa biblioteca (‘motor’) de auralização em tempo real que utiliza bases de dados de HRTF de acesso público. Para escolher o par de HRTF a utilizar em cada ciclo de processamento, o azimute e a elevação da fonte virtual são continuamente recalculados em função dos dados recolhidos sobre a pose do utilizador. Para avaliar o funcionamento da aplicação, identificar possíveis problemas e caracterizar as gamas mais adequadas para determinados parâmetros (e.g. tamanho de buffers, número de amostras por bloco de áudio, janela de filtragem dos dados GPS), efetuaram-se testes subjetivos preliminares, com dez sujeitos a percorrer uma rota criada para o efeito. Embora confirmando a capacidade de obter o efeito sonoro pretendido, os testes evidenciaram a necessidade de melhorar a precisão dos dados de posição, principal fator a afetar negativamente a qualidade da experiência. An audio-guiding system prototype was developed which makes it possible to associate virtual sound sources to the focal points of each tourist route and apply, in the stereophonic reproduction over headphones, a spatialisation effect controlled in real time by user pose (position and head orientation) relative to those points. An augmented reality effect is thus achieved, with the (virtual) audio content seemingly originating from specified (real) points. A route management program was developed to allow specification of the focal points (through GPS coordinates), audio content (monophonic file) intended for each and route point where its playback should be triggered. Position was detected by a GPS receptor plugged into the computing platform carried by the user; head-tracking was based on an inertial sensor (InertiaCube) attached to the headphone strap. The main application, developed in C++, implemented software buffers to stream audio through from the input files with the lowest possible latency. The processing resorts to a real-time auralisation engine using a public access HRTF database. In order to choose the appropriate HRTF pair for each processing cycle, the azimuth and elevation of the virtual source are continuously recalculated according to the acquired user pose data. In order to assess performance, identify possible problems and characterise the most appropriate application parameter ranges (e.g. buffer size, number of samples per audio block, filtering window for GPS data), preliminary subjective tests were carried out, with ten subjects following a route created for this purpose. Whilst confirming the ability to provide the desired audio spatialisation effects, the tests also evidenced the need to improve the precision of position data, as this was the main factor negatively affecting the experience. Mestrado em Engenharia Eletrónica e Telecomunicações

The below product proposal is inspired by the Waves NX application and plugin (Waves, 2018). It aims to show the digital audio signal processes that the author has implemented and researched over the Semester for this specific application.

The brainstem's lateral superior olive (LSO) is thought to be crucial for localizing high-frequency sounds by coding interaural sound level differences (ILD). Its neurons weigh contralateral inhibition against ipsilateral excitation, making their firing rate a function of the azimuthal position of a sound source. Since the very first in vivo recordings, LSO principal neurons have been reported to give sustained and temporally integrating 'chopper' responses to sustained sounds. Neurons with transient responses were observed but largely ignored and even considered a sign of pathology. Using the Mongolian gerbil as a model system, we have obtained the first in vivo patch clamp recordings from labeled LSO neurons and find that principal LSO neurons, the most numerous projection neurons of this nucleus, only respond at sound onset and show fast membrane features suggesting an importance for timing. These results provide a new framework to interpret previously puzzling features of this circuit. ispartof: ELIFE vol:7 ispartof: location:England status: published

The capacity of the auditory system to extract spatial information relies principally on the detection and interpretation of binaural cues, i.e., differences in the time of arrival or level of the sound between the two ears. In this review, we consider the effects of unilateral or asymmetric hearing loss on spatial hearing, with a focus on the adaptive changes in the brain that may help to compensate for an imbalance in input between the ears. Unilateral hearing loss during development weakens the brain's representation of the deprived ear, and this may outlast the restoration of function in that ear and therefore impair performance on tasks such as sound localization and spatial release from masking that rely on binaural processing. However, loss of hearing in one ear also triggers a reweighting of the cues used for sound localization, resulting in increased dependence on the spectral cues provided by the other ear for localization in azimuth, as well as adjustments in binaural sensitivity that help to offset the imbalance in inputs between the two ears. These adaptive strategies enable the developing auditory system to compensate to a large degree for asymmetric hearing loss, thereby maintaining accurate sound localization. They can also be leveraged by training following hearing loss in adulthood. Although further research is needed to determine whether this plasticity can generalize to more realistic listening conditions and to other tasks, such as spatial unmasking, the capacity of the auditory system to undergo these adaptive changes has important implications for rehabilitation strategies in the hearing impaired., Highlights • Unilateral hearing loss in infancy can disrupt spatial hearing, even after binaural inputs are restored. • Plasticity in the developing brain enables substantial recovery in sound localization accuracy. • Adaptation to unilateral hearing loss is based on reweighting of monaural spectral cues and binaural plasticity. • Training on auditory tasks can partially compensate for unilateral hearing loss, highlighting potential therapies.

International audience; This study evaluates several methods for reporting the perceived location of real sound sources. It is well known that the method used for collecting judgments in auditory-localization experiments has a strong influence on the accuracy of a subject’s response. Previous works on auditory-localization tasks revealed that egocentric pointing methods (which are based on a body-centered coordinate system) allow for more accurate judgments than verbal reporting or exocentric pointing techniques (which are based on a 2D or 3D reporting device). Three different egocentric methods are compared: the most commonly applied “manual pointing” and “head pointing” methods, and the “proximal pointing” method, which forces the participants to indicate the apparent direction by pointing in the proximal region of the head with a marker held at the fingertips. The two first methods involve a rotation of the body of the participant, whereas the third method only involves movements of the arm(s) and hand(s) with a fixed head. Sound stimuli were presented randomly over 24 loudspeakers that were uniformly distributed on the upper hemisphere around the subject. The merits of the different methods are compared and discussed with regard to localization errors and to practical considerations. Although they show similar trends, each of the different methods affects the pointing accuracy in a specific way. The proximal pointing method, for example, is more accurate for sources located at high elevation angles. However, at rear locations close to the median plane an increased bias appears due to difficulties in performing the motor task to reach these positions. The proximal pointing method shows faster response times, which may be advantageous when planning 3D sound localization experiments.

Departments and organaitaions involved in the research are noted below; School of Engineering, Trinity College Dublin, Dublin, Ireland (O'Sullivan) Dyson School of Design Engineering, Imperial College, London, UK (Picinali) Faculty of Technology, De Montfort University, Leicester, UK (Gerino) Digital Building Heritage Group, De Montfort University, Leicester, UK (Cawthorne) Tactile surfaces can display information in a variety of applications for all users, but can be of particular benefit to blind and visually impaired individuals. One example is the use of paper-based tactile maps as navigational aids for interior and exterior spaces; visually impaired individuals may use these to practice and learn a route prior to journeying. The addition of an interactive auditory display can enhance such interfaces by providing additional information. This article presents a prototype system which tracks the actions of a user's hands over a tactile surface and responds with sonic feedback. The initial application is an Audio-Tactile Map (ATM); the auditory display provides verbalised information as well as environmental sounds useful for navigation. Two versions of the interface are presented; a desktop version intended as a large-format information point and a mobile version which uses a tablet computer overlain with tactile paper. Details of these implementations are provided, including observations drawn from the participation of a partially-sighted individual in the design process. A usability test with five visually impaired subjects also gives a favourable assessment of the mobile version.

Sound pleasantness or annoyance perceived in urban soundscapes is a major concern in environmental acoustics. Binaural psychoacoustic parameters are helpful to describe generic acoustic environments, as it is stated within the ISO 12913 framework. In this paper, the application of a Wireless Acoustic Sensor Network (WASN) to evaluate the spatial distribution and the evolution of urban acoustic environments is described. Two experiments are presented using an indoor and an outdoor deployment of a WASN with several nodes using an Internet of Things (IoT) environment to collect audio data and calculate meaningful parameters such as the sound pressure level, binaural loudness and binaural sharpness. A chunk of audio is recorded in each node periodically with a microphone array and the binaural rendering is conducted by exploiting the estimated directional characteristics of the incoming sound by means of DOA estimation. Each node computes the parameters in a different location and sends the values to a cloud-based broker structure that allows spatial statistical analysis through Kriging techniques. A cross-validation analysis is also performed to confirm the usefulness of the proposed system. Ingeniería, Industria y Construcción

El trabajo de fin de grado consiste en la implementación de la tecnología Ambisonics como solución de audio espacial para la recreación de paisajes sonoros. Se han evaluado sus prestaciones tanto para la reproducción de audio en sistemas de altavoces, como en sistemas de escucha binaural. Durante el proyecto se profundiza en la síntesis de paisajes sonoros ficticios y la grabación de escenas reales, y se ha analizado su posterior reproducción utilizando los diferentes formatos existentes (Formato-A, Formato-B FuMa y Ambix). Se han propuesto diferentes aplicaciones y, finalmente, se ha realizado una valoración mediante test subjetivos. The final degree project consists of the implementation of the Ambisonics technology as a spatial audio solution for the recreation of sound landscapes. Its features have been evaluated both for audio reproduction in landspeaker systems and in binaural listening systems. During the project, the synthesis of fictitious soundscapes and the recording of real scenes is studied, and its subsequent reproduction has been analyzed using the different existing formats (Format-A, Format-B FuMa and Ambix). Different applications have been proposed and, finally, an assessment has been made by subjective tests. Graduado o Graduada en Ingeniería en Tecnologías de Telecomunicación por la Universidad Pública de Navarra Telekomunikazio Teknologien Ingeniaritzako Graduatua Nafarroako Unibertsitate Publikoan

El principal objetivo de este trabajo es la creación de un audiojuego, es decir, un juego sin ningún tipo de soporte visual. Aunque no dispongamos de la ayuda de gráficos para llevar a cabo esta propuesta, buscaremos aportar unas mecánicas y una historia interesantes, al igual que cualquier otro videojuego podría hacer. Por ello, será necesario conocer la última tecnología sonora y ser capaces de utilizarla para nuestros fines.

In studies investigating binaural processing in human listeners, relatively long and task-dependent time constants of a binaural window ranging from 10 ms to 250 ms have been observed. Such time constants are often thought to reflect “binaural sluggishness.” In this study, the effect of binaural sluggishness on binaural unmasking of speech in stationary speech-shaped noise is investigated in 10 listeners with normal hearing. In order to design a masking signal with temporally varying binaural cues, the interaural phase difference of the noise was modulated sinusoidally with frequencies ranging from 0.25 Hz to 64 Hz. The lowest, that is the best, speech reception thresholds (SRTs) were observed for the lowest modulation frequency. SRTs increased with increasing modulation frequency up to 4 Hz. For higher modulation frequencies, SRTs remained constant in the range of 1 dB to 1.5 dB below the SRT determined in the diotic situation. The outcome of the experiment was simulated using a short-term binaural speech intelligibility model, which combines an equalization–cancellation (EC) model with the speech intelligibility index. This model segments the incoming signal into 23.2-ms time frames in order to predict release from masking in modulated noises. In order to predict the results from this study, the model required a further time constant applied to the EC mechanism representing binaural sluggishness. The best agreement with perceptual data was achieved using a temporal window of 200 ms in the EC mechanism.

Introduction: Binaurally evoked auditory evoked potentials have good diagnostic values when testing subjects with central auditory deficits. The literature on speech-evoked auditory brainstem response evoked by binaural stimulation is in fact limited. Gender disparities in speech-evoked auditory brainstem response results have been consistently noted but the magnitude of gender difference has not been reported. Objective: The present study aimed to compare the magnitude of gender difference in speech-evoked auditory brainstem response results between monaural and binaural stimulations. Methods: A total of 34 healthy Asian adults aged 19–30 years participated in this comparative study. Eighteen of them were females (mean age = 23.6 ± 2.3 years) and the remaining sixteen were males (mean age = 22.0 ± 2.3 years). For each subject, speech-evoked auditory brainstem response was recorded with the synthesized syllable /da/ presented monaurally and binaurally. Results: While latencies were not affected (p > 0.05), the binaural stimulation produced statistically higher speech-evoked auditory brainstem response amplitudes than the monaural stimulation (p 0.80), substantive gender differences were noted in most of speech-evoked auditory brainstem response peaks for both stimulation modes. Conclusion: The magnitude of gender difference between the two stimulation modes revealed some distinct patterns. Based on these clinically significant results, gender-specific normative data are highly recommended when using speech-evoked auditory brainstem response for clinical and future applications. The preliminary normative data provided in the present study can serve as the reference for future studies on this test among Asian adults. Resumo: Introdução: Potenciais auditivos evocados de modo binaural apresentam bons valores diagnósticos ao testar indivíduos com déficits auditivos centrais. A literatura sobre a resposta do potencial evocado do tronco encefálico com estímulo de fala de modo binaural é, de fato, limitada. As diferenças de gênero nos resultados desse exame têm sido consistentemente observadas, mas a magnitude da diferença de gênero ainda não foi relatada. Objetivo: Comparar a magnitude da diferença de gênero nos resultados do potencial evocado do tronco encefálico com estímulo de fala entre estímulos monaural e binaural. Método: Um total de 34 adultos asiáticos saudáveis com idades entre 19 e 30 anos participaram deste estudo comparativo. Dezoito deles eram do sexo feminino (média de idade = 23,6 ± 2,3 anos) e os outros dezesseis do sexo masculino (média de idade = 22,0 ± 2,3 anos). Para cada indivíduo, o potencial evocado do tronco encefálico com estímulo de fala foi registrado com a sílaba sintetizada /da/ apresentada de forma monaural e binaural. Resultados: Embora as latências não tenham sido afetadas (p > 0,05), a estimulação binaural produziu amplitudes de potencial evocado do tronco encefálico com estímulo de fala estatisticamente maiores que a estimulação monaural (p 0,80), diferenças substanciais de gênero foram observadas na maioria dos picos de potencial evocado do tronco encefálico com estímulo de fala para ambos os modos de estímulo. Conclusão: A magnitude da diferença de gênero entre os dois modos de estímulo revelou alguns padrões distintos. Com base nesses resultados clinicamente significantes, os dados normativos específicos para o gênero são altamente recomendados quando se usa o potencial evocado do tronco encefálico com estímulo de fala para aplicações clínicas e futuras. Os dados normativos preliminares fornecidos pelo presente estudo podem servir como referência para futuros estudos sobre esse exame em asiáticos adultos. Keywords: Brainstem, Speech, Binaural, Monaural, Effect size, Palavras-chave: Tronco encefálico, Fala, Binaural, Monaural, Tamanho do efeito

This work is a study on source separation techniques for binaural music mixtures. The chosen framework uses a Convolutional Neural Network (CNN) to estimate time-frequency soft masks. This masks are used to extract the different sources from the original two-channel mixture signal. Its baseline single-channel architecture performed state-of-the-art results on monaural music mixtures under low-latency conditions. It has been extended to perform separation in two-channel signals, being the first two-channel CNN joint estimation architecture. This means that filters are learned for each source by taking in account both channels information. Furthermore, a specific binaural condition is included during training stage. It uses Interaural Level Difference (ILD) information to improve spatial images of extracted sources. Concurrently, we present a novel tool to create binaural scenes for testing purposes. Multiple binaural scenes are rendered from a music dataset of four instruments (voice, drums, bass and others). The CNN framework have been tested for these binaural scenes and compared with monaural and stereo results. The system showed a great amount of adaptability and good separation results in all the scenarios. These results are used to evaluate spatial information impact on separation performance.

Despite decades of microelectrode recordings, fundamental questions remain about how auditory cortex represents sound-source location. Here, we used in vivo two- photon calcium imaging to measure the sensitivity of layer II/III neurons in mouse primary auditory cortex (A1) to interaural level differences (ILDs), the principal spatial cue in this species. Although most ILD-sensitive neurons preferred ILDs favoring the contralateral ear, neurons with either midline or ipsilateral preferences were also present. An opponent-channel decoder accurately classified ILDs using the difference in responses between populations of neurons that preferred contralateral- ear-greater and ipsilateral-ear-greater stimuli. We also examined the spatial organization of binaural tuning properties across the imaged neurons with unprecedented resolution. Neurons driven exclusively by contralateral ear stimuli or by binaural stimulation occasionally formed local clusters, but their binaural categories and ILD preferences were not spatially organized on a more global scale. In contrast, the sound frequency preferences of most neurons within local cortical regions fell within a restricted frequency range, and a tonotopic gradient was observed across the cortical surface of individual mice. These results indicate that the representation of ILDs in mouse auditory cortex is comparable to that of most other mammalian species, and appears to lack systematic or consistent spatial order.

Binaural sensitivity is an important contributor to the ability to understand speech in adverse acoustical environments such as restaurants and other social gatherings. The ability to accurately report on binaural percepts is not commonly measured, however, as extensive training is required before reliable measures can be obtained. Here, we investigated the use of auditory evoked potentials (AEPs) as a rapid physiological indicator of detection of interaural phase differences (IPDs) by assessing cortical responses to 180° IPDs embedded in amplitude-modulated carrier tones. We predicted that decrements in encoding of IPDs would be evident in middle age, with further declines found with advancing age and hearing loss. Thus, participants in experiment #1 were young to middle-aged adults with relatively good hearing thresholds while participants in experiment #2 were older individuals with typical age-related hearing loss. Results revealed that while many of the participants in experiment #1 could encode IPDs in stimuli up to 1,000 Hz, few of the participants in experiment #2 had discernable responses to stimuli above 750 Hz. These results are consistent with previous studies that have found that aging and hearing loss impose frequency limits on the ability to encode interaural phase information present in the fine structure of auditory stimuli. We further hypothesized that AEP measures of binaural sensitivity would be predictive of participants' ability to benefit from spatial separation between sound sources, a phenomenon known as spatial release from masking (SRM) which depends upon binaural cues. Results indicate that not only were objective IPD measures well correlated with and predictive of behavioral SRM measures in both experiments, but that they provided much stronger predictive value than age or hearing loss. Overall, the present work shows that objective measures of the encoding of interaural phase information can be readily obtained using commonly available AEP equipment, allowing accurate determination of the degree to which binaural sensitivity has been reduced in individual listeners due to aging and/or hearing loss. In fact, objective AEP measures of interaural phase encoding are actually better predictors of SRM in speech-in-speech conditions than are age, hearing loss, or the combination of age and hearing loss.

Auditory neurons selectively respond to frequency and amplitude of sound. In the auditory midbrain, duration-tuned neurons (DTNs) are subsets of neurons that selectively respond to the duration of sound. DTNs may help further understand the neural mechanism underlying temporal processing in the central nervous system. Temporal processing has been shown to play important roles in speech, discriminating species-specific signals, and echolocation. The goal of this thesis is to explore the role of DTNs through single-unit electrophysiological recordings in the auditory midbrain of the big brown bat (Eptesicus fuscus). Monotic and dichotic paired-tone stimulation was used to evoke excitatory and inhibitory responses from DTNs. Two stimuli consisted of best duration (BD) excitatory and non-excitatory (NE) tones. In the monotic condition, both tones were presented to the contralateral ear, and when they were close in time, the NE tone always suppressed spikes evoked by the BD tone. In the dichotic condition, the BD tone was presented to the contralateral ear. The NE tone was presented to the ipsilateral ear and suppressed BD tone evoked spiking in ~50% of cells. Properties of the ipsilaterally-evoked inhibition were investigated by varying the frequency of the NE tone from the best excitatory frequency (BEF), throughout a cell’s excitatory bandwidth (eBW). We measured the inhibitory frequency response area, best inhibitory frequency (BIF), and inhibitory bandwidth (iBW) of each cell. We found inhibition became weaker as the frequency of the NE tone moved further from the middle of the eBW. We found that a DTN’s BEF and BIF closely matched, but the eBW was broader than the iBW and overlapped the iBW measured from the same cell. This suggests temporal selectivity of midbrain DTNs are created by monaural inputs, with binaural inputs playing a lesser role in shaping duration selectivity. Thesis Master of Science (MSc)

The video game industry is experiencing tremendous growth and developing games that stand out against the competition requires ever increasing production budgets. Graphics have been a selling point for video games for a long time, resulting in huge technical advancements in visuals. Audio has received more attention during the recent years, both in terms of sound-design and technical developments. This study compared two alternatives for spatializing audio over headphones in a game setting, while also comparing them against a more traditional stereo output. A commercial game was used to provide the game setting and participants rated the three different outputs based on three attributes and described their experience using Microsoft Product Reaction Cards. No statistically significant differences were found between the three outputs in any of the six rated attributes when doing a paired t-test or a Wilcoxon Signed-Rank Test. Further analysis of frequency content, participants’ comments and Microsoft Product Reaction Cards were done to find out what sets the spatializing alternatives and stereo apart from each other.

We present PREQUEL: Perceptual Reproduction Quality Evaluation for Loudspeakers. Instead of quantifying the loudspeaker system itself, PREQUEL quantifies the overall loudspeakers' perceived sound quality by assessing their acoustic output using a set of music signals. This approach introduces a major problem: subjects cannot be provided with an acoustic reference signal and their judgment is based on an unknown, internal, reference. However, an objective perceptual assessment algorithm needs a reference signal in order to be able to predict the perceived sound quality. In this paper, these reference signals are created by making binaural recordings with a head and torso simulator, using the best quality loudspeakers, in the ideal listening spot in the best quality listening environment. The reproduced reference signal with the highest subjective quality is compared to the acoustic degraded loudspeaker output. PREQUEL is developed and, subsequently, validated, using three databases that contain binaurally recorded music fragments played over low to high quality loudspeakers in low to high quality listening rooms. The model shows a high average correlation (0.85) between objective and subjective measurements. PREQUEL thus allows prediction of the subjectively perceived sound quality of loudspeakers taking into account the influence of the listening room and the listening position.

Most existing methods in binaural sound source localization rely on some kind of aggregation of phase-and level-difference cues in the time-frequency plane. While different ag-gregation schemes exist, they are often heuristic and suffer in adverse noise conditions. In this paper, we introduce the rectified binaural ratio as a new feature for sound source local-ization. We show that for Gaussian-process point source signals corrupted by stationary Gaussian noise, this ratio follows a complex t-distribution with explicit parameters. This new formulation provides a principled and statistically sound way to aggregate binaural features in the presence of noise. We subsequently derive two simple and efficient methods for robust relative transfer function and time-delay estimation. Experiments on heavily corrupted simulated and speech signals demonstrate the robustness of the proposed scheme., Comment: European Signal Processing Conference, Aug 2016, Budapest, Hungary. Proceedings of the 24th European Signal Processing Conference (EUSIPCO), 2016, 2016

A growing number of studies of auditory processing are being carried out in awake, behaving animals, creating a need for precisely controlled sound delivery without restricting head movements. We have designed a system for closed-field stimulus presentation in freely moving ferrets, which comprises lightweight, adjustable headphones that can be consistently positioned over the ears via a small, skull-mounted implant. The invasiveness of the implant was minimized by simplifying its construction and using dental adhesive only for attaching it to the skull, thereby reducing the surgery required and avoiding the use of screws or other anchoring devices. Attaching the headphones to a chronic implant also reduced the amount of contact they had with the head and ears, increasing the willingness of the animals to wear them. We validated sound stimulation via the headphones in ferrets trained previously in a free-field task to localize stimuli presented from one of two loudspeakers. Noise bursts were delivered binaurally over the headphones and interaural level differences (ILDs) were introduced to allow the sound to be lateralized. Animals rapidly transferred from the free-field task to indicate the perceived location of the stimulus presented over headphones. They showed near perfect lateralization with a 5dB ILD, matching the scores achieved in the free-field task. As expected, the ferrets’ performance declined when the ILD was reduced in value. This closed-field system can easily be adapted for use in other species, and provides a reliable means of presenting closed-field stimuli whilst monitoring behavioral responses in freely moving animals.

High quality headphones can generate a realistic sound immersion reproducing binaural recordings. However, most people commonly use consumer headphones of inferior quality, as the ones provided with smartphones or music players. Factors, such as weak frequency response, distortion and the sensitivity disparity between the left and right transducers could be some of the degrading factors. In this work, we are studying how these factors affect spatial perception. To this purpose, a series or perceptual tests have been carried out with a virtual headphone listening test methodology. The first experiment focuses on the analysis of how the disparity of sensitivity between the two transducers affects the final result. The second test studies the influence of the frequency response relating quality and spatial impression. The third test analyzes the effects of distortion using a Volterra kernels scheme for the simulation of the distortion using convolutions. Finally, the fourth tries to relate the quality of the frequency response with the accuracy on azimuth localization. The conclusions of the experiments are: the disparity between both transducers can affect the localization of the source; the perception of quality and spatial impression has a high correlation; the distortion produced by the range of headphones tested at a fixed level does not affect the perception of binaural sound; and that some frequency bands have an important role in the front-back confusions., The Spanish Ministry of Economy and Competitiveness supported this work under the projects TEC2012-37945-C02-01, TEC2015-68076-R and the grant BES-2013-065034.

The quality of temporal coding of sound waveforms in the monaural afferents that converge on binaural neurons in the brainstem limits the sensitivity to temporal differences at the two ears. The anteroventral cochlear nucleus (AVCN) houses the cells that project to the binaural nuclei, which are known to have enhanced temporal coding of low-frequency sounds relative to auditory nerve (AN) fibers. We applied a coincidence analysis within the framework of detection theory to investigate the extent to which AVCN processing affects interaural time delay (ITD) sensitivity. Using monaural spike trains to a 1-s broadband or narrowband noise token, we emulated the binaural task of ITD discrimination and calculated just noticeable differences (jnds). The ITD jnds derived from AVCN neurons were lower than those derived from AN fibers, showing that the enhanced temporal coding in the AVCN improves binaural sensitivity to ITDs. AVCN processing also increased the dynamic range of ITD sensitivity and changed the shape of the frequency dependence of ITD sensitivity. Bandwidth dependence of ITD jnds from AN as well as AVCN fibers agreed with psychophysical data. These findings demonstrate that monaural preprocessing in the AVCN improves the temporal code in a way that is beneficial for binaural processing and may be crucial in achieving the exquisite sensitivity to ITDs observed in binaural pathways.

This study investigated the effects of unilateral hearing loss (UHL), of either conductive or sensorineural origin, on stereo sound localization and related visual bias in listeners with normal hearing, short-term (acute) UHL, and chronic UHL. Time-delay-based stereophony was used to isolate interaural-time-difference cues for sound source localization in free field. Listeners with acute moderate (50 dB for more than 10 years) UHL showed poor localization and compressed auditory space that favored the intact ear. Listeners with chronic moderate (

This paper addresses the problem of direction-of-arrival (DOA) estimation both in azimuthal and elevation angle from binaural sound that is processed with a head-related transfer function (HRTF). Previously, we proposed a weighted Wiener gain (WWG) method for two-dimensional DOA estimation with two-directional microphones. However, for signals processed with HRTFs, peaks in the spatial spectra of WWG indicating true sources can mingle with spurious peaks. To resolve this situation, we propose to apply incremental source attenuation (ISA) in combination with WWG. In fact, ISA reduces spectral components originating from specified sound sources and thereby improves the localization accuracy of the next targeted source in the proposed incremental estimation procedure. We conduct computer simulations using directional microphones and four HRTF sets corresponding to four individuals. The proposed method is compared to two DOA estimation methods that are equivalent to two generalized cross-correlation functions and two high-resolution methods of multiple signal classification (MUSIC) and minimum variance method. For comparison purposes, we introduce binary coherence detection (BCD) to high-resolution methods for emphasizing valid spectral components for localization in multiple source conditions. Evaluation results demonstrate that, although MUSIC with BCD yield comparable performance to that of WWG in conditions where single speech source exists, WWG with ISA surpasses the other methods in conditions including two or three speech sources.