Method for acquiring audio signals, and audio acquisition system thereof

Method for acquiring audio signals is described, wherein a microphone probe (11) equipped with a plurality (Y) of microphone capsules (B) detects a plurality of audio signals, and wherein said detected audio signals are combined together in order to obtain a virtual microphone signal. The latter is generated as a function of characteristic probe data (IRs) measured during a probe characterization step, wherein the signals detected by each microphone capsule (B) are measured following a corresponding predetermined test signal. An audio acquisition system is also described which allows to implement the method

Metrics for Evaluating the Spatial Accuracy of Microphone Arrays

The interest in 3D audio is constantly growing, thus leading to the appearance on the market of many microphone arrays for recording spatial audio, having a variety of sizes, number of channels and shapes, mostly spherical. Among the various characteristics that may have an influence on the quality of these systems, the presented work will deal with the spatial accuracy. The availability of robust methods for evaluating the spatial performance of the microphone arrays allows to compare the systems and to study the effect of different geometries, or beamforming algorithms. On one side, the design of new solutions can be optimized, on the other side a user can identify an optimal system depending on his needs. In this paper, two metrics for evaluating the spatial performance of microphone arrays are described, and two common formats for spatial audio are employed, Ambisonics and Spatial PCM Sampling (SPS). In the first part, the parameters Spatial Correlation and Level Difference are used for assessing the accuracy of the Ambisonics format, which is based on Spherical Harmonics functions. In the second part two classic metrics for loudspeakers, i.e., directivity factor and half power beam width, are employed for evaluating the accuracy of unidirectional virtual microphones, which constitute the base of the SPS format. In the last section, four well-known spherical microphone arrays are analyzed and compared through the described metrics and spatial audio formats

Loudspeakers performance variance due to components and assembly process - Field assessment

This paper is the continuation of the study presented at the past convention "AES Berlin 2017-142nd International Convention" regarding the main causes of scrap during the production of a typical midrange loudspeaker. Various samples with reference and modified components parameters have been built and characterized in terms of frequency response, total harmonic distortion and electrical-mechanical parameters. In addition, a second set of samples has been built using reference components but varying the assembly process parameters and these samples also have been characterized as the previous ones. After measurements performed both in an anechoic chamber and in a real production line, a new set of measurements has been done inside a production car, in order to check if the results obtained in the preceding study would have been confirmed by field measurements. In more detail, authors aim was to verify that critical components individuated in the former paper would also have a relevant role after samples installation in a vehicle

Measurements in opera houses: comparison between different techniques and equipment

In room acoustics many objective parameters to quantify subjective impressions have been introduced. These quantities can be measured by using a wide variety of powerful tools and equipment. The results can be influenced by the measurement techniques and instruments used. Furthermore the results also depend on the position and condition of the hall in which the measurements are made. With the aim of obtaining a procedure to qualify a room, and in particular an opera house, which will give comparable and reproducible results anywhere else, an extensive measurement campaign was made. In this paper some of the results of the measurement campaign are presented. Comparisons were made both between different tools (real-time analyzer, DAT, PC-board, sources) and between different techniques (stationary, impulsive, pseudo-random)

Influence of artificial mouth’s directivity in determining Speech Transmission Index

In room acoustics, one of the most used parameters for evaluating the speech intelligibility is the Speech Transmission Index (STI). The experimental evaluation of this STI generally employs an artificial speaker (binaural head) and listener (artificial mouth). In this study, the influence on the measurements of the emission directivity of the artificial mouth was investigated for different acoustic environments and we have found that, in many cases (i.e. big rooms or systems of telecommunications) the results is not sensitive to modifications of the directivity; on the contrary, inside cars, the shape of the whole balloon of directivity is important for determining correct and comparable values and the different mouth studied gives really different results in the same situation

Recording, Analysis and Playback of Spatial Sound Field using Novel Design Methods of Transducer Arrays

Nowadays, a growing interest in the recording and reproduction of spatial audio has been observed. With virtual and augmented reality technologies spreading fast thanks to entertainment and video game industries, also the professional opportunities in the field of engineering are evolving. However, despite many microphone arrays are reaching the market, most of them is not optimized for engineering or diagnostic use and remains mainly confined to voice and music recordings. In this thesis, the design of two new systems for recording and analysing the spatial distribution of sound energy, employing arrays of transducers and cameras, is discussed. Both acoustic and visual spatial information is recorded and combined together to produce static and dynamic colour maps, with a specially designed software and employing Ambisonics and Spatial PCM Sampling (SPS), two common spatial audio formats, for signals processing. The first solution consists in a microphone array made of 32 capsules and a circular array of eight cameras, optimized for low frequencies. The size of the array is designed accordingly to the frequency range of interest for automotive Noise, Vibration & Harshness (NVH) applications. The second system is an underwater probe with four hydrophones and a panoramic camera, with which it is possible to monitor the effects of underwater noise produced by human activities on marine species. Finite Elements Method (FEM) simulations have been used to calculate the array response, thus deriving the filtering matrix and performing theoretical evaluation of the spatial performance. Field tests of the proposed solutions are presented in comparison with the current state-of-the-art equipment. The faithful reproduction of the spatial sound field arouses equally interest. Hence, a method to playback panoramic video with spatial audio is presented, making use of Virtual Reality (VR) technology, spatial audio, individualized Head Related Transfer Functions (HRTFs) and personalized headphones equalization. The work in its entirety presents a complete methodology for recording, analysing and reproducing the spatial information of soundscapes

Didattica blended: i problemi acustici e visivi la sconsigliano

In questi giorni si parla molto di didattica “blended” (la trasmissione in streaming delle lezioni erogate “in presenza” nelle aule, con un ridotto numero di studenti ammessi nelle stesse). Molti improvvisano e pochi fanno i conti con i limiti fisici e tecnici di questa modalità di erogazione. In questo articolo, Angelo Farina, docente di Applied Acoustics presso l’Università di Parma, spiega perché le problematiche acustiche ed illuminotecniche della didattica cosiddetta “blended” determinano sistematicamente un peggioramento qualitativo rispetto a lezioni in streaming effettuate da casa. Queste ultime sono a loro volta inferiori qualitativamente alla lezioni pre-registrate e liberamente scaricabili in modalità asincrona. Pur ritenendo non auspicabile l’erogazione di lezioni in streaming dalle aule, l’articolo offre una serie di indicazioni per cercare di garantire almeno una decente qualità dei segnali audio e video trasmessi. L’autore, resta però fermamente convinto che, nell’impossibilità di tornare alla normale attività didattica tutta in presenza, nel prossimo semestre sia meglio puntare su una didattica basata su lezioni frontali pre-registrate, su sessioni interattive con gli studenti di tipo “ricevimento” e di tipo “laboratorio”, e sulla messa a disposizione degli stessi dei files video liberamente scaricabili contenenti sia le prime che le seconde. Lasciando le aule vuote, sinché non si potrà finalmente tornare tutti assieme, senza restrizioni

3dof representation of the acoustic measurements inside the Comunale-Pavarotti Theatre of Modena

The investigation of the acoustics inside the Italian Opera theatres has been undertaken by scholars in order to deepening their scientific studies on the architectural and cultural heritage. This paper deals with alternative ways of how to represent acoustic data, in particular by adding a 3dof representation of the impulse response (IR) besides the graphs related to the main acoustic parameters in line with the standard requirements. The 3dof screen shots have been undertaken by an overlay elaboration, showing the particular architectural components of the theatre that contribute to the early and late sound reflections. A brief introduction of the historical background related to the Comunale-Pavarotti theatre of Modena has been given to understand the architectural characteristics of the entire structure

Acoustic parameters of the Municipal Theatre of Piacenza shown on different ways of representation

The Italian Opera theatres are always subject to scientific studies that try to investigate as deeply as possible this historical heritage to preserve the architectural and acoustical information for future generations. This paper deals with two ways of data representations based on the outcomes derived from the variety of equipment used during the measurements. In particular, a methodology in line with standards and regulations has been introduced to representing the graphs of the main acoustical parameters; besides, a video of the real-time room impulse response (RIR) has been snapped with a few shots in place of visualizing the sound reflections that occurred inside the entire volume. After a brief description of the historical background of the Municipal theatre of Piacenza, the authors introduce the two methods just discussed to highlight the completeness of data representation regarding any type of room that is intended to be analyzed acoustically