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At least 127 records · Page 7Linked to original sources
PubMed1992

Is NIDDM a risk factor for noise-induced hearing loss in an occupationally noise exposed cohort?

Little is known about what factors, other than chronic exposure to noise, predispose individuals to noise-induced hearing loss (NIHL). The current retrospective study was designed to identify risk factors for NIHL in a population of 229 men [age 55-68 (mean = 63 years)] employed at a metal assembly plant. All men had been chronically occupationally noise-exposed for approximately 30 years (> or = 89 dBA) with an average Ea noise emission level) of 104.5. The clinical examination included a pure-tone threshold audiometric evaluation, discrimination of speech in background noise [W-22 Max (> 60% indicating better hearing)], blood pressure measurement, evaluation of lifestyle (alcohol consumption, cigarette smoking, noisy hobbies) and occupational and military history. Severe NIHL was defined as > or = 65 db loss at 3, 4 or 6 kHz in at least one ear +/- 20 db threshold in the contralateral ear. History of non-insulin dependent diabetes mellitus (NIDDM) was reported by 16.4% of the 146 men with severe NIHL compared to 4.8% of the 83 men without severe NIHL (odds ratio = 3.9, C.I. 1.2-11.9, P = 0.05). Simultaneous evaluation of several potential risk factors using a multiple logistic regression indicates that the significant predictors of severe NIHL were diabetes (P < 0.05), Ea (P < 0.05) and age (P < 0.05). These results suggest that a person with NIDDM who is also occupationally noise-exposed is more likely to develop severe NIHL than those without NIDDM. Longitudinal studies are necessary to confirm the temporal relationship between NIDDM and NIHL and to determine the exact mechanisms that are involved with this increased risk of hearing loss.

Age Factors↗
PubMed2004

Effect of an initial noise induced hearing loss on subsequent noise induced hearing loss.

The effect of previous noise induced hearing loss (NIHL) on subsequent NIHL was studied in rats. Three groups of animals were initially exposed to different durations of 113 dB SPL broad band noise (21 days, 3 days or 0 days--unexposed). Their permanent threshold shifts (PTS) from this exposure (PTS1) were evaluated using auditory nerve-brainstem evoked responses (ABR). All the animals were then noise-exposed for an additional 12 days, and the incremental PTS following this exposure (PTS2) was also assessed. The 21 day group showed the greater PTS1 [mean +/- SD: 27.03 +/- 6.78 dB, compared with 11.67 +/- 10.47 dB (3 day group)] and the lowest PTS2 [9.84 +/- 8.19 dB, compared with 13.33 +/- 14.60 dB (3 day group) and 24.04 +/- 12.4 dB (0 day group)]. This group also showed the highest total PTS and lowest SD following the two noise exposures [36.88 +/- 6.29 dB, compared with 25.00 +/- 12.68 dB (3 day group) and 26.35 +/- 11.93 dB (0 day group)]. The results may be explained by the lower effective intensity of the second noise exposure for the animals with a large PTS1 compared to those with little or no NIHL from the first noise exposure.

Animals↗
PubMed1992

Effects of noise on mental performance with regard to subjective noise sensitivity.

Objective and subjective effects of moderate levels of recorded traffic noise [Leq = 55 dB(A) and 75 dB(A)] on mental performance were studied in a laboratory setting. A total of 45 subjects (23 males and 22 females) were investigated with respect to subjective noise sensitivity (SNS). Four cognitive tasks were applied involving different psychological functions: Short-Term Memory (STM), Search and Memory 5 (SAM 5) (vigilance), Hidden Figures (HF) (spatial reasoning) and Mental Arithmetic (MA) (parallel processing). Three groups of 15 subjects were defined according to their scores on Weinstein's Noise Sensitivity Scale as tolerant, moderately sensitive or highly sensitive to noise. A similar level of performance was observed in the three groups under quiet conditions [30 dB(A) Leq], but under noisy conditions significant differences (P < 0.05) were seen between them on the STM (words) and MA (total results) tasks, and the lowest performance accuracy was demonstrated by the noise-sensitive subjects. SNS was the primary factor responsible for these differences. There were no significant differences between the groups in respect of the SAM 5 and HF tasks, under either quiet or noisy conditions. Annoyance while performing tasks under noisy conditions was regularly and significantly higher among subjects judged to be noise sensitive on Weinstein's scale, as compared with those judged to have low or moderate SNS.

Adolescent↗
PubMed1986

High-frequency-noise-induced hearing loss: a field study on the role of intensity level and accumulated noise dose.

Based on audiometric tests in the range of 10 to 20 kHz, of 106 ultrasound operators, as well as on measurements of high-frequency noise, the problem of safety limits for high-frequency noise exposure was investigated. Analyzing the relation between noise levels of 1/3 octave bands at center frequencies of 10, 12.5 and 16 kHz and the accumulated noise dose on the one hand, and changes of hearing at 10 to 12, 11 to 13 and 14 to 16 kHz respectively, on the other hand, a harmless level up to 80 dB and a harmless noise dose up to 1 unit for people not older than 40 years have been found. For older people this level and this noise dose can be dangerous.

Adult↗
PubMed1994

Detection of bandlimited noise masked by wideband noise in the chinchilla.

Six chinchillas were trained to detect a 1 s bandlimited noise signal in the presence of a continuous, wideband noise masker. As the bandwidth of the noise signal increased, there was a decrease in detection threshold. Threshold signal-to-noise ratios for the bandlimited noise signal were independent of the level of the noise masker. The slope of the bandwidth function obtained for the chinchilla is similar to the slopes reported for human subjects, approximating the predicted slope of the ideal energy detector.

Acoustic Stimulation↗
PubMed2000

Effects of background noise on audiometric thresholds during positron emission tomography: passive and active noise-reduction.

Position emission tomography (PET) is used to assess the functional activity of the human auditory brain; however, the activity detected by PET could be affected by ambient acoustic noise from the PET equipment. To evaluate these effects, we compared behavioural thresholds in the PET camera with those measured in an audiometric sound booth. Thresholds were measured with: (i) ER2 earphones, (ii) ER2 earphones + Cabot earmuffs, (iii) ER2 earphones + Bose Series II Aviation Headset with active noise-reduction off, and (iv) ER2 earphones + Bose Series II Aviation Headset with active noise-reduction on. Overall ambient noise level in the camera was 73 dB SPL and the maximum octave-band SPL was 68 dB SPL at 250 Hz. Threshold elevations in the PET camera were greatest with ER2 (17 dB, 125 Hz) earphones and lowest with ER2 earphones + Bose Series II Aviation Headset (8 dB at 250 Hz) with active noise-reduction. Thus, PET scanner noise had little or no effect on threshold when stimuli were presented through ER2 earphones covered with an activated Bose Series II Aviation Headset.

Adult↗
PubMedDate not supplied

The impact of broadband noise on serial memory: changes in band-pass frequency increase disruption.

Irrelevant sound consisting of bursts of broadband noise, in which centre frequency changes with each burst, markedly impaired short-term memory for order. In contrast, a sequence of irrelevant sound in which the same band-pass noise burst was repeated did not produce significant disruption. Serial recall for both visual-verbal (Experiment 1) and visual-spatial items (Experiment 2) was sensitive to the increased disruption produced by changing irrelevant noise. The results provide evidence that sounds that are largely aperiodic can produce marked disruption of serial recall in a similar manner to periodic sounds (e.g., speech, musical streams, and tones), and thus show a changing-state effect.

Female↗
PubMed2005

The effect of audibility, signal-to-noise ratio, and temporal speech cues on the benefit from fast-acting compression in modulated noise.

The objective of the experiment was to investigate three aspects that might contribute to the benefit of fast-acting compression seen in normal-hearing listeners. Six normal-hearing listeners were tested with speech recognition in a fully modulated noise (FUM) either through a fast-acting compressor or through linear amplification. In the first experiment, three different presentation levels of the FUM noise (15, 30, and 45 dB SL) were tested. The second experiment manipulated the control signal of the compressor independently of the audio input signal at four signal-to-noise ratios (-15, 10, -5, and 0 dB). A signal correlated noise version of the speech signal was tested in the third experiment at three speech-to-noise ratios (-20, -15 and -10 dB). Results showed that performance was better with compression than with linear amplification through all of the tested conditions at least when the signal-to-noise ratio was negative. The results suggest that other aspects of the hearing impairment than those simulated here are involved in the degraded performance seen for some hearing-impaired listeners with fast-acting compression.

Acoustic Stimulation↗
PubMed1992

Effects of noise and noise suppression on speech perception by cochlear implant users.

The recognition of phonemes in consonant-vowel-consonant words, presented in speech-shaped random noise, was measured as a function of signal to noise ratio (S/N) in 10 normally hearing adults and 10 successful adult users of the Nucleus cochlear implant. Optimal scores (measured at a S/N of +25 dB) were 98% for the average normal subject and 42% for the average implantee. Phoneme recognition threshold was defined as the S/N at which the phoneme recognition score fell to 50% of its optimal value. This threshold was -2 dB for the average normal subject and +9 dB for the average implantee. Application of a digital noise suppression algorithm (INTEL) to the mixed speech plus noise signal had no effect on the optimal phoneme recognition score of either group or on the phoneme recognition threshold of the normal group. It did, however, improve the phoneme recognition threshold of the implant group by an average of 4 to 5 dB. These findings illustrate the noise susceptibility of Nucleus cochlear implant users and suggest that single-channel digital noise reduction techniques may offer some relief from this problem.

Adult↗
PubMed2003

1/f noise outperforms white noise in sensitizing baroreflex function in the human brain.

We show that externally added 1/f noise more effectively sensitizes the baroreflex centers in the human brain than white noise. We examined the compensatory heart rate response to a weak periodic signal introduced via venous blood pressure receptors while adding 1/f or white noise with the same variance to the brain stem through bilateral cutaneous stimulation of the vestibular afferents. In both cases, this noisy galvanic vestibular stimulation optimized covariance between the weak input signals and the heart rate responses. However, the optimal level with 1/f noise was significantly lower than with white noise, suggesting a functional benefit of 1/f noise for neuronal information transfer in the brain.

Baroreflex↗
PubMed1996

Sound localization in noise: the effect of signal-to-noise ratio.

The sound localization ability of human observers has been frequently examined in quiet environments, but there have been relatively few studies that have considered the effect of noise on sound localization. In this study, three subjects judged the perceived direction of broadband click-train signal in the quiet and in the presence of a broadband noise at nine signal-to-noise ratios, which varied over a 23 dB range. The signal could originate from any of 239 spatial locations that completely surrounded the subjects in azimuth 360 degrees) and ranged from -45 degrees to (+)90 degrees in elevation; the masker (when present) was always located directly in front of the subjects at 0 degrees azimuth and 0 degree elevation. The subjects indicated the perceived direction of the signal by pointing at a 20-cm-diam spherical model of auditory space. As the signal-to-noise ratio was lowered, the accuracy of localization judgments decreased nearly monotonically. However, the accuracy of judgments relative to the median plane (i.e., the left/right dimension) was less strongly influenced by the presence of noise than was the accuracy of judgments relative to the horizontal plane (i.e., the up/down dimension). The accuracy of judgments relative to the frontal plane (i.e., the front/back dimension) was most strongly influenced by noise.

Adult↗
PubMed2004

Challenges and recent developments in hearing aids. Part I. Speech understanding in noise, microphone technologies and noise reduction algorithms.

This review discusses the challenges in hearing aid design and fitting and the recent developments in advanced signal processing technologies to meet these challenges. The first part of the review discusses the basic concepts and the building blocks of digital signal processing algorithms, namely, the signal detection and analysis unit, the decision rules, and the time constants involved in the execution of the decision. In addition, mechanisms and the differences in the implementation of various strategies used to reduce the negative effects of noise are discussed. These technologies include the microphone technologies that take advantage of the spatial differences between speech and noise and the noise reduction algorithms that take advantage of the spectral difference and temporal separation between speech and noise. The specific technologies discussed in this paper include first-order directional microphones, adaptive directional microphones, second-order directional microphones, microphone matching algorithms, array microphones, multichannel adaptive noise reduction algorithms, and synchrony detection noise reduction algorithms. Verification data for these technologies, if available, are also summarized.

Algorithms↗
PubMed1994

Speech recognition in noise before and after a work-day's noise exposure.

A common complaint after a work-shift in high noise levels is fatigue, in the sense that listening to other people's spoken messages requires more effort than when well rested. The purpose of this study was to examine if this could be verified as reduced speech recognition in noise due to auditory fatigue. Speech recognition in noise, using low-redundancy sentence material, as well as pure-tone hearing thresholds were tested on 13 subjects at the beginning and end of a 7-8 hours work-shift with equivalent noise levels in the range 78-90 dBA as measured by personal noise dose meters. Seven of the test subjects wore hearing protectors during work while six did not. No significant shift in mean values from the beginning of the work-shift to its end could be found, neither in speech recognition in noise nor in hearing thresholds for pure tones and neither for those wearing hearing protectors nor for those without.

Adult↗
PubMed1998

[The effect of occupational exposure to noise among tractor drivers: assessment based on 'noise threshold'].

The effects of occupational exposure to noise was analysed among operators of agricultural tractors (n = 172). The assessment was based on a parameter called 'noise immission level' (dose connected with the period of employment). The study showed that the correlation between hearing loss and noise immission dose was stronger than that between hearing loss and the period of employment. Equations of simple regression presented in this paper allow us to make a prognosis concerning the risk of occupational deafness and to develop the system of the prevention interventions. The results obtained indicated that the parameter of hygiene evaluation of exposure to noise, called 'noise immission level' should be used more frequently for the noise measurement, especially in the prevention of occupational diseases.

Adult↗
PubMed2000

Noise attenuation of hearing protectors against heavy weapon noise.

This study evaluated the noise attenuation of earplugs and earmuffs or their combined use against heavy weapon noise in field conditions for military personnel. The noise attenuation was measured with a miniature microphone inserted into the ear canal. The subjects (13) were tested against pink noise and against the noise of explosions and bazooka, mortar, cannon, and howitzer. The attenuation (insertion loss) was 16 to 23 dB for earplugs, 10 to 20 dB for earmuffs, and 24 to 34 dB for the combined use of plugs and muffs. The transfer function of an open ear was 5 to 7 dB when measured as the C-weighted peak level. The combined use of earplugs and earmuffs gave smaller attenuation values than expected. If the limit for the C-weighted peak level is 140 dB for unprotected ears, then protection against low-frequency noise is provided for up to 156 dB by earplugs, up to 150 dB by earmuffs, and up to 165 dB by the combined use of plugs and muffs.

Ear Protective Devices↗
PubMed1975

[The difference between the noise deafness of the pitmans and the typical noise-induced hearing loss of the worker in metals (author's transl)].

Reffering to 92 expert evidences on the noise-deafness the signs are shown, in which the mining noise-deafness differs from the typical noise deafness in the metallurgical industry. In more than 80% of the cases a slope of the curve could be observed in the audiogram beginning at 125 cps. Therefore the hearing loss early impairs the ability to understand conversational speech. Only every second patient shows a positive result at the SISI-test; this is the reason, that the mining noise deafness frequently is misinterpreted. In these cases the cochlear hearing loss will be surely proved by the Langenbeck-audiogram and Békésy-audiogram. A secondary finding was the typical "mining ear-drum". These ear drums are bilaterally whitish, without reflex and thickened; they don't show any air-bone gap in the audiogram. The differences between the mining noise-deafness and the typical noise-induced hearing loss are explained by an additional baro-trauma which occurs, when the pitmans work at a depth of about 2000 feet.

Audiometry↗
PubMed2006

Different forward masking patterns of sustained noise burst and segmental noise burst in the inferior collicular neurons of the mouse.

Although there has been a growing body of literature showing the neural correlation of forward masking caused by a pure tone masker in the auditory neurons, relative few studies have addressed the description of how the forward masking caused by a noise burst, especially a sequence of noise burst, is transformed into neuronal representation in the central auditory system. Using a noise forward masking paradigm under free field stimuli conditions, this in vivo study was devoted to exploring it in the inferior collicular (IC) neurons of the mouse (Mus musculus KM). A total of 96 IC neurons were recorded. Rate-intensity functions (RIFs) with and without the presentation of masker, sustained noise burst (SNB) or segmental noise burst (SGNB), were measured in 51 neurons. We found that the relative masker intensities were distributed over a wide range between 21 dB below the minimum threshold (MT) and 19 dB above the MT of the corresponding probe tone. The masking effect of the SGNB on firing rate in nearly half of neurons (type I, 45.10%) was stronger than that of the SNB (P<0.001), whereas in a smaller fraction of neurons (type III, 17.65%), it was weaker than that of the SNB (P<0.001). There was no significant difference in masking effect between the SNB and SGNB in type II neurons (37.25%, P>0.05). Irrespective of type I or type III neurons, the inhibitory effects of both kinds of maskers were all greater at lower probe intensities but decreased significantly with the increase of probe intensity (P<0.001). Interestingly, as the probe intensity increased, the difference of masking effect between the SNB and SGNB disappeared (P>0.05). In addition, we observed that temporal masking pattern could be transformed when the masker was changed from the SNB to SGNB. The main type of this transformation was from early-inhibition to proportional-inhibition pattern (53.85%, 7/13). Our data provide the evidence that the inhibitory effects of these two maskers have differential weights over time and intensity domains of the IC neurons responding to a pure tone. This suggests that the forward masking of noise is by no means the source of simply suppression in neuronal firing rate. There might be a few of active neural modulating ways in which the coding of temporal acoustical information can be operated.

Acoustic Stimulation↗
PubMed1983

Evaluation of noise susceptibility: effects of noise exposure on acoustic reflex.

The threshold of acoustic reflex (AR) was measured in workers exposed to occupational noise. White noise (WN), and pure tones of 1 and 4 kHz were selected as activating stimuli for AR. The results were compared with the thresholds of AR (ART) in the normal group (Group C) reported by the authors previously. To examine in relation between noise exposure and ART, the exposed group was classified into two groups by their hearing levels (HL) at 4 and 8 kHz; i.e. Group D (HL(4k + 8k)/2 less than 25 dB) and Group E (HL(4k + 8k)/2 greater than or equal to 25 dB). A significant (P less than 0.001) elevation of ARTWN was observed not only in Group E (8.8 dB) but also in D (7.5 dB) with normal hearing acuity. A significant (P less than 0.001) lowering of ART1k was observed in Group E only. The difference between ART1k and ARTWN, [ART1k-ARTWN], was reduced significantly (P less than 0.001) in the exposed groups; i.e. 12.4 dB in Group C, 3.7 dB in Group D and 0.6 dB in Group E. These results suggested that the value of [ART1k-ARTWN] may be used as a sensitive and objective indicator for detecting and evaluating the early stages of noise-induced hearing impairment and individual susceptibility to noise.

Adolescent↗