Časopis Akustika je odborným recenzovaným časopisem o akustice a vibracích. V roce 2012 byl časopis Akustika zařazen do mezinárodní databáze SCOPUS. V roce 2018 byl časopis Akustika zařazen do Emerging Sources Citation Index (ESCI) - Web of Science Core Collection. Časopis Akustika vydáváme 2x ročně, a to vždy v březnu a září příslušného roku. Články v časopisu vychází česky nebo slovensky a anglicky. V časopisu publikují autoři jak z České republiky, ale i ze zahraničí, přičemž většina článků zahraničních autorů je publikována pouze v anglické verzi a není překládána do českého jazyka.
Časopis Akustika je odborný recenzovaný časopis zařazený v databázi Scopus a Web of Science. Obsah tohoto časopisu je chráněn autorským zákonem. Šíření či jeho další zpřístupňování obsahu či jeho části veřejnosti, a to jakýmkoliv způsobem, je bez předchozího souhlasu vydavatele časopisu výslovně zakázáno.
ACOUSTIC ANALYSIS OF VARIOUS BASSOON FINGERINGS IN MOZART´S INTROITUS
The work contains the analysis of selected bassoon fingerings, namely the first four bars of the Introitus part from W. A. Mozart’s Requiem. The takes were recorded in the anechoic room at the BUT Brno. The loudness curves, formants, spectral qualities using FFT are evaluated, and brightness, sharpness, spectral centroid are also measured. The duty cycles of the wave, including a pulse with a constant width, are taken into account, in connection with other double reed instruments. The analysis was performed both for entire phrases and for isolated tones. The fingering data are compared with each other (strengths and weaknesses) and evaluated from the point of view of aesthetics, i.e. how suitable the given fingering is for a different style and various interpretations.
Copyright (c) 2025 Ondřej Jirásek (Author) https://creativecommons.org/licenses/by-nc-nd/4.0
The paper is devoted to the acoustic analysis of a historical bell made in 1772. The paper presents basic measurements of the acoustic-vibrational characteristics of a small bell with subsequent analysis of selected parameters. Methods of analysis in the time, frequency and time-frequency domains were selected for the analysis. The conclusion presents an evaluation of the measurement method and evaluation. It also includes recommendations for further types of measurements and investigations.
Copyright (c) 2025 Jaroslav Smutný, Ladislav Pazdera, M Štukavec (Author) https://creativecommons.org/licenses/by-nc-nd/4.0
ACOUSTIC PARAMETERS OF DIFFERENT SHAPES OF MAPLE WOOD LOUDSPEAKER ENCLOSURES
This paper deals with the comparison of the "design" shape loudspeaker enclosure with the usually used block baffle of the same internal volume. Both enclosures were made of maple wood. Acoustic filling was also installed in both baffles, if it could improve the acoustic properties. Both speaker systems were subsequently tested in an anechoic room using the "sine sweep" method to compare their resonance characteristics and sound pressure level.
Loudspeaker enclosure, Sound pressure level, resonance characteristics, maple
Copyright (c) 2025 Petr Horák, Vlastimil Borůvka (Author) https://creativecommons.org/licenses/by-nc-nd/4.0
COCHLEA FREQUENCY-POSITION FUNCTION OBTAINED FROM ATTENUATION CHARACTERISTICS OF BASILAR MEMBRANE WAVE
This study focuses on the attenuation characteristics of the wave that propagates on the basilar membrane. The basilar membrane wave, which occurs from the interaction between the basilar membrane and fluid, plays a major role in the hearing system. Because the mass and stiffness of the basilar membrane are graded along its length, the basilar membrane wave peaks at a specific region along the cochlea depending on the acoustic wave frequency. We took the viscosity of the fluid into consideration and investigated the wave characteristics by conducting modal analysis. We found that the attenuation curve of the basilar membrane wave has an inflection point and the frequency-position function obtained from the inflection points matches well with the Greenwood function. This suggests that the mode of the basilar membrane wave drastically changes before and after the peak point.
Copyright (c) 2025 Toshiaki Kitamura (Author) https://creativecommons.org/licenses/by-nc-nd/4.0
INVESTIGATION ON INFLUENCE OF OUTER HAIR CELLS ON COCHLEA SLOW WAVE
This study focuses on the influence of the outer hair cells (OHCs) on the waves that propagate on the basilar membrane (BM). The human auditory system relies on the intricate organization of inner and outer hair cells within the cochlea. Inner hair cells serve as primary sensory cells, while the OHCs amplify signals. The activation of these hair cells is driven by the vibration of the BM and the overlying tectorial membrane. The spatial arrangement of hair cells along the cochlea enables frequency-specific responses, allowing the auditory system to process a wide range of sound frequencies. In this study, modal analysis is employed to explore the influence of the OHCs on the BM waves. The analysis model includes the BM and OHCs, with a comparison to a model excluding the OHCs. The frequency characteristics of propagation constants are compared between the two cases, shedding light on the structural dependence of propagation constants in the presence and absence of the OHCs.
EUROPEAN MOUNTAIN ASH AS A POSSIBLE SUBSTITUTE FOR HONDURAN ROSEWOOD IN THE PRODUCTION OF XYLOPHONES
The sound quality of a xylophone depends on the material it is made of. The xylophone produces sound through the vibration of the wooden bars. The bars are usually made of rosewood or padauk due to their properties, resonance, and durability. However, the Honduran rosewood is a protected wood species, so it is necessary to look for other suitable wood species. Based on the investigation of the physical and acoustical characteristics of the various wood species, it appears that the European mountain ash (also known as rowan) may be a suitable substitute for the Honduran rosewood. Unlike the Honduran rosewood, the European ash is not listed in the CITES appendices or on the IUCN Red List of Threatened Species. The effect of modification of the European mountain ash on the physical and acoustical characteristics (PACHs) and sound quality was investigated. The wood samples were modified in two ways: mechanical densification and a combination of mechanical densification and thermal modification. The PACHs (density of wood ρ w, modulus of elasticity along the wood grain EL , acoustical constant A, loss coefficient η, specific modulus of elasticity E sp, acoustic conversion efficiency ACE, speed of sound along the wood grain cL ) were measured before and after modification. These PACHs were compared with the characteristics of the Honduran rosewood. The sound quality of the xylophone bars produced before and after modification was also determined. Following the experiment results it can be stated that the wood of the European mountain ash, after combination mechanical densification and thermal modification, can be used as an alternative to the Honduran rosewood for the xylophones of lower quality.
Copyright (c) 2025 Martin Čulík, Anna Danihelová (Author) https://creativecommons.org/licenses/by-nc-nd/4.0
ASSESSMENT AND COMPARISON OF SOUND INSULATION OF SELECTED PARTITION CONSTRUCTIONS IN TWO WOODEN BUILDINGS
Acoustic comfort in an inhabited building is an important aspect from the point of view of a person’s quality of life, especially in the hotels and the buildings for the temporary accom- modation facilities. When evaluating the sound insulation of the partition walls and ceilings, measurements carried out in buildings are decisive, which can confirm the suitability of the material composition used and its correct application in the wooden building. The work deals the evaluation of the airborne and impact sound insulation of the partition constructions of a different thickness and material composition between the rooms in two different residential houses. The results of the airborne sound insulation measurements showed that, even after considering the required spectrum adaptation terms, the requirements of the standard STN 73 0532-2:2024 were not met in the first building, but they were met in the second building. The results of the impact sound insulation measurements showed that the requirements of the new standard STN 73 0532-2:2024 were not met in the first building after considering the required spectrum adaptation term Ci50-2500 but were met in the second building after considering all required spectrum adaptation terms.
standardized impact sound pressure level
Copyright (c) 2025 Martin Čulík, Michal Hrčka, Anna Danihelová (Author) https://creativecommons.org/licenses/by-nc-nd/4.0
Insights and Limitations of Acoustic Stress Tomography in Forestry Applications
Effective wood evaluation necessitates a thorough consideration of technical parameters, including both quantitative and qualitative features. The study aimed to practically verify the accuracy and applicability of the ARBOTOM acoustic stress tomograph under various forestry operations and research conditions. The tomograph was tested in a forest stand and a poplar plantation. A total of 165 standing tree trunks were evaluated using the acoustic tomograph: 108 oaks, 53 lindens, 4 pines, 1 fir in the forest, and 2 poplar trunks at the plantation. The median value for damage identified in the red color spectrum was 41.4% for oak and 58.3% for linden. In the violet color spectrum, the median values for damage were 13.75% for oak and 9.5% for linden. The results also indicated that the number of sensors did not significantly affect the identification of the extent of red or violet damage zones. The application on poplar trunks showed that the tomograph is not suitable for very thin trunks with naturally thinner wood. Integrating these technologies into forestry operations could help create favorable conditions for the use of modern information technologies in conjunction with the sustainable management of forest resources.
Copyright (c) 2025 Miloš Gejdoš, Katarína Michajlová, Miroslav Němec (Author) https://creativecommons.org/licenses/by-nc-nd/4.0
TRANSMISSION OF VIBRATIONS AND NOISE FROM THE PRIMARY SOURCE OF THE TANK WAGONS
The research, of which this article is a part, deals with the design, implementation and verification of the methodology of measuring the transmission of vibro-sound energy from the contact of the tread profile with the rail through the primary suspension blocks, side bearers, bogie pivot and brake system to the tank shell and measuring the generation of sound energy by the wagon bogie. It analyses the frequency distribution of vibro-sound energy of individual blocks (components) of the tank wagon and the intensity of vibration transmission by these blocks until the mounting of the tank shell. Using frequency spectra, the transmission loss of individual bogie blocks and tank at a maximum speed of 120 km/h is displayed. The measurement methodology, measured amplitudes and frequency distribution of vibrations and noise in motion are the basis for reducing the vibro-sound energy not only of the developed prototype tank wagon, but also of railway wagons with a similar bogie. As part of scientific research, the proposed methodology was also successfully applied to solving the dynamic load of high-speed spinning headstocks used in the textile industry.
Copyright (c) 2025 Stanislav Žiaran, Ondrej Chlebo, Ĺubomír Šoos (Author) https://creativecommons.org/licenses/by-nc-nd/4.0
ANALYSIS OF ACOUSTIC ATTENUATION SPECTRA OF PHOSPHATE ION CONDUCTING GLASSES BEFORE AND AFTER DEHYDRATION
In this paper, acoustic attenuation measurements are used to detect structural changes due to chemical processes related to dehydration. This paper presents the initial acoustic measurements conducted at a frequency of 13 MHz on a glass sample composed of 40Li2O-10BaO-50P2O5 (mol %) both in its non-dehydrated state and following hydration. The analysis revealed that the notable peak within the mid-temperature range was decreased after 1 and 3 hours of the dehydration process, and by the 6-hour, it was no longer present in the hydrated sample.
Copyright (c) 2025 Peter Hockicko, Karolína Pradeniaková, Francisco Munoz (Author) https://creativecommons.org/licenses/by-nc-nd/4.0
SOUND FREQUENCY SPECTRUM VERSUS LENGTH OF CLOSED ORGAN PIPES
In the history of the pipe organ, we can observe different pitch standards, which are connected to the musical aesthetics of the time or the intentions of the builder. These differences are often noted based on provenance, meaning the origin or location where the organ was made. Each historical period had its own aesthetic and technical requirements, which were reflected in the tuning and pitch of the organ. The retuning of organs occurred mainly at the turn of the 19th and 20th centuries, with a change in the intonation of these instruments. In the territory of Slovakia, this change primarily involved a shift from the original pitch of approximately 412 Hz to 440 Hz. This change, of course, affected mainly older instruments and was part of a broader process known as the romanticization of organs. This process marked a departure from the original sound ideal of the Baroque period and a transition to the romantic sound ideal. Study examines the limitations of tuning height for wooden closed organ pipes, specifically the Copula stop, which has undergone significant retuning and intonation adjustments in the past. By using a gradual retuning method, the research analyses the sound's frequency spectrum to determine the optimal tuning range. The results show that significant changes in tuning height can lead to substantial degradation in sound quality. The research emphasizes that ill-considered restorative modifications to the air column length of these organ pipes lead to undesirable and permanent changes in the instrument's sound characteristics.
Organ pipes, wood, sound, tuning, restoration
Copyright (c) 2025 Andrej Štafura, Ján Poničan, Štefan Nagy, Ľubomír Pavlík (Author) https://creativecommons.org/licenses/by-nc-nd/4.0
Acoustic and thermophysical properties of recycled materials based on newsprint
The paper deals with the acoustic and thermophysical properties of selected materials created from the recycling of newsprints with potential applications in the structural components of timber buildings. The samples for the study were produced by recycling paper in three forms: as pure paper, then with the addition of used coffee grounds, and then with the addition of rubber from crushed automotive tires. Based on the measurement of the Sound Absorption Coefficient (SAC) and Noise Reduction Coefficient (NRC), it can be concluded that these materials are among the less absorptive in terms of acoustics. The best results were achieved by the material made from newspaper mixed with coffee grounds (NRC is equal to 0.30), which can be classified into sound absorption class D. The other studied materials fall into class E, with an NRC of 0.20. From the perspective of thermophysical properties, the tested materials exhibit thermal conductivity coefficient values ranging from 0.083 to 0.103 W·m⁻¹·K⁻¹, indicating that they do not meet the thermal insulation properties commonly associated with standard insulating materials.
Copyright (c) 2025 Rastislav Igaz, Miroslav Němec, Miloš Gejdoš, Samuel Kočuta, Dagmara Bednárová (Author) https://creativecommons.org/licenses/by-nc-nd/4.0
ANALYSIS OF STEAM EDUCATIONAL ACTIVITIES FROM PRIMARY TO TERTIARY
One of the ways we can motivate young people is by implementing Children's Universities as a form of motivating young people for future studies in science and technology. Young people expect a wide use of information and communication technologies in education. They are eager to work actively and implement their own ideas. Children up to the age of 10 undoubtedly have a real but hidden interest in natural and technical sciences, they want to become scientists and explorers. However, after a few years of education at the primary level, the situation changes completely. Simple acoustic experiments included in the teaching from the lowest levels of the education system stimulate children from early childhood to explore and lead from initial play to subsequent experimentation and discovery of new knowledge. Initial playful experimentation that involves multiple child senses (hearing, sight, and touch) stimulates experimentation at the time of primary education and later at the time of secondary and tertiary education in technical universities motivates analysis and evaluation at higher levels of cognitive goals according to Bloom's taxonomy.
Copyright (c) 2025 Peter Hockicko, Gabriela Tarjányiová (Author) https://creativecommons.org/licenses/by-nc-nd/4.0
Long-Term Trends in Road Traffic Noise Exposure and Annoyance in a Model Region
Environmental noise, particularly road traffic noise, has been considered one of the most widespread environmental pollutants. The primary aim of this study was a 30-year longitudinal investigation of road traffic noise annoyance trends in a model region - Bratislava’s continuously monitored neighborhoods, with data collected at 10-year intervals. Using validated methods to assess noise annoyance and psychosocial well-being, along with direct sound level measurements, the study analyzed responses from 3,197 university students residing in exposed and control areas. Results showed a significant rise in traffic noise burden in exposed areas from 1989 to 1999 (LAeq=67.5 dB), a slight decrease by 2019 (LAeq=63.9 dB), and further reduction during lockdowns (LAeq=62.5 dB). At the control site, noise levels significantly decreased from LAeq = 50.2 dB in 2019 to LAeq = 46 dB in 2020. Road traffic noise annoyance initially rose sharply, with ORMH values increasing from 2.56 to 6.01 over the first 10-year interval, gradually declining to ORMH 3.26 by 2023. Despite this trend, road traffic noise annoyance remains a concern, highlighting the need for preventive measures and healthier urban transport solutions.
Environmental noise, Noise annoyance trends, Road traffic noise, University students, Bratislava region
Copyright (c) 2025 Lubica Argalasova, Alexandra Filova, Katarina Hirosova, Martin Samohyl, Jana Babjakova, Jana Jurkovicova (Author) https://creativecommons.org/licenses/by-nc-nd/4.0
THE ANALYSIS OF THE DYNAMIC LOADING OF HIGH-SPEED SPINNING HEADSTOCK COMPONENTS
The article deals with the effective design of vibro-diagnostics of sources caused by self-excited vibrations of a high-speed spinning headstock bearing generated by residual unbalance, the quality of production and assembly of high-speed spinning headstock components. It also analyses the dynamic load from external vibration sources, primarily from the guide and pressure pulleys of the drive belt, as well as the effect of the Eigen frequencies of the Eigen modes of the test equipment. The article suggests the possibilities of analysing the dynamic load of high-speed headstock bearings using diagnostic sensors and it also indicates the calculation of the sound power level from the vibration velocity of the high-speed spinning headstock and/or another analysed component. The aim of this article is therefore to contribute to the reduction of energetic, dynamic (vibration and noise) and economic demands using operational condition monitoring in the production of textile yarn by improving the performance properties of high-speed bearings of spinning headstocks, which form an essential part of spinning technology.
high-speed spinning headstock, diagnostic sensor, vibration and noise reduction, monitoring
Copyright (c) 2025 Stanislav Žiaran, Ondrej Chlebo, Ľubomír Šooš (Author) https://creativecommons.org/licenses/by-nc-nd/4.0
Generative artificial intelligence - AI, particularly language models, are transforming industries by automating content creation and enhancing human-computer interactions. The STEM education approach in our engineering program is crucial to develop skills and insights that complement and go beyond what language models can achieve. Students must be educated with a highly flexible STEM approach, as AI already can easily handle highly repeatable tasks at a fraction of the cost compared to employee salaries. Without this kind of education, they risk losing their jobs to automation. The aim of this work is to highlight the STEM approach in obtaining and simple processing of sound data using Raspberry Pi.
Copyright (c) 2025 Marian Janek, Peter Hockicko, Gabriela Tarjanyiová (Author) https://creativecommons.org/licenses/by-nc-nd/4.0
THE ACOUSTIC OF FATRA HOUSE OF ARTS IN ZILINA, SLOVAKIA
In this article, we present a concert hall of The Fatra House of Arts in Zilina Slovakia, describe the hall itself and examine the acoustical quality of the hall. The concert hall primarily serves for symphony, chamber orchestra and soloist but hosts various cultural and social events as well. The hall is being considered as acoustically exquisite space by many professional musicians and conductors all around the world for a long time. However, real measurement of the objective acoustical quality parameters, that could confirm the subjective assessment, has never been carried out. We per-formed the measuring and evaluated the reverberation-based, energy-based, spectral-based, and spatial impression-based objective criteria. The measured results of objective parameters prove the correlation with the recommended values of specialized literature for chamber orchestra performances.
Copyright (c) 2025 Peter Kasák, Roman Jarina, Maros Jakubec, Michal Chmulík (Author) https://creativecommons.org/licenses/by-nc-nd/4.0
--- STRUKTURÁLNÍ HLUK Z PROVOZU VODOVODNÍCH INSTALACÍ
Copyright (c) 2025 David Svoboda, Petra Berkova, Karel Cupr (Author) https://creativecommons.org/licenses/by-nc-nd/4.0
COMPARISON OF GRAND PIANOS ANT. PETROF AND MISTRAL
This paper describes the measurement of two Petrof grand pianos: Ant. Petrof and Mistral. The goal was to compare their parameters, i.e. harmonic spectra, decay time, relative sound level, spectral centroids, and cumulative line spectra (CLS). The complete range of 88 tones (keys) was measured in the anechoic chamber of Petrof, where we used a play-bench for precision. The obtained data were analysed and put into comparison. This analysis was supplemented by a comparison of selected samples (keys A2 and A4 played in forte and piano dynamics) to samples of three competing brands (Shigeru Kawai, Yamaha, Steinway).
Copyright (c) 2024 Ondřej Jirásek, Tomáš Peloušek https://creativecommons.org/licenses/by-nc-nd/4.0
This paper is dealing with the issue of D1 motorway surface(s) modernisation from the noise point of view. The surfaces of the individual sections were consecutively and longterm measured by the CPX method. The four analytical maps of the D1 road surface noise 1) before modernisation (year 2013); 2) after the modernisation (one year after the road section was put into operation); 3) difference map of noise before and after the modernisation; and 4) noise map in 2022 are the results. The analyses and measurement results show that the original assumption of the Road and Motorway Directorate – 2 dB reduction in average noise level after modernisation – has been significantly exceeded. It has also been demonstrated that D1, after the modernisation, had a lower average noise level than the reference (comparative) value specified in TKP 7. Reference value is based on long-term measurements of similar surfaces throughout the Czech Republic.
Copyright (c) 2024 Vítězslav Křivánek, Petra Marková, Jan Machanec, Blanka Hablovičová https://creativecommons.org/licenses/by-nc-nd/4.0
THE ANALYSIS OF DYNAMIC EFFECTS FROM THE TRAIN SET AT DIFFERENT DRIVING SPEEDS
Příspěvek je věnován problematice měření vybraných dynamických parametrů při rychlosti pojezdu od 160 km/h do 200 km/ hod. Příspěvek obsahuje teoretický úvod do problematiky, dále popisuje reálné měření dynamicko-akustických parametrů s následným vyhodnocením a srovnáním naměřených dat a parametrů. Závěr zahrnuje prezentaci získaných výsledků, doporučení pro další obdobná měření a zejména doporučení pro správce drážní infrastruktury.
Copyright (c) 2024 Jaroslav Smutný, Dušan Janoštík, Jan Pazdera, M Štukavec https://creativecommons.org/licenses/by-nc-nd/4.0
ROOM ACOUSTIC MEASUREMENT METHODS IN THE PAST, PRESENT AND FUTURE, INCLUDING THE IMPORTANCE OF THE ISO 3382 SERIES
The measurement of reverberation time in a room was introduced by W.C. Sabine a few years before 1900 with the purpose to handle acoustic problems in a lecture theatre. The sound source was organ pipes at the seven octave frequencies from 63 Hz to 4000 Hz. Later, the measurements were greatly improved by using interrupted white noise emitted by a loudspeaker and a microphone connected to a level recorder that could display the decay curve. This led to the first international standard on reverberation time measurements in 1963, intended for laboratory measurements of the sound absorption coefficient of materials. In 1975 appeared another international standard intended for reverberation time measurements, primarily in rooms for speech and music. A revision in 1997 introduced the impulse response as a basis for room acoustic measurements. This opened for derivation of other room acoustic parameters than the reverberation time, and this again led to a better understanding of how to design good rooms for music and speech. Some types of rooms are not sufficiently characterised by the reverberation time, and for that reason a new standard appeared in 2012 with a measurement method specifically intended for open-plan offices. Future development of room acoustic measurements may include faster and more reliable methods, better methods to overcome problems at low frequencies, a method to handle the influence the high-frequency problem of varying temperature and humidity of the air, and new ways to derive three-dimensional information on the sound reflections in a room.
Copyright (c) 2024 Jens Holger Rindel https://creativecommons.org/licenses/by-nc-nd/4.0
ON THE MECHANICAL VIBRATIONS OF A RIBBON LOUDSPEAKER’S STRIP WHIT RECTANGULAR SHAPE: CASE STUDY
This paper presents a case study focusing on the vibrations of a ribbon loudspeaker's strip. These vibrations induce surface deformation, resulting in a degradation of the reproduced sound quality. The phenomenon is briefly reviewed, and the theoretical foundations are outlined. Several modes of the loudspeaker's strip are analyzed using 3D and 2D simulations conducted in Matlab® and COMSOL Multiphysics. A video recording has been done that visually demonstrates the specific modes that were theoretically calculated. Conclusions drawn from the mode analysis are applicable to the design and manufacturing of loudspeakers.
Eigenfrequencies, Modes, Ribbon Loudspeaker, Rectangular Plate, Vibrations.
Copyright (c) 2025 Iliyan Iliev (Author) https://creativecommons.org/licenses/by-nc-nd/4.0
ACOUSTIC CHARACTERISTICS OF ROAD SURFACES
The article is focused on the tyre/road noise and vibration measurements of the motorway network in the Czech Republic between 2012 and 2020. Three different surfaces were measured, namely a conventional stone mastic asphalt pavement (SMA 11S) and two cement concrete pavements with different treatments – burlap drag and exposed aggregate. A basic statistical analysis of the noise values in different years after laying was performed. Cement concrete treated by burlap drag method has lower noise values than SMA 11S. This is to be expected as burlap drag method is considered a low-noise cement concrete treatment. However, it has worse skid resistance properties and so the exposed aggregate cement concrete (EACC) began to be used. SMA 11S and EACC have very similar noise levels in all years tested, suggesting that they behave acoustically in the same way. Vibrations were investigated during field measurements with an accelerometer mounted on the CPX trailer. The noise and vibration results could thus be compared with each other. There is a positive correlation between them.
tyre/road noise, stone mastic asphalt; exposed aggregate cement concrete; close proximity method (CPX)
Copyright (c) 2023 Petra Marková, Vítězslav Křivánek, Blanka Hablovičová, Jan Machanec https://creativecommons.org/licenses/by-nc-nd/4.0
This paper describes the innovation of Dreadnought guitars, especially braces on top plate. The goal was to increase the dynamic range of the instruments, not only in strength but also in spectral spread. The prolongation of tones in the Sustain and Release phases was also important. Mechanical and acoustic properties of instruments from Furch Guitars' production were measured (Chladni figures, frequency response), numerical simulation of innovated top plate in program ANSYS was prepared (by the matrix) and the changes in organisation of ribs were proposed as following. The new samples of innovated Dreadnought guitars were produced by the factory, again measured, analysed and evaluated.
Copyright (c) 2023 Ondřej Jirásek https://creativecommons.org/licenses/by-nc-nd/4.0
STANOVENIE HLADINY AKUSTICKÉHO VÝKONU EMITOVANEJ KOMPONENTOM STROJA MERANÍM KMITANIA
V článku je použitá metodika stanovenia akustického výkonu zvuku šíreného vzduchom, ktorý vzniká vibráciami strojných komponentov alebo stroja samotného. Výpočet hladiny akustického výkonu sa realizuje meraním zrýchlenia vibrácií a jeho integráciou do rýchlosti vibrácií pevného povrchu strojového zariadenia alebo jeho komponentu. Metodika je overená pri stanovení hladiny akustického výkonu prevádzkovaných spriadacích vreteníkov na skúšobnom zariadení. Nežiaduce emisie hluku ložísk točiaceho vreteníka, ako aj ich prevádzkový stav je možné sledovať meraním kinematických parametrov, meraním zrýchlenia vibrácií a jeho následnou integráciou. Rýchlosť vibrácií bola použitá na určenie A-váženej hladiny a Z-váženej hladiny akustického výkonu a súčasne na vyhodnotenie prevádzkového stavu dvoch vybraných spriadacích jednotiek. Článok hodnotí aj dôležitosť správneho výberu meracieho bodu analyzovaného zvlákňovacieho vreteníka na skúšobnom zariadení pri určovaní hladiny akustického výkonu, ktorý má rozhodujúci vplyv na neistotu merania.
Copyright (c) 2023 Stanislav Žiaran https://creativecommons.org/licenses/by-nc-nd/4.0
Akustická metoda hašení požárů na základě evropského výzkumu: přehled
V posledních několika letech se hledají nové metody hašení plamene, které by byly nákladově efektivní a zároveň šetrné k životnímu prostředí. Tento článek představuje podrobnou analýzu současných technik pro potlačování plamenů, včetně použití ohnivzdorných materiálů, tradičních hasicích prostředků a ekologického akustického hašení. Mezi těmito metodami se akustický přístup jeví jako obzvláště slibný. Na rozdíl od chemických přípravků jsou akustické vlny bezpečné pro životní prostředí, což z nich činí atraktivní možnost hašení plamenů. Článek se zaměřuje na využití akustických vln k hašení požárů s přihlédnutím k parametrům a složkám vln. Účinnost této metody je vyhodnocena a porovnána s jinými technikami.
Akustický hasicí přístroj; Akustické hašení; Elektrotechnika; Hašení plamene; Ohnivzdorné materiály; Hašení požáru
Copyright (c) 2023 Jacek Lukasz Wilk-Jakubowski https://creativecommons.org/licenses/by-nc-nd/4.0
OPTIMUM SOUND PROPAGATION IN OCEAN: THE COMPARISON BETWEEN NORMAL MODE AND EMPIRICAL FRANCOIS-GARRISON FORMULA
There are not only theory but also the empirical formula to deal with the problem of sound propagation in ocean. As such the Normal mode and Francois-Garrison are typical methods. Optimum sound propagation in ocean is the way we unify these two methods. In this paper, we investigate the transmission losses of both Normal mode and Francois-Garrison at some frequencies (170Hz, 800Hz, 100 KHz) at shallow water conditions (Tonkin gulf). The calculated and simulation results show that the optimum is achieved when the Normal mode is used at low frequencies whereas the Francois-Garrison is used at high frequencies.
Copyright (c) 2023 Tran Cao Quyen https://creativecommons.org/licenses/by-nc-nd/4.0
THE VIBRATION MEASUREMENT USING MICROCONTROLLERS
The contribution is devoted to the issue of measuring vibrations and possibly also noise using microcontroller technology. The contribution contains a theoretical introduction to the issue, and further describes the practical hardware implementation of the measuring system, the basis of which is a suitable microcontroller. Part of the contribution is also an analysis of the appropriateness of using such a measurement technique for application specifically in the field of railway constructions and buildings. The conclusion includes recommendations for other workplaces that would like to use this method of measurement.
Vibration, microcontroller, time domain analysis and frequency plane, identification of selected harmful phenomena, railway line.
Copyright (c) 2023 Jaroslav Smutný, Dušan Janoštík, Radovan Rímský, Petr Iunishchenko https://creativecommons.org/licenses/by-nc-nd/4.0
ÚTLUM HLUKU VZDUCHOTECHNICKÝCH DISTRIBUČNÍCH VYÚSTEK POMOCÍ 3D TIŠTĚNÝCH VÝPLŇOVÝCH STRUKTUR
Cílem tohoto výzkumu je snížení hlučnosti vzduchotechnických distribučních vyústek pomocí 3D tištěných výplňových struktur. Vyústky jsou instalovány na nově vyvíjeném autonomním větracím systému, jenž slouží pro decentrální větrání např. školních učeben. Bylo vytvořeno několik sacích a výdechových vyústek s funkční výplní ve tvaru gyroidu a plástve, které byly následně vytištěny na FDM 3D tiskárně. Na základě měření a analýzy maximálních hladin akustického tlaku v různých polohách mikrofonu okolo zařízení a při různých průtocích vzduchu byla vybrána kombinace vyústek s největším hlukovým útlumem. Výzkum je doplněn o další údaje jako je spektrální analýza hluku, měření rychlosti proudění vzduchu vyústkami a měření doby dozvuku místnosti. Užitím navržených vyústek bylo dosaženo významné redukce hluku a byly vyvozeny další závěry. Technologie 3D tisku se v tomto případě ukázala být velmi užitečným nástrojem.
Copyright (c) 2023 David Svoboda, Petra Berkova, Frantisek Vlach, David Beckovsky, Milan Gabzdyl, Martin Deutsch https://creativecommons.org/licenses/by-nc-nd/4.0