The efficiency of a noise barrier largely depends on its geometry. Besides the height of the barrier and its top element form, the cross-section of the barrier contributes to its performance as well. ...The Boundary Element Method is often used as the numerical tool for simulating the behavior of proposed barrier shapes, both in 2D and 3D spaces. This paper deals with the optimization of barrier cross-section, not only by taking into account its acoustical performance (sound insertion loss), but also considering the economic feasibility of using various materials and various shapes for building the barrier. Therefore, the economic feasibility coefficient is defined and used as a final numerical value for comparing the overall efficiency of barrier design. The optimization process is done by using a genetic algorithm. Five basic forms of barrier elements and five building materials were pre-defined and characterized for the optimization process. The number of candidate units in the starting population was varied in order to examine the influence of population size on the final results. Barrier performance was evaluated for a point sound source in a 3D simulation space, and both its total rating based on the economic feasibility coefficient and its acoustical performance itself were evaluated and compared to a reference concrete barrier of the same height.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The paper discusses the issue of adding artificial warning sounds to hybrid and fully electric vehicles, in order to increase traffic safety by making these vehicles audible at low speeds. The goal ...of this modification is to enable the pedestrians to perceive possible danger coming from such a vehicle in time to respond accordingly. Following the results of previous research which state that the sounds of internal combustion engines are valid candidates for artificial warning sounds to be added to hybrid or fully electric vehicles, a preliminary examination of the suitability and acceptability of different engine sounds in various modes of operation has been conducted. The chosen modes of operation are running in idle, at 2000 rpm and 3000 rpm with the vehicle stopped. Both gasoline and diesel engines were investigated. To expand the range of engine sounds, the type of vehicles was not limited to personal cars. The results show significant differences in suitability of engine sounds for the stated purpose, with vehicle type being the main differentiating factor.
The efficiency of noise barriers largely depends on their geometry. In this paper, the performance of noise barriers was simulated using the numerical Boundary Element Method (BEM). Traffic noise was ...particularly considered with its standardized noise spectrum adapted to human hearing. The cross-section of the barriers was varied with the goal of finding the optimum shape in comparison to classical rectangular barriers. The barrier performance was calculated at different receiver points for a fixed barrier height and source position. The magnitude of the insertion loss parameter was used to evaluate the performance change, both in one-third octave bands and as the broadband mean insertion loss value. The proposed barriers of varying cross-section were also compared with a typical T-shape barrier of the same height.
Previous research has shown that tranquil areas in the city, such as urban parks, are usually perceived as positive and have a restorative effect on visitors. However, visitors could experience these ...spaces differently depending on the meaning they assign to the concept of tranquility. To investigate how individuals’ personal views on tranquility affect their perception of the sonic environment, a soundscape study was conducted in several city parks in Antwerp, Belgium. Mobile sound measurements were combined with a questionnaire survey amongst 660 park visitors. Within the survey, the participants’ viewpoint on tranquility was evaluated using their agreement with a set of previously established prototypical statements, categorizing them into one out of three main tranquility viewpoint groups: people that associate tranquility with silence, those that associate it with hearing natural sounds, or those that associate it with social relationships. Next to this, the sounds that participants had heard during their visit were noted, and their perception of the overall quality of the soundscape and the degree to which it matched their expectation were assessed. Results show that the park visitors who associate tranquility with natural sounds or to silence are more often found amongst those that report hearing mechanical sounds a lot. The same groups of visitors rate the overall quality of the sonic environment of the park more often bad to very bad. These findings suggest that park visitors pay attention more to the sounds they do not expect to hear, and that the higher their expectations about the soundscape, the more critical they become in their appraisal of the soundscape.
The well known and established methods used for distortion measurements cannot be used for detecting the errors that appear in digital audio systems based on perceptual coding and decoding. A test ...stimulus has to be used that has the time-varying properties similar to real signals such as speech and music. Furthermore, the procedure of quality evaluation has to include an estimate of the temporal behaviour of human hearing. For the purpose of evaluation of digital audio systems based on perceptual coding, a new combined test signal was developed with the cumulative distribution of amplitude following the Gaussian distribution. Input and output signals are transformed from the objective domain to the excitation domain. Transparency reduction is defined as a measure of distortion, being the ratio of error excitation and stimulus excitation.
Prilikom projektiranja akustičkih filtara, velika je poteškoća proračun odgovarajuće frekvencijske karakteristike. Metoda raspodijeljenih parametara uz elektro-akustičke analogije omogućuje dobivanje ...realnih frekvencijskih karakteristika. Primjenom računala moguće je proračunati dimenzije i oblik akustičkog filtra odgovarajuće frekvencijske karakteristike i odgovarajuće razine gušenja.
Multimedia room acoustical design Domitrovic, H.; Fajt, S.; Krhen, M.
2009 International Symposium ELMAR,
2009-Sept.
Conference Proceeding
The room acoustics for multimedia room is complex problem which has to be take in consideration while designing the one. It consists of several parts, like analysing and calculating of acoustical ...parameters, measuring the real condition, simulating on computer, finding the cause and giving the solution for possible problems. Calculating and measuring methods, as well as their results, are analised and shown in this paper. At the end some proposals to obtain better conditions are given. Finally, the simulation with proposed actions was made, to find out if those proposals solved the problem found out in the real room.
Sound in multimedia systems Domitrovic, H.; Krhen, M.; Milicevic, D.
2009 International Symposium ELMAR,
2009-Sept.
Conference Proceeding
The Personal Computers are nowadays complex multimedia system. In the real everyday usage the sound card, or audio device, became the very important part of the system. It is used to record and ...reproduce the sound, whether the music is listened, the film is shown, or someone is talking with another party through the Internet, and so on. The most of modern PC motherboards already have audio device included on the board, but if someone wants to have better sound quality, then external sound cards/audio devices are used. It is possible to connect them through the slots on the board, like PCI interface, or via external ports, like USB. In this article the measuring methods, measuring results and their comparison are shown.
The aim of the present explorative study was to acoustically examine tarankanje - a special manner of singing typical for the folk music of Istrian-Littoral region. The tarankanje performances of ...twelve professional male folk singers were digitally recorded and analysed using long-term average spectrum (LTAS) in the PRAAT program. In order to reveal some perceptual features as well as vocal model the singers aim to achieve when performing tarankanje, subjective (self-perceptual) analysis was carried out as well. The results of the acoustic analysis gave no evidence of existence of the resonance phenomenon known as the singer’s formant. The LTAS curve showed two broad pronounced peaks in 2-4 kHz region. The more pronounced energy in this region suggested the existence of the speaker’s or actor’s formant. For this reason, a control sample of subject speakers (N=8) was included in the investigation afterwards. The LTAS and alpha-ratio (a measure roughly representing the vocal tract tension) were calculated for both subject samples. In order to quantify the spectral energy at higher frequencies, a parameter VF as a ratio of 2-4 kHz band to that of 0-5 kHz was calculated. The results showed that the spectral slope was flatter for tarankanje in comparison to speaking, thus alpha and VF values greater suggesting higher degree of vocal pressedness. Spectral energy balance in lower frequency band (0-2 kHz) and in higher frequency band (2-4 kHz) as well as between the two bands, i.e. “whitish" sound, is the result of interaction of voice source and supralaryngeal setting, that is, pressedness and nasality. Such a spectrum shape (voice quality) is produced by imitation of the folk instrument - sopile - that are known for its piercing and nasal tone. The results of the subjective self-perceptual assessment have shown that all attributes (overall vocal effort, beauty, pleasantness, loudness, melodiousness, genderness, throat openess and tension, voice pitch) were estimated as neutral. The exception is the darkness of the voice: tarankanje was evaluated as somewhat brighter. This may be related to the results of spectral analysis, that is, to pronounced energy at higher frequencies (higher formants). The overall vocal effort employed in tarankanje has been evaluated as somewhat higher.
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