Masking Conditions Research Articles

Subjective response to respirator use – comparison N95 respirator, surgical mask and face cover

Introduction: Health care workers are at risk of serious infectious diseases. Respiratory protective devices can reduce the risk. This project investigates how workers tolerate protective devices and if it affects activity. Objectives: To study the effects of using respirators in combination with face cover on various activity levels among female health care workers. Materials and methods: This study had a controlled experimental design with two factors: respirator type and activity type. Measures of effects were based upon a rating instrument (questionnaire) designed by the Saudi Arabia Medical Students team. Ratings were based on an ordinal six-point scale. The following factors were measured: breathing difficulty, clarity of speech, heat and sweating, level of concentration, vision and level of comfort. Tasks were designed to be comparable with common health care work. These included walking outdoors, climbing stairs carrying an object, reading out loud (comparable to patient interviewing) and level of concentration (comparable to attending meetings). The activities were pilot tested. Factors such as walking distance, pace, duration, temperature, voice level and object weight were standardized. Mask conditions were: N95 respirator (3M Model 1860, 3M, Saint Paul, MN, USA), basic surgical mask (Walgreens model # 023185056204, Walgreens, Deerfield, IL, USA), face cover+N95 combination and no mask. Results: There were statistically significant effects for both respirator type and activity level [mixed linear model, SAS (Statistical Analysis System; SAS Institute Inc., Cary, NC, USA) Proc Mixed]. Wearing a respirator (N95) combined with face cover showed the highest score in interference with breathing and level of comfort with an average of 2.01 and 2.45, respectively. These differences were seen at all levels of exertion. Conclusions: Better controlled studies are required to delineate if such findings could be extended to those who are of different age groups, of a different sex, such as bearded males, and individuals with acute or chronic diseases in the Kingdom of Saudi Arabia. Acknowledgements: We would like to extend our gratitude to all those people who helped and supported us in completing this project and Dr Philip I Harber for supervising this project.

Improving visual functions in adult amblyopia with combined perceptual training and transcranial random noise stimulation (tRNS): a pilot study.

Amblyopia is a visual disorder due to an abnormal pattern of functional connectivity of the visual cortex and characterized by several visual deficits of spatial vision including impairments of visual acuity (VA) and of the contrast sensitivity function (CSF). Despite being a developmental disorder caused by reduced visual stimulation during early life (critical period), several studies have shown that extensive visual perceptual training can improve VA and CSF in people with amblyopia even in adulthood. With the present study we assessed whether a much shorter perceptual training regime, in association with high-frequency transcranial electrical stimulation (hf-tRNS), was able to improve visual functions in a group of adult participants with amblyopia. Results show that, in comparison with previous studies where a large number sessions with a similar training regime were used (Polat et al., 2004), here just eight sessions of training in contrast detection under lateral masking conditions combined with hf-tRNS, were able to substantially improve VA and CSF in adults with amblyopia.

Auditory sensitivity of seals and sea lions in complex listening scenarios.

Standard audiometric data, such as audiograms and critical ratios, are often used to inform marine mammal noise-exposure criteria. However, these measurements are obtained using simple, artificial stimuli-i.e., pure tones and flat-spectrum noise-while natural sounds typically have more complex structure. In this study, detection thresholds for complex signals were measured in (I) quiet and (II) masked conditions for one California sea lion (Zalophus californianus) and one harbor seal (Phoca vitulina). In Experiment I, detection thresholds in quiet conditions were obtained for complex signals designed to isolate three common features of natural sounds: Frequency modulation, amplitude modulation, and harmonic structure. In Experiment II, detection thresholds were obtained for the same complex signals embedded in two types of masking noise: Synthetic flat-spectrum noise and recorded shipping noise. To evaluate how accurately standard hearing data predict detection of complex sounds, the results of Experiments I and II were compared to predictions based on subject audiograms and critical ratios combined with a basic hearing model. Both subjects exhibited greater-than-predicted sensitivity to harmonic signals in quiet and masked conditions, as well as to frequency-modulated signals in masked conditions. These differences indicate that the complex features of naturally occurring sounds enhance detectability relative to simple stimuli.

Brain activation to briefly presented emotional words: effects of stimulus awareness.

It is unknown to what extent briefly presented emotional words can be processed without awareness. By means of two independent functional magnetic resonance imaging studies, using either a block or an event-related design, we investigated brain activation to very briefly presented threat related and neutral words during two backward masking conditions (with and without gap between target and mask). In both experiments, emotional words were perceived during the supraliminal "with gap" condition, but they were not recognized during the subliminal "without gap" condition, as indicated by signal detection theory analysis. Imaging results of both experiments showed increased activation of the amygdala, the medial prefrontal cortex and language-processing cortical areas to negative versus neutral words during supraliminal but not subliminal conditions. These results suggest that even very briefly presented emotional words are capable of triggering increased cortical and subcortical processing; however, only when awareness of these stimuli is given.

An examination of the effects of broadband air-conduction masker on the speech intelligibility of speech-modulated bone-conduction ultrasound

Ultrasound can be heard by bone-conduction, and speech-modulated bone-conducted ultrasound (BCU) delivers the speech information to the human ear. One of the recognition mechanisms is the demodulation of the signals. Because some of the profoundly deaf can also hear speech-modulated BCU, another mechanism may also contribution to the recognition of speech-modulated BCU. In this study, eight volunteers with normal hearing participated. The intelligibilities of speech-modulated BCU were measured using a numeral word list under masking conditions. Because the masker can mask the demodulated sounds, the evaluation of the masking reveals the contribution of the demodulation to the recognition of speech-modulated BCU. In the current results, the masking of speech-modulated BCU differed from that of original non-modulated speech. Although the masking shifted the recognition curve for the original speech upward, the same results were not observed for the speech-modulated BCU. The masking generated the difference in the correct answers among the words for the speech-modulated BCU. The current results suggested the importance of the envelope of the modulated ultrasonic signal to the recognition under masking condition. Both demodulation and direct ultrasonic stimulation contribute to the recognition of speech-modulated BCU for the normal hearing individuals, and the direct ultrasonic stimulation plays an important role in the recognition for the profoundly deaf.

Enhancing Speech Intelligibility: Interactions Among Context, Modality, Speech Style, and Masker

The authors sought to investigate interactions among intelligibility-enhancing speech cues (i.e., semantic context, clearly produced speech, and visual information) across a range of masking conditions. Sentence recognition in noise was assessed for 29 normal-hearing listeners. Testing included semantically normal and anomalous sentences, conversational and clear speaking styles, auditory-only (AO) and audiovisual (AV) presentation modalities, and 4 different maskers (2-talker babble, 4-talker babble, 8-talker babble, and speech-shaped noise). Semantic context, clear speech, and visual input all improved intelligibility but also interacted with one another and with masking condition. Semantic context was beneficial across all maskers in AV conditions but only in speech-shaped noise in AO conditions. Clear speech provided the most benefit for AV speech with semantically anomalous targets. Finally, listeners were better able to take advantage of visual information for meaningful versus anomalous sentences and for clear versus conversational speech. Because intelligibility-enhancing cues influence each other and depend on masking condition, multiple maskers and enhancement cues should be used to accurately assess individuals' speech-in-noise perception.

Phoneme recognition in vocoded maskers by normal-hearing and aided hearing-impaired listeners.

This study compared modulation benefit for phoneme recognition obtained by normal-hearing (NH) and aided hearing-impaired (HI) listeners. Consonant and vowel recognition scores were measured using nonsense syllables in the presence of a steady-state noise and four vocoded speech maskers. Vocoded maskers were generated by modulating the steady-state noise, in either one or six frequency channels, with the speech envelope extracted from the speech of either a single talker or a four-talker babble. Aided HI listeners obtained lower consonant recognition scores than NH listeners in all masker conditions. Vowel recognition scores for aided HI listeners were comparable to NH scores, except in the six-channel vocoded masker conditions where they were relatively lower. Analysis using the extended speech intelligibility index developed by Rhebergen, Versfeld, and Dreschler [(2006). J. Acoust. Soc. Am. 120(6), 3988-3997] suggested that the signal-to-noise ratio deficit observed in aided HI listeners was largely due to uncompensated audibility loss. There was no significant difference between modulation masking release obtained by NH and aided HI listeners for both consonant and vowel recognition.

Effect of phenolic, phosphite, lactone, and their mixtures of antioxidants on Ziegler-Natta catalyst performance during propylene polymerization

This study investigated the use of antioxidants and mixtures of these antioxidants during slurry propylene polymerization using the Ziegler–Natta catalyst. Antioxidant masking using triethylaluminium is the key to reducing the destructive effect of antioxidants containing OH phenolic groups on Ziegler–Natta catalyst performance. According to the synergistic properties, antioxidant mixtures with different ratios were evaluated for their masking conditions and amounts of antioxidant added. Polymer characteristics such as catalyst activity, isotacticity, oxidative induction time, and particle-size distribution of the products in the presence of different amounts of antioxidants were evaluated. The results showed that phosphite and lactone antioxidants have more effect on catalyst performance during polymerization than phenolic antioxidants. J. VINYL ADDIT. TECHNOL., 21:299–304, 2015. © 2014 Society of Plastics Engineers

Increase in Speech Recognition due to Linguistic Mismatch Between Target and Masker Speech: Monolingual and Simultaneous Bilingual Performance

To examine whether improved speech recognition during linguistically mismatched target-masker experiments is due to linguistic unfamiliarity of the masker speech or linguistic dissimilarity between the target and masker speech. Monolingual English speakers (n = 20) and English-Greek simultaneous bilinguals (n = 20) listened to English sentences in the presence of competing English and Greek speech. Data were analyzed using mixed-effects regression models to determine differences in English recogition performance between the 2 groups and 2 masker conditions. Results indicated that English sentence recognition for monolinguals and simultaneous English-Greek bilinguals improved when the masker speech changed from competing English to competing Greek speech. The improvement in speech recognition that has been observed for linguistically mismatched target-masker experiments cannot be simply explained by the masker language being linguistically unknown or unfamiliar to the listeners. Listeners can improve their speech recognition in linguistically mismatched target-masker experiments even when the listener is able to obtain meaningful linguistic information from the masker speech.

Development and Preliminary Evaluation of a Pediatric Spanish–English Speech Perception Task

The purpose of this study was to develop a task to evaluate children's English and Spanish speech perception abilities in either noise or competing speech maskers. Eight bilingual Spanish-English and 8 age-matched monolingual English children (ages 4.9-16.4 years) were tested. A forced-choice, picture-pointing paradigm was selected for adaptively estimating masked speech reception thresholds. Speech stimuli were spoken by simultaneous bilingual Spanish-English talkers. The target stimuli were 30 disyllabic English and Spanish words, familiar to 5-year-olds and easily illustrated. Competing stimuli included either 2-talker English or 2-talker Spanish speech (corresponding to target language) and spectrally matched noise. For both groups of children, regardless of test language, performance was significantly worse for the 2-talker than for the noise masker condition. No difference in performance was found between bilingual and monolingual children. Bilingual children performed significantly better in English than in Spanish in competing speech. For all listening conditions, performance improved with increasing age. Results indicated that the stimuli and task were appropriate for speech recognition testing in both languages, providing a more conventional measure of speech-in-noise perception as well as a measure of complex listening. Further research is needed to determine performance for Spanish-dominant listeners and to evaluate the feasibility of implementation into routine clinical use.

Lifetime benefits of musical training.

Lifetime benefits of musical training.

Speech-on-speech masking with variable access to the linguistic content of the masker speech for native and nonnative english speakers.

Masking release for an English sentence-recognition task in the presence of foreign-accented English speech compared with native-accented English speech was reported in Calandruccio et al (2010a). The masking release appeared to increase as the masker intelligibility decreased. However, it could not be ruled out that spectral differences between the speech maskers were influencing the significant differences observed. The purpose of the current experiment was to minimize spectral differences between speech maskers to determine how various amounts of linguistic information within competing speech Affiliationect masking release. A mixed-model design with within-subject (four two-talker speech maskers) and between-subject (listener group) factors was conducted. Speech maskers included native-accented English speech and high-intelligibility, moderate-intelligibility, and low-intelligibility Mandarin-accented English. Normalizing the long-term average speech spectra of the maskers to each other minimized spectral differences between the masker conditions. Three listener groups were tested, including monolingual English speakers with normal hearing, nonnative English speakers with normal hearing, and monolingual English speakers with hearing loss. The nonnative English speakers were from various native language backgrounds, not including Mandarin (or any other Chinese dialect). Listeners with hearing loss had symmetric mild sloping to moderate sensorineural hearing loss. Listeners were asked to repeat back sentences that were presented in the presence of four different two-talker speech maskers. Responses were scored based on the key words within the sentences (100 key words per masker condition). A mixed-model regression analysis was used to analyze the difference in performance scores between the masker conditions and listener groups. Monolingual English speakers with normal hearing benefited when the competing speech signal was foreign accented compared with native accented, allowing for improved speech recognition. Various levels of intelligibility across the foreign-accented speech maskers did not influence results. Neither the nonnative English-speaking listeners with normal hearing nor the monolingual English speakers with hearing loss benefited from masking release when the masker was changed from native-accented to foreign-accented English. Slight modifications between the target and the masker speech allowed monolingual English speakers with normal hearing to improve their recognition of native-accented English, even when the competing speech was highly intelligible. Further research is needed to determine which modifications within the competing speech signal caused the Mandarin-accented English to be less effective with respect to masking. Determining the influences within the competing speech that make it less effective as a masker or determining why monolingual normal-hearing listeners can take advantage of these differences could help improve speech recognition for those with hearing loss in the future.

Masked speech recognition in school-age children and adults: Effects of age, masker type, and context

This study evaluated the influences of age, masker type, and context on masked speech recognition. A repeated-measures design compared the speech recognition thresholds of two age groups of children (5–7 and 9–13 years) and a group of adults (19–33 years) in a continuous speech-shaped noise or a two-talker speech masker. Target stimuli were disyllabic words that were familiar to young children. Masker level was fixed at 60 dB SPL, and signal level was adapted to estimate the SNR required for 70.7% correct performance. Each listener completed testing in each masker condition using both an open-set task requiring a verbal response, and a 4AFC closed-set task requiring a picture-pointing response. Consistent with previous studies, and regardless of response context, larger and more prolonged child-adult differences were observed in the two-talker compared to the speech-shaped noise masker. Poorer performance was observed for all three age groups using the open-set compared to the closed-set context. This performance gap was similar across the three age groups in the speech-shaped noise masker, but a developmental effect was observed in the two-talker masker. Specifically, the decrement in performance using the open-set compared to the closed-set procedure increased with age in the two-talker masker.

The role of modulation processing in binaural masking-patterns

Binaural masking pattern experiments indicate a continuous decrease in the binaural masking-level difference (BMLD) with increasing spectral distance of a tonal signal to a narrowband noise masker. Previous studies suggested that this decrease in BMLD is due to additional modulation cues in monaural off-frequency masking conditions. An own masking pattern experiment with an additional interferer to mask modulation cues supported this hypothesis. The interferer is positioned spectrally below/above the masker for the signal above/below the masker with a spectral distance equal to the distance between masker and signal. This interference tone has a large impact on the thresholds without a binaural cue, as expected. Such an increase in the diotic thresholds is predicted on the basis of a modulation-filterbank model, but only if an across-channel modulation processing is assumed. The interferer also increases the dichotic thresholds, indicating an influence of modulations processing also in conditions where binaural cues are present. Assuming that modulation cues are masked by the interference tone and thus the detection is based on energy cues, the binaural data indicate effectively wider binaural filter, as previously suggested on the basis of notched-noise experiments.

The “emotion misattribution” procedure: Processing beyond good and bad under masked and unmasked presentation conditions

In general, it is assumed that misattribution in the Affect Misattribution Procedure (AMP) is restricted to crude affect due to its unbound nature, especially under limited presentation conditions. In two experiments, we investigated whether emotion-specific misattributions occur using a four-category misattribution procedure. Experiment 1 yielded emotion-specific misattribution effects under clearly visible presentation conditions demonstrating that the procedure is principally susceptible for emotion-specific effects. In Experiment 2, we employed masked presentation conditions impeding conscious prime perception. A specific pattern of emotion-specific misattributions effects emerged indicating some emotion-specific processing at initial stages of processing. However, not each emotion was misattributed equally. We discuss the implications of these results for the non-conscious processing of emotional information, for the supposed mechanisms of the AMP and its implicit nature.

Morphological processing of printed nouns and verbs: Cross-class priming effects

Despite grammatical class being a fundamental organising principle of the human mental lexicon, recent morphological models of visual word identification remain silent as to whether and how it is represented in the lexical system. The present study addresses this issue by investigating cross-class morphological priming (i.e., the effect obtained when nouns prime verbs sharing the same root or vice versa) to clarify whether morphological stems subserving the formation of both nouns and verbs (e.g., depart-) have a unique, grammatical class–independent representation. Experiments 1 and 2 suggest this to be the case, as they show that morphological priming crosses grammatical class boundaries in overt paradigm conditions. Experiment 3 shows that, in masked priming conditions, cross-class facilitation emerges both for genuine derivations and pseudo-related pairs with a homographic stem (e.g., port-e, doors, and port-are, to carry), which is taken to suggest that grammatical class–free stem representations are located at a pre-lexical level of morphological processing.

Effects of linguistic experience on the ability to benefit from temporal and spectral masker modulation

Masked speech perception can often be improved by modulating the masker temporally and/or spectrally. These effects tend to be larger in normal-hearing listeners than hearing-impaired listeners, and effects of temporal modulation are larger in adults than young children [Hall et al. (2012). Ear Hear. 33, 340-348]. Initial reports indicate non-native adult speakers of the target language also have a reduced ability to benefit from temporal masker modulation [Stuart et al. (2010). J. Am. Acad. Aud. 21, 239-248]. The present study further investigated the effect of masker modulation on English speech recognition in normal-hearing adults who are non-native speakers of English. Sentence recognition was assessed in a steady-state baseline masker condition and in three modulated masker conditions, characterized by spectral, temporal, or spectro-temporal modulation. Thresholds for non-natives were poorer than those of native English speakers in all conditions, particularly in the presence of a modulated masker. The group differences were consistent across maskers when assessed in percent correct, suggesting that a single factor may limit the performance of non-native listeners similarly in all conditions.

Modeling the effects of a single reflection on binaural speech intelligibility

Recently the influence of delay and azimuth of a single speech reflection on speech reception thresholds (SRTs) was systematically investigated using frontal, diffuse, and lateral noise [Warzybok et al. (2013). J. Acoust. Soc. Am. 133, 269-282]. The experiments showed that the benefit of an early reflection was independent of its azimuth and mostly independent of noise type, but that the detrimental effect of a late reflection depended on its direction relative to the noise. This study tests if different extensions of a binaural speech intelligibility model can predict these data. The extensions differ in the order in which binaural processing and temporal integration of early reflections take place. Models employing a correction for the detrimental effects of reverberation on speech intelligibility after performing the binaural processing predict SRTs in symmetric masking conditions (frontal, diffuse), but cannot predict the measured interaction of temporal and spatial integration. In contrast, a model extension accounting for the distinction between useful and detrimental reflections before the binaural processing stage predicts the data with an overall R(2) of 0.95. This indicates that any model framework predicting speech intelligibility in rooms should incorporate an interaction between binaural and temporal integration of reflections at a comparatively early stage.

Micropatterning on cylindrical surfaces via electrochemical etching using laser masking

This paper proposes a method of selective electrochemical dissolution on the cylindrical surfaces of stainless steel shafts. Selective electrochemical dissolution was achieved via electrochemical etching using laser masking. A micropatterned recast layer was formed on the surface via ytterbium-doped pulsed fiber laser irradiation. The micropatterned recast layer could be used as a mask layer during the electrochemical etching process. Laser masking condition to form adequate mask layer on the planar surface for etching cannot be used directly on the non-planar surface. Laser masking condition changes depending on the morphological surface. The laser masking characteristics were investigated in order to form a uniform mask layer on the cylindrical surface. To minimize factors causing non-uniformity in the mask layer on the cylindrical surface, synchronized laser line scanning with a rotary system was applied during the laser masking process. Electrochemical etching characteristics were also investigated to achieve deeper etched depth, without collapsing the recast layer. Consequently, through a series process of laser masking and electrochemical etching, various micropatternings were successfully performed on the cylindrical surfaces.

Neuromusic research: some benefits of incorporating basic research on the neurobiology of auditory learning and memory

Neuromusic research: some benefits of incorporating basic research on the neurobiology of auditory learning and memory