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Effect of Curvature Shape of Transparent COVID-19 Protective Face Shields on the Speech Signal

Bjelić Miloš, Mijić Miomir, Miljković Tatjana, Šumarac Pavlović Dragana

Archives of Acoustics

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2024

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Vol. 49, nr 1

27--35

EN

Recent papers and studies over the course of last three years have shown that COVID-19 has a negative impact on the speech communication quality between people. This paper presents an influence analysis of the curvature shape of protective transparent shields on the speech signal. Five shields made of the same material and dimensions but with different curvatures were analyzed, from a completely flat to a very curved shield which has the same shape of curvature at its top and bottom and covers the entire face. The influence of the shield is analyzed with two types of experiments – one using dummy head with integrated artificial voice device, and the other using real speakers (female and male actors). It has been shown that usage of protective shields results in a relative increase in the speech signal level, in the frequency range of around 1000 Hz, compared to the situation when protective shields are not used. The relative increase in speech signal levels for large-curvature shields can be up to 8 dB. The possible causes of this phenomenon have been analyzed and examined.

2

Correction of Evanescent Wave Influence on the Flexural Wave Velocity and Wavelength Estimation Based on a Mode Shape Function

Pantelić Filip, Šumarac Pavlović Dragana, Mijić Miomir, Ridley-Ellis Daniel

Archives of Acoustics

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2022

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Vol. 47, No. 4

539--546

EN

The aim of this research is to use a simple acoustic method of a very near field recording, which enables measurement and display of oscillation modes, to estimate the velocity of flexural waves, based on the wavelengths of standing waves measured on the sample. The paper analyses cases of 1D geometry, flexural waves that occur on a beam excited by an impulse. Measurements were conducted on two different samples: steel and a wooden beam of the same length. Due to the appearance of evanescent waves at the boundary regions, the distance between the nodes of standing waves that occur deviates from half the wavelength, which can be compensated using a correction factor. Cases of fixed and free boundary conditions were analysed. By quantifying how much the boundary conditions change the mode shape function, it can be predicted how the mode of oscillation changes if the boundary conditions change, which can also find application in musical acoustics and sound radiation analysis.

3

Influence of Overpressure Breathing on Vowel Formant Frequencies

Vojnović Milan, Mijić Miomir, Šumarac Pavlović Dragana, Vojnović Nebojša

Archives of Acoustics

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2021

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Vol. 46, No. 1

177--181

EN

Voice controlled management systems are based on speech recognition techniques. The use of such systems in combat aircraft is complex due to a number of critical factors which affect the accuracy of speech recognition, such as high level of ambient noise and vibration, use of oxygen masks, serious psycho-physical stress of speakers, etc. One of the specificity of the oxygen mask application is overpressure breathing. The results of the simulations presented in this paper show that the presence of overpressure on the order of 1000 Pa in the vocal tract has a significant influence on the first two formant frequencies. The formants discrimination field is significantly reduced when oxygen mask is used, influencing both perceptive and automatic discrimination of spoken vowels.