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At least 235 records · Page 13Linked to original sources
PubMed2006

Noise-induced gastric lesions: a light and scanning electron microscopy study of the alterations of the rat gastric mucosa induced by low frequency noise.

INTRODUCTION: Exposure to low frequency noise (LFN) can lead to vibroacoustic disease (VAD), recognized as a systemic disease with lesions in a broad spectrum of organs. Although gastrointestinal complaints are common among individuals exposed to noise, only few studies tried to evaluate the digestive lesions. The authors performed this study in order to investigate gastric lesions in an animal model of VAD. MATERIAL AND METHODS: Adult Wistar rats were exposed to continuous LFN. After five weeks they were sacrificed. The stomachs were studied by light microscopy and scanning electron microscopy, and compared with stomachs of animals kept in silence. RESULTS: Superficial erosions were present in the noise-exposed animals. Massive cell death of the gastric epithelium was observed, both by light and electron microscopy. DISCUSSION: The erosions, reflecting cellular degeneration and death, occurred without inflammation, similar to what has been observed in other LFN-exposed organs.

Animals↗
PubMed1979

The effect of masking by noise on word discrimination scores in listeners with normal hearing and with noise-induced hearing loss.

Patients with high-frequency hearing loss often complain at the Workers' Compensation Board that they find it difficult to hear speech in a noisy environment. This study was undertaken to test the validity of their complaints. The experiment had a 2x3x3 factorial design. The factors were subject group (normal hearing versus sensorineural hearing loss), stimulus level (65, 75, and 85 dB SPL), and speech-to-noise ratio (5, 12, and 19 dB). There were 6 subjects in each condition. Each subject was tested for his speech discrimination with three CID W-22 50-word lists, one in each of the three different speech-to-noise ratios. Both speech and pink noise were presented through loudspeakers in a sound field. The results support the patients' complaints. Possible explanations for the results are discussed.

Adult↗
PubMed2005

Acceptable noise level, phoneme recognition in noise, and measures of auditory efferent activity.

Acceptable noise level (ANL) is unrelated to sentence recognition in noise but may be related to phoneme recognition in noise (PRN). Individual differences in efferent activity in medial olivocochlear bundle (MOCB) and acoustic reflex (AR) pathways may account for intersubject variability in ANL and PRN. Monotic and dichotic ANL, monotic PRN, contralateral suppression of transient evoked otoacoustic emissions, and ipsilateral and contralateral acoustic reflex thresholds were measured in 31 adults with normal hearing. Results indicate that monotic ANL and PRN are unrelated. Monotic and dichotic ANL are related, suggesting that nonperipheral factors mediate ANL. Intersubject variability in ANL cannot be accounted for by individual differences in MOCB or AR activation. Intersubject variability in PRN cannot be accounted for by individual differences in MOCB or contralateral AR activation. It may be influenced by the ipsilateral AR pathway. Efferent activity in the contralateral AR arc is correlated with efferent activity in the MOCB.

Adult↗
PubMed1976

[Effect of noise on the physiological functions in fowl. 1. Effect of primary strong noise on the 11-OHKS level in broilers and leghorns].

The effects of first noises on broilers and white leghorns were tested by plasma levels on 11-hydroxycorticosteroid (11-OHKS). The noises were 100 dB, 60 to 8,00 Hz, and applied 30 minutss to one group of broilers, aged 14, 28, and 56 days, and to another group of broilers and white leghorns in adult age. The reactions were compared. Acoustic stimulation was followed by temporary activation of the hypothalamic pituitary-suprarenal system. The rise of the plasma glucocorticosteroid level in leghorns was three times as high as that in adult broilers, which was interpreted as a reflection of stronger organic stress. Reactions differed in intensity, depending on age as well. Plasma-11-OHKS levels went up by 32 per cent maximum in broilers aged 56 days or by 73 per cent in animals aged 14 days or 120 per cent in those aged 28 days. The above results seemed to support the conclusion that noises of the above quantity and quality represented stress on fowl.

11-Hydroxycorticosteroids↗
PubMed1978

[Noise-induced hearing loss and the sisi test. on the assessment of noise-induced hearing loss (author's transl)].

In the assessment of noise-induced hearing loss problems arise mainly in those cases where the middle frequencies are involved in the hearing defects at a proportionally high degree, because this strongly impairs the speech discrimination and because such a hearing defect cannot be regarded as a typical case of noise-induced hearing loss. A recruitment test must be carried out in the middle or lower frequency range in order to diagnose any possible multifactorial genesis of the hearing defect. As concerns the widely used SISI test the result is shown to depend not only on the test intensity but also on the test frequency. Since the hearing threshold in the middle under discussion is usually better in the middle and lower frequency ranges than in the higher ones and since, as a consequence, the test intensity in the SISI test is lower, frequently lower SISI values can be observed here than in the case of higher frequencies. Since the test of the lower frequencies results in lower SISI values than for higher frequencies also in those cases where the hearing threshold in the lower frequency range is the same or even worse, we must assume that the results of the SISI test depend on the frequency. In the examination of patients with a hearing defect where the hearing threshold curve flattens obliquely, intensity dependence and frequency dependence are added in the lower frequency range; negative SISI values are not infrequent. It is not admissible to conclude from that a retrocochlear defect in the middle and lower frequency ranges in cases of noise-induced hearing loss in the high-tone range.

Audiometry↗
PubMed1995

[Comparison of methods for early detection of noise vulnerability of the inner ear. Amplitude reduction of otoacoustic emissions are most sensitive at submaximal noise impulse exposure].

Noise-induced temporary impairment of cochlear function was measured with several audiometric tests in order to evaluate which method best predicts a vulnerable cochlea. We tested 10 normally-hearing and 13 subjects who were positive for temporary threshold shifts (TTS). The latter were selected from 194 soldiers who demonstrated a TTS higher than 15 dB after regular training with firearms. Acoustic distortion products (DPOAE), click-evoked otoacoustic emissions (TEOAE), upper limit of hearing (ULH) and pure-tone and high-frequency audiometry were used to evaluate possible increased vulnerability of the cochlea. Tests were conducted at lower sound intensities (white noise, 90 dB SPL, 5 min; impact noise, 100 or 106 dB SPLs, 10 impulses/s, 5 min). Seventy per cent of the TTS-positive soldiers studied exhibited significant reductions of TEOAE amplitudes, whereas a stable emission was observed in all control subjects. DPOAE alterations were seen in 38% of the soldiers tested. These results indicate that TEOAE is the most sensitive, objective method for detecting a positive disturbance in cochlear function. Although the upper limit of hearing was also a very sensitive method, variability of this psychoacoustic method depended on the help and experience of the subjects being tested.

Adult↗
PubMed1999

Signal-to-noise ratio and signal-to-noise efficiency in SMASH imaging.

A general theory of signal-to-noise ratio (SNR) in simultaneous acquisition of spatial harmonics (SMASH) imaging is presented, and the predictions of the theory are verified in imaging experiments and in numerical simulations. In a SMASH image, multiple lines of k-space are generated simultaneously through combinations of magnetic resonance signals in a radiofrequency coil array. Here, effects of noise correlations between array elements as well as new correlations introduced by the SMASH reconstruction procedure are assessed. SNR and SNR efficiency in SMASH images are compared with results using traditional array combination strategies. Under optimized conditions, SMASH achieves the same average SNR efficiency as ideal pixel-by-pixel array combinations, while allowing imaging to proceed at otherwise unattainable speeds. The k-space nature of SMASH reconstructions can lead to oscillatory spatial variations in noise standard deviation, which can produce local enhancements of SNR in particular regions.

Abdomen↗
PubMed2000

A three-dimensional physical model of MRI noise based on current noise sources in a conductor.

Magnetic flux noise is generated by any conductor in equilibrium with a bath as a result of random fluctuating currents. A physical model of this flux noise is proposed, based on allowable current patterns in the conductor, which we describe as natural current modes. This model gives insight into the spatial characteristics of the magnetic noise which is encountered in a variety of magnetic measurements and imaging modalities such as magnetic resonance imaging (MRI).

Imaging, Three-Dimensional↗
PubMed2004

Context noise and item noise jointly determine recognition memory: a comment on Dennis and Humphreys (2001).

S. Dennis and M. S. Humphreys (see record 2001-17194-007) proposed a model with the strict assumption that recognition memory is not affected by interference from other items. Instead, confusions are due to noise generated by prior contexts in which the test item appeared. This model seems disparate from existing models of recognition memory but is similar in many ways that are not superficially obvious. One difference is the order in which item and context information are used as retrieval cues. A more critical difference is the assertion that only an item's history, and not other items, affects recognition memory. Conceptual arguments along with the results of 2 experiments make a persuasive case that both types of noise affect recognition. To illustrate the approach, the authors fit experimental data with a version of the retrieving effectively from memory model (R. M. Shiffrin & M. Steyvers, 1997) incorporating both sources of noise.

Association↗
PubMed2000

Noise sustained propagation: local versus global noise

We expand on prior results on noise supported signal propagation in arrays of coupled bistable elements. We present and compare experimental and numerical results for kink propagation under the influence of local and global fluctuations. As demonstrated previously for local noise, an optimum range of global noise power exists for which the medium acts as a reliable transmission "channel." We discuss implications for propagation failure in a model of cardiac tissue, and present a general theoretical framework based on discrete kink statistics. Valid for generic bistable chains, the theory captures the essential features observed in our experiments and numerical simulations.

Journal Article↗
PubMed2001

Noise-induced phase synchronization enhanced by dichotomic noise.

We study the nonlinear response of a stochastic bistable system driven by both a weak periodic signal and a dichotomic noise in terms of stochastic phase synchronization. We show that the effect of noise-induced phase synchronization can be significantly enhanced by the addition of a dichotomic noise.

Journal Article↗
PubMed2004

Itô versus Stratonovich white-noise limits for systems with inertia and colored multiplicative noise.

We consider the dynamics of systems in the presence of inertia and colored multiplicative noise. We study the limit where the particle relaxation time and the correlation time of the noise both tend to zero. We show that the limiting equation for the particle position depends on the magnitude of the particle relaxation time relative to the noise correlation time. In particular, the limiting equation should be interpreted either in the Itô or Stratonovich sense, with a crossover occurring when the two fast-time scales are of comparable magnitude. At the crossover the limiting stochastic differential equation is neither of Itô nor of Stratonovich type. This means that, after adiabatic elimination, the governing equations have different drift fields, leading to different physical behavior depending on the relative magnitude of the two fast-time scales. Our findings are supported by numerical simulations.

Journal Article↗
PubMed2002

Shot-noise-induced random telegraph noise in shuttle current.

Random telegraph noise in the electric current produced by shot noise is predicted for an array of movable colloid particles by Monte Carlo and molecular dynamics calculations. The electron transport is attributed to the shuttle mechanism where moving colloid particles carry charges. The colloid-particle motion induced by the source-drain voltage shows periodic and/or quasiperiodic vibrations, and the current value depends on the vibration modes. Shot noise that is uncorrelated with the colloid-particle motion causes transitions between the periodic and quasiperiodic vibration modes, resulting in random switching between the current levels corresponding to the vibration modes.

Journal Article↗
PubMed1995

Effects of undersampling on the proper interpretation of modulation transfer function, noise power spectra, and noise equivalent quanta of digital imaging systems.

The proper understanding of modulation transfer function (MTF), noise power spectra (NPS), and noise equivalent quanta (NEQ) in digital systems is significantly hampered when the systems are undersampled. Undersampling leads to three significant complications: (1) MTF and NPS do not behave as transfer amplitude and variance, respectively, of a single sinusoid, (2) the response of a digital system to a delta function is not spatially invariant and therefore does not fulfill certain technical requirements of classical analysis, and (3) NEQ loses its common meaning as maximum available SNR2 (signal-to-noise) at a particular frequency. These three complications cause the comparisons of MTF and NEQ between undersampled digital systems to depend on the frequency content of the images being evaluated. A tutorial of MTF, NPS, and NEQ concepts for digital systems is presented, along with a complete theoretical treatment of the above-mentioned complications from undersampling.

Fourier Analysis↗
PubMed2005

Noise performance and signal-to-noise ratio of shear strain elastograms.

In this paper, we develop a theoretical expression for the signal-to-noise ratio (SNR) of shear strain elastograms. The previously-developed ideas for the axial strain filter (ASF) and lateral strain filter (LSF) are extended to define the concept of the shear strain filter (SSF). Some of our theoretical results are verified using simulations and phantom experiments. The results indicate that the signal-to-noise ratio of shear-strain elastograms (SNRsse) improves with increasing shear strain and with improvements in system parameters such as the sonographic signal-to-noise ratio (SNRs) beamwidth, center frequency and fractional bandwidth. The results also indicate that the amount of axial strain present along with the shear strain is an important parameter that determines the upper bound on SNRsse. The SNRsse will be higher in the absence of additional deformation due to axial strain.

Computer Simulation↗
PubMed1994

The turbulent noise ratio: an estimation of noise power of the breathy voice using PARCOR analysis.

The degree of turbulent noise in the breathy voice of 25 patients with incomplete glottal closure was determined by PARCOR (PARtial autoCORrelation) analysis. From 10,000 acoustic data points, 44 PARCOR coefficients were calculated to form the residue wave which is representative of the glottal source. The power difference between the residue wave and the original acoustic wave was calculated in order to define a new measurement of acoustic power termed the turbulent noise ratio (TNR). The 25 patients were studied before and after Isshiki thyroplasty type I (IttI). The TNR became smaller in 24 of these patients following IttI, and corresponded closely with acoustic (Fukazawa's Br-Index), aerodynamic (Isshiki's AC/DC ratio), mean airflow rate during phonation, and videolaryngostroboscopic findings. Data affirm that the TNR accurately reflects the degree of turbulent noise at the glottal source.

Adult↗
PubMed2003

Noise-equivalent change in radiance for sampling noise in a double-sided interferogram.

The formula for the noise-equivalent change in radiance (NEdN) for sampling noise [Appl. Opt. 38, 139 (1999)] can work well when applied to the double-sided interferograms of radiance spectra dominated by isolated emission lines, but it does not work well when applied to broad, slowly varying radiance spectra such as a Planck blackbody curve. The modified formula for the sampling-noise NEdN works well when applied to the double-sided interferograms of both types of radiance spectra.

Journal Article↗
PubMed2003

Noise-equivalent change in radiance for misalignment noise in a double-sided interferogram.

Engineers designing optical alignment servo systems for Michelson interferometers and Fourier-transform infrared spectrometers need to predict the amount of noise expected from the small and randomly varying amounts of misalignment that occur as the servo attempts to maintain alignment while taking data. A formula is derived for the noise-equivalent change in radiance due to this effect and the formula's accuracy is demonstrated by comparison of its predictions to the errors found in simulated interferometer measurements contaminated by misalignment noise.

Journal Article↗