Evidence for proactive and retroactive temporal pattern analysis in simultaneous maskinga).

Amplitude modulation (AM) of a masker reduces its masking on a simultaneously presented unmodulated pure-tone target, which likely involves dip listening. This study tested the idea that dip-listening efficiency may depend on stimulus context, i.e., the match in AM peakedness (AMP) between the masker and a precursor or postcursor stimulus, assuming a form of temporal pattern analysis process. Masked thresholds were measured in normal-hearing listeners using Schroeder-phase harmonic complexes as maskers and precursors or postcursors. Experiment 1 showed threshold elevation (i.e., interference) when a flat cursor preceded or followed a peaked masker, suggesting proactive and retroactive temporal pattern analysis. Threshold decline (facilitation) was observed when the masker AMP was matched to the precursor, irrespective of stimulus AMP, suggesting only proactive processing. Subsequent experiments showed that both interference and facilitation (1) remained robust when a temporal gap was inserted between masker and cursor, (2) disappeared when an F0-difference was introduced between masker and precursor, and (3) decreased when the presentation level was reduced. These results suggest an important role of envelope regularity in dip listening, especially when masker and cursor are F0-matched and, therefore, form one perceptual stream. The reported effects seem to represent a time-domain variant of comodulation masking release.

Perceptual similarity between piano notes: Simulations with a template-based perception model.

In this paper, the auditory model developed by Dau, Kollmeier, and Kohlrausch [(1997). J. Acoust. Soc. Am. 102, 2892-2905] was used to simulate the perceptual similarity between complex sounds. As complex sounds, a set of piano recordings was used, whose perceptual similarity has recently been measured by Osses, Kohlrausch, and Chaigne [(2019). J. Acoust. Soc. Am. 146, 1024-1035] using a three-alternative forced-choice discrimination task in noise. To simulate this discrimination task, the auditory model required a new back-end stage, the central processor, which is preceded by several processing stages that are to a greater or lesser extent inspired by physiological aspects of the normal-hearing system. Therefore, a comprehensive review of the model parameters as used in the literature is given, indicating the fixed set of parameter values that is used in all simulations. Due to the perceptual relevance of the piano note onsets, this review includes an in-depth description of the auditory adaptation stage, the adaptation loops. A moderate to high correlation was found between the simulation results and existing experimental data.

Assessing the perceived reverberation in different rooms for a set of musical instrument sounds.

Previous research has shown that the perceived reverberation in a room, or reverberance, depends on the sound source that is being listened to. In a study by Osses Vecchi, Kohlrausch, Lachenmayr, and Mommertz [(2017). J. Acoust. Soc. Am. 141(4), EL381-EL387], reverberance estimates obtained from an auditory model for 23 musical instrument sounds in 8 rooms predicted a sound-source dependency. As a follow-up to that study, a listening experiment with 24 participants was conducted using a subset of the original sounds with the purpose of mapping each test sound onto a reverberance scale. Consistent with the literature, the experimental reverberance estimates were significantly dependent on the instrument sound being listened to, but on the top of that, the estimates were significantly correlated with simulated reverberance estimates for the test stimuli as well as for the previously reported long-duration sounds.

Perceptual similarity between piano notes: Experimental method applicable to reverberant and non-reverberant sounds.

In this paper an experimental method to quantify perceptual differences between acoustic stimuli is presented. The experiments are implemented as a signal-in-noise task, where two sounds are to be discriminated. By adjusting the signal-to-noise ratio (SNR) the difficulty of the sound discrimination is manipulated. If two sounds are very similar already, a low level of added noise (high SNR) makes the discrimination task difficult. For more dissimilar sounds, a higher amount of noise (lower SNR) is needed to affect discriminability. In other words, a strong correlation between SNR and similarity is expected. The experimental noises are generated to have similar spectro-temporal properties to those of the test stimuli. As a study case, the suggested method was used to evaluate recordings of one note played on seven Viennese pianos using (1) non-reverberant sounds (as recorded) and (2) reverberant sounds, where reverberation was added by means of digital convolution. The experimental results of the suggested method were compared with a similarity experiment using the method of triadic comparisons. The results of both methods were significantly correlated with each other.

Noise in the intensive care unit and its influence on sleep quality: a multicenter observational study in Dutch intensive care units.

BACKGROUND: High noise levels in the intensive care unit (ICU) are a well-known problem. Little is known about the effect of noise on sleep quality in ICU patients. The study aim is to determine the effect of noise on subjective sleep quality. METHODS: This was a multicenter observational study in six Dutch ICUs. Noise recording equipment was installed in 2-4 rooms per ICU. Adult patients were eligible for the study 48 h after ICU admission and were followed up to maximum of five nights in the ICU. Exclusion criteria were presence of delirium and/or inability to be assessed for sleep quality. Sleep was evaluated using the Richards Campbell Sleep Questionnaire (range 0-100 mm). Noise recordings were used for analysis of various auditory parameters, including the number and duration of restorative periods. Hierarchical mixed model regression analysis was used to determine associations between noise and sleep. RESULTS: In total, 64 patients (68% male), mean age 63.9 (± 11.7) years and mean Acute Physiology And Chronic Health Evaluation (APACHE) II score 21.1 (± 7.1) were included. Average sleep quality score was 56 ± 24 mm. The mean of the 24-h average sound pressure levels (LAeq, 24h) was 54.0 dBA (± 2.4). Mixed-effects regression analyses showed that background noise (ß = - 0.51, p < 0.05) had a negative impact on sleep quality, whereas number of restorative periods (ß = 0.53, p < 0.01) and female sex (ß = 1.25, p < 0.01) were weakly but significantly correlated with sleep. CONCLUSIONS: Noise levels are negatively associated and restorative periods and female gender are positively associated with subjective sleep quality in ICU patients. TRIAL REGISTRATION: www.ClinicalTrials.gov, NCT01826799 . Registered on 9 April 2013.

Cognitive disruption by noise-vocoded speech stimuli: Effects of spectral variation.

The effect of irrelevant sounds on short-term memory was investigated in two experiments using noise-vocoded speech stimuli (NVSS). Speech samples were systematically modified by a noise-vocoder and a set of stimuli varying from amplitude-modulated white noise to intelligible speech was created. Eight NVSS conditions, composed of 1-, 2-, 4-, 6-, 9-, 12-, 15-, and 18-bands, were used as the distracting stimuli in a digit-recall task next to the speech and silence conditions. The results showed that performance decreased with the number of frequency bands up to the 6-bands condition, but there was no influence of number of bands on performance beyond six bands. The results were analyzed using four acoustic metrics proposed in the literature: the frequency domain correlation coefficient (FDCC), the fluctuation strength, the speech transmission index (STI), and the normalized covariance measure (NCM). None of the metrics successfully predicted the results. However, the parameter values of the FDCC, the STI, and the NCM indicated that a prediction model for irrelevant sound effect should account for both temporal and spectral features of the irrelevant sounds.

Why orchestral musicians are bound to wear earplugs: About the ineffectiveness of physical measures to reduce sound exposure.

Symphony orchestra musicians are exposed to noise levels that put them at risk of developing hearing damage. This study evaluates the potential effectivity of common control measures used in orchestras on open stages with a typical symphonic setup. A validated acoustic prediction model is used that calculates binaural sound exposure levels at the ears of all musicians in the orchestra. The model calculates the equivalent sound levels for a performance of the first 2 min of the 4th movement of Mahler's 1st symphony, which can be considered representative for loud orchestral music. Calculated results indicate that risers, available space, and screens at typical positions do not significantly influence sound exposure. A hypothetical scenario with surround screens shows that, even when shielding all direct sound from others, sound exposure is reduced moderately with the largest effect on players in loud sections. In contrast, a dramatic change in room acoustic conditions only leads to considerable reductions for soft players. It can be concluded that significant reductions are only reached with extreme measures that are unrealistic. It seems impossible for the studied physical measures to be effective enough to replace hearing protection devices such as ear plugs.

Predicting the perceived reverberation in different room acoustic environments using a binaural auditory model.

In this paper a binaural auditory model was used to compute reverberance estimates in four simulated halls. For three of the halls different absorption conditions were evaluated. The model estimates (pRev) were obtained using music excerpts of an orchestra consisting of 23 instrument sections and then compared with the room acoustic parameters of reverberation time (T30) and early decay time (EDT) at mid frequencies. Although the results showed that pRev has a higher correlation with EDT rather than with T30, this relationship depends on the properties of the instruments. The simulations show that pRev depends on the presentation level and that for instruments with similar critical-band spectrum, pRev follows a similar trend across acoustic conditions. A computational framework and sound stimuli are provided to encourage the search of experimental evidence of the aspects addressed in this study.

Noise disturbance in open-plan study environments: a field study on noise sources, student tasks and room acoustic parameters.

The aim of this study is to gain more insight in the assessment of noise in open-plan study environments and to reveal correlations between noise disturbance experienced by students and the noise sources they perceive, the tasks they perform and the acoustic parameters of the open-plan study environment they work in. Data were collected in five open-plan study environments at universities in the Netherlands. A questionnaire was used to investigate student tasks, perceived sound sources and their perceived disturbance, and sound measurements were performed to determine the room acoustic parameters. This study shows that 38% of the surveyed students are disturbed by background noise in an open-plan study environment. Students are mostly disturbed by speech when performing complex cognitive tasks like studying for an exam, reading and writing. Significant but weak correlations were found between the room acoustic parameters and noise disturbance of students. Practitioner Summary: A field study was conducted to gain more insight in the assessment of noise in open-plan study environments at universities in the Netherlands. More than one third of the students was disturbed by noise. An interaction effect was found for task type, source type and room acoustic parameters.

The influence of APACHE II score on the average noise level in an intensive care unit: an observational study.

BACKGROUND: Noise levels in hospitals, especially in intensive care units (ICUs) are known to be high, potentially affecting not only the patients' well-being but also their clinical outcomes. In an observational study, we made a long-term measurement of noise levels in an ICU, and investigated the influence of various factors on the noise level, including the acute physiology and chronic health evaluation II (APACHE II) score. METHODS: The average noise level was continuously measured for three months in all (eight) patient rooms in an ICU, while the patient data were also registered, including the APACHE II score. The 24-hour trend of the noise level was obtained for the patients of length-of-stay (LOS) ≥1 day, which was compared to the timeline of the ICU routine events. For the patients with LOS ≥4 days, the average noise levels in the first four days were analyzed, and regression models were established using the stepwise search method based on the Akaike information criterion. RESULTS: Features identified in the 24-hour trends (n = 55) agreed well with the daily routine events in the ICU, where regular check-ups raised the 10-minute average noise level by 2~3 dBA from the surrounding values at night, and the staff shift changes consistently increased the noise level by 3~5 dBA. When analyzed in alignment with the patient's admission (n=22), the daytime acoustic condition improved from Day 1 to 2, but worsened from Day 2 to 4, most likely in relation to the various phases of patient's recovery. Regression analysis showed that the APACHE II score, room location, gender, day of week and the ICU admission type could explain more than 50% of the variance in the daily average noise level, LAeq,24h. Where these factors were argued to have causal relations to LAeq,24h, the APACHE II score was found to be most strongly correlated: LAeq,24h increased by 1.3~1.5 dB when the APACHE II score increased by 10 points. CONCLUSIONS: Patient's initial health condition is one important factor that influences the acoustic environment in an ICU, which needs to be considered in observational and interventional studies where the noise in healthcare environments is the subject of investigation.

Analysis of the soundscape in an intensive care unit based on the annotation of an audio recording.

The acoustic environments in hospitals, particularly in intensive care units (ICUs), are characterized by frequent high-level sound events which may negatively affect patient outcome. Many studies performed acoustic surveys, but the measurement protocol was not always reported in detail, and the scope of analysis was limited by the selected mode of sound level meters. Fewer studies systematically investigated the noise sources in ICUs by employing an observer in the patient room, which may potentially bias the measurement. In the current study, the soundscape of an ICU was evaluated where acoustic parameters were extracted from a ∼67-h audio recording, and a selected 24-h recording was annotated off-line for a source-specific analysis. The results showed that the patient-involved noise accounted for 31% of the acoustic energy and 11% of the predicted loudness peaks (PLPs). Excluding the patient-involved noise, the remaining acoustic energy was attributed to staff members (57%), alarms (30%), and the operational noise of life-supporting devices (13%). Furthermore, the contribution of each noise category to the PLPs was found to be more uneven: Staff (92%), alarms (6%), and device noise (2%). The current study suggests that most of the noise sources in ICUs may be associated with modifiable human factors.

Off-frequency BMLD: the role of monaural processing.

Large binaural masking-level differences (BMLDs) can be observed when a tonal signal with an interaural phase difference of π is presented against a diotic masker. The BMLD is large when the signal is spectrally centered in the masker and decreases strongly for off-frequency signals. No such reduction in BMLD would be expected, if monaural detection were governed by energy cues and binaural detection by changes in interaural cross-correlation. The reduction in BMLD thus suggests either that binaural processing is impaired or, alternatively, that additional monaural cues are available in off-frequency conditions. In this study, a stimulus paradigm is used that is expected to impair the processing of additional monaural cues. In the base experiment, a 25-Hz-wide band of diotic noise centered at 700 Hz served as masker. A target tone was presented at 0, 30, 60, and 100 Hz above the masker center frequency, either interaurally in phase (S 0) or out of phase (S π). In the extended experiment, an additional interference tone was always presented spectrally below the masker at the same frequency distance as the target tone was positioned above the masker. The interferer level was 6 dB below the level of the 65 dB masker. By presenting the interferer, a strong modulation is introduced, which should impair the detectability of the target tone based on the beating of masker and target. Results show a small off-frequency BMLD in the base experiment in line with literature. Adding the interference tone produced an increase in both N 0 S 0 and the N 0 S π thresholds, suggesting that monaural modulation cues were indeed used, but also -suggesting that detection performance in the N 0 S π condition was dominated by monaural processing. Additional conditions with modulated interference tones at 500 Hz further supported our hypothesis that monaural modulation cues contributed to reduced -off-frequency BMLDs.

Irrelevant speech effect under stationary and adaptive masking conditions.

The irrelevant speech effect was investigated in this study where the serial-recall task was performed under six different conditions: Silence, speech-only, noise-only, speech masked by a stationary noise at two different signal-to-noise ratios (SNRs), and speech masked by an adaptive noise. Measured in five test blocks distributed throughout the four test days, the error rate of the serial-recall task under the silence condition sharply decreased in the first few test blocks, halved after completing about seven blocks. When the adaptive masking scheme was used, the error rate of the serial-recall test was reduced compared to the speech-only condition (by 9%) and to the lower-SNR stationary noise (by 4.4%). However, the serial-recall performance was not significantly different between the stationary and the adaptive maskers when the average sound level was carefully matched. Speech Transmission Index (STI) and the correlation coefficient of power spectra were used as the estimators of the temporal and spectral distinctiveness between sound tokens, respectively. The comparison to the test results implied that the frequency-domain estimator may be a better predictor of the relative ISE especially for a non-stationary masker, although it was also suggested that such estimators may have to be combined possibly with an appropriate weighting.

Effects of diotic fringes on interaural disparity detection (L).

Detection thresholds were measured for interaural time differences (ITDs) and interaural level differences (ILDs) that were carried by probe segments embedded in otherwise diotic broadband noise (fringe). The duration of the probe was varied between 5 and 200 ms, and the duration of the fringe was between 5 and 100 ms. Consistent with results of Akeroyd and Bernstein [(2001). J. Acoust. Soc. Am. 110, 2516-2526], it was found that a 5-ms fringe placed before a 5-ms probe (forward fringe) led to a larger threshold elevation than a 5-ms fringe placed after the probe (backward fringe). As suggested by Akeroyd and Bernstein, this effect was accounted for by a model providing an onset emphasis of a factor of 2. In contrast, for longer probe and fringe durations, which have not been tested before, a backward fringe had a stronger effect than a forward fringe. This surprising effect was accounted for by an extended model that provided an offset emphasis of a factor of 11 for a 50-ms probe and a 100-ms fringe.

Temporal interval discrimination thresholds depend on perceived synchrony for audio-visual stimulus pairs.

Audio-visual stimulus pairs presented at various relative delays, are commonly judged as being "synchronous" over a range of delays from about -50 ms (audio leading) to +150 ms (video leading). The center of this range is an estimate of the point of subjective simultaneity (PSS). The judgment boundaries, where "synchronous" judgments yield to a predominance of "asynchronous" judgments, usually include physical synchrony, or the point of objective simultaneity (POS). When the POS is used as a standard in a delay discrimination paradigm, thresholds tend to be asymmetric; that is, smaller on the audio-leading side than on the video-leading side of the standard. We replicated this finding using different stimulus types, and standards distributed within and beyond the synchrony judgment boundaries. Thresholds were symmetric near the center of the synchrony range (PSS), but showed opposite patterns of asymmetry as the standard approached either of the two synchrony judgment boundaries. That is, apparent synchrony shows a type of categorical perception in that discriminations within the synchrony category are difficult, but those near the category boundary are easy.

Gaussian-noise discrimination and its relation to auditory object formation.

This study used a same/different experiment to assess the ability of human listeners to discriminate Gaussian-noise tokens with a spectral range of 350-850 Hz and a duration of 50 ms. For this duration, discrimination ability is high. However, when an identical 200-ms noise fringe with the same statistical properties as the 50-ms target tokens is appended to the end of the two target tokens, listeners show very poor discrimination. It was investigated whether altering the properties of the fringes with respect to those of the target improved the ability to discriminate the target tokens. This method was used to investigate the influence of changing fringe properties such as spectral range, level, interaural level difference, and interaural time delay on discrimination performance for the target. Spectral and temporal separation showed the strongest improvements, whereas no effect was found for doubling the fringe bandwidth, 5-dB level increases or decreases, or 10 dB interaural level differences. In the second experiment, subjects were asked to indicate whether they perceived one or two auditory objects for these stimuli. The results of the two experiments indicate that perceiving two objects is a necessary but not sufficient condition for good target discrimination.

On the influence of interaural differences on temporal perception of noise bursts of different durations.

The perception of a composite sound's temporal cues, like synchronous onsets, is considered essential to correct perceptual grouping of its constituent components. The processing of a single sound's spatial cues, already present at its onset, may interact with temporal perception of the onset. The current study investigated the influence of interaural differences on temporal perception of a sound's onset. As a measure of temporal perception, the ability to position the onset of a temporally displaced target sound to the regular meter of diotic reference marker sound onsets was measured for various target sound lateralizations, sensation levels, and target and marker sound durations. For target sounds presented in quiet, no influence of interaural differences on temporal positioning of the onset was found. However, increasing a sound's duration systematically shifted the perceived onset position into its "interior." For target sounds presented at low sensation levels in a noise masker, the precision of temporally positioning the onset generally degraded, though faster for dichotic conditions and for longer durations. The level below which temporal perception precision starts to degrade was found to depend on signal-to-noise ratio rather than on sensation level or duration, and is influenced by the presence of interaural differences.

On the ability to discriminate Gaussian-noise tokens or random tone-burst complexes.

This study investigated factors that influence a listeners' ability to discriminate Gaussian-noise stimuli in a same-different discrimination paradigm. The first experiment showed that discrimination ability increased with bandwidth for noise durations up to 100 ms. Duration had a nonmonotonic influence on performance, with a decrease in discriminability for stimuli longer than 40 ms. Further experiments investigated the cause for this performance decrease. They showed that discriminability could be improved when using frozen-noise tokens and by instructing listeners to focus on the stimulus endings. A final experiment, using a stimulus consisting of 5 ms Hanning-windowed tone-bursts randomly distributed over time, investigated whether stimulus duration and amount of information differently affect the processing capacity of the auditory system. Results showed that the number of degrees of freedom in the stimulus, not its duration, predominantly influenced the ability to discriminate. Overall, the results suggest that the discrimination performance for acoustic stimuli depends strongly on the amount of information per critical band and the capacity to process this information. This capacity seems to be limited in the temporal dimension, while extending the signal over more auditory filters does have a positive effect on performance.