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PubMed2006

Road traffic noise and sleep disturbances in an urban population: cross-sectional study.

AIM: To explore the relationship between sleep disturbances caused by traffic noise and relevant personality traits, such as extroversion-introversion, neuroticism, and subjective noise sensitivity. METHODS: A cross-sectional study was carried out from January to April 2005 in a central municipality of Belgrade, the capital of Serbia and Montenegro. Noise measurements were performed at 12 measurement sites three times at daytime and twice at night. On the basis of noise measurement results, three streets with the highest and three streets with the lowest values of equivalent sound pressure level (Leq) were chosen to represent noisy (>65 dB(A)) and quiet (<55dB(A)) areas, respectively. The respondents from both areas were asked to fill out the questionnaire on noise-related health problems. The final sample consisted of 310 respondents, 192 from noisy area and 118 from quiet area. RESULTS: Respondents from noisy area reported having significantly more difficulties with falling asleep, being woken up by noise at night more often, and having more difficulties with falling back to sleep. They also complained of poorer sleep quality and tiredness after sleep and they slept by an open window in summer less often. Noise annoyance, subjective noise sensitivity, and neuroticism were significantly correlated with difficulties with falling asleep, time needed to fall asleep, poorer sleep quality, tiredness after sleep, and use of sleeping pills. After adjustment for potential modifying personality traits including subjective noise sensitivity, neuroticism, and extroversion, residence in noisy area was shown to be a significant predictor for difficulties with falling asleep (odds ratio [OR], 2.71; 95% confidence interval [CI], 1.27-5.80), difficulties with falling back to sleep (OR, 1.87; 1.02-3.40), waking up at night (OR, 2.60; 1.49-4.52), sleeping by closed windows (OR, 13.51; 5.84-31.25), having poor sleep quality (OR, 2.99; 1.13-7.89), and feeling tired after sleep (OR, 2.50; 1.11-5.63). CONCLUSION: Urban population living in noisy area was at higher risk for sleep disturbances than population living in the quiet area. Furthermore, sleep disturbances were significantly and positively related to personality traits of neuroticism, subjective noise sensitivity, and noise annoyance.

Adult↗
PubMed1989

Basic studies on the objective evaluation method of noise using the anchor effect.

Current objective methods that estimate noise have a defect in that the measurement values are not stable and the noise can be measured only at pre- and post-exposure times. Some previous studies on the "anchor effect" suggested that noise can be objectively evaluated by evoked potentials (N1 and P2 components), when the noise exposure and the test stimuli to elicit the evoked potentials are given alternately. However, several basic experiments are required to establish this method for noise estimation. The differences in the time durations of stimuli be interchanged with the load of noise were studied in Experiment 1. As a result only N1 latency showed significant differences. This suggested that a continuous tone is suitable for intervening stimuli. In Experiment 2, the relation between evoked potentials and differences in the frequencies of intervening and test stimuli were studied in the wide frequency ranges of 250, 500, 1k, 2k, 4k, and 8k Hz. The results showed a tendency for the frequencies of intervening stimuli to become farther and farther removed from those of the test stimuli as the N1-P2 amplitudes of the latter become larger. This result revealed that pure tones are not suitable for test stimuli; therefore, white noise and pink noise were used as test stimuli in Experiment 3. The amplitude of response induced by white noise was not changed by the frequencies of the intervening stimulus. These results suggested that using evoked potential can be an objective method for noise estimation, when white noise is loaded as a test stimulus after the intervening stimulus.

Acoustic Stimulation↗
PubMed1993

The noise exposed factory workers: the prevalence of sensori-neural hearing loss and their use of personal hearing protection devices.

A total of 524 industrial workers were studied. They consisted of 442 noise exposed and 82 non-noise exposed workers. The purpose was to compare the prevalence of sensori-neural hearing loss among the noise exposed and the non-noise exposed workers, to study their knowledge on the hazard of noise to hearing and the workers' attitude towards the hearing protection devices. The prevalence of sensori-neural hearing loss was significantly higher among the noise exposed workers, i.e., 83% versus 31.7% (p < 0.01). However, the prevalence of hearing impairment was much lower for both groups, being 30.1% for the noise exposed and 3.7% for the non-noise exposed group. Although hearing protection devices were provided to 80.5% of the workers, only 5.1% were wearing them regularly. The possibility of developing hearing loss due to exposure to excessive noise was only known by 35.5% of the noise exposed workers. This awareness was found to have a positive correlation with the workers' compliance to the hearing protection devices. Our findings highlight the need for workers to be educated on the hazards of excessive noise exposure to hearing.

Auditory Threshold↗
PubMed1997

[Neurosensorial hearing loss caused by noises: results of a longitudinal study in iron and steel workers].

BACKGROUND: The detrimental effect of noise in the ear is well known. However, several countries debate the acceptance of hearing loss caused by exposure to noise as a professional disease. AIM: To assess the association of noise levels in an industrial environment with neurosensorial hearing loss. SUBJECTS AND METHODS: One thousands two hundred thirty two workers exposed to low, moderate and high noise levels were studied. All had a normal admission audiogram and at least one further audiogram. RESULTS: Four hundred forty five subjects, aged 40.4 +/- 8.2 years old, were exposed to low environmental noise, 341 subjects, aged 39 +/- 7.8 years old were exposed to moderate noise and 446, aged 39.2 +/- 7.3 years old were exposed to high noise for 16.7 +/- 8.1, 14.8 +/- 7.7 and 15.2 +/- 7.6 years respectively. The prevalence of hearing loss was 7.2, 11.7 and 13.2% among those exposed to low, moderate or high environmental noise. According to our legislation 0.4, 1.5 and 2.5% of those workers had a hearing impairment entitled to compensation. The regression slope for hearing loss was 0.5, 0.7 and 0.8 dB/year of age in workers exposed to low, moderate and high noise levels respectively. A significant effect of noise was observed after the age of 40 in those exposed to high levels, and after the age of 50 in those exposed to moderate levels. CONCLUSIONS: According to our safe noise exposure criteria, we are accepting that 18.2% of workers will suffer a disabling hearing loss at the end of their job life and that 0.4% will not attain an economic compensation in spite of their impairment.

Adult↗
PubMedDate not supplied

Health effects caused by noise: evidence in the literature from the past 25 years.

Traffic noise is the most important source of environmental annoyance. According to the Environmental Expert Council of Germany, severe annoyance persistent over prolonged periods of time is to be regarded as causing distress. Previously, extraaural noise effects were mostly assessed using a paradigm in which the sound level played the major role. On the basis of this paradigm the relatively low sound level of environmental noise was not considered to be a potential danger to health. In contrast to this numerous empirical results have shown long-term noise-induced health risks. Therefore a radical change of attitude - a change of paradigm - is necessary. For an immediate triggering of protective reactions (fight/flight or defeat reactions) the information conveyed by noise is very often more relevant than the sound level. It was shown recently that the first and fastest signal detection is mediated by a subcortical area - the amygdala. For this reason even during sleep the noise from aeroplanes or heavy goods vehicles may be categorised as danger signals and induce the release of stress hormones. In accordance with the noise stress hypothesis chronic stress hormone dysregulations as well as increases of established endogenous risk factors of ischaemic heart diseases have been observed under long-term environmental noise exposure. Therefore, an increased risk of myocardial infarction is to be expected. The results of individual studies on this subject in most cases do not reach statistical significance. However, according to the Environmental Expert Council, these studies show a consistent trend towards an increased cardiovascular risk if the daytime immission level exceeds 65 dB(A). Most of the previous studies on the extraaural effects of occupational noise have been invalidated by exposure misclassifications. In future studies on health effects of noise a correct exposure assessment is one of the most important preconditions.

Cardiovascular System↗
PubMed1985

[Is there a risk of noise-induced hearing loss in automobile drivers and in automobile sport racing?].

Professional racing drivers are exposed to extreme noise pollution by their high-capacity cars. For the purpose of evaluating the emissive noise of racing-cars, noise-level measurements on race-courses were undertaken. As a result noise-levels up to 130 dB (A) for the outer noises and 125 dB (A) for the inner region of the car were measured. Moreover, eighteen professional racing drivers as well as eleven employees, working in the pit, underwent audiometric investigations. Only one of the racing drivers showed noise deafness. This result can be explained by the short periods of exposure to the noise, which is 150-180 hours every year, and the regular wearing of ear-plugs. The employees working in the pits, however, showed distinct hearing impairments, explained above all, by their activities at the motor-test blocks. Incidentally this paper also deals with the noise sources of vehicles and the origin of noise deafness. There is no risk of noise deafness for this group of persons.

Audiometry, Pure-Tone↗
PubMed1997

Noise suppression digital filter for functional magnetic resonance imaging based on image reference data.

The central decision in every functional magnetic resonance imaging (fMRI) experiment is whether pixels in brain tissues are showing activation in response to neural stimulus or as a result of noise. Images are degraded not only by random (e.g., thermal) noise, but also by structured noise due to MR system characteristics, cardiac and respiratory pulsations, and patient motion. A novel digital filter has been developed to suppress cardiac and respiratory structured noise in fMRI images, using estimates of structured and random noise power spectra obtained directly from the images. It is an adaptive filter based on stationary noise statistics, and is equivalent in form to a Wiener filter. A mathematical model of the filtering process was developed to understand how the strength and distribution of structured and random noise power influenced filter performance. The filter was tested using images from an auditory activation study in ten subjects. In subjects whose structured noise power was localized to a relatively narrow frequency range, a strong relationship was found, both experimentally (R = 0.975, P < 0.0004 for H0: R = 0) and using the model, between filter performance and the level of structured noise power contaminating the experiment frequency. The filter significantly reduced the rate of false-positive activations in the subset of subjects whose experiment frequency was relatively heavily contaminated by structured noise. Notch filters, that simply eliminate unwanted frequencies, performed poorly in all subjects. Unlike the proposed Wiener filter, these filters did not suppress structured noise power at the experiment frequency that contributes to false-positive activations.

Brain↗
PubMed2005

Theoretical noise model for oxygenation-sensitive magnetic resonance imaging.

Contrast-to-noise ratio (CNR) in blood oxygenation level-dependent (BOLD) based functional MRI (fMRI) studies is a fundamental parameter to determine statistical significance and therefore to map functional activation in the brain. The CNR is defined here as BOLD contrast with respect to temporal fluctuation. In this study, a theoretical noise model based on oxygenation-sensitive MRI signal formation is proposed. No matter what the noise sources may be in the signal acquired by a gradient-echo echo-planar imaging pulse sequence, there are only three noise elements: apparent spin density fluctuations, S(0)(t); transverse relaxation rate fluctuations, R(2) (*)(t); and thermal noise, n(t). The noise contributions from S(0)(t), R(2) (*)(t), and n(t) to voxel time course fluctuations were evaluated as a function of echo time (TE) at 3 T. Both noise contributions caused by S(0)(t) and R(2) (*)(t) are significantly larger than that of thermal noise when TE = 30 ms. In addition, the fluctuations between S(0)(t) and R(2) (*)(t) are cross-correlated and become a noise factor that is large enough and cannot be ignored. The experimentally measured TE dependences of noise, temporal signal-to-noise ratio, and BOLD CNR in finger-tapping activation regions were consistent with the proposed model. Furthermore, the proposed theoretical models not only unified previously proposed BOLD CNR models, but also provided mechanisms for interpreting apparent controversies and limitations that exist in the literature.

Adolescent↗
PubMed2002

Noise reduction in BOLD-based fMRI using component analysis.

Principle Component Analysis (PCA) and Independent Component Analysis (ICA) were used to decompose the fMRI time series signal and separate the BOLD signal change from the structured and random noise. Rather than using component analysis to identify spatial patterns of activation and noise, the approach we took was to identify PCA or ICA components contributing primarily to the noise. These noise components were identified using an unsupervised algorithm that examines the Fourier decomposition of each component time series. Noise components were then removed before subsequent reconstruction of the time series data. The BOLD contrast sensitivity (CS(BOLD)), defined as the ability to detect a BOLD signal change in the presence of physiological and scanner noise, was then calculated for all voxels. There was an increase in CS(BOLD) values of activated voxels after noise reduction as a result of decreased image-to-image variability in the time series of each voxel. A comparison of PCA and ICA revealed significant differences in their treatment of both structured and random noise. ICA proved better for isolation and removal of structured noise, while PCA was superior for isolation and removal of random noise. This provides a framework for using and evaluating component analysis techniques for noise reduction in fMRI.

Adult↗
PubMed1993

Effects of luminance and exposure time on contrast sensitivity in spatial noise.

Using gratings with and without spatial noise we measured r.m.s. contrast sensitivity as a function of (i) retinal illuminance, (ii) amount of light added onto the screen, and (iii) exposure time. Our experiments showed that contrast sensitivity in external spatial noise was independent of decreasing retinal illuminance and exposure time as long as contrast sensitivity was lower with noise than without. Thereafter the decrease of contrast sensitivity was identical with and without noise. Although contrast sensitivity without external spatial noise was independent of the amount of added light, contrast sensitivity in external spatial noise was found to increase with the amount of added light until it reached the sensitivity measured without noise. Thereafter contrast sensitivities with and without noise were identical. Our results (i) provide experimental evidence for the validity of the generally accepted hypothesis that in the human contrast detection mechanism signal-to-noise ratio is constant at threshold and (ii) indicate that external spatial noise is the principal source of noise when it reduces contrast sensitivity.

Adult↗
PubMed1995

Elderly men and women are less responsive to startling noises: N1, P3 and blink evidence.

Previously we observed that the P3 component of the event-related brain potential (ERP) elicited by startling noises, and to a lesser extent P3 to target tones, is reduced in the elderly (Ford & Pfefferbaum, 1991). In the current experiment, we tried to eliminate possible effects of age-related hearing deficits on the responses to noises by filtering them to include only frequencies heard best by the elderly (0-1000 Hz) and by setting noise intensity relative to each subject's threshold (sensation level, SL). Twelve younger (mean 22 years) and 12 older (mean 69 years) men and women listened to three sequences of tones (80%, 500 Hz, 70 dB SPL) and noises (20%). One type of noise occurred in each sequence (wide band noise set to 107 dB SPL, narrow band noise set to 107 dB SPL, or narrow band noise set to approximately 65 dB SL). The order of the three sequences was counterbalanced across age and sex. Younger subjects blinked to the noise 4-5 times more often than older subjects and had N1 and P3 amplitudes that were 2-3 times larger, regardless of the noise type. N1 amplitude to the background frequent tones and non-startle blinks did not differ between groups. Thus, even when noises were narrow band and set relative to each subject's threshold, older subjects were less responsive to startling auditory stimuli than were younger.

Acoustic Stimulation↗
PubMed2006

Contrast detection in noise with positive and negative defocus in myopes.

PURPOSE: Previous studies have shown that myopes produce an asymmetrical loss in contrast sensitivity with positive and negative defocusing lenses at low-medium spatial frequencies (1-7c/deg) compared to non-myopes. The measurement of contrast detection in noise allows any given loss in visual sensitivity to be attributed to two components namely sampling efficiency and/or equivalent noise. Previous work has also shown that sampling efficiency gives an indication of the neural effects and in the absence of sampling efficiency changes, changes in equivalent noise levels are considered to be due to optical factors. We investigate whether the asymmetrical loss shown by myopes to defocus can be explained by changes in sampling efficiency or equivalent noise, or both. METHODS: Contrast thresholds in four different levels of externally added noise were measured in five myopic and five non-myopic subjects for Gabors of 3c/deg. Measurements were obtained under cycloplegia with 0 D, +/-0.50 D, and +/-1.00 D defocusing lenses. RMS wavefront aberrations were also measured using a Shack-Hartmann aberrometer. RESULTS: In the absence of noise, there was no significant difference in contrast sensitivity without defocus between myopes and emmetropes. When sampling efficiency and equivalent noise were measured from Contrast Detection in Noise functions, analysis of variance showed no significant difference in sampling efficiency between myopes and non-myopes (p=0.145). Myopes showed maximum levels of equivalent noise with +1.00 D defocus, decreasing to a minimum with -1.00 D defocus (p=0.009). Non-myopes showed a symmetrical increase in equivalent noise from zero for both positive and negative defocus. A significant correlation was found between equivalent noise and the total RMS of Wavefront aberrations of the eye (p=0.026). CONCLUSION: Optical factors explain the observed differences in contrast sensitivity with positive and negative defocus between myopes and non-myopes.

Accommodation, Ocular↗
PubMed1997

The effects of synaptic noise on measurements of evoked excitatory postsynaptic response amplitudes.

Spontaneously occurring synaptic events (synaptic noise) recorded intracellularly are usually assumed to be independent of evoked postsynaptic responses and to contaminate measures of postsynaptic response amplitude in a roughly Gaussian manner. Here we derive analytically the expected noise distribution for excitatory synaptic noise and investigate its effects on amplitude histograms. We propose that some fraction of this excitatory noise is initiated at the same release sites that contribute to the evoked synaptic event and develop an analytical model of the interaction between this fraction of the noise and the evoked postsynaptic response amplitude. Recording intracellularly with sharp microelectrodes in the in vitro hippocampal slice preparation, we find that excitatory synaptic noise accounts for up to 70% of the intracellular recording noise, when inhibition is blocked pharmacologically. Up to 20% of this noise shows a significant correlation with the evoked event amplitude, and the behavior of this component of the noise is consistent with a model which assumes that each release site experiences a refractory period of approximately 60 ms after release. In contrast with classical models of quantal variance, our models predict that excitatory synaptic noise can cause the apparent variance of successive peaks in an excitatory synaptic amplitude histogram to decrease from left to right, and in some cases to be less than the variance of the measured noise.

6-Cyano-7-nitroquinoxaline-2,3-dione↗
PubMed2001

Nonmonotonic noise tuning of BOLD fMRI signal to natural images in the visual cortex of the anesthetized monkey.

BACKGROUND: The perceptual ability of humans and monkeys to identify objects in the presence of noise varies systematically and monotonically as a function of how much noise is introduced to the visual display. That is, it becomes more and more difficult to identify an object with increasing noise. Here we examine whether the blood oxygen level-dependent functional magnetic resonance imaging (BOLD fMRI) signal in anesthetized monkeys also shows such monotonic tuning. We employed parametric stimulus sets containing natural images and noise patterns matched for spatial frequency and intensity as well as intermediate images generated by interpolation between natural images and noise patterns. Anesthetized monkeys provide us with the unique opportunity to examine visual processing largely in the absence of top-down cognitive modulations and can thus provide an important baseline against which work with awake monkeys and humans can be compared. RESULTS: We measured BOLD activity in occipital visual cortical areas as natural images and noise patterns, as well as intermediate interpolated patterns at three interpolation levels (25%, 50%, and 75%) were presented to anesthetized monkeys in a block paradigm. We observed reliable visual activity in occipital visual areas including V1, V2, V3, V3A, and V4 as well as the fundus and anterior bank of the superior temporal sulcus (STS). Natural images consistently elicited higher BOLD levels than noise patterns. For intermediate images, however, we did not observe monotonic tuning. Instead, we observed a characteristic V-shaped noise-tuning function in primary and extrastriate visual areas. BOLD signals initially decreased as noise was added to the stimulus but then increased again as the pure noise pattern was approached. We present a simple model based on the number of activated neurons and the strength of activation per neuron that can account for these results. CONCLUSIONS: We show that, for our parametric stimulus set, BOLD activity varied nonmonotonically as a function of how much noise was added to the visual stimuli, unlike the perceptual ability of humans and monkeys to identify such stimuli. This raises important caveats for interpreting fMRI data and demonstrates the importance of assessing not only which neural populations are activated by contrasting conditions during an fMRI study, but also the strength of this activation. This becomes particularly important when using the BOLD signal to make inferences about the relationship between neural activity and behavior.

Anesthesia↗
PubMed2000

Schizophrenia: reduced signal-to-noise ratio and impaired phase-locking during information processing.

OBJECTIVE: This study was performed in order to clarify the mechanisms which underlie the reduced signal-to-noise of event-related potentials in schizophrenic patients. Specifically, we wanted to find out, whether it is reduced activation and/or synchronization (phase-locking) in specific frequency bands of the ongoing EEG which is related to the decreased signal amplitude and signal-to-noise ratio in schizophrenics. METHODS: We investigated 41 unmedicated schizophrenics (10 of them drug-naïve) and compared them with healthy control subjects (n = 233) as well as unmedicated subjects with schizotypal personality (n = 21), who were considered to be high-risk subjects for schizophrenia, and unmedicated depressive patients (n = 71). We measured event-related activity during an acoustical choice reaction paradigm and calculated the signal-to-noise ratio, signal power and noise for a time interval of 50-200 ms after stimulus presentation. Signal-to-noise ratio was calculated from the power of the averaged trials (signal power) divided by the mean power of the single trials minus the power of the average (noise power). Also, we performed a frequency analysis of the pre- and poststimulus EEG based on a factor analytical approach. Group comparisons were performed with ANCOVA. RESULTS: As expected, a decreased signal-to-noise ratio of evoked activity was found in the schizophrenic and a non-significant trend in the schizotypal subjects and the depressive patients. We were able to show that the observed decrease is due to a reduced signal power and an increase of absolute noise power. Frequency analysis of the evoked activity revealed that normals, schizophrenics schizotypal subjects and depressive patients increased theta/delta activity between pre- and poststimulus interval to a similar extend. However, this theta/delta-augmentation does not correlate with signal power in schizophrenics. Also, normals and depressive subjects augment coherence between both temporal lobes during information processing, which is not found in schizophrenics and schizotypal subjects. In contrast, these two groups augment frontal lobe coherence, which goes along with an increase of noise. CONCLUSIONS: Reduced stimulus-induced phase-locking and bitemporal coherence of cortically evoked activity but not a failure to activate the cortex may be responsible for the observed low signal-to-noise ratio during information processing in schizophrenics. Accordingly, schizophrenics increase noise after stimulus presentation instead of building up a signal. This is discussed in the framework of the theory of stochastic resonance.

Acoustic Stimulation↗
PubMed2006

Noise in transcription negative feedback loops: simulation and experimental analysis.

Negative feedback loops have been invoked as a way to control and decrease transcriptional noise. Here, we have built three circuits to test the effect of negative feedback loops on transcriptional noise of an autoregulated gene encoding a transcription factor (TF) and a downstream gene (DG), regulated by this TF. Experimental analysis shows that self-repression decreases noise compared to expression from a non-regulated promoter. Interestingly enough, we find that noise minimization by negative feedback loop is optimal within a range of repression strength. Repression values outside this range result in noise increase producing a U-shaped behaviour. This behaviour is the result of external noise probably arising from plasmid fluctuations as shown by simulation of the network. Regarding the target gene of a self-repressed TF (sTF), we find a strong decrease of noise when repression by the sTF is strong and a higher degree of noise anti-correlation between sTF and its target. Simulations of the circuits indicate that the main source of noise in these circuits could come from plasmid variation and therefore that negative feedback loops play an important role in suppressing both external and internal noise. An important observation is that DG expression without negative feedback exhibits bimodality at intermediate TF repression values. This bimodal behaviour seems to be the result of external noise as it can only be found in those simulations that include plasmid variation.

Computer Simulation↗
PubMed2006

Gene network shaping of inherent noise spectra.

Recent work demonstrates that stochastic fluctuations in molecular populations have consequences for gene regulation. Previous experiments focused on noise sources or noise propagation through gene networks by measuring noise magnitudes. However, in theoretical analysis, we showed that noise frequency content is determined by the underlying gene circuits, leading to a mapping between gene circuit structure and the noise frequency range. An intriguing prediction from our previous studies was that negative autoregulation shifts noise to higher frequencies where it is more easily filtered out by gene networks--a property that may contribute to the prevalence of autoregulation motifs (for example, found in the regulation of approximately 40% of Escherichia coli genes). Here we measure noise frequency content in growing cultures of E. coli, and verify the link between gene circuit structure and noise spectra by demonstrating the negative autoregulation-mediated spectral shift. We further demonstrate that noise spectral measurements provide mechanistic insights into gene regulation, as perturbations of gene circuit parameters are discernible in the measured noise frequency ranges. These results suggest that noise spectral measurements could facilitate the discovery of novel regulatory relationships.

Algorithms↗
PubMed2000

Children's phoneme identification in reverberation and noise.

This study assessed the effects of reverberation, noise, and their combination on listeners' identification of consonants and vowels in naturally produced nonsense syllables presented at different sensation levels (re: speech recognition threshold). A secondary purpose of this study was to assess listeners' identification of voicing, manner, and place of articulation for consonants at 50 dB SL in the reverberation, noise, and combined conditions. Listeners, aged 6-30 years, identified consonant-vowel-consonant-vowel (CVCV) stimuli presented at four different sensation levels (re: speech recognition threshold) of 30, 40, 50, and 60 dB SL in 4 listening conditions: (a) an optimal listening situation (no reverberation, no noise), (b) reverberation only (1.3 seconds), (c) noise only (+13 dB S/N against a multitalker babble), and (d) reverberation plus noise. Results showed that all listener groups achieved maximum consonant identification performance at 50 dB SL. Vowel identification scores were unaffected by SL. Statistical analyses revealed that children's ability to identify consonants varied according to listening condition. For example, children's consonant identification abilities reached adult-like levels of performance at about age 14 years in the reverberation-only and noise-only listening conditions. However, in the reverberation-plus-noise listening condition, children's consonant identification abilities do not mature until the late teenage years. The ability to identify vowels, on the other hand, develops much earlier. A feature analysis of the consonant data showed that for all 3 features (voicing, manner, and place), identification scores were highest in the control condition, similar for the reverberation-only and noise-only conditions, and lowest in the reverberation-plus-noise condition. Voicing was easier for listeners to identify than manner or place of articulation features in reverberation and noise. Taken together, these results suggest that the ability to identify speech in reverberation and noise reaches adult-like level of performance at different ages for different components of the speech signal.

Adolescent↗