George Papanikolaou

Aristotle University of Thessaloniki | AUTH · Faculty of Engineering

A system for low-frequency noise control in small, enclosed sound fields is proposed, using compound sound sources optimized by a genetic algorithm (GA). It is the integration of the developed low-Bl driver compound sources with a GA computer program in the Python language, aiming to control the modal field. The lack of appropriate free space in sm...

This work concerns a technical study prepared on behalf of the Operator of the Thessaloniki Sewage Treatment Plant (SWTP), with the aim of suppressing the noise emitted by the plant's centrifugal air compressor complex. The study of the application of a muffler and sound trap in the air intake section for each of the turbochargers of the assembly i...

The subject of this work is the adaptation of an underground storage space in the buildings of the Thessaloniki Concert Hall (TCH) into a rehearsal room for the Megaro Symphonic Youth Orchestra (MOYSA). The challenge of the project was to create a room with an acoustic behavior suitable for its use, addressing the problem of its short hight, in rel...

This study presents the design and development of an automated speech audiometry application in the Greek language. The testing procedure employs algorithmically synthesized nonsense monosyllabic speech stimuli that are presented via commercial earphones or hearing aids. Ten participants repeatedly conducted speech recognition tests in quiet and in...

In this study, we propose an objective function for joint speech enhancement and amplification that can be parameterized to account for hearing loss based on the pure-tone audiogram. We employ the ConvTasNet model architecture for end-to-end speech enhancement and compare the personalized criterion to existing distance and metric-based objective fu...

Males of the olive fruit fly Bactrocera oleae vibrate and stridulate their wings at dusk producing sounds different from flight sounds with no confirmed behavior role. We recorded and performed a temporal-spectral analysis of this sound. Sound produced by male wing vibration/stridulation consists of intermittent pulses of highly variable duration a...

Background: Auditory-inspired signal processing strategies have successfully been used for the objective assessment of speech intelligibility and quality for a wide range of signal degradations, including signals that are processed by speech enhancement systems. Recent studies show that supervising a speech enhancement system to increase objective...

In this study, we aim to learn highly descriptive representations for a wide set of machinery sounds and exploit this knowledge to perform condition monitoring of mechanical equipment. We propose a comprehensive feature learning approach that operates on raw audio, by supervising the formation of salient audio embeddings in latent states of a deep...

The proposed compound sound sources for low-frequency noise control applications are composed of dipole sources. Their spatial radiation, which is critical in the modal field of small, closed spaces, is intended to be controlled with independent driving signals of each dipole. The need for small and efficient low-frequency elementary monopole sourc...

Modern feature-based methodologies in semantic audio applications attempt to capture the temporal dependency of successive feature observations, which form the so-called texture windows. This paper proposes an enhancement of this type of processing, known as temporal feature integration, by employing and testing alternative deployable strategies. S...

Perceptually motivated audio signal processing and feature extraction have played a key role in the determination of high-level semantic processes and the development of emerging systems and applications, such as mobile phone telecommunication and hearing aids. In the era of deep learning, speech enhancement methods based on neural networks have se...

In this paper, we develop a modular deep convolutional autoencoder with a dense bottleneck structure to perform the task of unsupervised anomaly detection in machine operating sounds. The proposed model consists of multiple sub-networks with identical encoder-decoder structures, trained to learn a mapping function between different mel-scaled frequ...

publication description During the recent years, convolutional neural networks have been the standard on audio semantics, surpassing traditional classification approaches which employed hand-crafted feature engineering as front-end and various classifiers as back-end. Early studies were based on prominent 2D convolutional topologies for image recog...

Male olive fruit flies, Bactrocera oleae (Diptera: Tephritidae), vibrate their wings at dusk and produce a characteristic sound which is part of their courtship behavior. The sound is a series of pulses possibly serving as an acoustic cue to attract females. We used professional digital sound recording equipment to capture this low intensity sound...

The design and construction of small sound sources, as the elementary building components of a compound source for low-frequency noise control applications, is investigated. The need for small volume cabinet loudspeakers has led to a vented design with low force factor (Bl) drivers, exploiting their high compliance and low-frequency resonance. The...

The design and construction of small sound sources, as the elementary building components of a compound source for low-frequency noise control applications, is investigated. The need for small volume cabinet loudspeakers has led to a vented design with low force factor (í µí°µí µí±™) drivers, exploiting their high compliance and low-frequency reson...

Objective: To develop and evaluate a software application capable of conducting Pure-Tone Audiometry tests in clinical practice. Design: We designed and developed a mobile software application for iPad devices that performs Pure- Tone Audiometry according to ANSI and IEC standards. The application is proposed to be operated by a trained audiologist...

Hearing impaired (ΗΙ) listeners often struggle to follow conversations when exposed in a complex acoustic environment. This is partly due to the reduced ability in recovering the target speech Temporal Envelope (ENV) cues from Temporal Fine Structure (TFS). This study investigates the enhancement of speech intelligibility in HI listeners, by proces...

Hearing impaired (ΗΙ) listeners often struggle to follow conversations when exposed in a complex acoustic environment. This is partly due to the reduced ability in recovering the target speech Temporal Envelope (ENV) cues from Temporal Fine Structure (TFS). This study investigates the enhancement of speech intelligibility in HI listeners, by proces...

A novel method of active noise control using adaptive radiation sound sources is investigated. A finite element model of a modal enclosed sound field is excited harmonically, representing a noise field in the low-frequency range. The control sources are comprised of elementary dipole sources for which the driving signals are adjusted by an optimiza...

Early components of the auditory evoked potentials (AEP) reflect the neural processing of acoustic stimuli in the brainstem and the sub-cortical regions. Relating AEP patterns to their stimulus characteristics is a notoriously difficult task, due to the variability of their morphology. In this study, tone-Burst evoked auditory brainstem and middle-...

The purpose of this study, which emerged in the context of a diplomatic dissertation, was to develop a distributed system used to measure environmental noise remotely using a professional sound level meter. As an initial effort, a simple structure was used to implement the system with a single measurement station which the user can control from a w...

This is a study of the construction and noise limit calculations of the exhaust system of a racing vehicle. The vehicle complies with the standards of the Formula SAE international student design competition in which it took part. The modelling of different types of resonators is done by the transfer matrix method both in Matlab and in specialized...

The utilization of dual channel exponential sweep, implemented in frequency domain, with an arbitrary spectral content and constant temporal envelope. To divide signal into two channels, active crossover technique was applied. This implementation aims to utilize the characteristics of a typical sweep - i.e. high SNR, immunity to distortion or time...

The current work focuses on the implementation of an online wavelet domain Wiener Filter denoiser (on the cloud), that is proposed for speech enhancement purposes. The outmost goal of the current project is to provide a quick and easy way to real-world speech denoising, with the easiest and most direct way feasible. Optimum configuration and adapta...

The industrialization and mobilization of human endeavor have led to increased noise production. Low-frequency noise is a major component of occupational noise, which is emitted from a variety of sources. Reduced perception abilities and risks to workers’ health and safety are some of the effects caused by the exposure to low-frequency noise. The m...

This paper presents the simulation of Active Noise Control (ANC) in a small enclose d workplace and modeling using the Finite Difference Time Domain (FDTD) method. The noise source is considered to be a rotating motor that is approximated by a sinusoid signal of a corresponding frequency. The control source is fed with the output of an adaptive fee...

The present paper focuses on high-accuracy block-based sub-pixel motion estimation utilizing a straightforward error minimization approach. In particular, the mathematics of bilinear interpolation are utilized for the selection of the candidate motion vectors that minimize the error criterion, by estimating local minima in the error surface with ar...

In this paper, an audio-driven algorithm for the detection of speech and music events in multimedia content is introduced. The proposed approach is based on the hypothesis that short-time frame-level discrimination performance can be enhanced by identifying transition points between longer, semantically homogeneous segments of audio. In this contex...

Το εκπαιδευτικό εργαλείο «Μιλώ Ελληνικά-SpeakGreek» είναι ένα σύγχρονο σύστημα διδασκαλίας της προφορικής ελληνικής γλώσσας με ελεύθερη πρόσβαση στο διαδίκτυο. Το “SpeakGreek” μπορεί να χρησιμοποιηθεί στην εκπαίδευση μαθητών της ελληνικής ως δεύτερης/ξένης γλώσσας καθώς και ατόμων με προβλήματα ακοής και ομιλίας. Η ομιλία του μαθητή οπτικοποιείται...

Semantic audio analysis has become a fundamental task in contemporary audio applications; consequently, further improvement and optimization of classification algorithms has also become a necessity. During the recent years, standard frame-based audio classification methods have been optimized and modern approaches introduced additional feature engi...

The task of general audio detection and segmentation is quite common in contemporary audio applications where computationally intensive processes are frequently involved. Machine learning is usually employed along with user-enabled data labeling that is intended to detect, segment, and semantically annotate the relevant audio events. This work focu...

In recent years, audiometric equipment remains expensive and unaffected by technological progress. This paper presents the design and development of an iOS-based application, which can be used to conduct audiometric tests comparable to a diagnostic audiometer, without additional external equipment, ergo updating the procedure and reducing the cost...

In order to estimate speech onset latencies in naming experiments, it is common to use technologies that rely on sound pressure changes, such as voice-key devices. These devices are used in online experiments and are prone to data loss. Moreover, several studies have revealed that voice-key devices suffer from low accuracy due to poor detection of...

In block-based sub-pixel motion estimation, most methods are based on a comparison of the target block to a number of sub-pixel shifted versions of a reference block. This means that the two blocks, reference and target, are not treated equally, as one is takes as-is, while the other suffers sub-pixel shifting, which invariably results in loss of i...

With this submission, a set of ensemble learning based methods for the MIREX 2015 Speech / Music Classification and Detection task is proposed and evaluated. The main algorithm for the Detection task employs a self-similarity matrix analysis technique to detect homogeneous segments of audio that can be subsequently classified as music or speech by...

This paper discusses a methodology for embedding sound localization techniques for spatial audio interaction, aiming at matching the low computing capabilities of mobile and embedded systems. The main goal is to implement a sound localization system, using a microphone array that combines increased accuracy with compromised computational load and a...

The task of general audio detection and segmentation based in means of machine learning is very popular and high-demanding procedure nowadays. Most relevant works in the last decade aim at modelling audio in order to conduct a semantics analysis and a high–level categorization. A generic strategy that would detect audio events as means of transitio...

Multimedia semantic analysis is a key element in managing the exponentially growing amount of produced multimedia content, available on the web and the social media. Towards this direction, a semantically enhanced Web-TV environment providing video-on-demand and simulcast streaming services, is proposed. The system offers content management and ana...

This paper investigates methods aiming at the automatic recognition and classification of discrete environmental sounds, for the purpose of subsequently applying these methods to the recognition of soundscapes. Research in audio recognition has traditionally focused on the domains of speech and music. Comparatively little research has been done tow...

Music structure analysis has been one of the challenging problems in the field of music information retrieval during the last decade. Past years advances in the field have contributed towards the establishment and standardization of a framework covering repetition, homogeneity and novelty based approaches. With this paper an optimized fusion algori...

The purpose of this paper is the review and evaluation of state of the art techniques and tools for the semantic analysis of audio content using Machine Learning algorithms. Available tools and techniques for annotation, audio features extraction and application of machine learning algorithms are referenced and investigated. In addition to reportin...

The current work focuses on the implementation of audiovisual production technologies for preservation and demonstration of local tradition and Cultural Heritage (CH). A methodological framework is proposed for the production, digitization, authoring and presentation of audiovisual (AV) content, related to traditional music and dances. The producti...

This paper presents the structure and first applications of SpeakGreek, an online biofeedback speech training tool that can be used in second/foreign language education and in clinical intervention for individuals with speech disorders. The tool provides training in the perception and production of key segmental and suprasegmental aspects of Greek....

Low-frequency sound field simulations in open and closed space, created by adaptive directivity compound sound sources, using Finite Element Method ABSTRACT Low-frequency sound field creation from compound sources, consisted of pair sources or dipolar sources in different setups , is studied in this paper. With the appropriate setup combination, di...

This paper presents the implementation of a mobile software environment that provides a suite of professional-grade audio and acoustic analysis tools for smartphones and tablets. The suite includes sound level monitoring, real-time time-frequency analysis, reverberation time, and impulse response measurements, whereas feature-based intelligent cont...

In the majority of the audio classification tasks that involve supervised machine learning, ground truth samples are regularly required as training inputs. Most researchers in this field usually annotate audio content by hand and for their individual requirements. This practice resulted in the absence of solid datasets and consequently research con...

This work involves the design, development and evaluation of a software sound level meter application for smartphones (iPhone). The paper investigates the potential of implementing a flexible and user-friendly environment for measuring sound levels, which can easily be used by non-specialists. The resulting software focuses on providing similar fun...

Background The perception of identity of solo playing musical instruments has been extensively examined. However, very few works are reported which systematically deal with aspects of timbre identification in concurrently sounding instruments. Consequently, the relationships between perceptual aspects of timbre and related elements of musical pract...

Previous works on computational approaches for the description of pitch phenomena have employed various methodologies, deterministic and probabilistic, which are based on psychophysiological auditory stimuli modeling, representations and transformations (e.g. spatial, temporal, spatiotemporal), both at peripheral and more central stages of the audi...

The current paper focuses on the implementation of hybrid expert systems for audiovisual content description and management, by means of pattern analysis. The proposed methodology combines audio detection–segmentation, surveillance-video motion-detection and hierarchical audio pattern recognition, using neural networks, statistical clustering and s...

Spectrotemporal information of the stimulus delivered to the auditory nerve by current Cochlear Implant (CI) technology is still insufficient in providing an accurate representation of the timbre of musical instruments at a perceptual level. This fact associates with poor performance in instrument identification by CI users, especially in cases whe...

The present study was carried out to determine whether recorded musical tones played at various pitches on a clarinet, a flute, an oboe, and a trumpet are perceived as being equal in loudness when presented to listeners at the same A-weighted level. This psychophysical investigation showed systematic effects of both instrument type and pitch that c...

Acoustics in small rooms suffer from resonances in low frequencies, resulting in the well-known sound colouration problem. In the present work, the finite element method was used to investigate specific case studies of proposed treatments of this problem. The treatments are based on techniques that make use of three basic mechanisms: wavelength, bo...

The current work describes a phoneme matching algorithm based on rough set concepts. The objective of this type of algorithms is focused on the localization of the phonemic content of a specific spoken occurrence. According to the proposed algorithm, a number of rough sets containing the multiple expected phonemic instances in a sequence are create...

The sound wave behavior at low frequencies in small sound recording, control, and reproduction rooms, results in resonant sound fields observed in both frequency and spatial domains. Finite Element Method (FEM) software applications provide potential analysis procedures for acoustics problems but there is a lack of tools focusing on room acoustics...

The estimation of the vocal tract resonance frequencies from acoustic voice signals has been widely employed and various methods have been proposed. Among them, a number of cepstrum based techniques have been implemented to disentangle the voice's spectral envelope from the harmonic components. Noticebly less research has been conducted for voices...

In this work we present the architecture of a system containing two artificial neural networks in cascade-a self-organizing neural network (called SARDNET) and a Multi-Layer Perceptron-that receives a sequence of temporal intervals (performed rhythm pattern) as input and maps it into a given set of prototypical rhythm patterns. Results provide stro...

A large number of pattern classification algorithms and methodologies have been proposed for the phoneme recognition task during the last decades. The current paper presents a prototype distance-based fuzzy classifier, optimized for the needs of phoneme recognition. This is accomplished by the specially designed objective function and a respective...

In this paper an overview of aspects, terminology and literature on contemporary research regarding timbre is presented. Timbre is a multidimensional entity, and research traces its multifaceted nature. The paper handles this structural complexity using a domain-task-results paradigm. Several domains of application are examined and various aspects...

The current paper focuses on spatial audio video / imaging and sound field visualization using ambisonic-processing, combined with MPEG-7 description schemes for multi-modal content description and management. Sound localization can be easily delivered using multi-band ambisonic processing under free-field and single point-source excitation conditi...

The current paper focuses on the use of multi-band ambisonic-processing for improved sound source localization. Energy-based localization can be easily delivered using soundfield microphone pairs, as long as free field conditions and the single omni-directional-point-source model apply. Multi-band SNR-based selective processing improves the noise t...

The current paper focuses on audio content management by means of joint audio segmentation and classification. We concentrate on the separation of typical audio classes, such as silence / background noise, speech, music and their combinations. A compact feature-vector subset is selected by a Correlation feature selection subset evaluation algorithm...

The paper introduces "Glottal Disturbogram" as a new tool for the discrimination, evaluation and representation of glottal disturbances which may be met in pathological voicing or singing. The "Glottal Disturbogram's" principles and related features also suit similar applications such as the acoustics of some families of musical instruments. Distur...

This work focuses on the implementation of an autonomous system appropriate for long-term, unsupervised monitoring of bowel sounds, captured by means of abdominal surface vibrations. The autonomous intestinal motility analysis system (AIMAS) promises to deliver new potentials in gastrointestinal auscultation, towards the establishment of novel non-...

The current work focuses on the design and implementation of an indoor surveillance application for long-term automated analysis of human activity, in a video-assisted biomedical monitoring system. Video processing is necessary to overcome noise-related problems, caused by suboptimal video capturing conditions, due to poor lighting or even complete...

The current paper focuses on validating an implementation of a state-of-the art audiovisual (AV) technologies setup for live broadcasting of cultural shows, via broadband Internet. The main objective of the work was to study, configure, and setup dedicated audio-video equipment for the processes of capturing, processing, and transmission of exten...

The current paper describes a wavelet-based method for long-term processing and analysis of gastrointestinal sounds (GIS). Windowing techniques are used to select sequential blocks of the prolonged multi-channel recordings and proceed to various wavelet-domain processing stages. De-noising, significant-activity detection, automated segmentation and...

The current work deals with audio event detection, segmentation and characterization, in order to be further utilized in post-production. Browsing, selection and characterization of audio-visual content is a tiresome task, especially in audio / video editing applications, where an enormous amount of recordings with different characteristics is usua...

This work focuses on the design and evaluation of efficient and accurate de-noising algorithms that combine robust signal enhancement and minimum signal distortion. The proposed method introduces novel, frequency depended, parametric, Wiener filtering techniques that involve Discrete Wavelet Transform and Wavelet Packets. Implementations of various...

The distribution of the low frequency room modes is important in room acoustics. The Finite Element Method (FEM) is a powerful numerical technique for analyzing the behavior of sound waves in enclosures, especially irregular ones. Also, it is the method which produces reliable results in the low frequency range where other methods like ray tracing...

An interesting part of the preserved ancient Greek buildings is that of the ancient odea. One of them is the odeion of Thessaloniki, which is at the ancient market (agora) in the center of the city. It's a small, amphitheatric hall whose exact shape and acoustical characteristics are not known, since its roof is not preserved. Acoustical measuremen...

Apart from the world famous ancient Greek theaters, whose acoustics often attracted engineers, smaller closed amphitheatric halls-called Odea (plural of the Greek word Odeion)-had been constructed and used through the Greek and roman periods. The acoustical characteristics for some of them and information concerning their location, use, history and...

The current paper presents a software application that conducts electroacoustic measurements using a digital approach to Time Delay Spectrometry. Development was focused on simplified hardware requirements such as a personal desktop or laptop computer. A friendly and flexible user interface has been designed. Linear and logarithmic sweep test signa...

Reliable estimates of the glottal function are of major importance in speech/voice processing for the characterization of voicing conditions, description of various phonation types, and identification of their parameters. This paper presents a new method for de-noising glottal wavelets (Differentiated Glottal Volume Velocity Pulses) and separation...

The current paper focuses on the development of a 3D character generation and multilingual talking emulation software application. Traditional lip sync techniques in D graphics productions require a careful (and painful) design at the pre-render phase, as well as the selection of the mostly matching phrases during audio dubbing. This paper proposes...

In this paper we present a multimedia-based system that facilitates teaching chemistry to pupils of Hellenic (Greek) high schools over a LAN. The system uses a variety of multimedia objects. An important aspect of the system is the central control the teacher can have over some aspects of a lesson. So, the teacher can enable the section to be taugh...

The current work focuses on the development of a web-based user-friendly environment, for the design and management of distance learning courses. Its objective is to promote the simple web service to a dynamically refashioning, multimedia enabled tool in the hands of the tutor, offering advanced learning facilities to the trainees. Based on the cor...

This work focuses on the design and implementation of a computerized psychophysiological monitoring engineering system that detects human responses to environmental noises. Classical human stimulus monitoring analysis tools were used to treat human bodily response under the presence of annoying noises. Applicable sound recording and reinforcement e...

For the development of a 3D sound reproduction system in a University Amphitheater, a complete acoustical study was carried out. Acoustic parameters were estimated via calculations and modeling. A full set of the appropriate measurements was made in order to confirm theoretical calculations. Architectural adaptations and the applicable electroacous...

The requirements in room acoustics and sound systems in a prototype classroom with videoconferencing facilities were the subjects of this study. Theoretical estimation, acoustical measurements, installation of dedicated sound system and electroacoustic measurements were the development steps. Useful recommendations and guidelines for the design of...

This paper focuses on the development of pilot digital audio distance lessons through the Internet. Web-based lectures enhanced with audio examples and animations were built as the main part of the learning process. Synchronous and asynchronous communication between teachers and distance learners were achieved. Evaluation of the results was accompl...

This paper presents a study for the optimum design and construction of an omnidirectional point source. The point source model of theoretical acoustics is used as an elementary unit for electroacoustic measurements in the area of room and free‐field acoustics. The spherical radiation requirement for the entire acoustic spectrum and the finite dimen...

Software for estimation and processing simulation of microphone line arrays was developed, based on the fundamentals of sensor array theory and the basic concepts governing the array beamforming. Periodical, nonperiodical, and logarithmic microphone line arrays can be designed in a convenient way. Spatial structures, directivity patterns, and other...

Musical rhythm patterns are mainly characterized by durational relationships between their different time levels. As written rhythmic values imply, these relationships are graphically represented by simple integer ratios and that fact reflects a basic criterion for their perceptual encoding into discrete perceptual categories. Temporal analysis of...

This paper presents the design of noninvasive systems for the investigation of the small bowel motility patterns. The basic idea was to implement dedicated devices for the recording and analysis of human bowel sounds. Properly modified transducers were used for the caption of gastrointestinal sound signals. A data acquisition ambulatory system, con...

In the present study, a mapping of the perceptual space between adjacent rhythm categories was attempted, through a systematic timing variation of simple rhythm patterns, as well as the investigation of the “perceptual magnet effect” at various musical tempi. Twenty-one musicians were participated in identification, goodness rating and discriminati...

Aspects of esophageal speech are investigated in this paper. Esophageal speech is produced by laryngectomized people who utter by expelling air constricted under the entrance of the esophagus, forcing the cricopharyngeal muscle to oscillate equivalently to vocal cords in normal speakers. Nine male esophageal speakers were used for the analysis. Spo...

This paper describes a new method for measuring the insertion loss of panels or partitions based on time delay spectrometry (TDS). Using a TEF 12. analyzer the insertion loss of single leaf steel panels were measured. The results are shown to be in reasonable agreement with existing measurements giving confidence to the use of the method for design...

The flogera is a simple structured bamboo woodwind and the most typical musical instrument played by the Greek shepherds. It consists of a cylindrical bore, with uniform internal diameter, open at both ends and a system of seven finger holes. The higher open end acts as the sound production mechanism, by blowing a narrow air stream against its shar...

This paper describes the design, construction and performance of a test facility for transmission loss measurement. The receiving portion of the facility consists of a 118 m3 reverberation room, while the source room is a 1·0 m3 pit with high sound insulation. The partition being measured makes up the top of the pit. A series of measurements concer...

In this paper the sound transmission through slits and circular apertures is examined. Approximate theoretical expressions for the transmission loss are derived using simple energy balance considerations. Both resonant and nonresonant transmissions are taken into account. Theoretical values of the transmission loss are compared with measurements.