Mesophilic, thermophilic and hyperthermophilic acidogenic fermentation of food waste in batch: Effect of inoculum source.

Distinctions in hydrolysis and acidogenesis were examined for a series of anaerobic batch reactors inoculated with three different anaerobic mixed cultures (mesophilic, thermophilic and hyperthermophilic anaerobic sludge) and operated at the temperature of inoculum's origin and additionally at 70 °C. Hyperthermophilic temperatures led to increased hydrolysis rates during the start-up stage but a rapid drop in pH limited the overall hydrolysis efficiency, indicating the importance of pH control to sustain the high reaction rates at higher temperatures. No significant difference (P > 0.05) was observed among hydrolysis efficiencies obtained for different reactors which ranged between 27 ±â€¯3% and 40 ±â€¯14%. The highest fermentation yield of 0.44 g COD of fermentation products/g VSS-CODadded was obtained under thermophilic conditions, followed by mesophilic (0.33 g COD ferm. prod./g VSS-CODadded) and hyperthermophilic conditions (0.05-0.08 g COD ferm. prod./g VSS-CODadded). Fermentative performance was better at mesophilic and thermophilic conditions as indicated by improved production of volatile fatty acids (VFA). VFAs accounted for 60-71% of the solubilised matter at thermophilic and mesophilic conditions. Acetic acid formed the primary VFA (70%) at mesophilic temperatures, while butyric acid was the major VFA at thermophilic (60%) conditions. Hyperthermophilic conditions led to increased production of lactic acid, which comprised up to 32% of the solubilised matter. Overall, the results indicate that different operating temperatures may not significantly affect the substrate degradation efficiency but clearly influence the biotransformation pathways.

Arabidopsis species deploy distinct strategies to cope with drought stress.

BACKGROUND AND AIMS: Water limitation is an important determinant of the distribution, abundance and diversity of plant species. Yet, little is known about how the response to limiting water supply changes among closely related plant species with distinct ecological preferences. Comparison of the model annual species Arabidopsis thaliana with its close perennial relatives A. lyrata and A. halleri, can help disentangle the molecular and physiological changes contributing to tolerance and avoidance mechanisms, because these species must maintain tolerance and avoidance mechanisms to increase long-term survival, but they are exposed to different levels of water stress and competition in their natural habitat. METHODS: A dry-down experiment was conducted to mimic a period of missing precipitation. The covariation of a progressive decrease in soil water content (SWC) with various physiological and morphological plant traits across a set of representative genotypes in A. thaliana, A. lyrata and A. halleri was quantified. Transcriptome changes to soil dry-down were further monitored. KEY RESULTS: The analysis of trait covariation demonstrates that the three species differ in the strategies they deploy to respond to drought stress. Arabidopsis thaliana showed a drought avoidance reaction but failed to survive wilting. Arabidopsis lyrata efficiently combined avoidance and tolerance mechanisms. In contrast, A. halleri showed some degree of tolerance to wilting but it did not seem to protect itself from the stress imposed by drought. Transcriptome data collected just before plant wilting and after recovery corroborated the phenotypic analysis, with A. lyrata and A. halleri showing a stronger activation of recovery- and stress-related genes, respectively. CONCLUSIONS: The response of the three Arabidopsis species to soil dry-down reveals that they have evolved distinct strategies to face drought stress. These strategic differences are in agreement with the distinct ecological priorities of the stress-tolerant A. lyrata, the competitive A. halleri and the ruderal A. thaliana.

Glass ionomer cement in otological microsurgery: experience over 16 years.

A retrospective evaluation of glass ionomer cement (GIC) in middle ear surgery with emphasis on short- and long-term safety was conducted at the tertiary referral center. GIC was applied between 1995 and 2006 in 444 patients in otologic surgery. Technical aspects, safety, benefits and complications due to GIC were analysed until 2011 (follow-up 5-16 years; mean 10 years). GIC was applied in stapes surgery (228 primary, 92 revisions), cochlear implants (108) and implantable hearing aids (7), ossiculoplasty (7), for coverage of opened mastoid air cells towards the external ear canal (1) and inner ear fistula closure (1). GIC turned out to be very handy in stapes surgery for optimal prosthesis fixation at the incus (260) and on the malleus handle (60) without complications. Results suggest that GIC may diminish the danger of incus necrosis in primary stapedotomy. In cochlear implants and implantable hearing aids, GIC was used for casing alone (74), casing and electrode fixation (27) and electrode alone fixation (14). Inflammatory reactions were observed in five cases (4.3%), mostly after trauma. Broken cement fragments appeared to promote foreign body rejection. In seven cases an incudo-stapedial gap was repaired with GIC with excellent hearing gain; in three cases (43%) revision surgery was needed due to cement breakage. In one case, GIC was applied for a watertight coverage of opened mastoid cells, and in the other for fistula closure of the lateral semi-circular canal over cartilage, covered with bone pathé; follow-up was uneventful. Targeted use of GIC in middle ear surgery rarely poses problems. GIC cannot be used in neuro-otosurgery in contact with cerebrospinal fluid because of possible aluminium encephalopathy.

Evidence of neuroendocrine disruption in freshwater mussels exposed to municipal wastewaters.

The purpose of this study was to test the hypothesis that exposure to municipal effluents can disrupt the neuroendocrine system in Elliptio complanata freshwater mussels. The capacity of ozonation to mitigate these effects was also examined. Mussels were exposed for 14 days to a continuous flow of increasing concentrations of the effluent before and after ozonation. Neuroendocrinal effects were examined by tracking changes in acetylcholinesterase, glutamate, gamma-aminobutyrate, serotonin, dopamine and their respective adenylcyclase activities in synapse membranes, monoamine oxidase and vitellogenin-like proteins. Oxidative stress and damage were examined by superoxide dismutase and lipid peroxidation, respectively, in the visceral tissues. The results revealed that the exposure of freshwater mussels increased the levels of vitellogenin-like proteins in both the primary-treated and ozonated effluents, dopamine and glutamate, and decreased the turnover of the neurostimulant acetylcholine. Moreover, these endpoints were significantly correlated with oxidative stress and damage. A canonical analysis of the responses revealed that dopamine and the neuroexcitatory neuromediators--acetylcholesterase and glutamate--were the endpoints more strongly related with oxidative stress and damage. Mussel morphology and estrogenic biomarkers (vitellogenin-like proteins, gonad lipid stores) were also significantly related, albeit to a lesser extent, to oxidative stress and damage. In general, ozone treatment was not sufficient to mitigate the observed neuroendocrinal effects in freshwater mussels. We conclude that the continuous exposure of freshwater mussels to municipal wastewater effluents leads to neuroendrocinal alterations and to oxidative stress.

Alterations in DNA metabolism in Elliptio complanata mussels after exposure to municipal effluents.

This study sought to examine the genotoxic potential in Elliptio complanata freshwater mussels exposed to a physically and chemically treated municipal effluent before and after ozone treatment. Mussels were continuously exposed to increasing concentrations of the effluents for 14 days. Genotoxicity was determined by tracking changes in key enzymes for purine and pyrimidine synthesis (dehydrofolate reductase and aspartate transcarbamoylase), catabolism of purines (xanthine oxido-reductase) and DNA strand-break levels as determined by the alkaline precipitation assay. Other biomarkers related to xenobiotic biotransformation (cytochrome P4503A and glutathione S-transferase activities), metal metabolism (labile zinc and redox state of metathioneins) and oxidative stress (superoxide dismutase activity) were also determined in the mussels. The data revealed that dehydrofolate reductase activity was reduced by the initial effluent and increased by the ozonated effluent. Aspartate transcarbamoylase activity was significantly induced only with the ozonated effluent. The levels of DNA strand breaks responded in a biphasic manner in mussels exposed to the physically and chemically treated effluent where an initial decrease was observed at a low effluent concentration (3% v/v) followed by an increase in DNA strand breaks at a higher effluent concentration (20%). This response pattern was lost in the ozonated effluent, where only a decrease in DNA breaks was found. Xanthine oxidoreductase activity was not significantly affected but did correlate significantly with dehydrofolate reductase activity. Multivariate factorial and canonical analyses revealed that oxidative stress and metal/xenobiotic metabolism markers were strongly correlated with DNA strand breaks in mussels, suggesting that the presence of metals (zinc) and planar hydroxylated hydrocarbons present in these effluents were strong contributors to the observed response. We conclude that municipal effluents contain a complex mixture of pollutants that could modulate DNA synthesis and repair mechanisms in mussels.

Development of an auditory implant manipulator for minimally invasive surgical insertion of implantable hearing devices.

OBJECTIVE: To present the auditory implant manipulator, a navigation-controlled mechanical and electronic system which enables minimally invasive ('keyhole') transmastoid access to the tympanic cavity. MATERIALS AND METHODS: The auditory implant manipulator is a miniaturised robotic system with five axes of movement and an integrated drill. It can be mounted on the operating table. We evaluated the surgical work field provided by the system, and the work sequence involved, using an anatomical whole head specimen. RESULTS: The work field provided by the auditory implant manipulator is considerably greater than required for conventional mastoidectomy. The work sequence for a keyhole procedure included pre-operative planning, arrangement of equipment, the procedure itself and post-operative analysis. CONCLUSION: Although system improvements are necessary, our preliminary results indicate that the auditory implant manipulator has the potential to perform keyhole insertion of implantable hearing devices.

The role of plastidial glucose-6-phosphate/phosphate translocators in vegetative tissues of Arabidopsis thaliana mutants impaired in starch biosynthesis.

Arabidopsis thaliana mutants impaired in starch biosynthesis due to defects in either ADP glucose pyrophosphorylase (adg1-1), plastidic phosphoglucose mutase (pgm) or a new allele of plastidic phosphoglucose isomerase (pgi1-2) exhibit substantial activity of glucose-6-phosphate (Glc6P) transport in leaves that is mediated by a Glc6P/phosphate translocator (GPT) of the inner plastid envelope membrane. In contrast to the wild type, GPT2, one of two functional GPT genes of A. thaliana, is strongly induced in these mutants during the light period. The proposed function of the GPT in plastids of non-green tissues is the provision of Glc6P for starch biosynthesis and/or the oxidative pentose phosphate pathway. The function of GPT in photosynthetic tissues, however, remains obscure. The adg1-1 and pgi1-2 mutants were crossed with the gpt2-1 mutant defective in GPT2. Whereas adg1-1/gpt2-1 was starch-free, residual starch could be detected in pgi1-2/gpt2-1 and was confined to stomatal guard cells, bundle sheath cells and root tips, which parallels the reported spatial expression profile of AtGPT1. Glucose content in the cytosolic heteroglycan increased substantially in adg1-1 but decreased in pgi1-2, suggesting that the plastidic Glc6P pool contributes to its biosynthesis. The abundance of GPT2 mRNA correlates with increased levels of soluble sugars, in particular of glucose in leaves, suggesting induction by the sugar-sensing pathway. The possible function of GPT2 in starch-free mutants is discussed in the background of carbon requirement in leaves during the light-dark cycle.

[Navigation and robotics of the lateral skull base]. / Navigation und Robotik an der Otobasis.

Computer-aided microscopic surgery of the lateral skull base is a rare intervention in daily practice. It is often a delicate and difficult minimally invasive intervention, since orientation between the petrous bone and the petrous bone apex is often challenging. In the case of aural atresia or tumors the normal anatomical landmarks are often absent, making orientation more difficult. Navigation support, together with imaging techniques such as CT, MR and angiography, enable the surgeon in such cases to perform the operation more accurately and, in some cases, also in a shorter time. However, there are no internationally standardised indications for navigated surgery on the lateral skull base. Miniaturised robotic systems are still in the initial validation phase.

Effects of ozone, ultraviolet and peracetic acid disinfection of a primary-treated municipal effluent on the immune system of rainbow trout (Oncorhynchus mykiss).

Municipal sewage effluents are complex mixtures that are known to compromise the health condition of aquatic organisms. The aim of this study was to evaluate the impacts of various wastewater disinfection processes on the immune system of juvenile rainbow trout (Oncorhynchus mykiss). The trout were exposed to a primary-treated effluent for 28 days before and after one of each of the following treatments: ultraviolet (UV) radiation, ozonation and peracetic acid. Immune function was characterized in leucocytes from the anterior head kidney by the following three parameters: phagocytosis activity, natural cytotoxic cells (NCC) function and lymphocyte (B and T) proliferation assays. The results show that the fish mass to length ratio was significantly decreased for the primary-treated and all three disinfection processes. Exposure to the primary-treated effluent led to a significant increase in macrophage-related phagocytosis; the addition of a disinfection step was effective in removing this effect. Both unstimulated and mitogen-stimulated T lymphocyte proliferation in fish decreased dramatically in fish exposed to the ozonated effluent compared to fish exposed to either the primary-treated effluent or to aquarium water. Stimulation of T lymphocytes proliferation was observed with the peracetic acid treatment group. In conclusion, the disinfection strategy used can modify the immune system in fish at the level of T lymphocyte proliferation but was effective to remove the effects on phagocytosis activity.

Immunotoxic effects on freshwater mussels of a primary-treated wastewater before and after ozonation: a pilot plant study.

The immunotoxic potential of a primary-treated municipal effluent following enhanced disinfection by ozonation was studied in the freshwater mussel Elliptio complanata. Mussels were exposed to increasing concentrations (0%, 1%, 3%, 10%, and 20% v/v) of the effluent before and after ozone treatment (approximately 10 mg/L of purged O(3)) in a continuous flow-through laboratory for 7 weeks. Immunocompetence was appraised by measuring phagocytosis, cell viability (fluorescein retention), cell adherence to polystyrene micro-wells, cyclooxygenase (COX) activity and total nitrite levels in peripheral hemocytes from the hemolymphs. The results showed that phagocytosis was significantly inhibited by the primary-treated effluent at a threshold concentration of 1.7% v/v. Cell viability was also significantly reduced three-fold compared to controls at the same effluent threshold concentration, but hemocyte adherence was unchanged. COX activity was increased 1.3-fold at a threshold concentration of 14% v/v. Total nitrite levels were significantly increased 2.2-fold at a threshold concentration of 5.5% v/v. Ozone treatment of the effluent was not successful in removing phagocytic inhibition, but did completely remove cytotoxicity from hemocytes. Ozonation also reduced cell adherence at a threshold concentration of 1.7% v/v. The inflammatory properties of the effluent appeared to be accentuated by the ozone, as evidenced by an increase in COX activity, which reached 2.6-fold activity compared to controls, as compared to the 1.3-fold increase witnessed in the primary-treated effluent. Furthermore, total nitrite levels reached a two-fold induction at a threshold concentration of 1.7% v/v in the ozone-enhanced effluent compared to 5.5% v/v in the primary-treated effluent. In conclusion, ozonation of a primary-treated effluent successfully reduced microbial loading and completely removed cytotoxicity, but increased the inflammatory properties of the effluent. Investigations aimed at examining the impacts of sustained inflammation on the host's capacity to remove potentially pathogenic bacteria are recommended.

Neurotoxicological effects of a primary and ozonated treated wastewater on freshwater mussels exposed to an experimental flow-through system.

The neurotoxic potential of a primary-treated and ozonated municipal effluent was examined using feral freshwater Elliptio complanata mussels. Specimens were exposed to increasing concentrations (0, 1, 3, 10 and 20% v/v) of a primary-treated effluent before and after treatment with 10 mg/L of ozone in a mesocosm-type experiment for 30 days. A suite of biomarkers was used to assess the potential neurotoxic stress of the wastewaters on these benthic invertebrates: opiate binding sites, gamma-aminobutyric acid (GABA) metabolism, monoamines levels (serotonin, dopamine), monoamine oxidase, acetylcholinesterase and lipid peroxidation. Gametogenic activity was also determined by the gonado-somatic index and by vitellogenin-like proteins. The results show that the number of opiate binding sites increased slightly, especially after ozonation. GABA metabolism was generally reduced, suggesting higher glutamate stimulation than GABA dampening effects in mussel ganglia. This excitatory state was further confirmed by decreased acetylcholinesterase activity in gonadal tissues. The turnover of dopamine was enhanced with increased serotonin levels, but accompanied by reduced catabolism, as evidenced by decreased monoamine oxidase activity. Moreover, oxidative stress was increased, as determined by lipid peroxidation in the gonad (containing ganglia), which was significantly correlated with acetylcholinesterase activity and dopamine metabolism. The gonado-somatic index was significantly reduced with increased levels of vitellogenin-like proteins, again confirming the estrogenic action of these wastewaters. The data suggest that exposure to a primary-treated municipal effluent before and after ozonation leads to an excitotoxic syndrome implicating perturbations in GABA, dopamine and acetylcholine signaling. The increase in dopamine metabolism may be associated with the occurrence of opiate-like compounds (i.e. morphine) in the effluent. In general, ozonation reduced the severity of the responses, indicating that this disinfection strategy does not increase neurotoxicity to mussels.

Audiological long-term results following stapedotomy with stapedial tendon preservation.

Various functions are attributed to the stapedial reflex: as a low-frequency filter, it improves hearing in noise and serves in the protection against acoustic trauma. Our study analyzed 25 patients who had undergone argon laser stapedotomy with preservation of the stapedial tendon compared to patients without tendon preservation. Long-term audiological results are presented. Seventy-six percent of the patients had a residual postoperative air-bone gap of 10 dB or better and 97% of the patients 20 dB or better following stapedotomy with preservation of the stapedial tendon; these results are equal to those of patients without tendon preservation. The comparison of the uncomfortable threshold level showed no statistical difference between patients with and without tendon preservation, but patients with tendon preservation showed a tendency to better results in the sound-noise ratio. These favorable results remained constant in long-term controls.

Evidence of increased average age of patients with otosclerosis.

Otosclerosis is an inflammatory disease of the human temporal bone which was assumed to affect up to 10% of the Caucasians. Histologic otosclerosis has an incidence of 3.4%. It is considered as a major cause of hearing loss in Western countries while a low incidence is observed among Africans. Many hypotheses about its origin had been formulated in the past. Otosclerosis genes (OTSC1-5) and collagen 1 genes are mutated in some familial cases of otosclerosis. On this genetic background, a common environmental factor such as a measles virus infection might be the triggering factor. Studies in the past indicated a distribution of otosclerosis among men and women of 1:1.4. Our study was designed to analyze the age of patients with otosclerosis at the time of surgery in the eighties and the nineties of the last century. Patients suffering from clinical otosclerosis who underwent stapedectomy between 1978 and 1999 with complete clinical data available (n = 1,351) were included in the study. Age and gender distribution, the age difference between men and women and the influence of gender and the year of recruitment were evaluated. Statistical analyses demonstrated an increase in the average age of patients with clinical otosclerosis from the eighties to the nineties (p = 0.012). The gender distribution showed no statistically significant variation (p = 0.398). These data might reflect an improved health consciousness among the elder population or could be the result of increased health awareness in the seventies and eighties. Finally, in the early seventies, measles virus vaccination was introduced in Germany and the shift of age could be the result of the measles virus immunization campaign.

[Verification of normative values for the Swiss version of the Freiburg speech intelligibility test]. / Uberprüfung der Bezugskurven der Schweizer Version des Freiburger Zahlen- und Einsilbertests.

BACKGROUND AND OBJECTIVE: In the Swiss version of the Freiburg speech intelligibility test five test words from the original German recording which are rarely used in Switzerland have been exchanged. Furthermore, differences in the transfer functions between headphone and loudspeaker presentation are not taken into account during calibration. New settings for the levels of the individual test words in the recommended recording and small changes in calibration procedures led us to make a verification of the currently used normative values. PATIENTS AND METHODS: Speech intelligibility was measured in 20 subjects with normal hearing using monosyllabic words and numbers via headphones and loudspeakers. RESULTS: On average, 50% speech intelligibility was reached at levels which were 7.5 dB lower under free-field conditions than for headphone presentation. The average difference between numbers and monosyllabic words was found to be 9.6 dB, which is considerably lower than the 14 dB of the current normative curves. CONCLUSIONS: There is a good agreement between our measurements and the normative values for tests using monosyllabic words and headphones, but not for numbers or free-field measurements.

Cogan's syndrome: clinical evolution of deafness and vertigo in three patients.

The aim of this study was to evaluate the clinical symptoms, the otoneurological examinations, the treatment and the clinical course of three patients suffering from Cogan's syndrome, a rare disease based on the clinical association of a non-syphilitic interstitial keratitis with a cochleo-vestibular deficit. This case series involved three patients with follow up. The clinical course of the three patients (aged 30, 48 and 49 years) with Cogan's syndrome during a follow-up period of 2 to 6 years is reported. All patients underwent complete otoneurological, ophthalmologic and rheumatologic examinations and were treated with immunosuppressive therapy such as glucocorticoids and cyclophosphamide in two and glucocorticoids and methotrexate in one patient. Using immunosuppressive therapy, ophthalmologic symptoms disappeared rapidly in two patients. Hearing improved only in one and stabilized in a second patient. One patient died after 6 years of treatment because of complications of generalized vasculitis. Early diagnosis and rapid initiation of a combined immunosuppressive therapy such as corticosteroids and cyclophosphamide seem to be important in controlling the disease and avoiding persistent deafness. Whether systemic complications and a fatal outcome also can be prevented is still questionable.

A quantitative analysis of anaesthetist-patient communication during the pre-operative visit.

Previous communication research in general medical practice has shown that effective communication enhances patient compliance, satisfaction and medical outcome. It is expected that communication is equally important in anaesthesia, since patients often suffer from anxiety and lack of knowledge about anaesthetic procedures. However, little is known about the nature of communication during routine anaesthetic visits. The present study of 57 authentic anaesthetic visits provides the first results on the structure and content of communication in the pre-operative setting using the Roter Interaction Analysis System (RIAS). Patient-centred communication behaviours of anaesthetists and the extent of patient involvement were particularly investigated. From the 57 pre-operative visits, 18 267 utterances were coded. The mean (SD) [range] duration of the visit was 16.1 (7.8) [3.7-42.7] min. Anaesthetists provided 169 (68) and patients 153 (82) utterances per visit (53.5% vs. 46.5%). Physician and patient gender had no impact on the distribution of utterances and the duration of the visit. Conversation mainly focussed on biomedical issues with little psychosocial discussion (< 0.1% of all anaesthetist utterances). However, anaesthetists quite frequently used emotional comments toward patients (7%) and involved them in the conversation. The use of facilitators, open questions and emotional statements by the anaesthetist correlated with high patient involvement. The amount of patient participation in anaesthetic decisions was assessed with the Observing Patient Involvement Scale (OPTION). Compared with general practitioners, anaesthetists offered more opportunities to discuss treatment options (mean (SD) OPTION score 26.8 (16.8) vs. 16.8 (7.7)).

Removal of metals in leachate from sewage sludge using electrochemical technology.

Heavy metals in acidic leachates from sewage sludge are usually removed by chemical precipitation, which often requires high concentration of chemicals and induces high metallic sludge production. Electrochemical technique has been explored as an alternative method in a laboratory pilot scale reactor for heavy metals (Cu and Zn) removal from sludge leachate. Three electrolytic cell arrangements using different electrodes materials were tested: mild steel or aluminium bipolar electrode (EC cell), Graphite/stainless steel monopolar electrodes (ER cell) and iron-monopolar electrodes (EC-ER cell). Results showed that the best performances of metal removal were obtained with EC and EC-ER cells using mild steel electrodes operated respectively at current intensities of 0.8 and 2.0 A through 30 and 60 min of treatment. The yields of Cu and Zn removal from leachate varied respectively from 92.4 to 98.9% and from 69.8 to 76.6%. The amounts of 55 and 44 kg tds(-1) of metallic sludge were respectively produced using EC and EC-ER cells. EC and EC-ER systems involved respectively a total cost of 21.2 and 13.1 CAN dollars per ton of dry sludge treated including only energy consumption and metallic sludge disposal. The treatment using EC-ER system was found to be effective and more economical than the traditional metal precipitation using either Ca(OH)2 and/or NaOH.

[The effects of acoustic overstimulation]. / Die Auswirkungen von überlautem Schall auf das Gehör.

Basic aspects of acoustic trauma are presented. Exposure to loud noise leads to an acoustic traumatization with a temporary threshold shift initially and, with increasing exposure, intensity and duration, a permanent hearing loss. Impulse sound such as hammer blows on metal, gun shots and other detonations reaching peak levels of 160 to 180 dB is particularly hazardous to the inner ear. Playing loud musical instruments such as trumpets or percussion may also lead to hearing damage. Less dangerous than often believed is listening to electronically amplified music with walkmen, at discos or rock concerts. The reason is that, while the sound level is quite high, the particularly dangerous sound peaks are absent, as loudspeakers usually have an output limit of 110-120 dB. Traffic noise (cars, trains, air planes) is usually not threatening to the ear, but it may represent a considerable subjective annoyance and a stress factor leading to psychosomatic disturbances (neurovegetative symptoms, sleeping disorders). An effective treatment for the acoustic trauma is still missing. The systematic and consequent prophylaxis either with individual ear protectors (plugs or ear muffs) or by reducing the noise level at the source by means of isolation, encapsulation, or by using motors that are less noisy remains very important. Increasing awareness of acoustic pollution and preventive means have led to a reduction in the incidence of the acoustic trauma in the last decades.