Home HomeDavid Alan Bies, University of Adelaide (Australia)
Begining with the work of Mammano and Nobili it is shown that in the passive state the cochlear partition may be modelled as an array of modally uncoupled independent mechanical oscillators. While uncoupled modally the oscillators of the cochlear partition are strongly coupled hydraulically through the forcing fields of the stapes and all other segments of the cochlear duct. Consequently, each mechanical oscillator of the cochlear partition responds modally in forced response dependent upon the motion of the stapes and the motions of all other segments of the cochlear partition. It is shown that the oscillators of the cochlear partition are linear in passive response to sound pressure levels of 110 dB re 20 uPa. Evidence is presented in support of the assumption that in the case of active response unclamping may be assumed to vary on a time scale which is long compared to the period of sound in the audio frequency range. In the latter case active response of the cochlea may also be described in terms of the same system of linear oscillators as in the passive case but with variable damping. It will be shown that the proposed active model is in good agreement with available data.
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Antonio Miguel Mendez, Laboratorio de Acustica y Luminotecnia CIC (Argentina)
Edmundo Carlos Rochaix, Acoustical Consultant (Argentina)
This paper contains basic information on the acoustical environment at several stands where members of the police force perform shooting practices. The object of the study is to gather information to improve the environment in existing and future constructions. Different types of guns where used for this study. Noise levels were recorded and analysed using instrumentation appropriated for this type of studies. The paper also includes details of the weapons used, the instrumentation and the shooting stands. Results are shown and analysed. Finally, recommendations regarding the construction of shooting stands are presented.
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Michael M. Samoylov, Baltic State Technical University (Russia)
G.M. Ponomarenko, Baltic State Technical University (Russia)
Pavel V. Vorobjev, Baltic State Technical University (Russia)
V.V. Zaytseva, Baltic State Technical University (Russia)
Unfavorable influence of high intensity subsonic oscillations on humans has been determined in numerous scientific researches. Elaborated by authors investigations showed that humans being under abnormally high or long nervous-psychophysiological overloads and other harmful factors significantly affect by subsonic even of low intensity. Being in a complex with other harmful factors subsonic causes such undesirable facts as delays of visual sensor reaction, enhancement of operator mistakes, space disorientation. Influence of subsonic of low intensity being together with other harmful factors especially presented in such human activity as aircraft running. This sort of human activity is characterized by near-extremal work conditions for the pilot or even for all crew when the pilot is under significant nervous-psychophysiological overloads caused by subsonic influence what may be the reason of an emergency situation. The highest levels of subsonic were fixed during flying up and landing of aircraft. Turbulent flows making by airflow streamlining over the chassis and wings elements are the main sources generate subsonic oscillations. Switching on of the engine reverse also gives hasty increase of subsonic level. It should be underlined that increase of subsonic level become especially dangerous during process of aircraft landing when the crew has being affected by different harmful factors, first of all by nervous-psychophysiological overloads, become being influenced by subsonic also. These situations cause quick increase of likelihood of crew actions which are not adequate to changes of flying what might be the reason of an emergency situation. Taking into account results of carried out investigations it is proposed by authors to review exist norms of subsonic for aircraft crew to make them more strict.
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Norman H. Clark, CSIRO National Measurement Laboratory (Australia)
Laurence P. Dickinson, CSIRO National Measurement Laboratory (Australia)
Measurements of vibration in the frequency range below 20 hertz, down to 0.1 hertze or even lower, are of interest to consultants, manufacturers and researchers in such fields as ground vibration due to blasting, impact testing of safety equipment (eg to AS1801 or AS1698), and human exposure to vibration (eg to AS2970 or AS2973). However, many vibration transducers, and the voltmeters or recorders used with them, may give incorrect readings at these low frequencies. If such instruments have not been calibrated in this range, the reading error cannot be corrected. In some cases measurements may not be legally acceptable, if the measuring equipment has not been calibrated in such a way that the measurements are traceable to the primary units of time, length and voltage. This paper briefly discusses low-frequency measurement errors and uncertainties, and the chain of traceability through calibrations performed at the National Measurement Laboratory.
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Reinhard Weber, Carl-von-Ossietzky University (Germany)
Christoph Eichenlaub, Carl-von-Ossietzky University (Germany)
The unpleasantness of 20 s-sequences of wind turbine noises is assessed by test persons (TPs) in paired comparison experiments. Noise rankings are deduced from the TPs unpleasantness judgements as well as from the calculated parameter data and theyare analysed by several statistical methods. The unpleasantness of wind turbine noises is estimated very similar by a large group of TPs. For the objective description of the noises psychoacoustical parameters are calculated. The judgement behaviour of the TPs ts very well to the rankings which have been computed for the psychoacoustic parameters, tonality and uctuation strength.
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H. Yanagawa, Chiba Institute of Technology (Japan)
Tetsuo Tagaeto, Kogakuin University (Japan)
H. Komatsu, Kogakuin University (Japan)
Analysis of the hearing characteristic and evaluation of sound fields are important if we want to reproduce a spatial impression of sound fields. To estimate the quality of the sound image and spatial impression, we use a burst white noise signal as a ation and the time window length used for TRICC analysis including the onset of sound.
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Takuji Koike, Tohoku University (Japan)
Hiroshi Wada, Tohoku University (Japan)
Toshimitsu Kobayashi, Nagasaki University School of Medicine (Japan)
Many middle ear prostheses are available for reconstruction of a missing or damaged ossicle. However, there are few studies, which investigate the acoustic properties of these prostheses, and the information that could lead to the design and development of better ossicular replacement prostheses is absent from the report. Clinical trials comparing many prostheses would be the best method of analysis, but these are difficult to perform and are contaminated by a large number of variables that are hard to control. Therefore, some experiments with ossicular substitution in animals and human temporal bones have been performed. However, animal studies are not very good for acoustic studies because of the anatomic differences, and the specimen is difficult to handle. In this study, three-dimensional finite-element models of a human intact middle ear and reconstructed middle ears using many types of incus replacement prosthesis are established. Then, an attempt is made to clarify the optimum method for reconstructing the middle ear.
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Barbara Griefahn, University of Dortmund (Germany)
Peter Broede, University of Dortmund (Germany)
Wolfgang Jaschinski, University of Dortmund (Germany)
Sixteen female and fifteen male subjects, 19-51 years of age participated in the present study. Its purpose was to determine various combinations of sinusoidal simultaneously presented (dual-axis) vertical and lateral whole-body vibrations that are sensed as equally strong as a preceding single-axis reference (aw = 1.25 ms-2 r.m.s.) which was applied in either of both directions only and which had the same frequency, namely 1.6, 3.15, 6.3 or 12.5 Hz. The test motion consisted of a constant predefined and a variable component. The first was applied in the same direction and with either of 5 predefined percentages of the acceleration of the reference (10, 25, 50, 75, 90%). The variable component was perpendicularly oriented to the first (resp. to the reference); its magnitude was varied by the subjects until the dual-axis test signal was judged as equally strong as the single-axis reference. The curves of equally sensed combinations determined for the 4 frequencies were bended right-downwards as expected due to ISO/DIS 2631. But there were remarkable quantitative discrepancies for frequencies above 1.6 Hz with an underestimation of lateral vibrations; the factor ky being 1.5 - 1.9 greater than in the standard. It is concluded that the weighting factors for lateral vibrations above 1.6 Hz need to be corrected for the proper evaluation of discomfort caused by multi-axis whole-body vibrations.
sv970258.pdf (Scanned) sv970258.pdf (From Postscript) TOPMarianna Mirowska, Building Research Institute (Poland)
The appliances installed in the residential buildings such as transformers, air-conditioners, freezers are often sources of low frequency noise. Although sound levels inside dwellings from these sources are low, the dwellers evaluate the noise as annoying. The paper presents the results of investigation of annoying low frequency noise in dwellings. Measurement results are shown and methods of annoyance assessment are discussed.
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Barbara Griefahn, University of Dortmund (Germany)
Peter Broede, University of Dortmund (Germany)
Wolfgang Jaschinski, University of Dortmund (Germany)
The hypothesis was proved that whole body vibrations transmitted through the seat impair spatial retinal resolution and oculomotor alignment parallel to the vibration axis. More specifically, it was assumed that the decrement increases gradually from single-axis lateral via single-axis vertical and dual-axis linear to dual-axis circular motions. 20 subjects (19-26 yrs, 14 men, 6 women) with good vision participated in the study where in separate experimental sessions either fixation disparity or contrast threshold for vertically and horizontally oriented test patterns were determined during 5 conditions. The latter comprized a control (az = ay = 0) and 4 conditions where 5 Hz sinusoidal vibrations of 1.2ms-2 r.m.s. were applied separately, either in the vertical or in the lateral direction or simultaneously in both directions, once without and once with a phase shift of 90 thus causing dual-axis linear or circular motions. The variability of vertical fixation disparity and contrast thresholds for horizontal gratings increased significantly whenever the subjects were exposed to vertical motions (alone or combined with lateral motions). These results indicate an increased difficulty to recognize properly characters and graphic patterns that contain horizontal lines. This may lead to the development of asthenopic complaints.
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Ross L. Dawe, Defence Science and Technology Organisation (Australia)
Edwin R. Galbreath, Defence Science and Technology Organisation (Australia)
This paper describes an investigation of the effect of the inclusion of colour coded signal information in frequency-time-intensity (lofargram) sonar displays on the detection threshold of human observers. An average measured colour gain for human observers gave a systemic improvement in performance which partially negated typical human factors losses associated with making detection decisions from sonar displays. The effect of good and poor contrast between colour hues was also studied for its effect on signal detectability and the quality of bearing information on the display. It was found that the relative brightness of the display cells was the dominating factor in signal detection on lofargrams, rather than the specific choice of colour hues, and that each display must have its choice of colour hues individually tuned for maximum benefit.
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