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Abstract

In October 2018, local digital radio was launched to cover the agglomeration of Wroclaw. The implementation of this undertaking required many tests, including qualitative ones, that refer to both music and speech. This paper presents the results of subjective tests based on the evaluation of speech quality of signals recorded at various points in Wroclaw. Measurements were carried out in accordance with the recommendations of the International Telecommunication Union as well as in ordinary acoustic conditions in listeners’ flats. The rating was made for male and female voices. The most important conclusion is that for speech signal assessment in meaning of the quality the test conditions do not influence the obtained results. The other fact confirmed in the experiment was that the receiving place of DAB+ signal in the Single-Frequency Network also does not affect the perceived voice quality.
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Authors and Affiliations

Stefan Brachmański
1
ORCID: ORCID
Maurycy Kin
1
Patrycja Zemankiewicz
1

  1. Wroclaw University of Science and Technology, Poland
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Abstract

Paper presents the results of quality assessment of speech and music signals transmitted via DAB+ system with the use of Single Frequency Network (SFN). The musical signals were evaluated in overall quality domain. The subjective research was provided with the use of Absolute Category Rating procedure according to the ITU recommendation and the results have been presented as the MOS values for various bit rates. The speech signals were additionally examined with PESQ method. The results have shown that the assumed quality of 4 MOS, for this kind of broadcasting could be achieved at 48 kb/s for speech and 64 kb/s for music. This fact was confirmed by both: subjective and objective research. The comparison between the results obtained for SFN broadcasting with three emitters with singleemitter broadcast was presented.

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Authors and Affiliations

Maurycy Kin
Stefan Brachmański
ORCID: ORCID
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Abstract

The paper presents a method of eliminating the tonal component of an acoustic signal. The tonal component is approximated by a sinusoidal signal of a given amplitude and frequency. As the parameters of this component: amplitude, frequency and initial phase may be variable, it is important to detect these parameters in subsequent analysis time intervals (frames). If the detection of the parameters is correct, the elimination consists in adding a sinusoidal component with the detected amplitude and frequency to the signal, but the phase shifted by 180 degrees. The accuracy of the reduction depends on the accuracy of parameters detection and their changes.
Detection takes place using the Discrete Fourier Transform, whose length is changed to match the spectrum resolution to the signal frequency. The operation for various methods of synthesis of the compensating signal as well as various window functions were checked. An elimination simulation was performed to analyze the effectiveness of the reduction. The result of the paper is the assessment of the method in narrowband active noise control systems. The method was tested by simulation and then experimentally with real acoustic signals. The level of reduction was from 6.9 to 31.5 dB.

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Bibliography

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Authors and Affiliations

Michał Łuczyński
1
Andrzej Dobrucki
1
Stefan Brachmański
1
ORCID: ORCID

  1. Wroclaw University of Science and Technology, Chair of Acoustics and Multimedia, Wroclaw, Poland
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Abstract

Courts in Poland, as well as in most countries in the world, allow for the identification of a person on the basis of his/her voice using the so-called voice presentation method, i.e., the auditory method. This method is used in situations where there is no sound recording and the perpetrator of the criminal act was masked and the victim heard only his or her voice. However, psychologists, forensic acousticians, as well as researchers in the field of auditory perception and forensic science more broadly describe many cases in which such testimony resulted in misjudgement. This paper presents the results of an experiment designed to investigate, in a Polish language setting, the extent to which the passage of time impairs the correct identification of a person. The study showed that 31 days after the speaker’s voice was first heard, the correct identification for a female voice was 30% and for a male voice 40%.
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Authors and Affiliations

Stefan Brachmański
1
ORCID: ORCID
Bartosz Hus
1
Piotr Staroniewicz
1
ORCID: ORCID

  1. Faculty of Electronics, Photonics and Microsystems, Department of Acoustics, Multimedia and Signal Processing Wrocław University of Science and Technology

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