Daniel L. Valente

Effects of reverberation on speech recognition in stationary and modulated noise by school-aged children and young adults

Objectives: The purpose of this study was to determine how combinations of reverberation and noise, typical of environments in many elementary school classrooms, affect normal-hearing school-aged children’s speech recognition in stationary and amplitude-modulated noise, and to compare their performance with that of normal-hearing young adults. In addition, the magnitude of release from masking in the modulated noise relative to that in stationary noise was compared across age groups in nonreverberant and reverberant listening conditions. Last, for all noise and reverberation combinations the degree of change in predicted performance at 70% correct was obtained for all age groups using a best-fit cubic polynomial. Design: Bamford-Kowal-Bench sentences and noise were convolved with binaural room impulse responses representing nonreverberant and reverberant environments to create test materials representative of both audiology clinics and school classroom environments. Speech recognition of 48 school-aged children and 12 adults was measured in speech-shaped and amplitude-modulated speech-shaped noise, in the following three virtual listening environments: nonreverberant, reverberant at 2 m, and reverberant at 6 m. Results: Speech recognition decreased in the reverberant conditions and with decreasing age. Release from masking in modulated noise relative to stationary noise decreased with age and was reduced by reverberation. In the nonreverberant condition, participants showed similar amounts of masking release across ages. The slopes of performance-intensity functions increased with age, with the exception of the nonreverberant modulated masker condition. The slopes were steeper in the stationary masker conditions, where they also decreased with reverberation and distance. In the presence of a modulated masker, the slopes did not differ between the two reverberant conditions. Conclusions: The results of this study reveal systematic developmental changes in speech recognition in noisy and reverberant environments for elementary-school–aged children. The overall pattern suggests that younger children require better acoustic conditions to achieve sentence recognition equivalent to their older peers and adults. In addition, this is the first study to report a reduction of masking release in children as a result of reverberation. Results support the importance of minimizing noise and reverberation in classrooms, and highlight the need to incorporate noise and reverberation into audiological speech-recognition testing to improve predictions of performance in the real world.

Effect of minimal/mild hearing loss on children's speech understanding in a simulated classroom.

Objectives: While classroom acoustics can affect educational performance for all students, the impact for children with minimal/mild hearing loss (MMHL) may be greater than for children with normal hearing (NH). The purpose of this study was to examine the effect of MMHL on children’s speech recognition comprehension and looking behavior in a simulated classroom environment. It was hypothesized that children with MMHL would perform similarly to their peers with NH on the speech recognition task but would perform more poorly on the comprehension task. Children with MMHL also were expected to look toward talkers more often than children with NH. Design: Eighteen children with MMHL and 18 age-matched children with NH participated. In a simulated classroom environment, children listened to lines from an elementary-age-appropriate play read by a teacher and four students reproduced over LCD monitors and loudspeakers located around the listener. A gyroscopic headtracking device was used to monitor looking behavior during the task. At the end of the play, comprehension was assessed by asking a series of 18 factual questions. Children also were asked to repeat 50 meaningful sentences with three key words each presented audio-only by a single talker either from the loudspeaker at 0 degree azimuth or randomly from the five loudspeakers. Results: Both children with NH and those with MMHL performed at or near ceiling on the sentence recognition task. For the comprehension task, children with MMHL performed more poorly than those with NH. Assessment of looking behavior indicated that both groups of children looked at talkers while they were speaking less than 50% of the time. In addition, the pattern of overall looking behaviors suggested that, compared with older children with NH, a larger portion of older children with MMHL may demonstrate looking behaviors similar to younger children with or without MMHL. Conclusions: The results of this study demonstrate that, under realistic acoustic conditions, it is difficult to differentiate performance among children with MMHL and children with NH using a sentence recognition task. The more cognitively demanding comprehension task identified performance differences between these two groups. The comprehension task represented a condition in which the persons talking change rapidly and are not readily visible to the listener. Examination of looking behavior suggested that, in this complex task, attempting to visualize the talker may inefficiently utilize cognitive resources that would otherwise be allocated for comprehension.

Subjective scaling of spatial room acoustic parameters influenced by visual environmental cues

Although there have been numerous studies investigating subjective spatial impression in rooms, only a few of those studies have addressed the influence of visual cues on the judgment of auditory measures. In the psychophysical study presented here, video footage of five solo music/speech performers was shown for four different listening positions within a general-purpose space. The videos were presented in addition to the acoustic signals, which were auralized using binaural room impulse responses (BRIR) that were recorded in the same general-purpose space. The participants were asked to adjust the direct-to-reverberant energy ratio (D/R ratio) of the BRIR according to their expectation considering the visual cues. They were also directed to rate the apparent source width (ASW) and listener envelopment (LEV) for each condition. Visual cues generated by changing the sound-source position in the multi-purpose space, as well as the makeup of the sound stimuli affected the judgment of spatial impression. Participants also scaled the direct-to-reverberant energy ratio with greater direct sound energy than was measured in the acoustical environment.

Temporal integration of loudness measured using categorical loudness scaling and matching procedures

Temporal integration of loudness of 1 kHz tones with 5 and 200 ms durations was assessed in four subjects using two loudness measurement procedures: categorical loudness scaling (CLS) and loudness matching. CLS provides a reliable and efficient procedure for collecting data on the temporal integration of loudness and previously reported nonmonotonic behavior observed at mid-sound pressure level levels is replicated with this procedure. Stimuli that are assigned to the same category are effectively matched in loudness, allowing the measurement of temporal integration with CLS without curve-fitting, interpolation, or assumptions concerning the form of the loudness growth function.

Comparing perceived auditory width to the visual image of a performing ensemble in contrasting bi-modal environments.

Despite many studies investigating auditory spatial impressions in rooms, few have addressed the impact of simultaneous visual cues on localization and the perception of spaciousness. The current research presents an immersive audiovisual environment in which participants were instructed to make auditory width judgments in dynamic bi-modal settings. The results of these psychophysical tests suggest the importance of congruent audio visual presentation to the ecological interpretation of an auditory scene. Supporting data were accumulated in five rooms of ascending volumes and varying reverberation times. Participants were given an audiovisual matching test in which they were instructed to pan the auditory width of a performing ensemble to a varying set of audio and visual cues in rooms. Results show that both auditory and visual factors affect the collected responses and that the two sensory modalities coincide in distinct interactions. The greatest differences between the panned audio stimuli given a fixed visual width were found in the physical space with the largest volume and the greatest source distance. These results suggest, in this specific instance, a predominance of auditory cues in the spatial analysis of the bi-modal scene.

Relative effects of increment and pedestal duration on the detection of intensity increments.

The detection of a brief increment in the intensity of a longer duration pedestal is commonly used as a measure of intensity-resolution. Increment detection is known to improve with increasing duration of the increment and also with increasing duration of the pedestal, but the relative effects of these two parameters have not been explored in the same study. In several past studies of the effects of increment duration, pedestal duration was increased as increment duration increased. In the present study, increment and pedestal duration were independently manipulated. Increment-detection thresholds were determined for four subjects with normal-hearing using a 500- or 4000-Hz pedestal presented at 60 dB sound pressure level (SPL). Increment durations were 10, 20, 40, 80, 160, and 320 ms. Pedestal durations were 20, 40, 80, 160, and 320 ms. Each increment duration was combined with all pedestals of equal or greater duration. Multiple-regression analyses indicate that increment detection under these conditions is determined primarily by pedestal duration. Follow-up experiments ruled out effects of off-frequency listening or overshoot. The results suggest that effects of increment duration have been confounded by effects of pedestal duration in studies that co-varied increment and pedestal duration. Implications for models of temporal integration are discussed.

A hybrid approach to rendering multichannel audio, using wave‐field synthesis and stereophonic techniques, with virtual microphone control

In the evolution of multichannel audio presentation, a number of formats have emerged including 5.1 surround and wave‐field synthesis (WFS). Due to the complexity and number of components required to realize an immersive WFS system, the use in a home theater environment is currently impractical. This study aims to investigate the perceptual advantages of integrating both systems into a hybrid array capable of providing immersive sound for a number of listeners, at a scale that is attainable for the consumer in terms of budget and complexity. In this approach the three front speakers (left, center, and right) are replaced with a linear line array allowing for a better lateral and depth imaging, while increasing the sweet spot. The rendering will be created using Virtual Microphone Control (ViMiC) for both WFS, simulating a line of omnidirectional microphones with ViMiC, and surround sound, which will allows dynamic source movement, speaker positioning, and scalability. The advantage of using this hybrid ap...

Acoustic quality of buildings: Contributions to the workers health of the health area

This work presents a case study carried through in a research center, education, assistance, and technological development in the areas of the health of the woman, child, and adolescent, situated in Rio de Janeiro, where pathologies of average and high complexity are taken care of. It intended detect environmental problems that could affect the health of workers of the institution, in order to support the elaboration of the action plan to mitigate urgent questions and to develop an architectonical project for a new center. The environments and processes of work had been evaluated, through a participative approach, being visited all the sectors of the center, carried through interviews half-structuralized with workers of all the sectors and promoted debates that had pointed the noise as one of the main factors of bother and stress. The observation in loco and analyze of the project allowed to detect that the architectural design and the disrespect of basic acoustics recommendations had contributed for this...

Effects of excessive noise and reverberation on listening and learning in a simulated classroom.

Elementary students often learn in dynamic discussions during typical classroom lessons. Many classrooms, though, have poor signal‐to‐noise ratios and long reverberation times. The presence of excessive noise and reverberation may increase a student’s listening effort and result in reduced performance during classroom learning. A simulated classroom environment was created which allowed for varying degrees of room reverberation and background noise. In this experiment, groups of elementary‐aged students were seated in the center of the simulated classroom environment and were presented a story read by either five talkers positioned around the student or a single talker in front of the student (reproduced by LCD monitors and loudspeakers). A post‐test was used to assess listener comprehension. Comprehension scores are compared to a group of adult subjects as well as a sentence‐recognition task in the same condition. Significant differences were seen in comprehension scores as a function of age and conditio...

A hybrid procedure for psychometric function estimation.

Threshold, defined as the stimulus level required for a predefined percent correct response, is often used to measure a listener’s performance. Psychometric functions (PFs) provide better insight to the underlying decision process. Two parameters, threshold (α) and slope (β), are sufficient to define a PF. Estimation of α and β from individual trials of adaptive procedure tracks is time‐consuming, costly, and dependent upon the step‐size choice. A procedure has been developed and written in MATLAB, which provides stable PF parameter estimates of α and β and also their confidence intervals. The procedure consists of three stages. First, signals are presented adaptively to estimate levels corresponding to 71% and 87% correct. Second, the signal is pseudo‐randomly presented at one of five fixed levels equally spaced over that range. Finally, the program implements a maximum‐likelihood procedure updated after every trial to estimate signal levels corresponding to 63%, 71%, 76%, 79%, and 87% correct. After 140...