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Background: The paper involves exposure to noise of the State Police officers connected with the use of firearms. The noise generated by these weapons is of short duration and high intensity., Methods: The research was carried out during the sessions of firearm training of State Police officers to assess exposure to noise., Results: The values of the various investigations, both audiometric and phonometric, carried out made it possible to demonstrate a significant exposure and a temporary increase in the threshold, above the frequency of 6000 Hz., Conclusion: Even taking account of the abatement from use of headphones, an exposure was demonstrated that was above the statutory limits, as was confirmed by the temporary hearing threshold shift.

This work describes the audiometry threshold assessment of 1000 workers employed in different artisan categories during a period of ten-year noise professional exposure. The hearing loss noise-induced rates were determined by analysing audiometric tests at the beginning of our period of study and after 5 and 10 years of noise exposure. Environmental noise exposures were on average 88 dB(A), but near 90 dB(A) in some work categories. Workers widely used hearing protection devices, nearly at 93%, during the period we studied. The Evidence Based Occupational Medicine should find out points of reference proving the efficiency and effectiveness of occupational physicians: in this case, a positive trend in the reduction of hearing loss rate will be expected to confirm the goodness of prevention practice. Our study suggests that the levels of protection so far accepted are not effective enough in order to reduce the incidence of noise-induced hearing loss in the course of the years: in despite of most accredited predicting models for hearing conservation programs, a significant percentage of workers exposed to industrial noise continues to present a high incidence of hearing loss. The Evidence Based Occupational Medicine suggests that the proposed prevention activities carried out in the described factories were not enough effective.

Background: The term auditory disability (AD) means the presence of auditory symptoms due to hearing loss. Until now the audiometric threshold cut-off between the presence or absence of AD was not clear., Objectives: In this study we attempted to define the value of audiometric threshold that could be considered as the limit between the presence or absence of weakness of auditory function, considered as the threshold as the 95th percentile of subjects that did not report AD., Methods: The study group consisted of 1641 males, 891 normally hearing and 750 affected by noise-induced hearing loss (NIHL) Each subject was submitted to a questionnaire specifically created in order to determine the presence of AD., Results: Statistical analysis confirmed the reliability of answers to items. AD was present in 577 subjects, not all affected by NIHL. Audiometric threshold and age correlated significatively with the degree of AD., Conclusions: The results obtained allowed the audiometric threshold values to be determined at the 95th percentile of subjects who did not report AD, in relation to the average of frequencies normally used in hearing loss evaluation.

The aim of the study was to assess the state of hearing levels in young Italian subjects via an epidemiological study, and also, by means of a questionnaire, to assess the attitude of young people to music, how they listen to music and how they perceive the risk of noise-induced hearing damage. The sample studied consisted of 391 youths undergoing their first medical examination for military service. The hearing threshold was assessed by means of a semiclinical tonal audiometry with sound-proof earphones calibrated to ISO Standard 389 following the method of ISO Standard 6189. At the end of the study 315 youths were judged eligible for the study, 81% of whom lived in the city of Milan. 63% said they went to a discotheque 1-4 times a week and 3% said they listened to music with earphones at maximum volume. These conditions are considered to be potentially dangerous for hearing since among youths leaving discotheques disorders have been observed that are indicative of hearing fatigue: lowering of the hearing level 7%, buzzing in the ears 37%, sense of muffled sound 12%. In the group studied, environmental noise was a factor of disturbance for sleep (13%), for study and reading (43%), listening to the radio, to music and watching TV (29%). Only 7 youths said their hearing was "not normal", but the thresholds were all higher than audiometric zero, which are clearly worse than the values observed in similar studies reported in the literature. This study reports the mean values, SD, minimum and maximum and centile values of the distribution of hearing thresholds, separately for right and left ears. A comparison was made between the hearing in the group least exposed: a significant difference was observed only for the right ear while for the left ear there was only a tendency. The authors conclude that hearing in young people to-day is worse than in the past, whatever be the causes, and that due account should be taken of this state of affairs, by encouraging prevention programmes for noise-induce hearing loss at all levels and on every possible occasion.

Until now the relationship between auditory threshold and age has been evaluated in normal subjects only. In this study the Author reports results obtained in a cross-sectional study on 416 subjects suffering from noise-induced hearing loss who were exposed to noise for 10 years at least. The results show that hearing loss over time was more correlated to age than to noise exposure. Moreover, the evolution of hearing loss over time had a linear shape while in noise-induced hearing loss evolution has a logarithmic shape and in presbyacusis it has an exponential shape. The differential threshold between 30 and 60 years obtained by applying the linear regression model was, at higher frequencies, significantly reduced compared to normal subjects. These results suggest that threshold values related to age obtained in normal subjects can not be applied in subjects affected by noise-induced hearing loss.

At the end of stapedioplasty, performed under local anesthesia, the surgeon usually tests the hearing function making questions to the patient turning his voice from a soft whisper to a loud tone. At the ENT Department, University of Parma Italy, a more precise method is employed in order to measure the air conduction threshold of the patient at the beginning and at the end of surgery. From April 1996 to October 1996, intraoperative pure-tone audiometry was performed in 36 patients who underwent stapedioplasty. A portable audiometer "Amplaid 161/C Amplifon" was used in the operating room. Air conduction thresholds were measured at 125-8000 Hz. Intraoperative pure-tone audiometry allows an instantaneous and a more accurate evaluation of the surgical functional results.

The purpose of the present work was to assess distortion-product otoacoustic emissions (DPOAE) in cochlear hearing loss and in its various morphologies. A total of 19 patients (30 ears) were selected for the study. They showed various pictures of neurosensorial hearing loss which were localized within the frequency range normally examined during audiometric tonal threshold testing. The DPOAEs were recorded using a Bray and Kemp ILO 92 instrument. The DPOAEs of several frequencies (750,1000,1500,2000,3000,4000 and 6000 Hz) were examined using an f2 tone of 696, 1001, 1587, 2002, 3147, 4004 and 6348 Hz, respectively. The results were as follows: a) At certain frequencies the overlap between hearing loss and the absence of, or reduction in, DPOAE amplitude was virtually total. b) There was a modest correlation between the degree of hearing loss and decrease in, or absence of, DPOAEs although there was a spectrum of intermediate hearing losses where the DPOAEs varied widely from one individual to another (this spectrum ranged from 10 to 45 dB HL on the audiometric tonal test). c) The absence of DPOAEs at 750 Hz is unable to predict hearing loss for this frequency as, at this frequency, there can be a lack of DPOAEs even when the 750 Hz audiometric threshold level is normal. Finally, what emerged from this study was that DPOAEs prove quite useful to complement the study of auditory brainstem responses (ABR), now universally accepted as the means for early diagnosis of hearing loss in children. In fact, ABRs provide precise data regarding a frequency field which is socially less important in terms of verbal communication and the development of spoken language. It is, however, unable to explore individual frequencies.

The authors report on the possible advantages acetazolamide, in conjunction with Positional Impedenzometry, can provide in the detection of minor labyrinthine hydrops and major labyrinthine fluid tension disorders. This study was carried out using the case/control method. The subjects were selected on the basis of symptoms and clinical examination revealing signs of endolymphatic hydrops. Tonal audiometry and positional impedenzometry according to Marullo were performed both before (pre-test) and after i.v. administration of 500 mg sodium acetazolamide (post-ACZ1 and post-ACZ2). Audiometry showed that in 77.2% of the cases there was a significant variation in threshold. In positional impedenzometry the average post-ACZ1 (delta PISC went from 22.06% (pre-test) to 13.16% and the post-ACZ2 (delta PISC went to 23.15%). On the other hand no significant changes were seen in the controls. Some hypotheses are offered on the mechanisms giving rise to these effects and particular attention is focused on the effect acetazolamide has on the carbon dioxide in the endolymphatic sac. In conclusion the authors consider the advantages this method offers over the "classical" tests used in diagnosing Ménière's Disease and minor hydrops.

The Authors investigated 200 patients, selected at random from an operative case-report of 1857 subjects, in order to evaluate hearing results of stapes surgery and to compare the recovery obtained using both small (0.7 mm footplate hole) and large fenestra stapedectomy. More precisely, after 1 week and 6 months, they examined audiological findings (air, bone conduction and cochlear reserve) before performing the operation in order to evaluate the following problems: persisting conductive gap at low frequencies, sensorineural hearing loss at high frequencies, prognosis in advanced stages (compromised pre-operative bone conduction), preservation of hearing over time. Firstly, data from our research indicate extremely successful results in stapes surgery; in particular, hearing improvement seems to be more frequent for middle-low tones (in 98% of patients), due to the higher rate of sensorineural deficit at high frequencies, which are however characterized by a more complete closure of the conductive gap. However with stapedotomy better hearing recovery is obtained and in a greater number of patients with a lower evidence of bone conduction impairment. Such an advantage increases even further from the time of surgery (p significant after 6 months on every frequency) and particularly in cases where disease is advanced.

Vestibular and auditory functions after glycerol intake were assessed correlated in twenty-eight patients diagnosed as menieric according to AAOO criteria. All patients had unilateral Ménière's disease confirmed by monolateral hypoacusia and labyrinthine hypofunction. Hearing thresholds were tested by tone-audiometry, according to the standard glycerol test. Variation in vestibular response were assessed comparing the VOR during the rotatory sinusoidal test as well as the caloric test, before glycerol intake and 2 hours after drug administration. Slow phase angolar velocity, directional preponderance percentile and percentile variation between basic and control observation were calculated. The audiometric glycerol test was positive in 58% of the cases. The vestibular glycerol test was positive in 30% of the cases and no correlation between and individual results hearing threshold result was found. The findings reported by other Authors regarding auditory and vestibular responses to glycerol intake were verified. Possible reasons which may account for variation with regard to reaction patterns in the acoustic and non acoustic labyrinth after glycerin administration are discussed. In the Authors' view, incoherence between vestibular and cochlear response might be linked to differences in the physiology of the fluid in the two labyrinths. In the vestibular district, glycerol might induce an early depletive effect and a later paradoxal effects due to mechanical modification of the ampulla function.

The value of "normal hearing" intended as the "base value of reference" to be used also for preventive as well as medical-legal purposes, is still subject of study and discussion. The Authors present the results relative to the definition of the hearing threshold in a vast "scrupulously screened" group of subjects between the ages of 15 and 65 (divided into 10 year bands), resident in industrial city areas and made up a homogeneous group of industrial workers with the same socioenvironmental characteristics. Distribution is calculated in hundreds of values relative to the average bilateral threshold for frequencies between 500 and 4000 Hz considering the 90th percentile the reference value.

Distortion Product Otoacoustic Emissions (DPOAEs) are elicited by simultaneous application of two tones to the ear canal. These emissions are a result of nonlinear mechanical characteristics of the cochlea at a specific point and have a precise mathematical relation with the frequencies of the two eliciting primary tones f1 and f2. This frequency-selective property of DPOAEs suggests that they should be regarded as useful monitor of localized cochlear function at any predetermined frequency. The present study was designed to investigate DPOAEs in patients with Menière's disease. DPOAEs were recorded before and after glycerol administration to verify if the fluctuation of the hearing threshold induced by this hyperosmotic agent causes selective changes in the activity of the outer hair cells. DPOAEs were present in patients in which the mean duration of the disease was shorter compared to those patients without measurable DPOAEs. An improvement of DPOAEs after glycerol intatte was observed in a half of our cases. The improvement of DPOAEs does not appear to be brought about by modifications of the auditory threshold induced by glycerol.

The paper analyzes the 8 KHz threshold in subjects with noise-induced hearing loss. The study group consisted of 315 subjects occupationally exposed to noise and suffering from acoustic trauma, which was considered as a mean threshold of more than 25 dB at 2, 3 and 4 KHz. The mean shape of audiograms was characterized by a neurosensory deficit which was more elevated at 4 and 6 KHz whereas the threshold at 8 KHz was better. However, this pattern was found in 60% of the cases whereas in the remaining 40% the threshold at 8 KHz was worse. Subjects with the most impaired audiometric threshold at 8 KHz were mainly older, although cases were found in a low percentage of younger subjects. The results demonstrate that in individual cases it is impossible, on the basis of the shape of the audiogram, to establish whether a hearing loss is due to noise or age.

The aim of this study was to determine the relationship existing between auditory disability, according to WHO 1980, and pure tone audiometry threshold in noise induced hearing loss. Disability was evaluated on the basis of a questionnaire submitted to 286 subjects with acoustic trauma. Answers obtained were considered reliable on the basis of statistical analysis. Results showed that subjects with disability have an higher pure tone threshold than subjects without auditory disability. However it appears difficult to determine a precise threshold level ever which auditory disability may be considered present. The Authors suggest that this limit could be determined on the basis of pure tone threshold at the 10th centile of the group of subjects with disability or at the 90th centile of subjects without disability.

The Authors evaluated patterns of click-evoked otoacoustic emissions (EOE) in a group of 184 patients exposed to noise in their working environment. The aim of the study was to detect changes in EOE patterns in this group compared to the EOE of healthy subjects. The clinical history of each subject was recorded and otoscopy, pure tone audiogram and impedance tests (tympanometry, stapedial reflex threshold) were carried out in all patients. Noise-induced hearing loss found in 97 patients, unilateral sensorineural hearing loss in 17, other hearing disorders in 24 and normal auditory threshold in 46. EOE recording was carried out in the group of patients with noise-induced hearing loss (97), in the group with normal threshold (46) and in a control group of 15 healthy subjects. EOE recording was obtained using the ILO 88 Otodynamic Analyzer. We introduce a probe into the external ear canal using a non-linear click stimulus (intensity at approximately 85 dB spl) at a 20/sec. rate with a 20 msec. window. Normal EOE were found in the control group. Abnormal EOE were found in 79 cases (81%) of the noise-induced hearing loss group, and in 22 (48%) of the normal threshold group. These data show that noise-exposed subjects have alterations of EOE such as threshold shift missing frequency bands, even in absence of an auditory threshold shift. When EOE were present, the frequency spectrum often showed lack of emissions at high frequencies. This study confirms that cochlear exposure to noise may produce significant alterations of EOE and that this test may be considered highly sensitive in detecting early cochlear damage in chronic acoustic trauma. Therefore, EOE may be used in screening and follow-up of high risk populations such as noise-exposed subjects.

The Speech Reception Threshold (SRT) was adaptively measured using sentences in two groups of subjects: young, normal-hearing subjects and elderly hearing-impaired subjects with high frequency loss. SRT was recorded in quiet and in noisy conditions with competition consisting in "speech noise" and continuous discourse delivered at intensities between 11.4 and 98.6 dBA SPL. A significant difference was found between the groups in that elderly subjects had higher SRTs in noise than the young counterparts expressed as signal to noise (s/n) ratio. Moreover, at noise intensities typical of everyday life, the SRTs of the elderly is 6 and 11.4 dBs/n higher than normal-hearing subjects, with speech noise and discourse respectively as competition. Communicative strategies that enhance s/n ratio should be considered in order to overcome the heavy effects of hearing loss in the elderly.

Interaction between continuous and impulse noise was studied. One group of chinchillas was exposed to octave band of noise of 0.5 kHz 95 dB SPL intensity. Three groups were exposed to impulse noises of 113, 119 and 125 prak SPL emitted at 1 imp/sec, 1 imp/4 sec and 1 imp/16 sec respectively. Three groups were exposed to noise created by a combination of above continuous and impulse noises. All exposures lasted for 5 days. Hearing thresholds were measured in 35 animals using auditory evoked potentials. The combined continuous and impulse noises showed equal energy contents, but the groups exposed to 119 and 125 dB impulse noise intensities developed an exacerbation of PTS and cell hair loss. Therefore, the critical level, under which the damage associated with noise exposure is related to the total noise energy (Equal Energy Hypothesis) was reduced when impulse noise was added to continuous noise.

In order to give a contribution to the genesis of the EOAEs, we have recorded echos in 24 subjects with unilateral sudden deafness (I. group); 20 ears with Menière disease (II. group); 22 ears with progressive sensorineural hearing loss (III. group) and 10 normally hearing young subjects as control group. The results have shown that the EOAEs were present in 100% (I. group), 84.6% (II. group) and 86.3% (III. group) in response to the tone-burst; while the echos were present only in the 57.1% (I. group), 38.4% (II. group) and 45.4% (III. group) in response to the click, although the audiometric threshold mean were greater than 45 dB HL for 2-4 KHz and 1 KHz in the three experimental groups except for 2-4 KHz in the subjects with Menière disease (37.5 dB HL). The properties of EOAEs (detection and saturation threshold, dynamic range and duration) depended on the degree of hearing loss. Our results seem to corroborate the hypothesis that EOAEs could be also produced by a passive intracochlear mechanism attributable to the travelling wave of the basilar membrane provoked by the perilymph. In the normal ear this passive mechanism could be superimposed by an active mechanism, linked to the contractile activity of the outer hair cells with a consequent increase in amplitude of the EOAEs for the same stimulus intensity.

Ten normal hearing subjects were subjected to repeated measurement of the stapedial reflex threshold (RT) and loudness discomfort threshold (DT) during five separate sessions. On the average DT was 4.8 dB higher than the RT. The sessions did not affect the intra-individual variance of either threshold. A regression analysis demonstrated that a significant linear relationship exists between RT and DT. However, DT may be lower than RT when the latter is shifted towards its upper variance boundary. Hence, RT and DT are not equivalent as indicators of the upper limit of loudness tolerance; since DT revealed a low intra-subject variance, such a psychoacoustic measurement may be reliably used for clinical purposes.

The Evoked Otoacoustic Emissions (EOE) are a sinusoidal wave complex coming from the contractile properties of the cochlea and particularly of the outer hair cells. This activity is influenced by the centrifugal pathways whose transmitter is acetylcholine. In order to study the effects of the functional block of the cochlea, ten young normal subjects were examined recording the EOE before and ten mins after the i.v. infusion of 1 mg of atropine. The statistical analysis of the results has shown a significant decrease only in EOE appearance threshold in absence of modifications of the saturation level. These data have led us to believe that atropine blocking of the centrifugal pathways causes a disfunction of the outer hair cells that accept less energy to be transduced into a neural stimulus and on the other hand more energy as EOEs.

In order to study the suprathreshold hearing phenomena for a differential diagnosis of sensorineural hearing losses Békésy Audiometry has been used at two different levels: a) Békésy threshold level; b) Békésy comfortable level. Are considered: the tracing's amplitude; the continuous decay; the gap between the two different threshold levels. Results has demonstrated that Békésy comfortable level give substantial contribution as decay test and as indirect recruitment test.

The main purpose of the study of evoked potentials has always been to objectively evaluate hearing thresholds in uncooperative subjects and it has become increasingly important in recent years with the introduction of auditory brainstem responses (ABR). Reading the ABR is relatively simple in terms of "audiometry" since it is based on the absence, or presence, of a marker peak wave V. Besides the strictly audiometric uses, study of the bioelectric brainstem complex even makes it possible to obtain important information regarding retrocochlear dysfunction. However, reading the response is not so simple for the otoneurologist since it is not based only on the observation of the absence or presence in order to compare the normal values obtained in homogeneous groups. For the above reason auditory brainstem response testing was performed on 692 subjects in order to define the normal values as well as any characteristic patterns for various audiological pathologies. For all subjects auditory brainstem responses were recorded mono-aurally with clicks of alternating polarity, 11 and 31 pps, at an intensity of 120 dB SPLpe. Use was made of ipsilateral stimulus derivations. Only for the right ear was absolute wave V latency measured at 100 and at 80 dB SPLpe. The amplifier of the bioelectric signal was set at a sensitivity of 20 microvolts with passing filters of 100 and 2000 Hz. Absolute latency, conduction time, symmetry indexes (IT I-V and ITV) and the shift in latency at the two stimulation cadences were statistically processed for homogeneous groups. Thus standards for normality were obtained. The results have shown that the following biological variables are to be taken into consideration: sex, age for males and type of deafness. The indexes most reliable in identifying a retrocochlear dysfunction proved to be: morphological completeness, central I-V conduction times and the two symmetry indexes IT I-V and ITV which are considered complementary. Again in terms of identifying a retrocochlear dysfunction, and in case of an incomplete response, the test can be interpreted thanks to the so-called minor responses which only take into account the absolute wave V latency. However, wave V latency behaviour is rather similar to what has been found in conductive hearing-loss. Finally, in cochlear deafness it was found that response did not vary with a variation in degree of deafness since the results produced were similar to those of normal hearing subjects except in those cases where there was a delay in the appearance of wave I.