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Abstract

The aim of this paper is to analyze the possibility of using a mobile phone with a voice recorder function as a phonocardiographic signal recorder. Test measurements were carried out by placing the phone at various points on the chest. For one selected point, measurements were carried out for a group of 120 people, using different models of mobile phones. Data on weight, height and age were collected through a survey. Participants of the study were also asked about diagnosed heart defects and potential problems related to the measurement. Signal quality was assessed using quality parameters. It was checked how the selected methods of signal pre-processing (editing of recordings, filtering) affect the values of quality parameters. The obtained recordings were subjected to automatic signal classification.
The result of this work is an extended analysis of the use of mobile phones as electronic stethoscopes and an analysis of the usefulness of signals obtained using this measurement method. The results of these studies are important for the field of medical diagnostics, especially in situations where access to traditional stethoscopes is limited. If mobile phones prove to be effective recorders of phonocardiographic signals, it will open new possibilities in the field of remote heart monitoring and telemedicine. However, it should be noted that further research, including validation and comparison of results obtained with mobile phones with those obtained with traditional stethoscopes, is needed before this technology is introduced into clinical practice.
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Authors and Affiliations

Michał Łuczyński
1

  1. Wroclaw University of Science and Technology
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Abstract

A set of microphones spatially arranged in space in a specific pattern is called a microphone array. It can be used to extract and enhance the signal of interest from its observation corrupted by other interfering signals, such as noise or to estimate the direction of arrival of a source. In this paper we focus on a problem in which the desired signal (speech signal) is interfered by other signal with fully overlapping bandwidth but with different localization. Our goal is to attenuate the interfering signal. We experimentally study the method in which microphones do not have to be equally spaced and all information regarding signal phase is hidden in a transfer function of the microphone. We focus on determining the microphones positions and FIR filter coefficients so that the actual output the beamformer is as close as possible to the desired one (the level of speech signal remains unchanged, while the interfering signal is attenuated) in the sense of ���� norm. To solve this problem, we use a metaheuristic algorithm. Next, we construct the array and make an experiment in anechoic chamber. The initial results of the experiment show that the proposed method can be applied for array designing.
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Authors and Affiliations

Agnieszka Wielgus
1
Bogusław Szlachetko
1
Michał Łuczyński
1

  1. Wrocław University of Science and Technology
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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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Authors and Affiliations

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

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

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