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1
Content available remote

On the Management of Direct and Reflected Sounds in the 5.0 Surround Sound Reproduction System

100%
Kleczkowski P., Król A., Małecki P.
Acta Physica Polonica A
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2015
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vol. 128
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issue 1A
A-11-A-16
EN
Direct and ambient sounds are usually reproduced through the same loudspeakers. In multichannel systems, with the use of anechoic recordings and auralization techniques it is possible to separate these sound components so that they are reproduced via different loudspeakers. Four basic options of management of direct and reflected sounds were investigated in a perceptual experiment. One sound source and the standard 5.0 surround sound system was used. It was found that listeners consistently preferred sound reproduction with direct sound radiated from only one loudspeaker.
2
Content available remote

Adaptive Approach to Acoustic Car Driving Detection in Mobile Devices

100%
Aksamit P.
Acta Physica Polonica A
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2013
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vol. 124
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issue 3
381-383
EN
The context awareness of mobile devices is broadly researched area as it improves the functionality, usability, safety of usage and intelligence of the device as perceived by its user. The special type of context is driving a car. The awareness of a mobile device whose user drives a car may allow to disable some features like making and taking phone calls and enable other features like e.g. navigation thus improving the safety of the user. The paper presents the results of a research on acoustic detection of car driving based on over 60 h of collected data. The modification of traditional k-nearest neighbors classification algorithm is proposed that allows for learning and adaptation of classifier configuration. The proposed approach significantly improves both the sensitivity and specificity of the classifier comparing to the classifier based only on offline training data. The challenges in performing the acoustic wave analysis using highly heterogeneous devices like mobile phones are discussed.
3
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Analysis of Acoustic Signals Interfering Diagnostic Measurements of Electric Power Transformer Tap Changers

100%
Boczar T., Cichoń A., Borucki S., Szczyrba T.
Acta Physica Polonica A
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2013
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vol. 124
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issue 3
387-390
EN
Subject matter of this paper applies to improvement of acoustic emission method used in the diagnosis of on load tap changers of high power transformers. During measurement of acoustic emission signals generated by damages or defects, which can appear in insulation system and in the power transformer tap changers, various forms of noise signals may occur. Interferences occurring during measurements under laboratory and under industrial conditions can be generated either by sources placed inside the studied electric power device or they can be emitted in their immediate vicinity. Sources of interfering signals are physical phenomena of a mechanical, electrical or acoustical nature. Interferences appearing during measurement of acoustic emission pulses generated by electrical discharges and other types of defects that overlap the measured waveforms may result in their distortion. As part of the research conducted, the results of which are presented in this paper, following was subjected under consideration: measurements of acoustic noise signals generated by partial surface discharges occurring on support and bushing insulators were performed.
4
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Influence Estimation of the Voltage Value on the Measurement Results for the Optical Radiation Generated by Partial Discharges on Bushing Isolator

100%
Frącz P.
Acta Physica Polonica A
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2011
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vol. 120
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issue 4
604-608
EN
The subject area of the paper concerns determination of possibility and application scope suggestion for the optical spectrophotometry method in the linear isolators diagnosis. Measurements results of the optical radiation emitted by partial discharges generated on a model of bushing isolator, which was placed in the air, are presented in the paper. Recording was done by use of a spectrophotometer that enabled for measurement of optical radiation in the range from 250 to 1700 nm. The main aim of laboratory research works performed was to estimate the influence of the supply voltage value changes in range from 0 to 60 kV on the intensity and character of the optical radiation spectrum emitted by surface partial discharges occurring on the ceramic insulating surface of the bushing isolator. In the scope of research works, analysis of voltage value changes influence on the gathered spectra was performed while its accretion and decrease was investigated. Furthermore, the measurements and analysis performed enclose the influence estimation of the time, when the voltage was attached to the high voltage electrode, on the proceeding of the optical phenomena connected with generation of surface partial discharges. In addition a comparative analysis of measurements results gathered for two designed and implemented models of bushing insulators, which differ in geometric dimensions, was performed.
5
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Analysis and Elaboration of an Air-Coupled Ultrasound Wideband Sensor Array

100%
Herman K., Stach L.
Acta Physica Polonica A
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2013
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vol. 123
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issue 1
31-33
EN
In this paper a design process of 64 sensor matrix is described. This study presents adaptation of well known sonar engineering methods of analysis in order to design air operating ultrasound beamforming system. The elaborated system is based on wideband micro electro-mechanical systems. A full digital beamformer with advanced digital signal processing block description is also included. The main goal of the system is direct of arrival of ultrasound wave estimation.
6
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The Application of the Correlative Analysis and the Regression Function for Determining Correlations οf the Measurement Results of Acoustic Emission Generated by Partial Discharges

100%
Boczar T., Frącz P.
Acta Physica Polonica A
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2009
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vol. 116
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issue 3
281-284
EN
The subject matter of this paper is connected with development of the assessment methods of results obtained at measurements of partial discharges occurring in insulation systems of power transformers using the acoustic emission method. The paper presents the results connected with determining correlation between partial discharge generation voltage and selected descriptors characterizing the emitted signals of acoustic emission in the frequency domain. Authors use the selected descriptors as comparative criteria for recognition of the basic partial discharge forms that may occur in paper-oil insulation of power transformers. The correlation coefficient and regression function were used to determine the correlation degree between the variables under study.
7
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Convolutive Blind Signal Separation Spatial Effectiveness in Speech Intelligibility Improvement

100%
Kociński J., Sęk A., Libiszewski P.
Acta Physica Polonica A
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2011
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vol. 119
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issue 6A
996-999
EN
Blind signal separation is one of the latest methods to improve the signal to noise ratio. The main objective of blind source separation is the transformation of mixtures of recorded signals to obtain each source signal at the output of the procedure, assuming that they are statistically independent. For acoustic signals it can be concluded that the correct separation is possible only if the source signals are spatially separated. That finding suggests analogies with the classical spatial filtering (beamforming). In this study we analyzed an effect of the angular separation of two source signals (i.e. speech and babble noise) to improve speech intelligibility. For this purpose, we chose the blind source separation algorithm based on the convolutive separation, based on second order statistics only. As a system of sensors a dummy head was used (one microphone inside each ear canal), which simulated two hearing aids of a hearing impaired person. The speech reception threshold, before and after the blind source separation was determined. The results have shown significant improvement in speech intelligibility after applying blind source separation (speach reception threshold fell even more than a dozen dB) in cases where the source signals were angularly separated. However, in cases where the source signals were coming from the same directions, the improvement was not observed. Moreover, the effectiveness of the blind source separation, to a large extent, depended on the relative positions of signal sources in space.
8
Content available remote

Precise Psychoacoustic Correction Method Based on Calculation of JND Level

100%
Piotrowski Z.
Acta Physica Polonica A
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2009
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vol. 116
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issue 3
375-379
EN
This paper constitutes a proposal of a method of spectral shaping of the watermark signal without adjusting the interception point based directly on psychoacoustics of the human auditory system and the proposed calculation formula. The proposed calculation formula enables correction of watermark signal both as regards its spectrum shape and adjustment of watermark signal to the host's JND.
9
Content available remote

Cavity Enhanced Absorption Spectroscopy Sensor

100%
Nowakowski M., Wojtas J., Bielecki Z., Mikołajczyk J.
Acta Physica Polonica A
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2009
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vol. 116
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issue 3
363-367
EN
The paper presents opportunities of cavity enhanced absorption spectroscopy technique application in nitrogen oxides (NO_{x}) detection. In this method the concentration of an absorbing gas is determined by measure of decay time of the light pulse trapped in an optical cavity. The measurements are not sensitive to fluctuation of both laser power and photodetector sensitivity. The cavity enhanced absorption spectroscopy technique is a modification of cavity ring down spectroscopy technique where the off-axis adjustment of the resonator is used. NO_{x} detection is carried out in the visible and infrared range. The signal is registered with a developed low noise photoreceiver. Features of the presented sensor show that it is possible to build a portable trace gases sensor. Its sensitivity could be comparable with chemical detectors. Such a system has several advantages: relatively low price, small size and weight, and detection possibility of other gases.
10
Content available remote

Intraoperative Impedance Measurements for the Evaluation of Perimodiolar Location οf Cochlear Implant Electrode - Own Experience

100%
Stieler O., Karlik M., Szyfter W.
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issue 1
161-163
EN
Evaluation of insertion of a cochlear implant electrode into the cochlea includes radiological techniques: plain X-ray of the skull, cochlear projection (based on Stenvers projection), computer tomography. These methods allow generally postoperative evaluation. During surgery the insertion of the electrode is assessed based on anatomical structures and markers placed on the electrode. The measurement of the electrode impedance is also an important tool. 60 patients implanted with the Contour cochlear implant with pre-shaped electrode were examined. Age o patients: mediana 4.25 (1.5-54.5). Examination includes intraoperative impedance measurement performed in two stages: (1) after the electrode insertion, and (2) after removal of the stylet. Measurements were done in Common Ground (CG) and Monopolar 1 (MP1) stimulation modes. Measurements recorded in two modes and in 3 different parts of the cochlea (apical, middle, basal) were compared. The average difference value (before-after) was for the CG mode: 0.45 kΩ, and for the MP1 mode: 0.39 kΩ. For the CG mode the difference values were: 0.64, 0.44 and 0.28 toward apical part. For the MP1 mode the difference values were: 0.47, 0.43 and 0.27 toward apical part of the cochlea.
11
Content available remote

Cardiac Activity Based on Acoustic Signal Properties

100%
Czopek K.
Acta Physica Polonica A
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2012
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vol. 121
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issue 1A
A-42-A-45
EN
The influence of sleeping conditions on human health and well-being is now fully understood, but still underestimated. Sleep disorders e.g. snoring, wheezing or sleep apnea are widespread among people of all ages, although prevalent amidst the male population, obese people with a high value of BMI, people who suffered a stroke, have hypertension or other heart diseases. Medical support is needed in order to ensure a good night's sleep for patients suffering from sleep disorders. Sleep monitoring is also very important in case of emergencies. This research was aimed at finding a correlation between sleep disorders represented by acoustic signals and heart activity parameters. The measurement of breathing through simultaneously acquired acoustic and ECG signals is used to quantify the respiratory obstruction during sleep. The information collected by synchronized recording of acoustic effects and the ECG signal partly overlaps, giving an opportunity to improve accuracy of measurement. Results indicate that the aspect of sleep analysis can be extended using this method. The information collected by simultaneous recording of acoustic effects and the ECG signal is provided and the results are described.
12
Content available remote

Analysis of Polish Pathological Speech by Higher Order Spectrum

100%
Wszołek W., Kłaczyński M.
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issue 1
190-191
EN
This paper presents a next, consecutive stage of the authors' research, concerning the search for additional signal processing methods, which could be used for objective detection and registration of pathological changes in the larynx and vocal tract area. This paper presents pathological speech analyzing by suitably directed higher order spectra analysis (HOSA).
13
Content available remote

Application of Vibratometry in Evaluation of Frequency Detection and Signal Intensity in Patients with Unilateral Cochlear Implants - Preliminary Results

100%
Sekula A., Pruszewicz A., Stieler O., Gibasiewicz R., Karlik M., Komar D.
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EN
Vibratometry is a unique audiological test used in patients with bilateral profound sensori-neural hearing loss. An acoustic stimulus is presented using the bone conduction. The study comprised 15 patients with bilateral profound hearing loss with unilaterally implanted cochlear implant. Vibration detection thresholds were noted. Measurements were done at the implanted side with speech processor either switched on or switched off, as well as at the contralateral side with speech processor switched on. All the patients have perceived stimulus used for testing. The average detection thresholds of vibration stimulus and average thresholds in bone conduction using tonal stimulus have shown better perception of vibration delivered by bone conduction than tonal stimulus. The average detection threshold of vibration stimulus in the implanted ear showed significantly better results in case of speech processor switched on. Patients perceived high frequency stimuli during vibratometry testing despite of no reaction to tonal stimulation during bone conduction test. Vibration could be a supplementary stimulation in patients with bilateral perceptive profound hearing loss.
14
Content available remote

Identification of Deformation Processes within Power Oil Transformers Using Maps of ADC Descriptors in Selected Frequency Bands

75%
Olszewska A.
Acta Physica Polonica A
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2013
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vol. 124
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issue 3
525-528
EN
The paper presents identification results of deformation processes within power oil transformers where - according to dissolved gas analysis investigation results - partial discharges took place. The original method worked out for analysis of acoustic emission signals recorded within tested transformer and particularly maps of ADC descriptors have been applied. Analysis has been carried out within chosen frequency bands in order to distinguish signals coming from different sources (among other things partial discharges, Barkhausen's effect, circulation of the oil, and outer acoustic sources). One source of partial discharges has been identified within the tested transformer as a result of analysis of acoustic emission signals.
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