Effect of adding artificial reverberation to speech-like masking sound

Time-reversed speech has been known to effectively mask information for speech privacy applications. However, the annoyance and distraction caused by the time-reversed speech-like masking sound is higher than other masking sound. This study investigates the effects of adding artificial reverberation to the time-reversed speech. Subjective listening tests have been conducted to measure the intelligibility of target speech, annoyance and distraction caused by the masking sound. The experimental results suggest that adding artificial reverberation to a speech-like masking sound has a significant effect to reduce the annoyance level while maintaining the masking effectiveness of the original masking sound. A trend was also observed that the addition of artificial reverberation could reduce the level of distraction caused by the masking sound.     

Verifying two commercial software implementations of impulse-response-based speech intelligibility measurements

A number of objective evaluation methods are currently used to quantify the speech intelligibility in a built environment, including the speech transmission index (STI), rapid speech transmission index (RASTI), articulation index (AI), and the percent articulation loss of consonants (%ALCons). Certain software programs can quickly evaluate STI, RASTI, and %ALCons from a measured room impulse response. In this project, two impulse-response-based software packages (WinMLS and SIA-Smaart Acoustic Tools) were evaluated for their ability to determine intelligibility accurately. In four different spaces with background noise levels less than NC 45, speech intelligibility was measured via three methods: (1) with WinMLS 2000; (2) with SIA-Smaart Acoustic Tools (v4.0.2); and (3) from listening tests with humans. The study found that WinMLS measurements of speech intelligibility based on STI, RASTI, and %ALCons corresponded well with performance on the listening tests. SIA-Smaart results were correlated to human responses, but tended to under-predict intelligibility based on STI and RASTI, and over-predict intelligibility based on %ALCons.     

高频语抗噪声通讯系统的语言可懂度实验研究

通过对高频语抗噪声通讯系统的研究，并经实验证明该系统的高频语通讯具有很强的抗环境噪声功能，较好地解决了噪声环境中的传递语音，高频语生成的数学表达。高频语通讯装置的研究设计；采用该装置在实验室内分别用语音声级85、90，95dB(A)在高于该声级的噪声环境下作或懂度实验研究；高频语声级90dB（A)在舰船主机舱室105dB(A)环境下载与不载耳塞的可懂度试验，该系统的形成，在语音，环境噪声比为－10至－15dB时语言可懂度可达90％以上，从理论上升到研制装置成功，突破了传统的语言传递遵循部位机理的信噪比必须为＋5dB的论点。     

低频随机振动和正弦振动对汉语清晰度的影响

目的：探索随机振动和正弦振动因素下生成语音在听觉效果上的变化规律。方法：随机振动采用频率范围2-20Hz,加速度为0.3G、0.5G、0.7G(有效值,下同）,正弦振动采用频率4、6、8、10、12Hz,加速度为0.3G、0.5G;在安静及信噪比分别为0dB和-6dB三种状态下对随机振动组、正弦振组及对照组3个组的语音材料进行清晰度测试。结果：和对照组相比,随机振动组,清晰度几科没有变化,正弦振动组,0.3G时4Hz、0.5G时6Hz和8Hz作用下语音清晰度有明显降低,检验结果非常显著。研究还发现,清晰度的降低随听音环境的信噪比的降低而变得严重;结论：正弦振动对发音人发音的影响,会使通话效果变差,并且在听音环境恶劣时尤为突出。     

Prediction of speech intelligibility for public address systems in traffic tunnels

Traffic tunnels are generally hostile acoustic environments, both in terms of reverberation and ambient noise levels. Public address (PA) systems used to convey spoken warnings must meet stringent design requirements in order to produce sufficiently intelligible speech. To be able to predict PA system performance at tunnel design time, two different speech transmission index (STI) calculation procedures were implemented. The first procedure predicts the STI based on ray-tracing simulations. Comparison with measured STI data showed that this simulation approach yields accurate intelligibility estimates. However, the procedure is time-consuming and too complex to be used by non-specialists. For this reason, a second (simpler and more efficient) procedure was developed, based on fixed non-linear regression, statistically deriving prediction functions from measured data and ray-tracing results. This procedure was compared to the approach based on ray tracing, and found to yield STI predictions closely matching those of the ray-tracing model.     

Perceptual confusions of high-pitched sung vowels

Questions exist as to the intelligibility of vowels sung at extremely high fundamental frequencies and, especially, when the fundamental frequency (F0) produced is above the region where the first vowel formant (F1) would normally occur. Can such vowels be correctly identified and, if so, does context provide the necessary information or are acoustical elements also operative? To this end, 18 professional singers (5 males and 13 females) were recorded when singing 3 isolated vowels at high and low pitches at both loud and soft levels. Aural-perceptual studies employing four types of auditors were carried out to determine the identity of these vowels, and the nature of the confusions with other vowels. Subsequent acoustical analysis focused on the actual fundamental frequencies sung plus those defining the first 2 vowel formants. It was found that F0 change had a profound effect on vowel perception; one of the more important observations was that the target tended to shift toward vowels with an F1 just above the sung frequency.