| 1. |
- Lagö, Thomas L, et al.
(författare)
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Evaluation of Field Tests for a MIMO ANC System Used in a Fishing Boat
- 1997
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Konferensbidrag (refereegranskat)abstract
- The sound levels in the sleeping quarters and the mess-room of fishing boats are sometimes too high. It is especially important to keep the sound levels down since the crew have to spend several days on the boat. This implies a long exposure time to low frequency noise. Even during sleep the crew does not have a hearing rest. It is therefore of interest to decrease sound levels in specific areas to give the crew hearing rest. The advantage with an ANC system is that it can be used as a retrofit kit, and the installation does not force the owner to keep the boat in the harbor for long times, compared to a passive treat of the noise problem. In order to evaluate how much sound level decrease it is possible to achieve, a volumetric ANC system has been tested. The typical fishing boat is equipped with one main engine. The engine is typically mounted using a passive isolation, but this does not decrease the sound levels enough. A brief review and discussion of the background noise situation are made in this paper. Since the boat has one engine, a single reference, multiple input, multiple output active noise control system, SR-MIMO ANC, was used using loudspeakers and microphones and an adaptive system based on a DSP. The SR-MIMO ANC system consists of one reference signal, four loudspeakers and six microphones. The results from a field test are presented in the paper and the results are commented.
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| 2. |
- Emgård, Per, et al.
(författare)
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An animal model for external otitis.
- 1997
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Ingår i: European Archives of Oto-Rhino-Laryngology. - 0937-4477 .- 1434-4726. ; 254:3, s. 115-119
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Tidskriftsartikel (refereegranskat)abstract
- External otitis was produced in 12 Sprague-Dawley rats by mechanical stimulation through a plastic micropipette inserted into the right external auditory canal (EAC). The EAC was later evaluated regarding the color of the skin, swelling and the presence of fluid. Within 1 day all rats developed an external otitis that was characterized by a red, swollen ear canal containing an opalescent fluid. The tympanic membrane and middle ear cavity appeared to be normal. No healed EACs were seen within the initial 10 days of follow-up and 4 of 6 rats still exhibited external otitis at day 21. Light microscopy of biopsy specimens revealed pronounced edema of the dermis of the ear canal. Mast cells were more numerous in the early phase of the otitis present, although very few inflammatory cells were found in tissues despite the marked inflammatory reaction produced. Findings show that this animal model for external otitis can be used to investigate pathogenesis as well as to test various treatment strategies.
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| 3. |
- Emgård, Per, et al.
(författare)
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Effects of betamethasone dipropionate plus an antihistamine in patients with external otitis
- 1999
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Ingår i: Current Therapeutic Research. - 0011-393X .- 1879-0313. ; 60:7, s. 364-370
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Tidskriftsartikel (refereegranskat)abstract
- In a prospective multicenter, randomized, double-masked trial, 30 patients with external otitis received betamethasone dipropionate in a 0.05% solution for 11 days. Fifty percent of the patients were assigned randomly to receive concomitant treatment with loratadine to help control itching, and 50% received placebo. The status of the external auditory canal (EAC) was assessed on days 0, 3, 7, 11, and 21 according to a new scoring system that graded color, the extension of redness outside the EAC, swelling, and effusion. Eighteen patients underwent sampling for a bacteriologic culture at the start of treatment; 14 cultures showed positive findings. The EAC status improved rapidly, and by day 11 it was almost normal in all patients. Pain and sleep disturbances disappeared by day 7; at which point itching was either nonexistent or mild. All patients were able to resume work after 3 days of treatment. At the end of the study, 29 (97%) of the 30 patients were cured. The addition of loratadine to the treatment did not improve results significantly. External otitis is generally treated with a combination of a steroid and an antibiotic. Results of this study suggest that external otitis, whether culture-positive or not, can be cured using a group III steroid alone.
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| 4. |
- Lagö, Thomas L, et al.
(författare)
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Analysis of Helicopter Sound for the Development of A New Generation Active Headset
- 1997
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Konferensbidrag (refereegranskat)abstract
- Helicopters generate substantial noise levels, especially at low frequency. These noise levels are normally not harmful for the ear. However, the low frequency content masks the speech. Therefore, pilots tend to set the communication system at maximum level so that the sound levels reach severe amplitudes for the ear. These high sound levels are exposing the ear to fatigue and hearing loss. The low speech intelligibility caused by the background noise is also a safety issue since it is most important that all commands can be understood correctly. The risk of noise induced hearing loss can normally be evaluated by sound pressure level measurements. However, in some cases, the standardized methods for these measurements does not take into account some secondary effects of the frequency distribution of the sound pressure levels. This paper addresses a noise exposure situation where the noise level itself is not harmful for hearing but is still the reason for increased risk for noise induced hearing loss. Military helicopter crews in Sweden have recent shown an increase in noise induced hearing loss. A combined active passive technique has been chosen as a possible solution. Therefore, the dominant sound sources have to be identified and the number of harmonics for each source determined. An investigation of the coupling between the structure borne sound and the air borne sound was also performed. This analysis is the basis for the development of a new generation active headset, and is presented in this paper.
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