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    Tytuł:
    Frequency Discrimination for Amplitude Modulated Sinusoidal Signals at High Carrier Frequencies
    Autorzy:
    Sęk, A.
    Kordus, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/1359956.pdf
    Data publikacji:
    2014-04
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    43.66.Fe
    43.66.Hg
    Opis:
    The current study is a continuation of experiments presented by Sęk and Bukała (Acta Physica Polonica A 123, 1106 (2013)). The purpose of the present study was to investigate frequency discrimination of amplitude modulated high frequency carriers. Using 2AFC procedure, the subjects were presented with two observation intervals of which the first interval contained four pulses of the same high frequency signal (called SSSS), while in the second interval (called SHSH) the second and fourth pulses had higher frequencies values (i.e. shifted upwards by Δ f). The carrier frequency (in S pulses) was fixed and equal to 10 kHz. Modulation rates were equal to 100, 200, 337, 500, 600, 733, and 800 Hz. The value of the modulation rate was limited to keep all components of the sinusoidal modulation within one auditory filter (17% of the center frequency) centered at the carrier frequency. Two different types of modulation were used: a simple sinusoidal modulation with the modulation depth m set to 100%, and a logarithmic modulation with the modulation depth m set to 50 dB. Results indicate a strong relationship between frequency discrimination threshold and modulation type. The thresholds are significantly higher for logarithmic modulation in comparison to sinusoidal modulation. Amplitude modulation as well as logarithmic modulation applied to the high frequency carrier cause significant increase in the frequency discrimination threshold. For high frequency sinusoidal signal carriers (i.e. close to 10 kHz), frequency discrimination thresholds do not depend on amplitude modulation rates up to about 800 Hz. In general, the excitation pattern mechanism was a primary cue enabling frequency discrimination of modulated and unmodulated signals to compare with the mechanism based on the temporal fine structure. However, the excitation pattern was not the only mechanism responsible for the frequency discrimination.
    Źródło:
    Acta Physica Polonica A; 2014, 125, 4A; A-149-A-154
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Effects of Low- and High-Frequency Side Bands of Notched Noise on Masking and Auditory Filter Shape at Very High Frequencies
    Autorzy:
    Kordus, M.
    Kowalewski, B.
    Powiązania:
    https://bibliotekanauki.pl/articles/177387.pdf
    Data publikacji:
    2015
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    auditory filters
    notched noise
    Patterson’s method
    masking
    Opis:
    This paper is concerned with the determination of the auditory filter shape using the notched noise method with noise bands symmetrically located above and below a probe frequency of 10 kHz. Unlike in the classical experiments conducted with the use of Patterson method the levels as well as power spectrum densities of the lower and upper component bands of the notched noise masker were not the same and were set such as to produce the same amount of masking at the 10-kHz frequency. The experiment consisted of three conditions in which the following values were determined: (I) the detection threshold for a 10-kHz probe tone in the presence of a noise masker presented below the tone’s frequency; (II) the level of a noise masker presented above the 10-kHz probe tone frequency, at which the masker just masked the probe tone, (III) the detection threshold for a probe tone in the presence of a notched-noise masker. The data show a considerable amount of variability across the subjects, however, the resulting frequency characteristics of the auditory filters are consistent with those presented in the literature so that the Equivalent Rectangular Bandwidth is less than 11% of their centre frequency.
    Źródło:
    Archives of Acoustics; 2015, 40, 3; 329-336
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Loudness Functions and Binaural Loudness Summation in Bilateral Cochlear Implant Users
    Autorzy:
    Kordus, M.
    Zera, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/177754.pdf
    Data publikacji:
    2017
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    loudness
    binaural loudness
    loudness function
    binaural summation
    cochlear implant
    Opis:
    Loudness functions and binaural loudness summation was investigated in acoustically stimulated bilaterally implanted cochlear implant users. The study was aimed at evaluating growth of loudness functions and binaural loudness summation in cochlear implant subjects as a function of stimulus presentation level at different frequencies. Loudness was assessed using a rating procedure on a scale of 0 to 100. Three experimental conditions were tested: monaural right, monaural left and binaural, each with bands of noise with center frequencies of 0.25, 1, and 4 kHz. Fifteen implanted and five normal-hearing subjects (control group) participated in the experiments. Results demonstrated large variability in the slopes of the loudness functions and the presence of loudness summation in bilateral cochlear implant users, with large individual differences among subjects.
    Źródło:
    Archives of Acoustics; 2017, 42, 3; 351-364
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Binaural masking of amplitude modulation
    Autorzy:
    Kordus, M.
    Sęk, A.
    Kociński, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/177557.pdf
    Data publikacji:
    2005
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    masking
    masking in the modulation domain
    modulation filterbank
    Opis:
    A new concept concerned with the transformation of acoustic stimuli in the auditory system postulates the existence of a form of spectral analysis applied to the amplitude changes of the stimuli. It is assumed that this analysis takes place in the so-called modulation filters, i.e. bandpass linear filters tuned to different rates of the amplitude changes. The most striking argument supporting this idea is an effect of masking in the amplitude modulation domain whose nature can be easily explained basing on this concept. As the modulation filters are situated on the higher levels of the auditory system, it is also assumed that this form of masking is entirely a central process. However, most of the studies concerned with masking in the modulation domain used monaural listening only. Therefore, the main purpose of the presented here experiments was to investigate whether this type of masking is entirely a central process. Using a Three-Alternative Forced-Choice (3AFC) procedure the binaural and monaural masked thresholds of amplitude modulation were determined. A sinusoidal carrier at a frequency of 4 kHz was amplitude modulated by a specially designed band of noise characterized by a very low value of the crest factor, which was used as a masking signals. Different bandwidths of the modulating masking signals were used as well as different center frequencies to investigate whether the masking patterns in the modulation domain depend on the masker bandwidth and its center frequency. The modulating target (masked) signal was a pure tone at a frequency range from 2 to 256 Hz. Both modulating signals were applied to the same sinusoidal carrier signal. The most effective masking was noticed when the rate of the sinusoidal modulation was close to the center frequency of the masking signal or when it was in its spectral range and decreased outside of this range. The character of this dependence confirms the existence of some form of a frequency selectivity in the modulation rate domain similarly to the audible frequency domain. The thresholds for monaural and binaural listening were very close to each other. This implies that masking in the modulation domain is a central process.
    Źródło:
    Archives of Acoustics; 2005, 30, 1; 5-17
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    An Influence of Directional Microphones on the Speech Intelligibility and Spatial Perception by Cochlear Implant Users
    Autorzy:
    Kordus, M.
    Tyler, R. S.
    Żera, J.
    Oleson, J. J.
    Powiązania:
    https://bibliotekanauki.pl/articles/177968.pdf
    Data publikacji:
    2015
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    localization
    bilateral cochlear implants
    adults
    microphone
    beamformer
    Opis:
    The objective of the study is to assess the hearing performance of cochlear implant users in three device microphone configurations: omni-directional, directional, and beamformer (BEAMformer two-adaptive noise reduction system), in localization and speech perception tasks in dynamically changing listening environments. Seven cochlear implant users aided with Cochlear CM-24 devices with Freedom speech processor participated in the study. For the localization test in quiet and in background noise, subjects demonstrated significant differences between different microphone settings. Confusion matrices showed that in about 70% cases cochlear implant subjects correctly localized sounds within a horizontal angle of 30–40◦ (±1◦ loudspeaker apart from signal source). However localization in noise was less accurate as shown by a large number of considerable errors in localization in the confusion matrices. Average results indicated no significant difference between three microphone configurations. For speech presented from the front 3 dB SNR improvements in speech intelligibility in three subjects can be observed for beamforming system compared to directional and omni-directional microphone settings. The benefits of using different microphone settings in cochlear implant devices in dynamically changing listening conditions depend on the particular sound environment.
    Źródło:
    Archives of Acoustics; 2015, 40, 1; 81-92
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Wpływ pojemności przechwytywacza na podstawowe parametry ciśnieniowe aparatu udojowego
    The effect of vacuum tank on basic vacuum parameters of a milking unit
    Autorzy:
    Wiercioch, M.
    Kordus, R.
    Powiązania:
    https://bibliotekanauki.pl/articles/286586.pdf
    Data publikacji:
    2006
    Wydawca:
    Polskie Towarzystwo Inżynierii Rolniczej
    Tematy:
    dój maszynowy
    przechwytywacz
    parametry ciśnieniowe doju
    machine milking
    vacuum tank
    milking unit
    vacuum parameters of milking
    Opis:
    Analizowano wpływ zmiany pojemności przechwytywacza (Vz) w dojarce bańkowej na średnie podciśnienie ssania (pss), amplitudę podciśnienia ssania (aps), różnicę podciśnień między końcem strzyka a kolektorem (dp1max1) oraz na dynamikę narastania podciśnienia na końcu strzyka (Sr). Stwierdzono istotny wpływ pojemności przechwytywacza na analizowane parametry ciśnieniowe doju przy zmiennym natężeniu cieczy mlekozastępczej Qm w zakresie od 2 do 8 kg/min.
    The basic vacuum parameters of milking were analyzed: average vacuum during suction phase (pss), the fluctuation of vacuum during suction phase (aps), the differences in vacuum levels between the teat end and the milk claw (dp1max1), increase of vacuum rate on the teat end (Sr) using vacuum tank 20-150 dm3 in bucket milking machine. The effect of vacuum tank during simulated outflow of liquid Qm was determined.
    Źródło:
    Inżynieria Rolnicza; 2006, R. 10, nr 4(79), 4(79); 327-333
    1429-7264
    Pojawia się w:
    Inżynieria Rolnicza
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Stabilność podciśnienia roboczego przy zmiennym obciążeniu układu próżniowego dojarki mechanicznej
    The effect of the vacuum system stress on stabilization of the working vacuum milking machine
    Autorzy:
    Kordus, R.
    Wiercioch, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/289239.pdf
    Data publikacji:
    2006
    Wydawca:
    Polskie Towarzystwo Inżynierii Rolniczej
    Tematy:
    dój mechaniczny
    aparat udojowy
    stabilność układu podciśnienia
    machine milking
    milking units
    stabilization system vacuum
    Opis:
    Analizowano stabilność podciśnienia roboczego Dsp (iloczyn maksymalnej amplitudy spadku podciśnienia a i czasu stabilizacji podciśnienia tsp) w krótkim przewodzie mlecznym podczas podłączania kolejnych aparatów udojowych przy zmiennym natężeniu cieczy. Stwierdzono istotne różnice pomiędzy wynikami uzyskanymi podczas pomiarów przy braku przepływu cieczy (Qm = 0 kg/min), oraz w obecności zmiennego natężenia przepływu w zakresie od 2 do 8 kg/min. Wraz ze wzrostem liczby podłączonych aparatów udojowych wzrastała wartość Dsp. Znaleziono równanie empiryczne opisujące parametr Dsp.
    The pressure parameters of vacuum systems were described (the amplitude of drop of vacuum a, the time of stabilization of vacuum the tsp, Dsp=a * tsp). Essential differences between theoretical research Qm=0 kg/min and results of studies Qm=2 - 8 kg/min were noted. Dsp value increased with increase of the connected milking unit.
    Źródło:
    Inżynieria Rolnicza; 2006, R. 10, nr 3(78), 3(78); 119-125
    1429-7264
    Pojawia się w:
    Inżynieria Rolnicza
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-7 z 7

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