The goal of the present study was to investigate the human factors issues related to acoustic beacons used for auditory navigation. Specific issues addressed were: (1) the effect of various beacon characteristics on human accuracy in turning toward the direction of the acoustic beacon; (2) the difference between real and virtual environments on human accuracy in turning toward the acoustic beacon; and (3) the perceived sound quality of various acoustic beacons. Three experiments were conducted in which acoustic beacons were presented in a background of 80 dBA pink noise. Results of the localization tasks revealed that (a) presentation mode (continuous versus pulsed beacon sound) did not affect the overall localization accuracy or number of front-back confusion errors; and (b) the type of acoustic beacon affected the size of localization error. Results of the sound quality assessment indicated that listeners had definite preferences regarding the type of sound being used as a beacon, with (a) non-speech beacons preferred over speech beacons, (b) a beacon repetition rate of 1.1 rps preferred over either the 0.7 or 2.5 rps rates, and (c) a continuous operation of a beacon preferred over a pulsed operation. Finally, sound quality ratings and localization errors were highly negatively correlated. This finding demonstrates the usefulness and practical values of sound quality judgements for audio display design and evaluation.
Background/Aim: Phenotype-driven screening of a great pool of randomly mutant mice and subsequent selection of animals showing symptoms equivalent to human kidney diseases may result in the generation of novel suitable models for the study of the pathomechanisms and the identification of genes involved in kidney dysfunction. Methods: We carried out a large-scale analysis of ethylnitrosourea (ENU)-induced mouse mutants for albuminuria by using qualitative SDS-polyacrylamide gel electrophoresis. Results: The primary albuminuria screen preceded the comprehensive phenotypic mutation analysis in a part of the mice of the Munich ENU project to avoid loss of mutant animals as a consequence of prolonged suffering from severe nephropathy. The primary screen detected six confirmed phenotypic variants in 2,011 G1 animals screened for dominant mutations and no variant in 48 G3 pedigrees screened for recessive mutations. Further breeding experiments resulted in two lines showing a low phenotypic penetrance of albuminuria. The secondary albuminuria screen was carried out in mutant lines which were established in the Munich ENU project without preceding primary albuminuria analysis. Two lines showing increased plasma urea levels were chosen to clarify if severe kidney lesions are involved in the abnormal phenotype. This analysis revealed severe albuminuria in mice which are affected by a recessive mutation leading to increased plasma urea and cholesterol levels. Conclusion: Thus, the phenotypic selection of ENU-induced mutants according to the parameter proteinuria in principle demonstrates the feasibility to identify nephropathy phenotypes in ENU-mutagenized mice.
A series of experiments was conducted to evaluate 3D auditory beacons to be used by drivers of remote-controlled vehicles. The auditory beacons were generated from an external sound source, conditioned using the ConvolvotronTM and then presented through Sennheiser HD-580 earphones. In addition, a pink noise masker was presented through an overhead loudspeaker at a level of 80 dBA measured under the earphones. Ten listeners with normal hearing were asked to (1) judge sound quality of nine auditory beacons, and (2) move a beacon from a predetermined starting location to a position directly in front of the listener in the 3D display. The beacons differed regarding type of sound as well as rate and mode (continuous versus noncontinuous and single versus oscillating sound source) presentation. Results of the experiments indicate that listeners preferred (1) continuous versus interrupted presentation of the beacons, (2) nonspeech versus speech beacons, and (3) a rate of 1.1 repetitions per second over 0.7 or 2.5 repetitions per second. Mode of presentation did not affect the overall localization accuracy or the number of front versus back confusions made by the listeners. Results of the experiments will assist in the selection of beacons for auditory displays used for operation of remote-controlled vehicles.
In everyday listening situations, binaural information enhances the ability to understand speech messages in multitalker environments. For applications to virtual auditory technology in such environments, the importance of preserving characteristics of the natural listening environment is not clear. The purpose of this study was to assess listeners’ ability to monitor target (T) messages in the presence of synchronous competing (C) messages in an anechoic and a reverberant environment in three modes: (1) through loudspeakers at ±45° and ±90° with the subject seated in the actual room; (2) through the same loudspeakers with the subject listening remotely to the stimulus presented to a manikin in the actual room; and (3) with the environment simulated to create virtual sources at ±45° and ±90° azimuth under earphones. Fourteen subjects listened to messages selected from four lists of 2034 ten-syllable sentences. In every listening condition, the T message was presented 40 times to the subject in the presence of 0, 1, 2, and 3 C messages; subjects recorded the T messages. Results demonstrate that the ability to understand the T messages decreases as the number of C messages increases. As expected, speech recognition is better in the anechoic environment than the reverberant environment when C messages are present. Performance is degraded whenever the subjects do not listen with their own ears. [Work supported by the U. S. Army Research Lab.]
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