Effect of a single lateral diffuse reflection on spatial percepts and speech intelligibility.

This study examines the influence of an early lateral reflection on spatial perceptual attributes and speech reception. To this aim, a diffuse reflection is compared with a specular one. Although diffusive surfaces have widespread applications in room acoustics design, the knowledge of the perceptual and behavioral outcomes of these surfaces has yet to be fully developed. Two experiments were conducted to investigate how the reflection type, its temporal delay, and its azimuth affect spatial percepts (source distance, width, and focus) and speech intelligibility (SI) in diffuse stationary noise. The experimental setup included ecological elements: field measurements, a speaker-like source directivity, and real flat and diffusive surfaces. The results indicate that the presence of a single diffuse reflection reduces the perceived distance of a frontal speech source and makes it clearer. SI is higher with a diffuse reflection than with a specular one. Perceptual and behavioral outcomes both depend on the angle of reflection given the frequency- and angular-dependent properties of the diffusing surface and the directivity of the speech source. The results are interpreted with reference to loudness and binaural cues and to the precedence effect. Implications of the findings for acoustic design are also discussed.

An Italian matrix sentence test for the evaluation of speech intelligibility in noise.

OBJECTIVE: Development of an Italian matrix sentence test for the assessment of speech intelligibility in noise. DESIGN: The development of the test included the selection, recording, optimization with level adjustment, and evaluation of speech material. The training effect was assessed adaptively during the evaluation measurements with six lists of 20 sentences, using open- and closed-set response formats. Reference data were established for normal-hearing listeners with adaptive measurements. Equivalence of the test lists was investigated using the open-set response format at three signal-to-noise ratios (SNRs). STUDY SAMPLE: A total of 55 normal-hearing Italian mother-tongue listeners. RESULTS: The evaluation measurements at fixed SNRs resulted in a mean speech reception threshold (SRT) of -7.3 ± 0.2 dB SNR and slope of 13.3 ± 1.2 %/dB. The major training effect of 1.5 dB was observed for the first two consecutive measurements. Mean SRTs of -6.7 ± 0.7 dB SNR and -7.4 ± 0.7 dB SNR were found from the third to the sixth adaptive measurement for open- and closed-set test response formats, respectively. CONCLUSIONS: A good agreement has been found between the SRTs and slope and those of other matrix tests. Since sentences are difficult to memorize, the Italian matrix test is suitable for repeated measurements.

On the perception of speech in primary school classrooms: ranking of noise interference and of age influence.

It is well documented that the interference of noise in the classroom puts younger pupils at a disadvantage for speech perception tasks. Nevertheless, the dependence of this phenomenon on the type of noise, and the way it is realized for each class by a specific combination of intelligibility and effort have not been fully investigated. Following on a previous laboratory study on "listening efficiency," which stems from a combination of accuracy and latency measures, this work tackles the problems above to better understand the basic mechanisms governing the speech perception performance of pupils in noisy classrooms. Listening tests were conducted in real classrooms for a relevant number of students, and tests in quiet were also developed. The statistical analysis is based on stochastic ordering and is able to clarify the behavior of the classes and the different impacts of noises on performance. It is found that the joint babble and activity noise has the worst effect on performance whereas tapping and external traffic noises are less disruptive.