Jianxin Peng

Relationship between Chinese speech intelligibility and speech transmission index in rooms based on auralization

Based on simulated monaural and binaural room impulse responses, the relationship between Chinese speech intelligibility scores and speech transmission index (STI) including the effect of noise is investigated using a phonetically balanced test in virtual rooms. The results show that Chinese speech intelligibility scores increase monotonically with STI values. The correlation coefficients are 0.95, 0.90 and the standard deviation is 5.6%, 6.7% under diotic and dichotic listening conditions, respectively. Compared with diotic listening based on monaural room impulse responses, dichotic listening based on binaural room impulse responses can improve by 2.7dB signal-to-noise ratio for Chinese speech intelligibility. The STI method can better predict and evaluate Chinese speech intelligibility in rooms.

Chinese speech intelligibility and its relationship with the speech transmission index for children in elementary school classrooms

The present study investigated Chinese speech intelligibility in 28 classrooms from nine different elementary schools in Guangzhou, China. The subjective Chinese speech intelligibility in the classrooms was evaluated with children in grades 2, 4, and 6 (7 to 12 years old). Acoustical measurements were also performed in these classrooms. Subjective Chinese speech intelligibility scores and objective speech intelligibility parameters, such as speech transmission index (STI), were obtained at each listening position for all tests. The relationship between subjective Chinese speech intelligibility scores and STI was revealed and analyzed. The effects of age on Chinese speech intelligibility scores were compared. Results indicate high correlations between subjective Chinese speech intelligibility scores and STI for grades 2, 4, and 6 children. Chinese speech intelligibility scores increase with increase of age under the same STI condition. The differences in scores among different age groups decrease as STI increases. To achieve 95% Chinese speech intelligibility scores, the STIs required for grades 2, 4, and 6 children are 0.75, 0.69, and 0.63, respectively.

Characteristic analysis of cavitation bubbles in carbon dioxide fluid

After analysing the characteristics of bubble cavitation in high-pressure carbon dioxide (CO2) fluid, cavitation conditions and some correlative physical characteristics are investigated. The results show that the ultrasonic intensity of liquid carbon dioxide to make cavitation occur is affected by the initial radius of the bubbles, hydrostatic pressure, temperature and vapour pressure within the bubbles in liquid CO2. At the low frequency of ultrasound, the phase-speed of the liquid CO2 gradually approaches the sound speed of the pure liquid when void fraction increases. At high frequency, the phase-speed is nearly equal to the sound speed in the liquid under different void fractions. The attenuation of ultrasound in liquid carbon dioxide reaches a maximum near the resonance frequency and then decreases when frequency either increases or decreases. At the resonance frequency, the phase-speed and the attenuation increase when the void fraction increases.

Improved computation of pressure coefficient and temperature coefficient of ultrasonic velocity in organic liquids

Based on Jacobson’s molecular free length theory in liquids and the relationship between the ultrasonic velocity and the molecular free length in organic liquids, the equations of pressure coefficient and temperature coefficient of ultrasonic velocity in organic liquids are derived. The calculated pressure coefficient and temperature coefficient of ultrasonic velocity are in good agreement with the measured results.