87 research outputs found
RTF-Based Binaural MVDR Beamformer Exploiting an External Microphone in a Diffuse Noise Field
Besides suppressing all undesired sound sources, an important objective of a
binaural noise reduction algorithm for hearing devices is the preservation of
the binaural cues, aiming at preserving the spatial perception of the acoustic
scene. A well-known binaural noise reduction algorithm is the binaural minimum
variance distortionless response beamformer, which can be steered using the
relative transfer function (RTF) vector of the desired source, relating the
acoustic transfer functions between the desired source and all microphones to a
reference microphone. In this paper, we propose a computationally efficient
method to estimate the RTF vector in a diffuse noise field, requiring an
additional microphone that is spatially separated from the head-mounted
microphones. Assuming that the spatial coherence between the noise components
in the head-mounted microphone signals and the additional microphone signal is
zero, we show that an unbiased estimate of the RTF vector can be obtained.
Based on real-world recordings, experimental results for several reverberation
times show that the proposed RTF estimator outperforms the widely used RTF
estimator based on covariance whitening and a simple biased RTF estimator in
terms of noise reduction and binaural cue preservation performance.Comment: Accepted at ITG Conference on Speech Communication 201
Optimal Binaural LCMV Beamforming in Complex Acoustic Scenarios: Theoretical and Practical Insights
Binaural beamforming algorithms for head-mounted assistive listening devices
are crucial to improve speech quality and speech intelligibility in noisy
environments, while maintaining the spatial impression of the acoustic scene.
While the well-known BMVDR beamformer is able to preserve the binaural cues of
one desired source, the BLCMV beamformer uses additional constraints to also
preserve the binaural cues of interfering sources. In this paper, we provide
theoretical and practical insights on how to optimally set the interference
scaling parameters in the BLCMV beamformer for an arbitrary number of
interfering sources. In addition, since in practice only a limited temporal
observation interval is available to estimate all required beamformer
quantities, we provide an experimental evaluation in a complex acoustic
scenario using measured impulse responses from hearing aids in a cafeteria for
different observation intervals. The results show that even rather short
observation intervals are sufficient to achieve a decent noise reduction
performance and that a proposed threshold on the optimal interference scaling
parameters leads to smaller binaural cue errors in practice.Comment: To appear in Proc. IWAENC 201
Magnetic excitations in SrCu2O3: a Raman scattering study
We investigated temperature dependent Raman spectra of the one-dimensional
spin-ladder compound SrCu2O3. At low temperatures a two-magnon peak is
identified at 3160+/-10 cm^(-1) and its temperature dependence analyzed in
terms of a thermal expansion model. We find that the two-magnon peak position
must include a cyclic ring exchange of J_cycl/J_perp=0.09-0.25 with a coupling
constant along the rungs of J_perp approx. 1215 cm^(-1) (1750 K) in order to be
consistent with other experiments and theoretical results.Comment: 4 pages, 3 figure
Comparison of large-angle production of charged pions with incident protons on cylindrical long and short targets
The HARP collaboration has presented measurements of the double-differential
pi+/pi- production cross-section in the range of momentum 100 MeV/c <= p 800
MeV/c and angle 0.35 rad <= theta <= 2.15 rad with proton beams hitting thin
nuclear targets. In many applications the extrapolation to long targets is
necessary. In this paper the analysis of data taken with long (one interaction
length) solid cylindrical targets made of carbon, tantalum and lead is
presented. The data were taken with the large acceptance HARP detector in the
T9 beam line of the CERN PS. The secondary pions were produced by beams of
protons with momenta 5 GeV/c, 8 GeV/c and 12 GeV/c. The tracking and
identification of the produced particles were performed using a small-radius
cylindrical time projection chamber (TPC) placed inside a solenoidal magnet.
Incident protons were identified by an elaborate system of beam detectors.
Results are obtained for the double-differential yields per target nucleon d2
sigma / dp dtheta. The measurements are compared with predictions of the MARS
and GEANT4 Monte Carlo simulations.Comment: 43 pages, 20 figure
Forward production of charged pions with incident on nuclear targets measured at the CERN PS
Measurements of the double-differential production cross-section
in the range of momentum 0.5 \GeVc \leq p \le 8.0 \GeVc and angle 0.025 \rad
\leq \theta \le 0.25 \rad in interactions of charged pions on beryllium,
carbon, aluminium, copper, tin, tantalum and lead are presented. These data
represent the first experimental campaign to systematically measure forward
pion hadroproduction. The data were taken with the large acceptance HARP
detector in the T9 beam line of the CERN PS. Incident particles, impinging on a
5% nuclear interaction length target, were identified by an elaborate system of
beam detectors. The tracking and identification of the produced particles was
performed using the forward spectrometer of the HARP detector. Results are
obtained for the double-differential cross-sections mainly at four incident pion beam
momenta (3 \GeVc, 5 \GeVc, 8 \GeVc and 12 \GeVc). The measurements are compared
with the GEANT4 and MARS Monte Carlo simulationComment: to be published on Nuclear Physics
Large-angle production of charged pions by 3 GeV/c - 12 GeV/c protons on carbon, copper and tin targets
A measurement of the double-differential production cross-section
in proton--carbon, proton--copper and proton--tin collisions in the range of
pion momentum 100 \MeVc \leq p < 800 \MeVc and angle 0.35 \rad \le \theta
<2.15 \rad is presented. The data were taken with the HARP detector in the T9
beam line of the CERN PS. The pions were produced by proton beams in a momentum
range from 3 \GeVc to 12 \GeVc hitting a target with a thickness of 5% of a
nuclear interaction length. The tracking and identification of the produced
particles was done using a small-radius cylindrical time projection chamber
(TPC) placed in a solenoidal magnet. An elaborate system of detectors in the
beam line ensured the identification of the incident particles. Results are
shown for the double-differential cross-sections at four incident proton beam
momenta (3 \GeVc, 5 \GeVc, 8 \GeVc and 12 \GeVc)
Measurement of the production of charged pions by protons on a tantalum target
A measurement of the double-differential cross-section for the production of
charged pions in proton--tantalum collisions emitted at large angles from the
incoming beam direction is presented. The data were taken in 2002 with the HARP
detector in the T9 beam line of the CERN PS. The pions were produced by proton
beams in a momentum range from 3 \GeVc to 12 \GeVc hitting a tantalum target
with a thickness of 5% of a nuclear interaction length. The angular and
momentum range covered by the experiment (100 \MeVc \le p < 800 \MeVc and
0.35 \rad \le \theta <2.15 \rad) is of particular importance for the design
of a neutrino factory. The produced particles were detected using a
small-radius cylindrical time projection chamber (TPC) placed in a solenoidal
magnet. Track recognition, momentum determination and particle identification
were all performed based on the measurements made with the TPC. An elaborate
system of detectors in the beam line ensured the identification of the incident
particles. Results are shown for the double-differential cross-sections
at four incident
proton beam momenta (3 \GeVc, 5 \GeVc, 8 \GeVc and 12 \GeVc). In addition, the
pion yields within the acceptance of typical neutrino factory designs are shown
as a function of beam momentum. The measurement of these yields within a single
experiment eliminates most systematic errors in the comparison between rates at
different beam momenta and between positive and negative pion production.Comment: 49 pages, 31 figures. Version accepted for publication on Eur. Phys.
J.
Large-angle production of charged pions by 3 GeV/c - 12.9 GeV/c protons on beryllium, aluminium and lead targets
Measurements of the double-differential production cross-section
in the range of momentum 100 \MeVc \leq p < 800 \MeVc and angle 0.35 \rad
\leq \theta < 2.15 \rad in proton--beryllium, proton--aluminium and
proton--lead collisions are presented. The data were taken with the HARP
detector in the T9 beam line of the CERN PS. The pions were produced by proton
beams in a momentum range from 3 \GeVc to 12.9 \GeVc hitting a target with a
thickness of 5% of a nuclear interaction length. The tracking and
identification of the produced particles was performed using a small-radius
cylindrical time projection chamber (TPC) placed inside a solenoidal magnet.
Incident particles were identified by an elaborate system of beam detectors.
Results are obtained for the double-differential cross-sections at six incident
proton beam momenta (3 \GeVc, 5 \GeVc, 8 \GeVc, 8.9 \GeVc (Be only), 12 \GeVc
and 12.9 \GeVc (Al only)) and compared to previously available data
Measurement of the production cross-section of positive pions in the collision of 8.9 GeV/c protons on beryllium
The double-differential production cross-section of positive pions,
, measured in the HARP experiment is presented.
The incident particles are 8.9 GeV/c protons directed onto a beryllium target
with a nominal thickness of 5% of a nuclear interaction length. The measured
cross-section has a direct impact on the prediction of neutrino fluxes for the
MiniBooNE and SciBooNE experiments at Fermilab. After cuts, 13 million protons
on target produced about 96,000 reconstructed secondary tracks which were used
in this analysis. Cross-section results are presented in the kinematic range
0.75 GeV/c < < 6.5 GeV/c and 30 mrad < < 210 mrad in
the laboratory frame.Comment: 39 pages, 21 figures. Version accepted for publication by Eur. Phys.
J.
A Precise Measurement of the Muon Neutrino-Nucleon Inclusive Charged Current Cross-Section off an Isoscalar Target in the Energy Range 2.5 < E_\nu < 40 GeV by NOMAD
We present a measurement of the muon neutrino-nucleon inclusive charged
current cross-section, off an isoscalar target, in the neutrino energy range
GeV. The significance of this measurement is its
precision, % in GeV, and % in GeV regions, where significant uncertainties in previous
experiments still exist, and its importance to the current and proposed long
baseline neutrino oscillation experiments.Comment: 14 pages, 3 figures, submitted to Phys.Lett.
- …