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    Wyświetlanie 1-4 z 4
    Tytuł:
    Funkcja autokorelacji w analizie szerokopasmowych sygnałów krótkookresowych
    Autocorrelation function in wide band transient signals analysis
    Autorzy:
    Kiciński, W.
    Powiązania:
    https://bibliotekanauki.pl/articles/152633.pdf
    Data publikacji:
    2010
    Wydawca:
    Stowarzyszenie Inżynierów i Techników Mechaników Polskich
    Tematy:
    szumy krótkookresowe
    funkcja autokorelacji
    falka Malvara
    transient noise
    autocorrelation function
    Malvar wavelet
    Opis:
    Artykuł dotyczy analizy krótkookresowych sygnałów szerokopa-smowych, będących przejawem aktywności obiektów w środowisku podwodnym. Zaproponowany sposób detekcji sygnałów nie wymaga przyjęcia założeń o gaussowskim rozkładzie szumów środowiska pomiarowego. Jego istotą jest analiza ciągów próbek wartości chwilowej sygnału pomiarowego za pomocą falki Malvara, usunięcie redundantnych współczynników przekształcenia falkowego a następnie badanie charakteru zmienności funkcji autokorelacji współczynników falkowych.
    The problem of transient hydroacoustic signals detection has been considered. The presented method of transient detection differs from the methods discussed in literature, where gaussian probability distribution is usually assigned. The proposed procedure does not need any assumptions about probability distribution of ambient noise. This is very important, because the probability distribution of ambient noise in underwater environments is not gaussian, especially in coastal range. The presented method combines two powerful detection tools: the wavelet analysis and the analysis of the autocorrelation function curvature. The proposed algorithm uses the Malvar wavelet transformation and the procedure of signal denoising in wavelet coefficients space. The procedure of transient detection has been based on the properties of the autocorrelation function, which slowly goes to zero for noise with oscillatory ingredients and very quickly approaches zero for noise signals. The performance of the presented method has been illustrated on example of three real transient signals caused by air bubbles accompanying object activities in an underwater environment.
    Źródło:
    Pomiary Automatyka Kontrola; 2010, R. 56, nr 8, 8; 897-900
    0032-4140
    Pojawia się w:
    Pomiary Automatyka Kontrola
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Hearing Ability in Orchestral Musicians
    Autorzy:
    Pawlaczyk-Łuszczyńska, M.
    Dudarewicz, A.
    Zamojska, M.
    Śliwińska-Kowalska, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/177978.pdf
    Data publikacji:
    2010
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    musicians
    exposure to orchestral noise
    hearing impairment
    pure-tone audiometry
    transient-evoked otoacoustic emissions
    Opis:
    Pure-tone audiometry (PTA) and transient-evoked otoacoustic emissions (TEOAEs) were determined in 57 classical orchestral musicians along with a questionnaire inquiry using a modified Amsterdam Inventory for Auditory Disability and Handicap ((m)AIADH). Data on musicians’ working experience and sound pressure levels produced by various groups of instruments were also collected. Measured hearing threshold levels (HTLs) were compared with the theoretical predictions calculated according to ISO 1999:1990. High frequency notched audiograms typical for noise-induced hearing loss were found in 28% of the subjects. PTA and TEOAE consistently showed a tendency toward better hearing in females vs. males, younger vs. older subjects, and lower- vs. higher-exposed to orchestral noise subjects. Audiometric HTLs were better than theoretical predictions in the frequency range of 2000–4000 Hz. The (m)AIADH scores indicated some hearing difficulties in relation to intelligibility in noisy environment in 26% of the players. Our results indicated a need to implement a hearing conservation program for this professional group.
    Źródło:
    Archives of Acoustics; 2010, 35, 4; 579-594
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    A Numerical Study of The Heat Transfer Intensification Using High Amplitude Acoustic Waves
    Autorzy:
    Rulik, S.
    Wróblewski, W.
    Powiązania:
    https://bibliotekanauki.pl/articles/177492.pdf
    Data publikacji:
    2018
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    cavity noise
    sound wave cooling
    flow over a cavity
    transient cooling
    blade cooling intensification
    Opis:
    The current practice in the efforts aiming to improve cooling conditions is to place emphasis on the application of non-stationary flow effects, such as the unsteady jet heat transfer or the heat transfer intensification by means of a high-amplitude oscillatory motion. The research presented in this paper follows this direction. A new concept is put forward to intensify the heat transfer in the cooling channels with the use of an acoustic wave generator. The acoustic wave is generated by a properly shaped fixed cavity or group of cavities. The sound generated by the cavity is a phenomenon analysed in various publications focused on the methods of its reduction. The phenomenon is related to the feedback mechanism between the vortices flowing from the leading edge and the acoustic waves generated within the cavity. The acoustic waves are generated by the interaction between the vortices and the cavity walls. Strong instabilities can be observed within a certain range of the free flow velocities. The investigations presented in this paper are oriented towards the use of the phenomenon for the purposes of the heat transfer process intensification. The first part of the work presents the numerical model used in the analysis, as well as its validation and comparison with empirical relations. The numerical model is constructed using the commercial CFD Ansys CFX-16.0 commercial program. The next part includes determining of the relationship between the amplitude of the acoustic oscillations and the cooling conditions within the cavity. The calculations are performed for various flow conditions.
    Źródło:
    Archives of Acoustics; 2018, 43, 1; 31-47
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Hearing Status in Young People Using Portable Audio Players
    Autorzy:
    Pawlaczyk-Łuszczyńska, M.
    Zaborowski, K.
    Zamojska-Daniszewska, M.
    Rutkowska-Kaczmarek, P.
    Dudarewicz, A.
    Śliwinska-Kowalska, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/176501.pdf
    Data publikacji:
    2017
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    portable audio players
    PAPs
    pure-tone audiometry
    transient-evoked otoacoustic emissions
    TEOAEs
    hearing threshold levels
    high-frequency notches
    noise-induced hearing loss
    Opis:
    The aim of this study was to evaluate the hearing status in young adults using portable audio players (PAPs) in relation to their listening habits. The study included 58 subjects, aged 22.8±2.8 years, non-occupationally exposed to noise. Questionnaire inquiry aimed at collecting personal data, the information on PAPs usage habits, self-assessment of hearing status and identification of risk factors for noise-induced hearing loss (NIHL) were performed in study subjects. Hearing tests included pure-tone audiometry (PTA) and transient-evoked optoacoustic emission (TEOAE). All subjects were PAPs users. Depending on listening habits they were divided into the subgroups of “frequent” users (>1 h/day) and “non-frequent” users (≤1 h/day). There were no significant differences between subgroups in prevalence of NIHL risk factors and self-assessment of hearing status. However, frequent users more often complained of tinnitus and hyperacusis. Majority (81.9 %) of participants had normal hearing. Nevertheless, 6.9 % of audiograms showed high-frequency notches typical for NIHL. Both, the PTA and TEOAE indicated worse hearing in non-frequent users compared to frequent users. No significant differences in prevalence of high-frequency notches between subgroups were noted. The outcomes do not support some previous studies results that the excessive exposure to music listened through PAPs might result in accelerating of development of NIHL loss in young adults.
    Źródło:
    Archives of Acoustics; 2017, 42, 1; 113-120
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-4 z 4

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