Spelling suggestions: "subject:"microphone""
41 |
Stereo techniques and time delay compensation in classical music recording, the impact on the preferred spot microphone level in a mixThor, Oscar January 2023 (has links)
This study investigates whether different stereo techniques used as a main array influences the preferred level from spot microphones when combined in a mix. Time delay compensation and its influence on spot microphone level was also examined. A clarinet soloist and a violin & piano duo were recorded as stimuli. A listening test was conducted where subjects were asked to set the level on spot microphone channels of a clarinet, and violin in combination with several stereo techniques. A/B, X/Y, ORTF, and Blumlein were examined. In general, results suggested that there wasn’t a significant difference in preferred spot microphone level between stereo techniques. Time delay compensation could not be proven to significantly influence the preferred spot microphone level.
|
42 |
Scan-Based Near-Field Acoustical Holography on Partially Correlated SourcesGardner, Michael D. 13 August 2009 (has links) (PDF)
Scan-based near-field acoustical holography (NAH) is applied to partially correlated sources. Partial field decomposition via the virtual coherence method is used to implement the scan-based NAH. The background and theory of these methods are developed. Multiple stationary reference microphones are required for the partial field decomposition. Guidelines for reference microphone placement in the literature thus far have been limited. Improved guidelines for reference microphones are given after the results of two sets of experiments. The first set involves discrete, partially correlated sources, both physical and numerical. The second set of experiments is strictly numerical and involves continuous sources. Fewer microphones are required for partially correlated sources as compared to completely uncorrelated sources. Reference microphone number is found to be more critical to reducing holography reconstruction errors than is placement or location. For the continuous results, an appropriate figure of merit is created: reference microphones per coherence length. Based upon the definition of coherence length, two reference microphones per coherence length are required to minimize reconstruction error. Further practical reference microphone guidelines are given. These guidelines are to assist in preparing for a full-scale application of scan-based near-field acoustical holography to a military aircraft jet.
|
43 |
Unsteady dynamics of corner separation in a linear compressor cascade / Dynamiques instationnaires du décollement de coin dans une grille d’aube de compresseurZambonini, Gherardo 02 December 2016 (has links)
Le présent travail concerne l'étude du décollement de coin de compresseurs par des investigations expérimentaux sur le banc d'essai subsonique grille d'aubes situé au LMFA (Re = 3.8 x 105, M = 0,12, profil NACA 65-009). Habituellement, cette particulière séparation tridimensionnelle a lieu dans le coin entre l'aubage et la paroi du moyeu des rangées d'aubes, également dans les stators et les rotors.Les performances de l’étage sont ainsi dégradées à cause des pertes de charge et du blocage conséquent à la séparation de l’écoulement. Bien que les caractéristiques stationnaires sont bien connues par la littérature, uniquement des récentes études expérimentales avancées combinées aux améliorations de simulations numériques, telles que URANS et LES, ont permis de découvrir le comportement très instable du décollement de coin. Des études préalables sur le même banc d'essai ont rapporté un comportement intermittent du décollement, appelé comportement bimodal. Dans la présente thèse de doctorat, il est montré que le comportement bimodal correspond à deux états spécifiques du champ fluide: une séparation fermée, presque supprimée, et une séparation ouverte caractérisée par un blocage massif. Il est clair que cette commutation bimodale du décollement de coin apparaissant dans une machine réelle pourrait avoir un impact fortement déstabilisant. En utilisant la méthode de mesure PIV haute vitesse couplée à des mesures de pression résolues en temps sur la surface de l'aubage, l'écoulement d'un canal inter-aube a été étudié pour deux différentes incidences. Les mesures PIV fournissent pour la première fois des visualisations résolues en temps et étendues à toute la section de l'aubage de la variation bimodale du décollement. L'interaction des grandes structures aléatoires de la couche limite à l'amont avec le bord d'attaque de l'aubage déstabilise le front du décollement et agrandit la région de recirculation. Une séparation ainsi massive persiste jusqu'à ce que le blocage dans le canal inter-aube provoque la rupture des plus grandes structures constituant la zone de recirculation. Successivement le débit recommence à accélérer et la séparation est presque supprimée. Cette dynamique coïncide avec le régime d'écoulement hautement instationnaire et apériodique des diffuseurs, appelé large transitory stall, caractérisé par des grandes amplitudes d'énergie dans la gamme des basses fréquences du spectre. Des moyennes conditionnelles de pression et la décomposition orthogonale modale (POD) des champs de vitesse ont été appliquées pour montrer l'effet rétroactif du blocage induit par la séparation ouverte sur l'angle local au bord d'attaque. Ces résultats supportent l’hypothèse d'une instabilité auto-entretenue causée par la diffusion imposée dans le stator. En fin, des mesures de pression totale résolues en temps ont été effectuées en utilisant des capteurs à haute réponse en fréquence, situés à la même position dans les différents canaux adjacents. La cohérence et la linéarité de l'angle de phase trouvée entre les capteurs confirment que l'instabilité du décollement peut se propager d'un canal a l'autre, en analogie avec les perturbations tournantes (rotating instabilities) apparaissant dans les bancs d'essai annulaires. Ceci montre pour la première fois que, même dans une grille d'aubes linéaire de compresseur, l'instabilité intrinsèque du décollement de coin peut déclencher la propagation d'instabilités. / The present work focuses on the study of the corner separation phenomenon in compressors carried out by experimental investigations on a subsonic linear cascade test rig (Re=3.8x105, M=0.12, blade profile NACA 65-009). Usually, this particular three-dimensional separation takes place in the corner between the blade and the endwall of compressor rows, mostly at hub, both in stators and rotors.Its main features are high total pressure losses and blockage of the flow, with consequent impacts on the efficiency. Whereas time averaged characteristics are well known from the past, only recent advanced experimental studies and improvements of numerical simulations, such as URANS and LES, have permitted to uncover the highly unsteady behavior of corner separation in compressors. Precedent studies on the same test rig have reported an intermittent unsteady behavior of corner separation, called bimodal behavior. In the present thesis it is shown that the bimodal behavior corresponds to two specific states of the flow: a closed separation, almost suppressed, and an open separation characterized by massive blockage and losses. Clearly hub-separation bimodal switches appearing in a real machine could have a first order detrimental effect on the stability of the flow in the compressor. By using high speed PIV coupled with unsteady pressure measurements on the surface of the blade the flow in a single blade passage has been investigated for different incidences. The PIV measurements provide, for the first time, time-resolved flow visualizations of the size switch of the separation with an extended field of view covering the entire blade section. The interaction of random large structures of the incoming boundary layer with the blade is found to be a predominant element that destabilizes the separation boundary and enlarges the recirculation region. Such a massive separation persists until the blockage in the passage causes the breakdown of the largest structures in the aft part of the blade, reestablishing the closed separation state. Such dynamics coincide with the aperiodic intermittent flow regime of diffusers, called transitory stall regime, and the associated Fourier spectra show the largest energy amplitudes in the low frequency range. Conditional ensemble averages of pressure and proper orthogonal decomposition (POD) of velocity fields have been applied to show the feedback effect of the blockage of the separation on the flow angle around the blade leading edge. These results draw the picture of a self-sustained instability caused by the diffusion imposed by the inter-blade passage. To answer the question about the interaction between adjacent corner separations, time-resolved total pressure measurements have been carried out by using high frequency response sensors positioned in bimodal points of multiple passages. The coherent propagation velocity and the linearity of the phase angle found between the signals confirm that the unsteadiness of the separation can propagate in pitch-wise direction. It is interesting to underline that equivalent elements characterize rotating disturbances appearing in annular test rigs. This finally shows that, even in an isolated stator blade row, the intrinsic unsteadiness of corner separation can start the propagation of instabilities. It is the first time that such a propagation effect is observed in a linear compressor cascade.
|
44 |
Analyse et synthèse de champs sonoresGuillaume, Mathieu 11 1900 (has links) (PDF)
Cette thèse a pour objectif de reproduire au mieux un champ sonore enregistré par une antenne de microphones au moyen d'un réseau de sources secondaires. Pour y parvenir, nous avons dans un premier temps réalisé une étude approfondie des représentations harmoniques et intégrales des champs sonores. Dans un deuxième temps, nous avons mis au point des algorithmes qui utilisent la représentation du champ sonore en ondes planes pour effectuer l'analyse et la synthèse.L'algorithme d'analyse proposé est un algorithme de formation de voies donnant une solution analytique au problème de la minimisation du repliement. Le problème de l'optimisation de la géométrie de l'antenne est aussi abordé. L'algorithme utilisé pour la synthèse est un algorithme flexible pour l'égalisation dans un contexte multicanal, qui permet de réduire les artefacts des méthodes traditionnelles, tels que le pré-écho et le post-écho. Finalement, l'efficacité de ces algorithmes d'analyse et de synthèse est démontrée par des simulations et validée par des manipulations.
|
45 |
3D audio technologies : applications to sound capture, post-production and listener perceptionCengarle, Giulio 29 November 2012 (has links)
La llegada del sonido 3D está imponiendo cambios en varias etapas del flujo de trabajo, desde los sistemas de captación hasta las metodologías de postproducción y las configuraciones de altavoces. Esta tesis trata varios aspectos relacionados con el audio 3D: en la parte de captación, presentamos un estudio sobre las características de los micrófonos tetraédricos y una solución para obtener las componentes Ambisonics del segundo orden usando un pequeño número de transductores del primer orden; en la parte de producción, se presenta una aplicación para la mezcla automatizada de eventos deportivos, para reducir la complexidad del multicanal en tiempo real; para la restitución del audio independiente del sistema de altavoces, en el que los niveles de salida a los altavoces son una incógnita hasta la decodificación, se propone un detector de clipping independiente del layout. Finalmente, se presentan test psico-acústicos para validar aspectos perceptivos relacionados con el audio 3D. / The advent of 3D audio is dictating changes in several stages of the audio work-flow, from recording systems and microphone configurations, to post-production methodologies and loudspeaker configurations. This thesis tackles aspects related to 3D audio arising in the various stages of production. In the recording part, we present a study on the accuracy of tetrahedral microphones and a solution for obtaining second-order Ambisonics responses from first-order transducers using a small number of sensors; in the production stage, we introduce an application for automated assisted mixing of sport events, to reduce the complexity of managing multiple audio channels in real time; a clipping detector is proposed for the rendering of layout-independent audio content to generic playback systems, where the signal levels sent to the speakers are unknown until the decoding stage; finally, psychoacoustic experiments are presented for the validation of perceptual and aesthetic aspects related to 3D audio.
|
46 |
Anténní systém pro bezdrátové mikrofony / Antenna system for wireless microphonesBartoš, Adam January 2018 (has links)
Master's thesis deals with the design of an antenna system for wireless sound transmission used mainly in professional sound reinforcement. The introductory part deals generally with wireless microphones, frequency bands used and proven antenna types. Next, this work deals with signal distribution that is realized using the antenna splitter. The antenna parts is focused on easy production and real usage, therefore were selected antennas with appropriate properties suitable for small series production. This thesis includes simulation of each device, their real construction design and measurements of built prototypes and final products. All three produced devices – the rack splitter, /4 antenna and Helix antenna are fully working, achieve good parameters and are ready for further manufacturing and easy modifications in case of frequency band change requirement. The conclusion includes an overall assessment of the results achieved.
|
47 |
Testovaní zařízení UFR – Unmeasured Flow Reducer / Testing of Unmeasured Flow Reducer equipmentMatoška, Martin January 2012 (has links)
The master´s thesis describes the basic information on the reporting of water losses. Means and methods to reduce water losses. Devices used to monitoring water supply, or detect malfunctioning of water supply line. Describes and evaluates the functionality of UFR on the laboratory model.
|
48 |
Modeling Speech Sound Radiation With Different Degrees of Realism for Articulatory SynthesisBirkholz, Peter, Ossmann, Steffen, Blandin, Rémi, Wilbrandt, Alexander, Krug, Paul Konstantin, Fleischer, Mario 11 June 2024 (has links)
Articulatory synthesis is based on modeling various physical phenomena of speech production, including sound radiation from the mouth. With regard to sound radiation, the most common approach is to approximate it in terms of a simple spherical source of strength equal to the mouth volume velocity. However, because this approximation is only valid at very low frequencies and does not account for the diffraction by the head and the torso, we simulated two alternative radiation characteristics that are potentially more
realistic: the radiation from a vibrating piston in a spherical baffle, and the radiation from the mouth of a detailed model of the human head and torso. Using the articulatory speech synthesizer VocalTractLab, a corpus of 10 sentences was synthesized with the different radiation characteristics combined with three different phonation types. The synthesized sentences were acoustically compared with natural recordings of the same sentences in terms of their long-term average spectra (LTAS), and evaluated in terms of their naturalness and intelligibility. The intelligibility was not affected by the type of radiation characteristic. However, it was found that the more similar their LTAS was to real speech, the more natural the synthetic sentences were perceived to be. Hence, the naturalness was not directly determined by the realism of the radiation characteristic, but by the combined spectral effect of the radiation characteristic and the voice source. While the more realistic radiation models do not per se improve synthesis quality, they provide new insights in the study of speech production and articulatory synthesis.
|
49 |
Mediacentral för skogsmaskiner : Ny konstruktion för Komatsu Forest AB / Media center in forestry machines : New design for Komatsu Forest ABLindmark, Isak January 2017 (has links)
Komatsu Forrest AB have a demand for a media solution where the user can select between different input sources as well as output channels. The input sources are Radio, Bluetooth, AUX, two microphones and PC. The system shall also be able to mix sound from an ANC unit (Active Noise Control). Due to the demands from the company, the system must be able to be digitally controlled. The goal is to present a concept that offers the solution for these demands.To specify the needs from the user a dialog with employees with more knowledge about the user’s use have resulted in a table. From this a technical design has been created and resulted in a technical design requirement. With the design structure as a base, simulations have been done. After the structure has been verified by simulations a prototype with the basic functions have been designed and programmed and verified to clarify the function.Simulations and measurements have shown that the design works as desired. The result shows that the unit can meet the requirements set by the company in a user-friendly manner. The project has resulted in different solutions and these evaluated for pros and cons compared to the chosen solution. / Komatsu Forest AB behöver en multimedialösning för att uppfylla specifika behov exempelvis simultant användande av två mobiltelefoner och två mikrofoner. Enheten ska klara av att hantera ljud från flertalet ljudkällor samt två mikrofoner och aktiv bullerreducering. Systemet ska styras digitalt från till exempel en PC. Målet är att presentera ett koncept som erbjuder en lösning för dessa problem.Utformningen av enheten har gjorts genom att utvärdera användarens bruksområden tillsammans med den vision som legat till grund för projektet. Detta har genom samtal med anställda på företaget medfört en sammanställning över förarens användnings-områden. Utifrån denna sammanställning av användningsområdena har en teknisk skiss för enhetens uppbyggnad möjliggjorts. Efter att funktionen för skissen har verifierats med simuleringar har ett prototypkort för enhetens grundstomme konstrueras, programmerats samt verifierat konstruktionen.Simuleringar och mätningar verifierar att konstruktionen fungerar som önskat. Resultatet visar att enheten skulle uppfylla de uppsatta önskemålen på ett bra och användarvänligt sätt. Då flera lösningar har tagits fram under projektets gång diskuteras för och nackdelar med dessa samt motiveras varför den valda lösningen är bäst anpassad.
|
Page generated in 0.049 seconds