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1

The influence of the surface of ventilation duct on sound attenuation in the airflow

Kopania Joanna Maria, Wójciak Kamil, Gaj Patryk, Bogusławski Grzegorz

Archives of Acoustics

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2026

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Vol. 51, nr 2

317--331

EN

These studies focus on acoustical parameters of steel flat-oval ducts as a function of their roughness. The four types of steel ducts were measured: raw steel, galvanised steel, painted steel, and aluminium as the reference one. The roughness of the duct was measured, and roughness parameters were specified. The sound power level was obtained on the specially constructed stand test with an outlet to the reverberation room. Insertion losses to evaluate the acoustic attenuation performance of the studied steel ducts were obtained. In the present study, an aluminium duct, which is very smooth with minimal airflow friction, was treated as a low-noise object (‘silencer’). These studies have shown that for each of the tested steel ducts, the self-noise is higher than for the aluminium duct. The largest differences in this self-noise were observed at a velocity of 12 m/s for the galvanised duct and the raw steel duct compared to the aluminium duct. Insertion losses in straight ducts are consistent with literature and are very low for flat-oval steel ducts. Aluminium duct performs better acoustically than the other ducts studied at lower velocities; however, as airflow velocity increases, the differences in acoustic performance between the materials become less pronounced. This suggests that aerodynamic effects dominate over material surface treatments at higher velocities.

2

Impact of perforated sheet geometry on the insertion loss of absorptive silencers

Wójciak Kamil, Kopania Joanna Maria, Gaj Patryk

Archives of Acoustics

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2026

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Vol. 51, nr 2

415--426

EN

This study evaluates the influence of perforated sheet geometry on the acoustic and aerodynamic performance of absorptive silencers. A modular silencer is developed, enabling the installation of six different perforated metal sheets with varying hole shapes (round, square, elongated), sizes (2 mm to 20 mm), and open area ratios (22 % to 45 %). Glass wool is used as the sound-absorbing filling. Insertion loss, self-noise, and pressure drop are measured in a large reverberation chamber, within the frequency range from 50 Hz to 10 000 Hz, for airflow velocities of 4 m/s, 6 m/s, and 8 m/s. The results indicate that all configurations provide comparable attenuation at low frequencies. Silencers with small round perforations (diameter 2 mm to 6 mm) ensure higher insertion loss and lower self-noise in the mid-frequency range of 1000 Hz to 5000 Hz, without any measurable increase in pressure drop compared to variants with larger or elongated holes. For frequencies above 6300 Hz, perforated sheets with larger holes perform better. Pressure loss differences between all configurations do not exceed 1 Pa at a given flow velocity. The results confirm that aperture size is the primary parameter affecting silencer acoustic effectiveness, while aperture shape and perforation ratio are secondary. These findings provide practical guidelines for optimal silencer design in ventilation systems, ensuring maximum noise reduction with minimal airflow resistance.

3

The acoustic performance of the different types of plenum boxes for ceiling panels

Kopania Joanna Maria, Bogusławski Grzegorz, Wójciak Kamil, Gaj Patryk

Vibrations in Physical Systems

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2025

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Vol. 36, nr 1

art. no. 2025103

EN

The aerodynamic noise generated by side entry plenum boxes intended for ceiling diffusers was studied. The plenum boxes in the inflow duct were tested in an anechoic room at low to moderate Reynolds numbers. Two characteristic phenomena were discussed: a way of fixing the cross-bar into the plenum box and vertical or horizontal throttle placement on the junction of the channel and plenum box on the acoustic parameters of plenum boxes. The characteristic peak in the LAeq spectrum moves to the higher frequencies with increased flow velocity linked with the flow around the crossbar inside the boxes. Additionally, the different positions of the throttle inside the plenum box were important for the acoustic parameters of the studied boxes. The vertical and horizontal positions of the throttle give various signals in the acoustic spectrum of studied objects.

4

Acoustic properties of the absorption silencers with a micro-perforated channel in the air-flow

Wójciak Kamil, Kopania Joanna Maria, Gaj Patryk

Vibrations in Physical Systems

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2025

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Vol. 36, nr 1

art. no. 2025112

EN

Micro-perforated panels (MPPs) are known as thin sheets. There are perforated thickness-through hole with sized in the sub-millimetre range. With holes on such a small scale, the panels alone can provide high acoustic resistance and low acoustic reactance, conducive to effective sound absorption. Micro-perforated liners can be useful for attenuation in the low-frequency noise in ducted. The main objective of the paper is to compare the influence of testing facilities on the measured aeroacoustic performance of tested prototype silencers under an airflow between 4 and 12 m/s. This standard specifies the methods of ISO 7235 for determining the sound power level of the flow noise generated by silencers, the total pressure of silencers, and the insertion loss of silencers with and without airflow by using the substitute object. In this work, we focused on the correlation between the size of the hole in the studied silencers and its acoustic parameters, and also its relation to the insertion loss of silencers.

5

The noise study of ceiling swirl diffuser with serrated adjustable blades

Kopania Joanna Maria, Bogusławski Grzegorz, Wójciak Kamil, Gaj Patryk

Vibrations in Physical Systems

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2024

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Vol. 35, nr 2

art. no. 2024202

EN

In this study, measurements of the aeroacoustic properties of air terminal devices (ATDs) control room ventilation. As a study object the ceiling swirl air diffuser with adjustable blades was chosen. These are mechanical devices designed to control fluid flow and create a swirl to supply air into rooms. They are also the source of the noise in rooms. In this work, the new construction of blades was proposed based on the owl's wings. The blades were printed on a 3D printer from ABS and polished. The two positions of attached blades to the front panel of the diffuser were studied - when the serrated and unseratted edge was leading edge. The front panel of the diffuser with blades was installed on the plenum box with a side entry without the damper. The measurements were made in the reverberation room according to ISO 5135 to find the blade's position with lower noise parameters.

6

Noise testing of multi-disc fan

Wójciak Kamil, Gaj Patryk, Kopania Joanna Maria

Vibrations in Physical Systems

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2024

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Vol. 35, nr 2

art. no. 2024216

EN

The impeller of a multi-disc fan was made of rotating smooth discs spaced close together. The concept of such a machine came from Nikola Tesla in 1909. The fluid, based on the principle of friction against the rotating surfaces of the discs, flows outwards from the disc pack into an outlet. According to the literature, such a design is characterized by low noise emissions. Based on calculations, a prototype of a multi-disc fan was designed and then manufactured. Tests were carried out for the sound power level emitted from the fan's outlet. The examination was performed in a reverberation chamber according to the ISO 3741:2010 standard. The noise source was visualized using an acoustic camera. The aerodynamic characteristics were also determined experimentally according to the ISO 5801:2017 standard. The aim of this study is provide insight into the acoustic and aerodynamic characteristics of a multi-disc fan.

7

Zagrożenia BHP pracowników firm zewnętrznych wykonujących prace na obiektach energetycznych

Karczewski Jacek, Kopania Joanna, Gaj Patryk, Wójciak Kamil

Energetyka

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2024

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nr 10

420--423

PL

W artykule omówiono zagrożenia, na jakie narażeni są pracownicy wykonujący prace na obiektach energetycznych. W szczególności dotyczy to pracowników firm zewnętrznych zatrudnionych w energetyce. Podano wyniki autorskich badań ankietowych przeprowadzonych wśród tych pracowników. Opracowano specyfikację rodzajów zagrożeń związanych z wykonywaniem prac przy urządzeniach elektroenergetycznych z podziałem na podsektory: wytwarzania, przesyłu, dystrybucji i użytkowania energii elektrycznej oraz dokonano analizy zagrożeń i ich możliwych skutków. Omówiono stan prawny dotyczący zagadnień BHP w zakresie przepisów Unii Europejskiej i prawa krajowego.

EN

Presented are here risks that can face the employees working on power objects. This especially concerns the outsourced staff employed in the power sector. Given are resuls of the Author's own surveys of these workers. Developed is the specification of types of risks relating to execution of works on the electric power equipment with segmentation Into subsectors: generation, transmission, distribution and the use of electric energy as well as there is made an analysis of risks and their possible effects. Discussed is the actual legal state of OSH issues in the scope of the EU regulations and our domestic law.

8

Problematyka hałasu w energetyce

Karczewski Jacek, Kopania Joanna, Gaj Patryk, Wójciak Kamil

Energetyka

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2024

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nr 10

424--427

PL

W artykule omówiono zagadnienia związane z hałasem generowanym w energetyce. Omówiono źródła hałasu związane z wytwarzaniem (generacja konwencjonalna i OZE) i przesyłem energii elektrycznej. Zwrócono uwagą na związane z hałasem czynniki zagrażające zdrowiu ludzi oraz uwarunkowania środowiskowe. Podano przepisy regulujące zagadnienia związane z walką z hałasem oraz zaprezentowano dopuszczalne poziomy hałasu w środowisku, powodowanego przez poszczególne grupy źródeł hałasu. Omówiono środki i sposoby (bierne i aktywne) redukcji hałasu (tłumiki, osłony akustyczne, ATH).

EN

Discussed are here problems relating to the noise generated in the power industry. Described are noise sources connected with generation (conventional and RES) and transmission of the electric energy. Attention is paid to factors related to the noise and threatening human health as well as to the environmental conditions. Given are regulations concerning the issues connceted with noise reduction and presented are admissible in the environment levels of noise caused by various groups of noise sources. Discussed are ways and means (active and passive) of noise reduction (silencers, acoustic shields, ATH).

9

Correlation between the shape of substitution ducts and insertion loss of silencers

Wójciak Kamil, Kopania Joanna Maria

Vibrations in Physical Systems

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2022

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Vol. 33, nr 2

art. no. 2022212

EN

Silencers are typical devices used for the reduction of noise in ventilation systems, which can be found in almost all industrial, service or residential installations. Determination of acoustic parameters for specific HVAC devices, like silencers, is within the scope of specialised laboratories. With the silencers, two main parameters should be taken care of: the first one is sound attenuation and the second one is pressure losses. In the presented paper, the focus is on measurement methods described by standard ISO 7235:2009. This standard specifies the methods for determining the sound power level of the flow noise generated by silencers, the total pressure of silencers and the insertion loss of silencers with and without airflow by using the substitute object. In this work, we focused on the correlation between the shape of the substitution duct and its acoustic parameters and its relation to this with the final result of insertion loss of a silencer.

10

Aeroacoustical study of the serrated ventilation dampers

Kopania Joanna Maria, Bogusławski Grzegorz, Wójciak Kamil, Gaj Patryk

Vibrations in Physical Systems

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2022

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Vol. 33, nr 3

art. no. 2022313

EN

The serrated ventilation dampers for regulation of airflow volume were tested. The computer fluid flow analysis was conducted using the Comsol program. The nature of the flow through the serrated ventilation damper was analyzed to identify the different turbulence regions formed on the airflow field. Additionally, the aerodynamical and acoustical parameters of these blades of ventilation dampers with different serrated trailing and/or leading-edge were studied. The aeroacoustic studies were done in the reverberation room. The sound power level and loss coefficient were determined for the studied models.

11

Influence of shell shape on flow and acoustic parameters of a steam silencer

Gaj Patryk, Sobczak Krzysztof, Kopania Joanna, Wójciak Kamil

Archives of Thermodynamics

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2021

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Vol. 42, no. 4

141--154

EN

Steam discharge produces noise due to rapid expansion and a temperature drop of ejected steam. This is why steam silencers are used to change one-stage into multi-stage expansion, which reduces the intensity of pressure and temperature drop during this process and shifts emitted noise into higher frequencies, which are easier to dampen. This paper presents a flow-acoustic numerical model of a steam silencer. It is meant to help to obtain a precise analysis of phenomena occurring in steam silencers and improve the process of designing this type of device. The model described in this paper was based on the parameters of a real working unit manufactured in the Institute of Power Engineering – Thermal Technology Branch. Most of the steam silencers are designed based on construction guidelines that have not been changed for a long time. This restrained an increase in the acoustics efficiency of the steam silencers. An improvement of their flow and acoustic properties allows for the development of smaller, more efficient, and lighter construction. The current version of the model was used for the analysis of flow and acoustic changes which occur after modifying the lower region of a shell of the steam silencer. The proposed modification allowed for a 19% increase in mass flow rate through the silencer and noise reduction in the low-frequency range.

12

The impact of the damper blade position on the generated noise and pressure losses in plenum box with swirl diffusers

Wójciak Kamil, Gaj Patryk, Kopania Joanna, Bogusławski Grzegorz

Vibrations in Physical Systems

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2019

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Vol. 30, nr 1

art. no. 2019103

EN

The article presents the effect of setting the throttle in the plenum box with swirl diffuser on the generated noise and the pressure losses. The sound power levels of the source was determined using the precision method in the reverberation room in accordance with the PN-EN ISO 3741:2011 standard. The examination was carried out for damper blade position set vertically and horizontally for full opening and at a 45 degree angle in both directions. In order to confirm the universality of the conducted experiment, the tests were carried out for two different face swirl diffuser with different shapes of air control blades and holes in the plate and for different flow rates. The multi-criteria optimization methods were used to select the best throttle position.

13

Noise radiation from circular rods at low-moderate Reynolds number

Kopania Joanna Maria, Bogusławski Grzegorz, Gaj Patryk, Wójciak Kamil

Vibrations in Physical Systems

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2019

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Vol. 30, nr 1

art. no. 2019116

EN

The well-known dominant sources of airframe noise are associated with unsteadiness of separated and/or vortical flow regions around the high-lift system (flaps, slats) and the aircraft undercarriage (landing gear). Current practical landing gear noise prediction models are individual component - based, which means that the various components are divided into groups according to the frequency range, in which they predominantly radiate noise. Since the far-field noise spectra are approximately Strouhal - based, the emitted frequency is assumed to be directly related to their size: the large elements are responsible for the low frequency region of the spectra, and the small components for the high frequency region. On the basis of such understanding of the noise generation mechanism, the special configurations that lead to considerable noise suppression were proposed. One element of these configurations are rods with different shape and cross section. In this work the situation when circular rods are in area of laminar-turbulent flow were analysed. The measurements were carried out for single circular rod with different diameters to study the noise effect depended on Reynolds number. Far field noise for broad range of Reynolds numbers was also examined depending on distance from the source of noise.

14

Determination of sound power level by using a microphone array and conventional methods

Bogusławski Grzegorz, Kopania Joanna Maria, Gaj Patryk, Wójciak Kamil

Vibrations in Physical Systems

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2019

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Vol. 30, nr 1

art. no. 2019139

EN

Sound power is measured to make objective comparisons between the same type of products, but also because legislation requires it. To release a new product, it is often compulsory to certify it according to International Organization for Standardization (ISO) standards, and also with national and local regulations. Determining of sound power is not a straightforward process. Sound power can be determined through the measurement of sound pressure (series 3740 methods) or sound intensity (series 9614 methods). Selecting one of the above methods depends on the purpose of the test, as well as the available equipment, desired grade of accuracy, background noise level or the test environment. Nowadays the additional methods, such as microphone arrays are used to located of the noise source and determined of pressure sound level. But the results obtained with acoustic cameras cannot be, for now, used for legislative purposes (are not ISO compliant). In this work the differences in the determination of sound power level by using conventional ISO methods and microphone arrays are determined. The system composed of a loudspeaker and a fan were used as a sound source of the noise. Sound power levels according to ISO 3746 and ISO 9614-1 were determined and were compared with the developed method by using microphone arrays techniques.

15

Assessment of sound absorbing properties of composite made of recycling materials

Gaj Patryk, Kopania Joanna, Wójciak Kamil, Bogusławski Grzegorz

Vibrations in Physical Systems

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2019

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Vol. 30, nr 1

art. no. 2019109

EN

In modern world we are searching methods to reuse most of industrial disposals produced during manufacturing. Some kinds of materials, like scraps from acoustic foam, however are not so easily utilized using recycling methods for its primary usage. Disposals produced during the manufacturing process can be compressed and reused as sound absorbing material. The purpose of this article is to examine sound absorbing properties of material made of acoustic foam disposals and compare it with sound protection materials, which are commonly used. Sound absorbing damping were tested using Kundt’s tube and reverberation room examination method. Tests were carried out according to standard PN-EN ISO 354:2005, for reverberation room examination, and according to Bruel&Kjaer electronic instruments technical manual for Kundt’s tube examination.