Siniša Fajt

Sound source influence to the room acoustics quality measurement

Objective parameters of the room acoustics quality are obtained from the impulse response, which is measured using the appropriate PC based acoustic measurement system with two types of loudspeakers. Such measurement gives the impulse response that is the result of measurement of the entire system, which consists of the room and electro acoustics equipment. In order to investigate the real influence of loudspeakers on the measurement results, the research was made in the same measuring conditions. Impulse responses were measured with the same measuring system. Measuring point was selected at the optimum listening position in the room, and all measurements were carried out in the same place. The loudspeakers were placed at the optimum and characteristic positions in the room, and rotated around their axes in order to determine the impact of their position and directivity characteristics on the measurement of objective parameters of room acoustic quality.

Principal Component Analysis in Determining the Best Setup for Acoustic Measurements in Sound Control Rooms

Measuring process of acoustic quality parameters in sound control room in order to determine the best setup is described. Measurements of six sound control rooms impulse response have been made. The measurements are executed in accordance with the standard ISO3382. In all sound control rooms the same measurement method is used, but the measurement setups are changed. In the first scenario built-in monitor loudspeakers were used. In the second scenario, omnidirectional sound source was used. Omnidirectional measuring microphone and an artificial head were used as receivers. They were placed at the optimal listening position. Principal components analysis method is used to get the most accurate result from measured data obtained under different scenarios and measuring setups. Hence, the measuring conditions and setups which determine the value of subjective assessments of the sound control room are obtained. The results shall be used to calculate correlation between objective measurements and subjective assessments.

Sound quality assessment in VOIP environment

The need for measuring the sound quality in VOIP environment is a basic requirement of modern multimedia communication systems due to technical, commercial and legislative reasons. Measuring the sound quality using objective methods is not standardized up till now. Expected measurement results should be in correlation with subjective tests of sound quality. The usage of application for measurement of acoustic qualities of the space is explored, with an emphasis on evaluating speech intelligibility as the main parameter. In this work we present measurement method and influence of codec choice on different hardware platforms. Objectively measured small differences showed possibility to evaluate the sound quality of voice internet protocol.

Correlation between objective and subjective acoustic quality parameters of professional sound control rooms

Original scientific paper Various studies performed so far have not provided unique answers to the acoustic quality evaluation of the sound control rooms, as no influence of specific features of the respective sound control room have been taken into account. In a process described in this paper, all the specific features that these rooms have are taken into consideration and sound is evaluated by means of reproduction through high quality professional equipment. Also, a listening area is a small, exactly given place for optimal listening for sound control engineer.The optimal sound control room must provide a complete and clear perception of reproduced sound with all specific features, and the rooms spatial characteristics may not influence nor change the characteristics of the reproduced sound. Conjoint Analisys method is used to obtain estimation of the impact of the room objective acoustic quality parameters on the subjective assessment of the professional sound control room. Thereby, the use of modern statistical method (Conjoint Analysis CA) shows dependence of one subjective parameter on more than one objective parameter. This principle determines more accurately real-life conditions, where all ratings are subject to complex dependence on more objective parameters.

Acoustical-Mechanical Modelling of Voice Tract

Modelling voice tract using an acoustical—mechanical analogy is shown in this article. The process of modelling voice tract is often reduced to one-dimensional acoustical model, i.e. planar waveguide model. With this acoustical-mechanical model, computer programs are utilized to analyze and synthesize the voice tract. Hence, it is possible to calculate models which describe the voice tract with satisfactory quality and detail level and these models can be used in practice and applied to particular cases. In this article the process of producing a voice tract model is presented. The process includes the usage of three different computer programs, each of them dedicated to one segment of modelling. Recordings for three speakers were made and the analysis of voice parameters was performed. After the analysis is completed, a two-dimensional model of the voice tract was made, which resulted in a mechanical model consisting of specific number of tubes. Finally, the evaluation procedure for the model is done by applying a software developed specifically for this purpose, in order to determine whether the resulting model truly represents the voice tract of each speaker.

Stochastic Based Simulations and Measurements of Some Objective Parameters of Acoustic Quality: Subjective Evaluation of Room Acoustic Quality with Acoustics Optimization in Multimedia Classroom (Analysis with Application)

This chapter offers an original scientific research about stochastic based simulations and measurements of some objective parameters of acoustic quality and subjective evaluation of room acoustic quality, with acoustics optimization in multimedia classroom, complete scientific analysis, and application. The organisation of this chapter is very simple. After a short introduction that is an overview of completed research there are two main chapter parts with some definitions and explanations on the main subjects and research done. The conclusion to this research is contained in the final chapter segment.

The high‐power acoustical warning systems

The high‐power acoustical warning and informing systems are necessary for various aims. Mostly these systems work in open space, particularly in urban areas (towns, villages, river valleys). The useful coverage depends upon used transducers‐emitters and installed electrical power. Almost all such systems have omnidirectional coverage, i.e., equal acoustical energy is radiated in all directions. The environmental conditions (air temperature and humidity, strength and direction of wind, etc.) and miscellaneous barriers (buildings, land configuration, trees) have an influence on the sound propagation for warning and informing systems. The other important point is that these systems are also used for spoken messages, not only for alarm. The computer simulation was done which takes all these parameters into account, and enables calculation of needed acoustical and electrical parameters.

The acoustical properties of large studios

New studios for Croatian Radio‐Television were planned with the starting user conditions. The background noise level must fulfill N15 or N20 criteria. Demanded reverberation time for a 400 m2 radio studio is Tr=0.6 s, for TV studios of the same area, Tr=0.7 s, and for the 1000 m2 TV studio, reverberation time is 1 s. Since all three studios with built‐in control rooms were built in an urban area with excessive noise, it was necessary to obtain very good protection against noise, and at the same time, using the same elements, achieve the desired reverberation time. Special attention was given to flutter echoes and achievement of diffuse sound fields. The inner shell construction was built up using special acoustical building blocks. Besides using double walls, the broad analysis was done in order to avoid any possible problem in sound insulation. The achieved coincident frequency for walls and floors is 7.6 Hz, and this is quite satisfactory. The computer simulation was used during the design of internal s...

Space‐induced distortion of starting transient of musical sound

Musical sound can be defined as complex sound that begins with a starting transient followed by a (more or less) steady sound and ends with a decaying sound. After that, continuous movement from one frequency to the another follows. The rate of change of loudness for partial tones that are greater than a certain threshold and their relative starting times are different for miscellaneous musical instruments. Recognition of a particular musical instrument depends upon short starting and ending transients. Relative starting time of the starting transient’s partial is limited by the rate of change of loudness that is greater than 600 dB/s. The envelope of all rates of change defines the maximum rate of change for loudness levels and partials that dominates in a certain time interval. The beginning transient is the complex phenomena, assessed with early sound and rate and synchronized with the rise of loudness and dominant partial tone in the observed time interval. The just‐noticeable threshold of rates of lo...