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Abstract

The Chinese word identification and sentence intelligibility are evaluated by grades 3 and 5 students in the classrooms with different reverberation times (RTs) from three primary school under different signal-to-noise ratios (SNRs). The relationships between subjective word identification and sentence in- telligibility scores and speech transmission index (STI) are analyzed. The results show that both Chinese word identification and sentence intelligibility scores for grades 3 and 5 students in the classroom in- creased with the increase of SNR (and STI), increased with the increase of the age of students, and decreased with the increase of RT. To achieve a 99% sentence intelligibility score, the STIs required for grades 3, grade 5 students, and adults are 0.71, 0.61, and 0.51, respectively. The required objective acoustical index determined by a certain threshold of the word identification test might be underestimated for younger children (grade 3 students) in classroom but overestimated for adults. A method based on the sentence test is more useful for speech intelligibility evaluation in classrooms than that based on the word test for different age groups. Younger children need more favorable classroom acoustical environment with a higher STI than older children and adults to achieve the optimum speech communication in the classroom.
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Abstract

Chinese is a tonal language, which differentiates it from non-tonal languages in the Western countries. A Chinese character consists of an initial, a final, and a tone. In the present study, the effects of noise and reverberation on the Chinese syllable, initial, final, and tone identification in rooms were investigated by using simulated binaural impulse responses through auralization method. The results show that the syllable identification score is the lowest, the tone identification score is the highest, and the initial identification scores are lower than those of the final identification under the same reverberation time and signal-to-noise ratio condition. The Chinese syllable, initial, and final identification scores increase with the increase of signal-to-noise ratio and decrease of the reverberation time. The noise and reverberation have insignificant effects on the Chinese tone identification scores under most room acoustical environments. The statistical relationship between the Chinese syllable articulation and phoneme articulation had been experimentally proved under different noise and reverberation conditions in simulated rooms.
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Abstract

This article presents the results of the research of noiseimmunity of wireless communication systems using signals that are formed on the basis of eight-position quadrature-amplitude modulation (8-QAM) and eight-position amplitude modulation of many components (8-AMMC). The research was conducted using simulation of a wireless communication system, built using a detector, implemented on the basis of a phase locked loop. The influence of phase locked loop parameters on the detection quality of these signals in the condition of the interference in the communication channel was researched, and a comparative analysis of the noise immunity of wireless communication systems using these signals was carried out.
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Abstract

This paper provides an overview of the effects of timing jitter in audio sampling analog-to-digital converters (ADCs), i.e. PCM (conventional or Nyquist sampling) ADCs and sigma-delta (ΣΔ) ADCs. Jitter in a digital audio is often defined as short-term fluctuations of the sampling instants of a digital signal from their ideal positions in time. The influence of the jitter increases particularly with the improvements in both resolution and sampling rate of today's audio ADCs. At higher frequencies of the input signals the sampling jitter becomes a dominant factor in limiting the ADCs performance in terms of signal-to-noise ratio (SNR) and dynamic range (DR).
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