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At least 109 records · Page 6Linked to original sources
PubMed1983

Monaural and binaural auditory frequency resolution measured using bandlimited noise and notched-noise masking.

Several studies using bandlimited masking noise have indicated that NOSO frequency resolution is better than that for NOS pi. The present study examined NOSO and NOS pi frequency resolution with two different masking methods: bandlimited noise and notched noise. Noise spectrum levels of 10, 30, and 50 dB/Hz were used. Thresholds were determined for a 500-Hz signal, using a three-alternative forced-choice adaptive procedure, as a function of masker bandwidth and notchwidth. For NOSO presentation, 3-dB down points were comparable for the notched-noise and bandlimiting methods. For NOS pi presentation, 3-dB down points were generally greater for the bandlimiting method than the notched noise method. Furthermore, for NOS pi presentation, the 3-dB down estimate increased as noise level increased for the bandlimiting method, but stayed constant for the notched-noise method. It is suggested that the two masking methods measured different aspects of binaural processing.

Acoustic Stimulation↗
PubMed2006

Automated estimation of white Gaussian noise level in a spectrum with or without spike noise using a spectral shifting technique.

Various tasks, for example, the determination of signal-to-noise ratios, require the estimation of noise levels in a spectrum. This is generally accomplished by calculating the standard deviation of manually chosen points in a region of the spectrum that has a flat baseline and is otherwise devoid of artifacts and signal peaks. However, an automated procedure has the advantage of being faster and operator-independent. In principle, automated noise estimation in a single spectrum can be carried out by taking that spectrum, shifting a copy thereof by one channel, and subtracting the shifted spectrum from the original spectrum. This leads to an addition of independent noise and a reduction of slowly varying features such as baselines and signal peaks; hence, noise can be more readily determined from the difference spectrum. We demonstrate this technique and a spike-discrimination variant on white Gaussian noise, in the presence and absence of spike noise, and show that highly accurate results can be obtained on a series of simulated Raman spectra and consistent results obtained on real-world Raman spectra. Furthermore, the method can be easily adapted to accommodate heteroscedastic noise.

Journal Article↗
PubMed2000

The effects of interrupted noise exposures on the noise-damaged cochlea.

A variety of interrupted noise exposure paradigms will produce a toughening effect in the mammalian auditory system. That is, the threshold shift will gradually become smaller with each successive daily exposure. The ability of the system to be toughened has not been explored in subjects with a pre-existing noise-induced hearing loss. Using the chinchilla as the experimental animal, evoked potential audiometry to obtain thresholds, and surface preparation histology to quantify the sensory cell population, the issue of toughening was examined in the noise-damaged auditory system. Toughening was produced by a 1.0 kHz, narrow-band impact at 115 dB peak SPL for 10 days, 6 h/day, and trauma was produced by a 1.0 kHz, narrow-band impact at 121 dB peak SPL for 5 days, 24 h/day. Four groups of animals were used. Group 1: traumatic exposure followed 30 days later by the toughening exposure. Group 2: toughening exposure followed 30 days later by the traumatic exposure. Group 3: a trauma-only control. Group 4: a toughening-only control. Group 2 that received the toughening exposure 30 days prior to the traumatic exposure showed a 10 to more than 20 dB toughening effect between the 0.5 and 4.0 kHz test frequencies, while Group 1 that received the traumatic exposure followed 30 days later by the toughening exposure showed no toughening. The permanent changes in the evoked response audiograms and sensory cell populations were the same in Groups 1, 2 and 3 that were exposed to the traumatic noise, regardless of whether or not the animals were ever subjected to the toughening noise or whether the toughening noise preceded or followed the traumatic noise.

Acoustic Stimulation↗
PubMed1990

Noise-induced hearing loss: a possible marker for high blood pressure in older noise-exposed populations.

The present study assessed the relationships among occupational noise exposure, noise-induced hearing loss, and high blood pressure. The study population consisted of 245 retired metal assembly workers from Pittsburgh aged 56 to 68 with chronic noise exposure of 30 or more years at greater than or equal to 89 dBA. Results of the audiometric testing indicated 52% of the younger workers (ages 56 to 63) have severe noise-induced hearing loss (greater than or equal to 65 dBA loss at 3, 4, or 6 kHz) and 67% of older workers (ages 64 to 68). Body mass index and alcohol intake were significantly related to systolic and diastolic blood pressure. Among older men, there was a marginally significant increased prevalence of high blood pressure (greater than or equal to 90 mm diastolic or taking blood pressure medicine) among those with severe noise-induced hearing loss (P = .05). Moreover, another measure of hearing loss at high frequencies, speech discrimination score in noise (measured in the better ear), referred to as the W-22 MAX score, was also found to be related to the prevalence of high blood pressure in the older (64 to 68) age group (P less than .05). Multiple regression analysis revealed W-22 MAX and severe noise-induced hearing loss were independent predictors of hypertension in the older, but not in the younger group of retired workers.

Age Factors↗
PubMed1994

[Communication and noise. Speech intelligibility of airplane pilots with and without active noise compensation].

Noise exposure measurements were performed with pilots of the German Federal Navy during flight situations. The ambient noise levels during regular flight were maintained at levels above a 90 dB A-weighted level. This noise intensity requires wearing ear protection to avoid sound-induced hearing loss. To be able to understand radio communication (ATC) in spite of a noisy environment, headphone volume must be raised above the noise of the engines. The use of ear plugs in addition to the headsets and flight helmets is only of limited value because personal ear protection affects the intelligibility of ATC. Whereas speech intelligibility of pilots with normal hearing is affected to only a smaller degree, pilots with pre-existing high-frequency hearing losses show substantial impairments of speech intelligibility that vary in proportion to the hearing deficit present. Communication abilities can be reduced drastically, which in turn can affect air traffic security. The development of active noise compensation devices (ANC) that make use of the "anti-noise" principle may be a solution to this dilemma. To evaluate the effectiveness of an ANC-system and its influence on speech intelligibility, speech audiometry was performed with a German standardized test during simulated flight conditions with helicopter pilots. Results demonstrate the helpful effect on speech understanding especially for pilots with noise-induced hearing losses. This may help to avoid pre-retirement professional disability.

Adult↗
PubMed2000

Reducing noise pollution in the hospital setting by establishing a department of sound: a survey of recent research on the effects of noise and music in health care.

A proposal for a solution to reduce stress and anxiety in the hospital setting by combining the problems of excess noise in a hospital setting with the efficacy of music therapy is supported through an analysis of research in the field of noise, hospital noise pollution, and music medicine. Included in this overview are articles describing the effects of noise on health, the problems of noise pollution in the health care setting, and the benefits of replacing noise with music to reduce heart rate, blood pressure, breathing rate, emotional anxiety, and pain. By combining these areas of research, the authors propose the establishment of a department assigned to (1) control the amount of noise in a hospital and (2) provide a center of music therapy for all individuals in the hospital setting, including in-patients, out-patients, doctors, and staff. Due to the large specificity of these areas, this unifying source, or "Department of Sound," is suggested to aid in thoroughly addressing and combining these two concepts most effectively.

Anxiety↗
PubMed1993

An analysis of relationships among environmental noise, annoyance and sensitivity to noise, and the consequences for health and sleep.

The complex relationship among long-term exposure to environmental noise, self-reports of health, and sleep was investigated in a multifactorial design. Forty-seven women and 35 men living beside a street with moderate to heavy traffic took part. They answered questions concerning health complaints, usual sleep patterns, sleep the actual week of testing, their subjective responses to noise, psychosocial relations, anxiety, stressful life events, type A behavior, and attitudinal factors that could explain their responses to noise. No detrimental relations among objective noise levels, health, and sleep could be shown. There were, however, strong correlations between the subjective noise responses of annoyance and sensitivity and health complaints. Only women revealed a relationship between poor sleep quality and sensitivity. The stronger relationship among noise sensitivity, health complaints, and poor sleep quality for women than for men could be explained by the degree of exposure to noise as evidenced by their longer residence and greater time spent at home.

Adult↗
PubMed2006

EEG reveals the effect of fMRI scanner noise on noise-sensitive subjects.

One drawback of fMRI is that subjects must endure intense noise during testing. This may be annoying to some people and acceptable to others. The aim of this study was to examine, by means of event-related potentials (ERPs), the possible influence of this noise on brain activity while performing a mental reasoning task. Subjects carrying out tasks in a silent environment were compared with two groups executing the same tasks in an "fMRI-like" noisy environment, one of which consisted of subjects who were annoyed by the noise and the other of subjects who tolerated it easily. Subjects who were annoyed performed less well (i.e., produced more errors compared to the "no noise" group) and "not annoyed" subjects showed a speed-accuracy trade-off (i.e., reacted faster but made more errors compared to "no noise" subjects). Noise led to more pronounced N1 and P2 peaks but attenuated N2. As early ERP components are influenced by attention, this observation most likely reflects different attentional requirements. The slow cortical negative shift during task processing was significantly attenuated with "annoyed" subjects compared to "not annoyed" subjects. Emotion-related subcortical structures may be responsible for the observed difference. These findings suggest that individual reactions to fMRI scanner noise should be taken into account when designing fMRI studies and interpreting results.

Adolescent↗
PubMedDate not supplied

Aircraft noise annoyance and average versus maximum noise levels.

A questionnaire study was performed in seven areas located around the airports of Landvetter and Save, Gothenburg, in an attempt to elucidate the extent of annoyance in populations exposed to aircraft noise. Noise exposure was estimated as the energy equivalent level (Aircraft Noise Level--FBN) or as the number of aircraft with levels that exceeded 70 dBA, combined with the maximum noise level. The results were compared with data obtained from the earlier Scandinavian Aircraft Noise Investigation. The results supported the conclusion that the annoyance reaction is better related to the number of aircraft and the maximum noise level than to energy equivalent levels for noise exposure.

Adolescent↗
PubMed2001

Monaural masking release in random-phase and low-noise noise.

Two masking-release paradigms thought to involve across-channel processing are comodulation masking release (CMR) and profile analysis. Similarities between these two paradigms were explored by comparing signal detection in maskers that varied only in degree of envelope fluctuation. The narrow-band-noise maskers were 10 Hz wide and their envelope fluctuations were manipulated using the low-noise noise algorithm of Pumplin [J. Acoust. Soc. Am. 78, 100-104 (1985)]. Masking conditions included the classic CMR conditions of an on-frequency band, multiple (five) incoherent bands, or multiple coherent bands. Detection was compared using both random-phase noise (RPN) and low-noise noise (LNN) maskers. In one set of conditions, the signal was identical to the on-frequency masker, yielding an intensity discrimination task. Conditions that included RPN maskers and tonal signals resembled the classic CMR paradigm, whereas conditions including LNN and noise signals more closely resembled the classic profile analysis paradigm. Other conditions may be considered hybrids. This combination of conditions provided a wide variety of within- and across-channel cues for detection. The results suggest that CMR and profile analysis could be based upon the same set of stimulus cues and perhaps the same perceptual processes.

Adult↗
PubMed1975

[Noise level measurements of the air noise during drilling and grinding on the fresh isolated temporal bone (author's transl)].

Aerial sound measurements with different drilling instruments were performed during dry running and preparations of the bone. Registered were the values of the small drilling instruments Sirona, Dentatus-Air, and Electro-Torque-Ritter. Also tested were the KaVo-Technique-machine, the Hall-machine, the Air-Orbit-turbine, and the Sirona-turbine. During dry running most of them already reached the allowed marginal value of noise nuisance for the ear of 85 dB (A) at a distance of 35 cm. Only the Air-Orbit-machine showed a slightly lower value of 80 dB (A). The level increases with the used handpieces. Normal handpieces 1:1 exert only a minimal influence, gear handpieces 2:1, however, markedly increase the level. The verticity is of no importance in the range of normal rotations between 10,000 r/min. and 80,000 r/min. Only rotations in the lower frequency range of 2,000 r/min. markedly decrease the noise level. During bone drilling, the kind and size of the drilling bit have an influence on the intensity of the noise level. Quadruple wing milling cutters create a very high noise level (at a distance of 15 cm still above 110 dB [A!]), big rose cutters (R 16) create noise levels of 95 dB (A) and above, and only diamond round bits create less noise (approximately 88 db [A]). Small drilling bits make such a faint noise, that it is overroared by the drilling instrument. The turbines create only slightly higher levels than during dry running. Larger drilling bits cannot be employed here on principle. Wing milling cutters can lead to persistent damages of the inner ear. The frequent use of dental drilling instruments for bone preparations can also lead to a hearing loss of the operator in the long run.

Humans↗
PubMed2004

Occupational noise and effects on blood pressure: exploring the relationship of hypertension and noise exposure in workers.

Hearing loss is the second most self reported occupational illness or injury. According to the National Institute for Occupational Safety and Health, approximately 30 million workers are exposed to hazardous noise on the job. Often only hearing loss is thought of when one refers to occupational noise, but there may be other factors to consider when addressing occupational noise such as blood pressure. What is not clear, however, is whether noise contributes to changes in blood pressure. Occupational noise is a problem in various settings and comes with known and possible health consequences. To identify and prevent possible health related effects, workplace monitoring, audiometry, and blood pressure screenings are essential. When in work settings with elevated noise exposures, occupational and environmental health nurses should be focused on creating a program designed to prevent exposure to high levels of occupational noise.

Audiometry↗
PubMed1989

Noise levels and the sources of noise pollution in Karachi.

The menace of noise is a by-product of civilization and its hazards are well known. Noise levels were measured in Karachi, at different places and at different times of the night and day, using an Amplaid noise meter. The leg for Karachi came to 80 dB (A), the General Noise Index x (G.N.I.) to 460, and the noise pollution level (N.P.L.) to 99 dB (A). These values are significantly higher (P less than 0.01) than the available international data. The sources of noise production were indentified as, the road traffic, human activity, industrial and civil works, mechanical and engineering workshops. The most noticeable sources of noise pollution in Karachi, are the autorickshaws, trail motor bikes and the fag horns of public transport (JPMA 39-62, 1989).

Environmental Pollutants↗
PubMed1997

Noise exposures. Effects on hearing and prevention of noise induced hearing loss.

1. Over 30 million workers are exposed to hazardous noise on the worksite. Continual exposure to high noise levels damages and destroys hearing cells within the ear, making noise induced hearing loss an irreversible impairment. 2. Hearing conservation programs are required by law for workers in industrial settings where noise exposures equal or exceed 85 dB(A). Many workers, such as those in construction and agricultural industries, are not covered by these programs. 3. Reducing noise through engineering or administrative controls is the first line of defense. When this is not sufficient, two types of personal hearing protection devices are available: passive hearing protection devices such as ear muffs, canal caps, and ear plugs, which reduce noise mechanically; and active noise reduction devices, which electronically cancel sound waves at the ear. 4. The most effective hearing protection devices are those with which the worker is most comfortable will use 100% of the time. The occupational health nurse has a major role in promoting increased use of hearing protection devices through continued contact with workers, administrators, and safety personnel.

Ear Protective Devices↗
PubMed1987

Maximizing signal-to-noise and contrast-to-noise ratios in FLASH imaging.

This paper presents an analysis of signal-to-noise and contrast-to-noise ratios from small tip angle, gradient reversal (FLASH) imaging. Analytic and numerical techniques are used to determine the delay times and tip angles that maximize signal-to-noise per unit time from a single tissue. Similar procedures are used to determine the delay times and tip angles that maximize both T1-induced and T-2*-induced contrast-to-noise per unit time for a pair of tissues as a function of tissue characteristics and pulse sequence sampling times. The advantage of optimized FLASH imaging over optimized spin-echo imaging is quantitated by comparing signal-to-noise and contrast-to-noise ratios per unit time from the two sequences. Images are used to confirm these numerical results, to compare noise levels resulting from gradient reversals versus 180 degrees rephasing pulses and to assess the possible adverse effects of static magnetic field inhomogeneities on FLASH imaging.

Humans↗
PubMed2006

Mapping the MRI voxel volume in which thermal noise matches physiological noise--implications for fMRI.

This work addresses the choice of the imaging voxel volume in blood oxygen level dependent (BOLD) functional magnetic resonance imaging (fMRI). Noise of physiological origin that is present in the voxel time course is a prohibitive factor in the detection of small activation-induced BOLD signal changes. If the physiological noise contribution dominates over the temporal fluctuation contribution in the imaging voxel, further increases in the voxel signal-to-noise ratio (SNR) will have diminished corresponding increases in temporal signal-to-noise (TSNR), resulting in reduced corresponding increases in the ability to detect activation induced signal changes. On the other hand, if the thermal and system noise dominate (suggesting a relatively low SNR) further decreases in SNR can prohibit detection of activation-induced signal changes. Here we have proposed and called the "suggested" voxel volume for fMRI the volume where thermal plus system-related and physiological noise variances are equal. Based on this condition we have created maps of fMRI suggested voxel volume from our experimental data at 3T, since this value will spatially vary depending on the contribution of physiologic noise in each voxel. Based on our fast EPI segmentation technique we have found that for gray matter (GM), white matter (WM), and cerebral spinal fluid (CSF) brain compartments the mean suggested cubical voxel volume is: (1.8 mm)3, (2.1 mm)3 and (1.4 mm)3, respectively. Serendipitously, (1.8 mm)3 cubical voxel volume for GM approximately matches the cortical thickness, thus optimizing BOLD contrast by minimizing partial volume averaging. The introduced suggested fMRI voxel volume can be a useful parameter for choice of imaging volume for functional studies.

Artifacts↗
PubMed1997

The local noise property in positron volume imaging and optimal conditions for the signal-to-noise ratio of the 3D reconstructed image.

The local noise property of a 3D PET reconstructed image is investigated for a uniform-activity sphere distributed in a constantly attenuating spherical object. The positional dependence of the statistical noise is approximately derived and calculated for some special cases. It is suggested that a larger diameter of the activity sphere causes noise amplification, and the noise property for the large attenuating sphere is close to that for a non-attenuating object with the same total number of measuring counts. By considering noise propagation of two spherical activity distributions, we suggest that the signal-to-noise ratio of the image depends on a set of projection directions and the sizes and intensities of the activity distributions. In a simple case, we derive an optimal value of the maximum acceptance angle for the projection directions to improve the signal-to-noise ratio of the image.

Humans↗
PubMed2005

Salt-and-Pepper noise removal by median-type noise detectors and detail-preserving regularization.

This paper proposes a two-phase scheme for removing salt-and-pepper impulse noise. In the first phase, an adaptive median filter is used to identify pixels which are likely to be contaminated by noise (noise candidates). In the second phase, the image is restored using a specialized regularization method that applies only to those selected noise candidates. In terms of edge preservation and noise suppression, our restored images show a significant improvement compared to those restored by using just nonlinear filters or regularization methods only. Our scheme can remove salt-and-pepper-noise with a noise level as high as 90%.

Algorithms↗