Wyniki wyszukiwania - BazTech

1

IR detection module with integrated real-time FIR filter implemented in FPGA

Achtenberg Krzysztof, Mikołajczyk Janusz, Bielecki Zbigniew

International Journal of Electronics and Telecommunications

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2024

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Vol. 70, No. 1

175--182

EN

Infrared detectors are usually characterized by 1/f noise when operating with biasing. This type of noise significantly reduces detection capabilities for low-level and slow signals. There are a few methods to reduce the influence of 1/f noise, like filtering or chopper stabilization with lock-in. Using the first one, a simple 1st-order analog low-pass filter built-in amplifier usually cuts off 1/f noise fluctuations at low frequencies. In comparison, the stabilization technique modulates the signal transposing to a higher frequency with no 1/f noise and then demodulates it back (lock-in amplifiers). However, the flexible tuned device, which can work precisely at low frequencies, is especially desirable in some applications, e.g., optical spectroscopy or interferometry. The paper describes a proof-of-concept of an IR detection module with an adjustable digital filter taking advantage of finite impulse response type. It is based on the high-resolution analog-to-digital converter, field-programmable gate array, and digital-to-analog converter. A microcontroller with an implemented user interface ensures control of such a prepared filtering path. The module is a separate component with the possibility of customization and can be used in experiments or applications in which the reduction of noises and unexpected interferences is needed.

2

Environmental impact of noise from mining operations

Mocek Piotr

Zeszyty Naukowe Akademii Morskiej w Szczecinie

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2023

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nr 73 (145)

15--28

EN

The article presents the results of measurements of environmental noise caused by devices operating in the surface facilities of hard coal mines and by the technological processes related to the loading and transport of spoil and materials necessary for production. The research results are part of the program “Consequences of excessive noise in the mining environment of hard coal mines”, the overarching goal of which is to reduce the emission of industrial noise. A sampling method was used to determine the actual values of noise levels emitted to the external environment from mines and mining plants as well as to identify the acoustic power levels of devices and processes constituting the main sources of noise in mines. The results showed that mines and mining plants are often not fully aware of the scale of the environmental impact of the undesirable noise they emit. Therefore, the current periodic measurements of environmental noise should be replaced with permanent monitoring, which will be beneficial not only for the environment and residents of housing estates located near mines but also for the mining plants themselves.

3

Psychoacoustic metrics in the psychological diagnosis of noise annoyance

Radosz Jan

Vibrations in Physical Systems

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2023

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Vol. 34, nr 1

art. no. 2023101

EN

Aim of the study was to asses noise annoyance in relation to psychoacoustic metrics of sound in an office environment. The Vienna Test System was used for this purpose. Virtual office acoustic environments were developed with sources of different psychoacoustic parameters (loudness, sharpness, fluctuation strength, roughness) but with a constant A-weighted sound pressure level of 55 dB - sound environment with conversations, sound environment with office equipment (computers, printers, telephones) and sound environment with all office noise sources together. The reference environment was a quiet office room with no additional noise sources. Recorded real noise sources were transferred to a virtual 3D sound environment and converted into binaural sound, which was then played back on headphones. During the exposure to each of the acoustic environments, the subjects performed the ALS test (work performance series) and COG test (measurement of attention and concentration) and then assessed the given environment using a questionnaire. The paper presents the results of the statistical analysis - despite different psychoacoustic metrics of office noise sources in the examined acoustic environments, no statistically significant differences were observed in the results of psychological tests.

4

Modelling of the acoustic wave scattering on the aircraft surface using the boundary element method

Nowicki Dawid, Suder-Dębska Katarzyna, Czajka Ireneusz

Vibrations in Physical Systems

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2023

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Vol. 34, nr 1

art. no. 2023107

EN

Sound localization tools are important in the environmental protection and the human searches. The article is one of the stages of the implementation of the concept of using aircraft to localize sound sources. The use of a fixed-wing aircraft instead of a multirotor would increase the total flight time, and expand the surveyed area. It is important to determine the most favourable positions of the receivers on the surface of the aircraft. The scattering effects of the sound waves coming from the ground source and aircraft engine on the acoustic field on the aircraft surface are not homogeneous. In the article the authors present the modelling of the scattering of the sound waves over the airplane surface with the usage of boundary element methods. After determining the effects from the sound source on earth and from the aircraft engine the conclusion was made, that the influence from the engine noise is greater than that from the ground source, and in order to localize the low amplitude signals, the aircraft need to glide. Considering only the effects of the ground source, the optimal areas for the microphones placement were determined.

5

Vibroacoustic Helicopter Impact on Elevated Helipad

Cieślak Sławomir, Krzymień Wiesław

Transactions on Aerospace Research

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2023

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Nr 1 (270)

1--9

EN

A helicopter landing and taking off on an elevated helipad is a source of noise that affects the environment and causes vibrations of the landing pad or the building infrastructure. Vibrations are also excited by the air stream flowing through the main rotor and transferred to the landing pad by contact of the helicopter chassis. Vibrations are transferred to the building through the structure of the helipad. Depending on the damping properties of the structure and the vibro-isolating elements used, vibrations can be felt in rooms used by people and also transmitted to devices located in the building. The subject of the study described in this paper is the vibroacoustic effects of an EC-135 helicopter on an elevated landing pad during landing, standstill with the propulsion system engaged and take-off. Measurements of vibrations and noise were made at points located both on the landing pad and in the building. The paper presents selected results of measurements in various phases of flight and helicopter manoeuvres. The frequency analyses of the fragment of the measurement data for the flight phase, in which the highest levels of impact were recorded, were also performed and included. The results are presented as graphs and annotated.

6

Strefa uciążliwości hałasu turbin wiatrowych ze względu na możliwość realizacji przez pracowników ich podstawowych zadań

Pleban Dariusz, Radosz Jan

Rynek Energii

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2023

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Nr 1

49--54

PL

Zagadnienia z obszaru oddziaływania hałasu turbin wiatrowych na człowieka są tematami licznych prac i publikacji naukowych, które jednak w zdecydowanej większości dotyczą skutków tego hałasu u osób zamieszkałych w pobliżu farm wiatrowych. W Centralnym Instytucie Ochrony Pracy – Państwowym Instytucie Badawczym zrealizowano badania dotyczące oddziaływania hałasu turbin wiatrowych na człowieka, lecz w przeciwieństwie do innych badań dotyczyły one wpływu tego hałasu jako czynnika uciążliwego na możliwość realizacji przez pracowników ich podstawowych zadań. Przeprowadzono pomiary dotyczące wyznaczenia wartości poziomów hałasów turbin wiatrowych w funkcji odległości od farm wiatrowych. Obiektami badań były 3 farmy wiatrowe, zaś pomiary przeprowadzono w punktach pomiarowych zlokalizowanych w odległościach od 100 m do 3000 m od farm wiatrowych. Największe wartości równoważnego poziomu dźwięku A zostały zmierzone w punktach pomiarowych zlokalizowanych w odległości 100 m od farm wiatrowych (od 50,5 dB do 55,4 dB), a zwiększanie odległości od farm wiatrowych skutkowało zmniejszeniem mierzonych wartości poziomów hałasu turbin wiatrowych. Stwierdzono, że strefa uciążliwości hałasu turbin wiatrowych ze względu na możliwość realizacji przez pracownika jego podstawowych zadań to obszar wokół farmy/turbiny wiatrowej, na którym równoważny poziom dźwięku A hałasu turbin wiatrowych jest równy lub większy od 50 dB, zaś zasięg tej strefy nie przekracza odległości 500 m od farmy wiatrowej.

EN

Issues in the area of the impact of wind turbine noise on humans are the topics of numerous scientific works and publications, which in the vast majority concern the effects of this noise on people living near wind farms. The Central Institute for Labour Protection — National Research Institute carried out a research task on the impact of wind turbine noise on humans, but unlike other studies, it concerned the impact of this noise as an annoyance factor on the ability of employees to perform their basic tasks. The sound pressure levels of wind turbines noise as a function of distance from 3 wind farms were carried out. The measurement positions were located at distances from 100 mto 3000 m from the wind farms. The highest values of the equivalent A—weighted sound pressure level were measured in the measurement positions located at a distance of 100 m from the wind farms (from 50.5 dB(A) to 55.4 dB(A)), and increasing the distance from the wind farms resulted in the decrease in the measured values of sound pressure levels of wind turbine noise. It was found that the wind turbine noise annoyance zone due to the ability of employees ability to perform their basic tasks is the area around the wind farm/turbine, where the equivalent A-weighted sound pressure level of wind turbine noise is equal to or greater than 50 dB(A), and the range of this zone does not exceed a distance of 500 m from the wind farm.

7

Zastosowanie sieci neuronowych do detekcji impulsów o znanym kształcie w obecności silnego szumu i trendu

Betka Szymon, Blok Marek

Przegląd Telekomunikacyjny + Wiadomości Telekomunikacyjne

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2023

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nr 4

220--223

PL

Detekcja impulsów w odebranym sygnale radiowym, zwłaszcza w obecności silnego szumu oraz trendu, jest trudnym zadaniem. Artykuł przedstawia propozycje rozwiązań wykorzystujących sieci neuronowe do detekcji impulsów o znanym kształcie w obecności silnego szumu i trendu. Na potrzeby realizacji tego zadania zaproponowano dwie architektury. W pracy przedstawiono wyniki badań wpływu kształtu impulsu, mocy zakłóceń szumowych oraz trendu obecnego w sygnałach wejściowych sieci, na skuteczność detekcji zaproponowanych rozwiązań.

EN

Detecting pulses in a received radio signal, especially in the presence of strong noise and trend, is a difficult task. The article presents proposed solutions based on neural networks for the detection of pulses of known shape in the presence of strong noise and trend. Two architectures are proposed for the purpose. The paper presents the results of the study of the influence of the pulse shape, the noise power, and the trend present in the input signals of the network on the detection performance of the proposed solutions.

8

Analiza skuteczności smarownic torowych w wybranych lokalizacjach na terenie Wrocławia

Skiba Magdalena

Przegląd Komunikacyjny

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2023

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R. 78, nr 2

2--8

PL

Z uwagi na narastający problem negatywnego oddziaływania hałasu tramwajowego podjęto próbę jego ograniczenia poprzez montaż sma rownic torowych w kilku lokalizacjach we Wrocławiu. W artykule przedstawiono wyniki pomiarów na terenie wybranych pętli tramwajowych przed i po zamontowaniu smarownic torowych. Zestawiono i przeanalizowano zebrane dane wraz ze wskazaniem dalszego kierunku badań.

EN

Due to the growing problem of the negative impact of noise, an attempt was made to reduce it by installing track lubricators in several locations in Wroclaw. The article presents the results of measurements in selected tram loops before and after the installation of track lubricators. The collected data were compiled and analyzed together with an indication of the further direction of research.

9

Hałas jako szkodliwy czynnik w budownictwie

Ibadov Nabi, Krzemiński Michał

Przegląd Budowlany

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2023

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R. 94, nr 11-12

83--87

PL

Artykuł porusza kwestię hałasu, który towarzyszy pracom budowlanym. Przedstawione zostały regulacje prawne, które określają dopuszczalne poziomy hałasu i sposoby jego mierzenia. Autorzy podkreślają, że hałas w miejscach prac budowlanych może być szczególnie uciążliwy, z powodu charakteru wykonywanych prac i stosowania ciężkiego sprzętu. W artykule opisano również negatywne skutki hałasu dla zdrowia, takie jak uszkodzenia słuchu, nadmierny stres i problemy z koncentracją. W związku z tym autorzy przedstawiają sposoby zabezpieczania przed hałasem, które można zastosować w trakcie prac budowlanych. Wśród tych sposobów są między innymi środki indywidualne, takie jak słuchawki czy nauszniki, oraz środki zbiorowe, takie jak ekrany akustyczne i ścianki dźwiękochłonne.

EN

The article discusses the issue of noise that accompanies construction work. Legal regulations are presented that determine permissible noise levels and methods of measurement. The author’s emphasizes that noise in construction workplaces can be particularly burdensome due to the nature of the work and the use of heavy equipment. The article also describes the negative effects of noise on health, such as hearing damage, excessive stress, and concentration problems. Therefore, the author’s presents ways to protect against noise that can be applied during construction work. Among these methods are individual measures, such as headphones or earplugs, and collective measures, such as acoustic screens and sound-absorbing walls.

10

Noise quantization simulation analysis of optical convolutional networks

Zhang Ye, Zhang Saining, Zhang Danni, Su Yanmei, Yi Junkai, Wang Pengfei, Wang Ruiting, Luo Guangzhen, Zhou Xuliang, Pan Jiaoqing

Optica Applicata

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2023

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Vol. 53, nr 3

483--493

EN

Optical neural network (ONN) has been regarded as one of the most prospective techniques in the future, due to its high-speed and low power cost. However, the realization of optical convolutional neural network (CNN) in non-ideal cases still remains a big challenge. In this paper, we propose an optical convolutional networks system for classification problems by applying general matrix multiply (GEMM) technology. The results show that under the influence of noise, this system still has good performance with low TOP-1 and TOP-5 error rates of 44.26% and 14.51% for ImageNet. We also propose a quantization model of CNN. The noise quantization model reaches a sufficient prediction accuracy of about 96% for MNIST handwritten dataset.

11

Extreme separations of bottle posts in the southern Baltic Sea – tentative interpretation of an experiment-of-opportunity

Callies Ulrich, Storch von Hans

Oceanologia

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2023

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Vol. 65 (2)

410--422

EN

During an experiment-of-opportunity in July 2019, 27 drift bottles were released in the southern Baltic Sea. Ten of these bottles were found and reported at locations that were surprisingly widespread. In this study, we explore the chances to reproduce these findings with a numerical drift model. While trajectories may be considered as completely deterministic, in practice their prediction as well as reconstruction has a strong stochastic component, because of ubiquitous gradients on even the smallest scales. We illustrate different aspects of uncertainty including specification of leeway, random dispersion, and stretching along Lagrangian coherent structures. By and large, the results of numerical ensemble simulations seem to be in reasonable agreement with the observational evidence available. Some drift bottle findings suggest a bias in simulations, but without knowing the drift bottles’ full drift paths, a basis for more detailed model tuning is missing.

12

Badania pomieszczeń testowych w skali laboratoryjnej o przeznaczeniu mieszkalnym i dydaktycznym

Nowoświat Artur, Żuchowski Rafał, Olechowska Mercelina, Marchacz Michał

Inżynieria i Budownictwo

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2023

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R. 79, nr 11-12

648--651

PL

W artykule przedstawiono wyniki pomiarów czasu pogłosu oraz tła akustycznego w modelu laboratoryjnym pomieszczenia mieszkalnego oraz dydaktycznego. Model laboratoryjny jest zbudowany w skali rzeczywistej. Celem tego typu badań jest przygotowanie modelu oraz środowiska laboratoryjnego w taki sposób, aby można było badać systemy wentylacji przy różnych strumieniach powietrza wentylacyjnego. Systemy wentylacji mają spełniać wymagania dotyczące równoważnego poziomu dźwięku nieprzekraczającego 40 dB. Dla tak postawionego zadania zbudowano model, dla którego otrzymano wyniki poziomu tła akustycznego na poziomie 20,8 dB. Równoważny poziom dźwięku z nawiewem wentylacji wynosił 50,4 dB. Ponadto zbudowano model w oprogramowaniu ODEON, który skalibrowano, w celu późniejszego modelowania różnych parametrów akustycznych badanego wnętrza.

EN

The article presents the results of reverberation time and acoustic background measurements in a laboratory model of a living quarter and didactic room. The laboratory model is built in real scale. The purpose of this type of research is to develop a model and the laboratory environment in the way that makes it possible to test ventilation systems with various ventilation air streams. Ventilation systems have to meet the requirements for an equivalent sound level not exceeding 40 dB. To meet the above objective, a model was built for which the results of the acoustic background level of 20.8 dB were obtained. The equivalent sound level with ventilation air inflow was 50.4 dB. In addition, a model was built in the ODEON software, which was calibrated for later modeling of various acoustic parameters of the tested interior.

13

Program wspomagający ocenę narażenia zawodowego na hałas przy zastosowaniu strategii pomiarowej uwzględniającej podział na czynności wykonywane przez pracownika

Makarewicz Grzegorz, Zawieska Wiktor M.

Bezpieczeństwo Pracy : nauka i praktyka

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2023

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nr 12

20-24

PL

Hałas w środowisku pracy wciąż jest jednym z dominujących czynników szkodliwych lub uciążliwych oddziałujących na człowieka. Niezależnie od metod eliminacji hałasu istotną kwestią jest możliwość szybkiej oceny narażenia na hałas w miejscu pracy zgodnie z obowiązującymi przepisami. Czasochłonność tego procesu zależy m.in. od sposobu realizacji czynności prowadzonych w ciągu dnia pracy oraz zastosowanej strategii pomiarowej. Niekiedy przeprowadzenie oceny narażenia wymaga wykonania nie tylko pomiarów, lecz także dodatkowych złożonych obliczeń. Coraz większą rolę w tym zakresie odgrywa Internet, w którego zasobach pojawiają się programy wspomagające wymienione operacje. Przykładem takiego programu jest przedstawiony w artykule skrypt wspomagający ocenę narażenia na hałas na stanowisku pracy przy zastosowaniu strategii pomiarowej z podziałem na czynności, które pracownik wykonuje w ramach swojej pracy. Program wyznacza wartości redukcji poziomów hałasu i czasu narażenia w odniesieniu do każdej czynności prowadzącej do osiągnięcia wartości dziennego poziomu ekspozycji na hałas zgodnego z obowiązującymi przepisami.

EN

Despite the progress in noise reduction in work environment, noise is still a dominant harmful or bothersome factor affecting humans. Regardless of the noise control methods, it is important to quickly assess occupational exposure to noise in accordance with applicable regulations. The time needed to complete this process depends, among other factors, on the complexity of activities carried out during the working day and on the measurement strategy in place. Noise exposure assessment often requires not only measurements, but also additional, complex calculations. The Internet plays an increasingly important role in this respect, with programs supporting the above-mentioned operations appearing on its resources. An example of such a program is the script presented in the article supporting the assessment of noise exposure at the workplace with the use of a measurement strategy divided into activities performed by employees as part of their work. The program determines the reduction values for noise levels and exposure time for each activity leading to the daily noise exposure level in accordance with applicable regulations.

14

Nowe rozwiązanie układu przekazywania dźwięku użytkownikowi ochronnika słuchu - koncepcja i konstrukcja

Młyński Rafał, Kozłowski Emil, Morzyński Leszek

Bezpieczeństwo Pracy : nauka i praktyka

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2023

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nr 3

16-22

PL

Stosowanie ochronników słuchu wiąże się z ograniczaniem dźwięku docierającego do uszu ich użytkownika, przez co ograniczona jest również możliwość percepcji dźwięków, których odbiór jest istotny w miejscu przebywania pracownika. Z tego względu coraz powszechniej stosowane są rozwiązania w postaci układów elektronicznych wbudowanych w ochronniki słuchu, umożliwiające przekazywanie pod te ochronniki odpowiednio przetworzonych dźwięków. Rozwiązania obecnie stosowane w ochronnikach słuchu z regulowanym tłumieniem oferują możliwość wpływu na właściwości dźwięku przekazywanego użytkownikowi ograniczoną do prostej regulacji ogólnego wzmocnienia w torze odtwarzania sygnału. W artykule przedstawiono koncepcję rozwiązania przeznaczonego do wykorzystania w ochronniku słuchu i umożliwiającego dopasowanie właściwości przenoszonego dźwięku do potrzeb użytkownika dzięki poprawie odbioru użytecznych dźwięków poprzez kształtowanie charakterystyki częstotliwościowej przenoszonego dźwięku.

EN

The use of hearing protectors reduces the sound reaching the wearer's ears. As a result, the possibility of perceiving sounds, the perception of which is important in the environment of a worker's presence, is also limited. For this reason, solutions in the form of electronic systems built into hearing protectors are more and more commonly used, enabling the transmission of properly processed sounds under the hearing protectors. Solutions currently used in level-dependent hearing protectors offer the possibility of influencing the properties of the sound transmitted to the user limited to a simple adjustment of the general gain in the signal audio path. The aim of the article is to present the concept of the solution intended for use in a hearing protector and enabling the adjustment of the properties of the transmitted sound to the needs of the user, i.e. improving the reception of useful sounds. This is done by shaping the frequency response of the transmitted sound.

15

Materiał dźwiękowy wspierający przygotowanie się osób z dysfunkcją wzroku do udania się w nieznane im środowisko

Młyński Rafał, Kozłowski Emil

Bezpieczeństwo Pracy : nauka i praktyka

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2023

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nr 1

18-22

PL

W Polsce liczba osób z dysfunkcjami wzroku (uszkodzeniami i chorobami narządu wzroku), w tym osób z niepełnosprawnościami prawnymi oraz deklarujących ograniczenia w wykonywaniu normalnych czynności, stanowi aż 1/3 ogółu ludności. Powszechnie wiadomo, że słuch odgrywa ważną rolę w funkcjonowaniu osób z niepełnosprawnością narządu wzroku. Jednocześnie osoby te często boją się opuścić znane im otoczenie, np. własne domy. Istotnym wsparciem osób z niepełnosprawnością narządu wzroku byłaby możliwość zapoznania się z takimi dźwiękami, które mogą napotkać w środowisku zewnętrznym. W toku badań w CIOP-PIB zebrano zestaw dźwięków, które mogą być wykorzystane przez osoby z niepełnosprawnością narządu wzroku do zapoznania się z otoczeniem, do którego potencjalnie mogą się udać. Dźwięki nagrywano z wykorzystaniem techniki ambisonicznej oraz binauralnie za pomocą mikrofonów wbudowanych w zestaw słuchawkowy. Rozwiązania te pozwoliły na uzyskanie wrażenia przestrzennego związanego z prawidłowym kierunkiem docierania dźwięku. Materiał dźwiękowy obejmuje szereg sytuacji, w których osoba z niepełnosprawnością narządu wzroku może się znaleźć, i zawiera dźwięki zarejestrowane nie tylko w domu, lecz także np. w pobliżu skrzyżowań czy w budynkach biurowych. Dokonano niezbędnych konwersji danych w celu uzyskania plików w formacie, który można odtwarzać na słuchawkach podłączonych do komputera. Pozyskane dane przeznaczone są do wykorzystania w oprogramowaniu służącym do zapoznania osób z niepełnosprawnością narządu wzroku z potencjalnie nowymi dla nich.

EN

In Poland, the number of people with visual impairment (damage and disease of the visual organ), including legal disabilities and those who declare that they have limitations in carrying out normal activities is 1/3 of the total population. It is well known that the hearing plays an important role in the functioning of people with visual impairment. At the same time, these people are often afraid of leaving their well-known environment, such as their homes. It would be important for people with visual impairment to become familiar with surrounding sounds that they might encounter in an external environment. During the research carried out in CIOP-PIB a set of sounds has been collected that can be used by people with visual impairment to familiarize with the environment to which they can potentially go. The Ambisonics technique was used and sounds were binaurally recorded with the use of microphones built into the headset. These solutions allowed to obtain the spatial impression associated with the correct direction of the sound. The audio material includes a number of situations in which a person with a visual impairment could potentially be found, recorded not only at home but also, for example, near junctions or in office buildings. Necessary data conversions were used to obtain files in a format that could be played back over headphones connected to a PC. The data obtained is intended for use in the software familiarizing people with visual impairment with potentially new situations for them.

16

Assessment of traffic noise levels in the city of Pila

Gorzelańczyk Piotr, Sobczak Kamil, Ližbetinová Lenka

Archiwum Motoryzacji

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2023

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Vol. 100, nr 2

75--84

EN

The last few decades have been characterised by the rapid development of technology and various industries around the world, as well as increasing levels of urbanisation. The development of technology has resulted in the emergence of many inventions, vehicles and equipment. This has resulted in many unforeseen consequences generating threats to the environment in which humans’ function. One of these hazards is the noise emitted by vehicles. For this reason, environmental protection was created in response to threats to human existence (this work is to determine the level of noise resulting from traffic transportation in the city of Pila. In order to achieve the given objective in the city, sound values will be adopted and an acoustic map will be developed on their basis. A large amount of noise in the city of Pila is caused by road transportation, but from the results of the study it can be said that it is minimally exceeded only on two streets by less than five decibels and on three other streets where it is equal to the permissible noise value. The main places where the most noise is generated are two-lane roads and traffic lights and roundabouts. A lot of noise is generated when there are a large number of vehicles slowing down and starting in these places. A very big plus in the fight against noise in Pila is public transportation.

17

Study on Noise Attenuation Characteristics of Hydrofoil with Specific Cavitation Number

Xiaohui He, Zhongle Liu, Chao Yang, Zhiyong Yuan

Archives of Acoustics

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2023

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Vol. 48, No. 3

359--372

EN

In this study, the modified Sauer cavitation model and Kirchhoff-Ffowcs Williams and Hawkings (K-FWH) acoustic model were adopted to numerically simulate the unsteady cavitation flow field and the noise of a three-dimensional NACA66 hydrofoil at a constant cavitation number. The aim of the study is to conduct and analyze the noise performance of a hydrofoil and also determine the characteristics of the sound pressure spectrum, sound power spectrum, and noise changes at different monitoring points. The noise change, sound pressure spectrum, and power spectrum characteristics were estimated at different monitoring points, such as the suction side, pressure side, and tail of the hydrofoil. The noise characteristics and change law of the NACA66 hydrofoil under a constant cavitation number are presented. The results show that hydrofoil cavitation takes on a certain degree of pulsation and periodicity. Under the condition of a constant cavitation number, as the attack angle increases, the cavitation area of the hydrofoil becomes longer and thicker, and the initial position of cavitation moves forward. When the inflow velocity increases, the cavitation noise and the cavitation area change more drastically and have a superposition tendency toward the downstream. The novelty is that the study presents important calculations and analyses regarding the noise performance of a hydrofoil, characteristics of the sound pressure spectrum, and sound power spectrum and noise changes at different monitoring points. The article may be useful for specialists in the field of engineering and physics.

18

Numerical investigation of noise generated by an axial fan installed in a pipeline

Romik Dawid

Vibrations in Physical Systems

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2022

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Vol. 33, nr 1

art. no. 2022104

EN

The article presents the results of numerical calculations of noise generated by an axial fan installed in a ventilation duct with a circular cross-section. The research takes into account the installation of the axial fan due to the distance of the rotor from the curvature of the pipeline. The uRANS turbulent flow modeling methods were used in the calculations. The uRANS stands for the Navier-Stokes equation with Reynolds averaging in the version that takes into account the non-stationarity of the flow. The purpose of the work is to determine the sound power in the vicinity of the sound source. The decisive parameters affecting the noise emitted will be the length of the installation in front of and behind the rotor. The propagation of acoustic disturbances in the far field was modeled using the aeroacoustic analogy of Ffowcs-Williams and Hawkings. Based on the calculations, the directional characteristics of the sound source were determined.

19

Acoustic indicators in the analysis of the acoustic environment of the Koscieliska Valley in the Tatra National Park

Młynarczyk Dorota, Wiciak Jerzy

Vibrations in Physical Systems

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2022

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Vol. 33, nr 3

art. no. 2022325

EN

The development of our civilization and increasing noise pollution are strongly connected. In 2021, the Tatra National Park was visited by a record number of tourists - about 4 million 600 thousand. The previous record was broken in 2018 - then the Polish Tatra Mountains were visited by 3 million 800 thousand. people. The aim of the paper is the analysis of noise pollution and soundscape of the most popular national park in Poland - Tatra National Park. The Koscieliska Valley was selected for the study, because it is the second area in the park in terms of the number of tickets sold according to the statistics kept by the Tatra National Park. The paper presents the results of the analysis of acoustic measurements and ambisonic recordings made during four seasons using classical method and the soundscape method. In addition, psychoacoustic parameters and soundecology indicators such as: loudness, sharpness or roughness, ACI (acoustic complexity index), NDSI (normalized difference soundscape index), BIO (bioacoustic index), ADI (acoustic diversity index), AEI (acoustic evenness index) were calculated.

20

Technologies for monitoring the technical condition of transport infrastructure objects based on the coefficient of correlation between critical values of noise and useful signals

Aliev Telman, Musaeva Naila

Transport Problems

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2022

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T. 17, z. 2

213--224

EN

Transport infrastructure objects are exposed to a large number of loads, which cause the formation of displacements, bends, wear, cracks, breakdowns, corrosion, and other defects. It is shown that at the moment of initiation of malfunctions in objects, the noise of the noisy signals coming from the corresponding sensor takes critical values that correlate with useful signals. Therefore, algorithms are developed for calculating the probability of random noise accepting critical values, a coefficient of correlation between the critical values of the noise and the useful component, and a relay cross-correlation function. Technologies for monitoring the technical condition of transport infrastructure objects are proposed based on the estimates of the developed noise characteristics. Computational experiments are conducted, and the reliability of the developed algorithms and technologies is confirmed.