Wyniki wyszukiwania - BazTech

1

Application of an ambisonic microphone for the measurements of room acoustic parameters

Jasiński Maciej, Żera Jan

Vibrations in Physical Systems

|

2022

|

Vol. 33, nr 3

art. no. 2022312

EN

The most commonly used measurement technique in room acoustics employs a single omnidirectional microphone for recording the room impulse response and further derivation of such acoustical parameters as T30, EDT, C50 or C80. Instead, ambisonic technology makes it possible to measure a spatial room impulse response. Ambisonics decomposes the signal from the spherical microphone array into spherical harmonics to shape the directivity. Ambisonics lets to go beyond basic acoustical parameters and allows to determine spatial features of a sound field at the measurement point. This study presents the comparison of fundamental acoustic parameters measured in the recording studio by an actual omnidirectional microphone and virtual omnidirectional microphones derieved from ambisonic microphones of the first and third order. The results show the usefulness of ambisonic technology in terms of assessing basic room parameters.

2

Analysis of the Usefulness of Measurement on a Board at Ground Level for Assessing the Noise Level from a Wind Turbine

Wszołek Tadeusz, Pawlik Paweł, Mleczko Dominik, Chronowska Jagna

Archives of Acoustics

|

2020

|

Vol. 45, No. 1

165--175

EN

The specific working conditions of the wind turbine in strong wind cause a number of problems in the measurement of noise indicators used in its short and long-term assessment. The wind is a natural working environment of the turbine, but it also affects the measurement system, moreover, it can be a secondary source of other sounds that interfere with the measurement. One of the effective methods of eliminating the direct impact of wind on the measurement system is placing the microphone on the measurement board at ground level. However, the obtained result can not be directly compared with the admissible values, as it has to be converted to a result at a height of 4 m. The results of previous studies show that this relation depends, inter alia, on the speed and direction of the wind. The paper contains the results of measurements on the measurement board, according to EN 61400-11:2013, and at a height of 4 m above ground made simultaneously in three points around the 2 MW turbine at various instantaneous speeds and changing wind directions. Analysis of the impact of measuring point location on the measurement result of noise indicators and the occurrence of additional features affecting the relationship between the values measured on the board and at the height of 4 m, and especially the tonality, amplitude modulation and content of low frequency content, was made.

3

Analysis of the usefulness of distinctive noise features from rail and wheel in assessing their impact on the overall railway noise level

Wszołek Tadeusz, Majchrowicz Justyna

Diagnostyka

|

2019

|

Vol. 20, No. 4

103--109

EN

The interaction of the wheel and rail is the main source of railway noise over a wide speed range. The relationship between wheel and rail noise on the overall level depends on the pass-by speed, with the dominance of noise from the rail at low speeds and the reverse relationship at higher speeds. Therefore, as part of the work the issue of analyzing the characteristic features of the acoustic signal generated on a selected section of the railway line from three different passenger trains TLK, Stadler and Pendolino was taken. The spectra of LEQ levels and their spread in 1/3 octave bands and spectral moments were adopted as the main distinctive features. The degree of aggregation of permanent features assigned to the track and variable features characteristic for passing-by trains were analysed. There were also tested their usefulness in the assessment of the impact of noise from wheels and rails on the overall level of railway noise from the tested units. The obtained results confirm the usefulness of the features based on the analysis of the spread of results in 1/3 octave bands in differentiating noise sources from rail and wheel, with slightly less usefulness of spectral moments.

PL

Interakcja koła z szyną jest głównym źródłem hałasu kolejowego w szerokim zakresie prędkości. Relacja pomiędzy wpływem hałasu od koła i szyny na poziom ogólny zależy od prędkości przejazdu, z dominacją hałasu od szyny przy niskich prędkościach i relacji odwrotnej przy prędkościach wyższych. Dlatego w ramach pracy podjęto zagadnienie analizy cech dystynktywnych sygnału akustycznego generowanego na wybranym odcinku linii kolejowej od trzech różnych jednostek - pociągów osobowych TLK, Stadler oraz Pendolino. Jako główne cechy przyjęto widma poziomów LEQ i ich rozrzuty w czasie przejazdu w pasmach 1/3 oktawy oraz momenty widmowe. Analizowano stopień agregacji cech stałych przypisanych do torowiska oraz cech zmiennych charakterystycznych dla przejeżdżających pociągów i ich przydatności w ocenie wpływu hałasu od kół i szyn na poziom ogólny hałasu kolejowego od badanych jednostek na danym odcinku. Otrzymane wyniki potwierdzają niezłą przydatność cech opartych o analizę rozrzutu wyników w pasmach 1/3 oktawy w różnicowaniu źródeł hałasu od szyny i koła, przy nieco mniejszej przydatności momentów widmowych.

4

Identification of probability distribution form for results of sound level measurements

Batko W., Przysucha B.

Mechanics and Control

|

2013

|

Vol. 32, no. 1

6--12

EN

The authors focus their attention on the identification of the probability distribution density function of the sound level, which constitutes the basis for the proper statistical inferences and uncertainty assessments in the environment acoustical hazard control. Their functional form is a metric for the analysis of acoustical measurement results burdened with random errors. Its proper selection conditions the rightness of statistical inferences in relation to the analysed noise effect. The problem of identification of the noise level probability distribution form was presented on the grounds of the sound LA level monitored at one of the main streets in Lublin. The analysis of differences and references to the normal distribution form, commonly applied to statistical analysis of the acoustical measurement results, was carried out. It is the aim of the authors, that the presented results should become the basis of a broader discussion concerning new estimation procedures of the controlled noise indicators and their uncertainty assessment. Also new verification procedures of the rightness of model acoustical formalisms, assumed in numerous environment acoustic investigations, are required.

XX

W artykule przedstawiono sposób estymacji funkcji gęstości rozkładu prawdopodobieństwa dla losowej próby wyników pomiaru poziomów dźwięku LA przesuniętym rozkładem gamma. Sformułowano potrzebę jej znajomości w kontekście środowiskowych akustycznych badań kontrolnych i związanych z nimi ocen ich niepewności. Dokonano analizy różnic i odniesień do postaci rozkładu normalnego, powszechnie wykorzystywanego w statystycznych analizach wyników pomiarów akustycznych. W zamierzeniu autorów zaproponowane rozwiązanie winno stać się podstawą szerszej dyskusji nad poszukiwaniami nowych algorytmów estymacji kontrolowanych wskaźników hałasu oraz ocen ich niepewności, a także procedur identyfikacji i weryfikacji akustycznych formalizmów modelowych przyjmowanych w badaniach

5

Assessment of Teachers' Exposure to Noise in Selected Primary Schools

Augustyńska D., Kaczmarska A., Mikulski W., Radosz J.

Archives of Acoustics

|

2010

|

Vol. 35, No. 4

521-542

EN

The assessment of teachers’ exposure to noise in primary schools was carried out on the basis of: questionnaire studies (covering 187 teachers in 3 schools), noise measurements at the teachers’ workplaces, measurements of the school rooms acoustic properties (reverberation time and speech transmission index STI in 72 classrooms), analysis of statistical data regarding hazards and occupational diseases in the education sector. The studies have shown that noise is the main factor of annoyance in the school environment. Over 50% of questioned teachers consider noise as annoying and near 40% as very annoying or unbearable. A-weighted equivalent continuous sound pressure levels measured in classrooms, teacher rooms and common rooms are in the range of 58–80 dB and they exceed 55 dB (criteria of noise annoyance). The most frequently reported subjective feelings and complaints (over 90%) are: growth of psychical and emotional tension, irritation, difficulties in concentrating, hoarseness, cough. Noise in schools is also a harmful factor. High A-weighted equivalent continuous sound pressure levels ranging from 80 to 85 dB, measured in corridors during pauses and in sports halls, can cause the risk of hearing damage among PE teachers and persons oversensitive to noise. The latter concerns both teachers and pupils. High background noise levels (55–65 dB) force teachers to raise their voice. It can lead to the development of an occupational disease – chronic voice disorders due to excessive vocal effort lasting for at least 15 years. In the education sector 785 new cases of this disease were reported only in 2008. Poor acoustics in classrooms (reverberation time ranging from 0.8 to 1.7 s, STI < 0.6 in 50% of classrooms) have an adverse influence on speech reception and make the teaching and learning processes difficult.

6

Spatial audio reproduction by headphones using binaural room impulse responses measured individually by the listener

Mickiewicz W., Sawicki J.

Pomiary Automatyka Kontrola

|

2007

|

R. 53, nr 6

30-33

EN

Listening via headphones in opposition to a loudspeaker reproduction introduces changes in the perception of acoustic atmosphere and spaciousness (internalisation effect). This can be changed using the Head Related Transfer Function (HRTF) technology. In the paper there is presented an idea of the headphones processor which uses an individualized Binaural Room Impulse Response (BRIR) measured for a given listener and for a given acoustical environment. There is investigated the influence on the performance of the individualized headphones processor of acoustical properties of the room, length of the BRIR and electroacoustical chain quality. The main goal of this research was to evaluate the minimum requirements, which have to be fulfilled by the processing algorithm to obtain a good subjective performance.

PL

Odsłuch słuchawkowy w porównaniu z odsłuchem przez głośniki wprowadza zmiany w postrzeganej atmosferze akustycznej i przestrzenności nagrania (efekt internalizacji). Można to zmienić korzystając z technologii HRTF (ang. Head Related Transfer Function). W niniejszym artykule przedstawiono koncepcję procesora słuchawkowego wykorzystującego dwuuszne odpowiedzi impulsowe pomieszczenia (BRIR) mierzone w konkretnym pomieszczeniu odsłuchowym przez końcowego użytkownika systemu. Przeprowadzono badania dotyczące wpływu akustyki pomieszczenia, długości użytych BRIR i jakości elektroakustycznego toru pomiarowego na skuteczność działania procesora. Głównym celem tych badań było określenie minimalnych wymagań, jakie musi spełnić proponowany algorytm, aby zapewnić zadowalające efekty subiektywne.

7

Ryzyko zawodowe związane z narażeniem na hałas na stanowiskach pracy przy młotach kuźniczych

Wawrzeńczyk-Zdżyłowska A.

Bezpieczeństwo Pracy : nauka i praktyka

|

2003

|

nr 11

24-26

PL

Przedmiotem artykułu jest ocena ryzyka zawodowego związanego z narażeniem na hałas na stanowiskach pracy przy młotach kuźniczych w kuźni zakładu mechanicznego. W konkluzji stwierdzono, że ryzyko zawodowe na tym stanowisku jest nieakceptowane i zalecono stosowanie odpowiednich ochronników słuchu.

EN

This article discusses occupational risk assessment related to exposure to noise at workstations with forging hammers in a forging shop of a mechanical plant. The conclusion is that occupational risk in this workstation is unacceptable. Appropriate hearing protectors are recommended.