Speech intelligibility

Linear-phase digital filters can remove the problem of filter interactions, but speech intelligibility results for multi-channel digital systems are no more encouraging than those for their analog counterparts [Kollmeier et al., 1993],... 

Brey et ah, 1987] Brey, R., Robinette, M., Chabries, D., and Christiansen, R. (1987). Improvement in speech intelligibility in noise employing an adaptive filter with normal and hearing-impaired subjects. J. Rehab. Res. and Devel., 24 75-86. 

Skinner, 1980] Skinner, M. (1980). Speech intelligibility in noise-induced hearing loss Effects of high-frequency compensation. J. Acoust. Soc. Am., 67 306-317. 

Stone and Moore, 1992] Stone, M. and Moore, B. (1992). Spectral feature enhancement for people with sensorineural hearing impairment Effects on speech intelligibility and quality. J. Rehab. Res. andDevel., 29 39-56. 

The choice of optimum compression parameters to maximize speech intelligibility or speech quality is still open to contention. Rapid attack time constants (less than 5 ms) are accepted in the industry and also by researchers to prevent transients from saturating the output power amplifier. Arguments for fast release times (less than 20 ms), also termed syllabic compression, are based on considerations of the syllabic variations in speech and the desire to amplify soft speech sounds on a nearly instantaneous basis... 

Weiss et al., 1975] Weiss, M., Aschkenasy, E., and Parsons, T. (1975). Study and development of the INTEL technique for improving speech intelligibility. Technical report, Rome Air Devel. Ctr. 

Most respirators have some sort of speech module to help overcome the muffling and attenuating effect and improve speech intelligibility. Speech modules are normally mounted on the respirator mid-line for direct speech, or one cheek of the facepiece for indirect speech, e.g. using telephones or radios. Direct speech modules are usually circular or annular in shape and incorporate a thin sheet of polyester such as Mylar , about 5 cm in diameter (the minimum for acceptable speech intelligibility) tensioned on a frame and protected by grilles inside and outside the respirator. 

The most important perceptual-motor effects of respirators are on vision and speech intelligibility. It is common experience that respirators restrict the visual field, depending not only on the eyepiece shape, size and eye-relief (distance from eye to eyepiece), but also on intrusion of filter canisters and other components into the visual field. Respirators can also impair visual acuity if the eyepieces are not well-designed or become misted. 

Johnson RF and Sleeper LA (1985). Effects of thermal stress and chemical protective clothing on speech intelligibility. In Proceedings of the 29th Meeting of the Pluman Factors Society, pp. 541-545, Santa Monica, CA, USA. 

Nelson WR and Mozo BT (1985). Effects of XM-40 chemical protective mask on peal-ear attenuation and speech intelligibility characteristics of the SPH-4 aviator helmet, Report 85-2. Fort Rucker, AL, USA US Army Aeromedical Research Laboratory. 

P Interference with On-the-Job Communicatbn - Woikers with normal hearing can have improved speech intelligibility when using hearing protection in very noisy environments, while hearing-impaired woikers often have more difficulty understanding speech. 

One index for assessing the ability to communicate verbally is the Preferred-Octave Speech Interference Level (PSIL). PSIL is the numerical average sound level (decibels) measured for each of three octave bands (500, 1000, and 2000 Hz). A study of the relationship between PSIL and speech intelligibility in different ambient noise conditions... 

Niederjohn, R.J. and Grotelueschen, J.H. 1976. The enhancement of speech intelligibility in high noise levels by high-pass filtering followed by rapid ampUtude compression. IEEE Trans. Acoustics, Speech and Signal Processing 24(Aug.) 202-207. 

Active noise control has also been applied inside earmuffs and coiiununication headsets to reduce noise exposure and improve speech intelligibility. Earmuffs and headsets with built-in... 

Improving Low Pass Filtered Speech Intelligibility Usii Nonlinear Frequency Compression with Cepstrum and Spectral Envelope Transformation... 

Keywords— Frequency compression, spectral envelope, low pass filtered speech, speech intelligibility, h h frequency hearing loss. 

By manipulating the frequency spectrum of the speech, we can assist the hearing impaired person to improve their speech intelligibility of the high frequency components [7 9], At the same time, we need to preserve the lower frequency component involving formants that are important in word classification and discrimination [5 8],... 

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