Read by QxMD icon Read

Beamforming noise

Benjamin Dieudonné, Tom Francart
Many hearing-impaired listeners struggle to localize sounds due to poor availability of binaural cues. Listeners with a cochlear implant and a contralateral hearing aid - so-called bimodal listeners - are amongst the worst performers, as both interaural time and level differences are poorly transmitted. We present a new method to enhance head shadow in the low frequencies. Head shadow enhancement is achieved with a fixed beamformer with contralateral attenuation in each ear. The method results in interaural level differences which vary monotonically with angle...
March 12, 2018: Hearing Research
Thomas Wesarg, Bettina Voss, Frederike Hassepass, Rainer Beck, Antje Aschendorff, Roland Laszig, Susan Arndt
OBJECTIVE: To investigate the impact of the wearing position of an off-the-ear-processor (OTE) on speech perception in quiet and noise. PATIENTS: The study group consisted of 16 adult subjects with bilateral severe-to-profound sensorineural hearing loss, 2 of them unilaterally, and 14 bilaterally provided with cochlear implants. MAIN OUTCOME MEASURES: Speech perception in quiet and noise was measured for frontal presentation with the recipients behind-the-ear processor CP810 or CP910 and the OTE processor Kanso (Cochlear Limited, Sydney, Australia)...
April 2018: Otology & Neurotology
Miguel V Drummond, Vanessa C Duarte, André Albuquerque, Rogério N Nogueira, Leontios Stampoulidis, Georg Winzer, Lars Zimmermann, Stephen Clements, Javad Anzalchi
The design and dimensioning of a photonic-aided payload for a multi-beam high-throughput communications satellite is a complex problem in which the antenna, RF and photonic subsystems must be considered as a whole for achieving best performance with lowest mass and power consumption. In this paper, we propose and dimension the receiving stage of a communications satellite comprising a phased array antenna (PAA) feeding a multibeam photonic beamforming system (PBS). The PBS uses a single wavelength and resorts to heterodyne detection such that the retrieved beams are frequency downconverted...
March 5, 2018: Optics Express
Britta U Westner, Sarang S Dalal, Simon Hanslmayr, Tobias Staudigl
Single-trial analyses have the potential to uncover meaningful brain dynamics that are obscured when averaging across trials. However, low signal-to-noise ratio (SNR) can impede the use of single-trial analyses and decoding methods. In this study, we investigate the applicability of a single-trial approach to decode stimulus modality from magnetoencephalographic (MEG) high frequency activity. In order to classify the auditory versus visual presentation of words, we combine beamformer source reconstruction with the random forest classification method...
March 12, 2018: PLoS Computational Biology
Thomas J Deal
The cross-spectral density between pressure and particle velocity channels of two vector sensors with arbitrary orientation and separation is developed for a noise field consisting of directional sources distributed on a plane. Equations for arbitrary sensor orientations are necessary because cross-spectral density is an averaged product of two sensors' outputs that cannot be projected onto another direction after it is calculated. This prevents the use of existing methods, which calculate cross-spectral density for orthogonal particle velocity sensors, for sensors with different orientations...
February 2018: Journal of the Acoustical Society of America
Martin Siderius, Jie Li, Peter Gerstoft
Seismic interferometry recovers the Green's function between two receivers by cross-correlating the field measured from sources that surround the receivers. In the seismic literature, it has been widely reported that this processing can produce artifacts in the Green's function estimate called "spurious multiples" or the "virtual refracted wave." The spurious multiples are attributed to the head wave and its multiples and travels in the seabed. The head wave phenomenon is shown to be observable from both controlled active sources and from ocean ambient noise and for both vertical and horizontal arrays...
February 2018: Journal of the Acoustical Society of America
Michael F Dorman, Sarah Natale, Louise Loiselle
BACKGROUND: Sentence understanding scores for patients with cochlear implants (CIs) when tested in quiet are relatively high. However, sentence understanding scores for patients with CIs plummet with the addition of noise. PURPOSE: To assess, for patients with CIs (MED-EL), (1) the value to speech understanding of two new, noise-reducing microphone settings and (2) the effect of the microphone settings on sound source localization. RESEARCH DESIGN: Single-subject, repeated measures design...
March 2018: Journal of the American Academy of Audiology
Anthony T Herdman, Alexander Moiseev, Urs Ribary
Adaptive and non-adaptive beamformers have become a prominent neuroimaging tool for localizing neural sources of electroencephalographic (EEG) and magnetoencephalographic (MEG) data. In this study, we investigated single-source and multi-source scalar beamformers with respect to their performances in localizing and reconstructing source activity for simulated and real EEG data. We compared a new multi-source search approach (multi-step iterative approach; MIA) to our previous multi-source search approach (single-step iterative approach; SIA) and a single-source search approach (single-step peak approach; SPA)...
February 15, 2018: Brain Topography
Moein Mozaffarzadeh, Yan Yan, Mohammad Mehrmohammadi, Bahador Makkiabadi
Photoacoustic imaging (PAI) is a promising medical imaging modality providing the spatial resolution of ultrasound imaging and the contrast of optical imaging. For linear-array PAI, a beamformer can be used as the reconstruction algorithm. Delay-and-sum (DAS) is the most prevalent beamforming algorithm in PAI. However, using DAS beamformer leads to low-resolution images as well as high sidelobes due to nondesired contribution of off-axis signals. Coherence factor (CF) is a weighting method in which each pixel of the reconstructed image is weighted, based on the spatial spectrum of the aperture, to mainly improve the contrast...
February 2018: Journal of Biomedical Optics
Sibei Cheng, Qingjun Zhang, Mingming Bian, Xinhong Hao
For the conventional FDA-MIMO (frequency diversity array multiple-input-multiple-output) Radar with uniform frequency offset and uniform linear array, the DOFs (degrees of freedom) of the adaptive beamformer are limited by the number of elements. A better performance-for example, a better suppression for strong interferences and a more desirable trade-off between the main lobe and side lobe-can be achieved with a greater number of DOFs. In order to obtain larger DOFs, this paper researches the signal model of the FDA-MIMO Radar with nested frequency offset and nested array, then proposes an improved adaptive beamforming method that uses the augmented matrix instead of the covariance matrix to calculate the optimum weight vectors and can be used to improve the output performances of FDA-MIMO Radar with the same element number or reduce the element number while maintain the approximate output performances such as the received beampattern, the main lobe width, side lobe depths and the output SINR (signal-to-interference-noise ratio)...
February 8, 2018: Sensors
Moein Mozaffarzadeh, Ali Mahloojifar, Mahdi Orooji, Karl Kratkiewicz, Saba Adabi, Mohammadreza Nasiriavanaki
In photoacoustic imaging, delay-and-sum (DAS) beamformer is a common beamforming algorithm having a simple implementation. However, it results in a poor resolution and high sidelobes. To address these challenges, a new algorithm namely delay-multiply-and-sum (DMAS) was introduced having lower sidelobes compared to DAS. To improve the resolution of DMAS, a beamformer is introduced using minimum variance (MV) adaptive beamforming combined with DMAS, so-called minimum variance-based DMAS (MVB-DMAS). It is shown that expanding the DMAS equation results in multiple terms representing a DAS algebra...
February 2018: Journal of Biomedical Optics
Giulia Matrone, Alessandro Ramalli, Piero Tortoli, Giovanni Magenes
Tissue Harmonic Imaging (THI) mode is currently one of the preferred choices by the clinicians for its ability to provide enhanced ultrasound images, thanks to the use of the second harmonic component of backscattered echoes. This paper aims at investigating whether the combination of THI with Filtered-Delay Multiply And Sum (F-DMAS) beamforming can provide further improvements in image quality. F-DMAS is a new non-linear beamformer, which, similarly to THI, is based on the use of the second harmonics of beamformed signals and is known to increase image contrast resolution and noise rejection...
January 4, 2018: Ultrasonics
Alexander MacGillivray
Underwater noise from impact pile driving of 512 -m-long conductor casings was measured at a deep-water offshore oil platform in the Santa Barbara Channel. Beamforming measurements, obtained with a vertical array, confirmed that the primary wave front generated by hammering the conductor casing was a Mach cone propagating at an angle of 17.6° below the horizontal. Analysis of the processed array data also revealed the presence of high-frequency secondary waves at angles steeper than 45° below the horizontal...
January 2018: Journal of the Acoustical Society of America
Erin M Picou, Todd A Ricketts
OBJECTIVE: The purpose of this study was to evaluate the reliability and validity of four subjective questions related to listening effort. A secondary purpose of this study was to evaluate the effects of hearing aid beamforming microphone arrays on word recognition and listening effort. DESIGN: Participants answered subjective questions immediately following testing in a dual-task paradigm with three microphone settings in a moderately reverberant laboratory environment in two noise configurations...
January 30, 2018: International Journal of Audiology
Clemens Honeder, Rudolfs Liepins, Christoph Arnoldner, Hana Šinkovec, Alexandra Kaider, Erich Vyskocil, Dominik Riss
OBJECTIVE: To determine the impact of the fixed and adaptive beamforming technology of the new MED-EL SONNET cochlear implant audio processor on speech perception in noise. METHODS: The study cohort comprises 18 postlingually deafened adult cochlear implant recipients with at least six months of experience. Speech reception thresholds were measured with the Oldenburg Sentence Test in continuous, speech-shaped noise. Target sentences were presented in front of the listener, with noise sources placed at -135° and 135°, respectively...
2018: PloS One
Nick Bottenus
The focused transmit beam is a standard tool for clinical ultrasound scanning, concentrating energy from a number of array elements toward an imaging target. However, above and below the transmit focus, much of the energy in the beam is spread in a broadened main lobe and long off-axis tails that are ignored by conventional beamforming methods. This paper proposes a method to decompose a set of focused transmit beams into their constituent components-diverging waves from individual array elements. The recovery of this complete data set enables synthetic transmit focusing at all points in the field of view without beam shape or focal depth artifacts commonly associated with virtual source synthetic aperture beamforming...
January 2018: IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
Moein Mozaffarzadeh, Masume Sadeghi, Ali Mahloojifar, Mahdi Orooji
In ultrasound (US) imaging, delay and sum (DAS) is the most common beamformer, but it leads to low-quality images. Delay multiply and sum (DMAS) was introduced to address this problem. However, the reconstructed images using DMAS still suffer from the level of side lobes and low noise suppression. Here, a novel beamforming algorithm is introduced based on expansion of the DMAS formula. We found that there is a DAS algebra inside the expansion, and we proposed use of the DMAS instead of the DAS algebra. The introduced method, namely double-stage DMAS (DS-DMAS), is evaluated numerically and experimentally...
December 22, 2017: Ultrasound in Medicine & Biology
Frank Neugebauer, Gabriel Möddel, Stefan Rampp, Martin Burger, Carsten H Wolters
Beamformers are a widely-used tool in brain analysis with magnetoencephalography (MEG) and electroencephalography (EEG). For the construction of the beamformer filters realistic head volume conductor modeling is necessary for accurately computing the EEG and MEG leadfields, i.e., for solving the EEG and MEG forward problem. In this work, we investigate the influence of including realistic head tissue compartments into a finite element method (FEM) model on the beamformer's localization ability. Specifically, we investigate the effect of including cerebrospinal fluid, gray matter, and white matter distinction, as well as segmenting the skull bone into compacta and spongiosa, and modeling white matter anisotropy...
2017: Frontiers in Neuroscience
Nicole van Klink, Arjen Mol, Cyrille Ferrier, Arjan Hillebrand, Geertjan Huiskamp, Maeike Zijlmans
OBJECTIVE: Surface EEG can show epileptiform ripples in people with focal epilepsy, but identification is impeded by the low signal-to-noise ratio of the electrode recordings. We used beamformer-based virtual electrodes to improve ripple identification. METHODS: We analyzed ten minutes of interictal EEG of nine patients with refractory focal epilepsy. EEGs with more than 60 channels and 20 spikes were included. We computed ∼79 virtual electrodes using a scalar beamformer and marked ripples (80-250 Hz) co-occurring with spikes in physical and virtual electrodes...
January 2018: Clinical Neurophysiology: Official Journal of the International Federation of Clinical Neurophysiology
Sarah K Patch, Daniel E M Hoff, Tyler B Webb, Lee G Sobotka, Tianyu Zhao
PURPOSE: Range errors constrain treatment planning by limiting choice of ion beam angles and requiring large margins. Ionoacoustic range verification requires recovering the location of an acoustic source from low frequency signals. A priori information is applied to stably overcome resolution limits of inverse acoustic source imaging in this simulation study. In particular, the accuracy and robustness of ionoacoustic range verification for lateral and oblique delivery of high-energy protons to the prostate is examined...
November 20, 2017: Medical Physics
Fetch more papers »
Fetching more papers... Fetching...
Read by QxMD. Sign in or create an account to discover new knowledge that matter to you.
Remove bar
Read by QxMD icon Read

Search Tips

Use Boolean operators: AND/OR

diabetic AND foot
diabetes OR diabetic

Exclude a word using the 'minus' sign

Virchow -triad

Use Parentheses

water AND (cup OR glass)

Add an asterisk (*) at end of a word to include word stems

Neuro* will search for Neurology, Neuroscientist, Neurological, and so on

Use quotes to search for an exact phrase

"primary prevention of cancer"
(heart or cardiac or cardio*) AND arrest -"American Heart Association"