2,679 research outputs found
Noise exposure and auditory thresholds of German airline pilots: a cross-sectional study
Objective: The cockpit workplace of airline pilots is a noisy environment. This study examines the hearing thresholds of pilots with respect to ambient noise and communication sound.
Methods: The hearing of 487 German pilots was analysed by audiometry in the frequency range of 125 Hz16 kHz in varying age groups. Cockpit noise (free-field) data and communication sound (acoustic manikin) measurements were evaluated.Results The ambient noise levels in cockpits were found to be between 74 and 80 dB(A), and the sound pressure levels under the headset were found to be between 84 and 88 dB(A).The leftright threshold differences at 3, 4 and 6 kHz show evidence of impaired hearing at the left ear, which worsens by age.In the age groups 40/=40 years the mean differences at 3 kHz are 2/3 dB, at 4 kHz 2/4 dB and at 6 kHz 1/6 dB.In the pilot group which used mostly the left ear for communication tasks (43 of 45 are in the older age group) the mean difference at 3?kHz is 6?dB, at 4 kHz 7 dB and at 6 kHz 10 dB. The pilots who used the headset only at the right ear also show worse hearing at the left ear of 2 dB at 3 kHz, 3 dB at 4 kHz and at 6 kHz. The frequency-corrected exposure levels under the headset are 711 dB(A) higher than the ambient noise with an averaged signal-to-noise ratio for communication of about 10 dB(A).
Conclusions: The left ear seems to be more susceptible to hearing loss than the right ear. Active noise reduction systems allow for a reduced sound level for the communication signal below the upper exposure action value of 85 dB(A) and allow for a more relaxed working environment for pilots
Dynamics and decoherence in the central spin model using exact methods
The dynamics and decoherence of an electronic spin-1/2 qubit coupled to a
bath of nuclear spins via hyperfine interactions in a quantum dot is studied.
We show how exact results from the integrable solution can be used to
understand the dynamic behavior of the qubit. It is possible to predict the
main frequency contributions and their broadening for relatively general
initial states analytically, leading to an estimate of the corresponding decay
times. Furthermore, for a small bath polarization, a new low-frequency time
scale is observed.Comment: 4 pages, 2 figures. Published version. See also
http://www.physik.uni-kl.de/eggert/papers/index.htm
Detection of single trial power coincidence for the identification of distributed cortical processes in a behavioral context
Poster presentation: The analysis of neuronal processes distributed across multiple cortical areas aims at the identification of interactions between signals recorded at different sites. Such interactions can be described by measuring the stability of phase angles in the case of oscillatory signals or other forms of signal dependencies for less regular signals. Before, however, any form of interaction can be analyzed at a given time and frequency, it is necessary to assess whether all potentially contributing signals are present. We have developed a new statistical procedure for the detection of coincident power in multiple simultaneously recorded analog signals, allowing the classification of events as 'non-accidental co-activation'. This method can effectively operate on single trials, each lasting only for a few seconds. Signals need to be transformed into time-frequency space, e.g. by applying a short-time Fourier transformation using a Gaussian window. The discrete wavelet transform (DWT) is used in order to weight the resulting power patterns according to their frequency. Subsequently, the weighted power patterns are binarized via applying a threshold. At this final stage, significant power coincidence is determined across all subgroups of channel combinations for individual frequencies by selecting the maximum ratio between observed and expected duration of co-activation as test statistic. The null hypothesis that the activity in each channel is independent from the activity in every other channel is simulated by independent, random rotation of the respective activity patterns. We applied this procedure to single trials of multiple simultaneously sampled local field potentials (LFPs) obtained from occipital, parietal, central and precentral areas of three macaque monkeys. Since their task was to use visual cues to perform a precise arm movement, co-activation of numerous cortical sites was expected. In a data set with 17 channels analyzed, up to 13 sites expressed simultaneous power in the range between 5 and 240 Hz. On average, more than 50% of active channels participated at least once in a significant power co-activation pattern (PCP). Because the significance of such PCPs can be evaluated at the level of single trials, we are confident that this procedure is useful to study single trial variability with sufficient accuracy that much of the behavioral variability can be explained by the dynamics of the underlying distributed neuronal processes
Generation of N00N-like interferences with two thermal light sources
Measuring the th-order intensity correlation function of light emitted by
two statistically independent thermal light sources may display N00N-like
interferences of arbitrary order . We show that via a particular
choice of detector positions one can isolate -photon quantum paths where
either all photons are emitted from the same source or photons are
collectively emitted by both sources. The latter superposition displays
N00N-like oscillations with which may serve, e.g., in astronomy, for
imaging two distant thermal sources with -fold increased resolution. We
also discuss slightly modified detection schemes improving the visibility of
the N00N-like interference pattern and present measurements verifying the
theoretical predictions.Comment: 9 pages, 6 figure
- …