18 research outputs found
Simulation of soft tissue stimulation - Indication of a skull bone vibration mechanism in bone conduction hearing
No full textSoft tissue conduction has been proposed as an alternative to bone conduction (BC) for hearing vibrations applied at soft tissue positions at the human head. Arguments for soft tissue conduction originate primarily from experimental studies with stimulation applied to different positions such as the neck, the eye, and directly to the dura. To investigate the mechanism for hearing when stimulations are at soft tissue positions, experimental studies were replicated using the finite element model for BC research, the LiUHead. The vibrations at the cochlear promontory and the sound pressure in the cerebrospinal fluid (CSF) close to the inner ear were extracted from simulations in the LiUHead. The LiUHead simulations were able to replicate data in the literature of cochlear promontory vibration levels and CSF sound pressures with stimulation applied at the soft tissue positions and at the skin covered mastoid. It was shown that the mechanical point impedance of the soft tissue positions affected the output of the BC transducer at frequencies below 1 kHz. The LiUHead simulated cochlear promontory velocities predicted the soft tissue positions hearing thresholds reported in the literature within the inter-study range. This indicates that the hearing mechanism for stimulation at soft tissue positions equals the hearing mechanism for conventional BC hearing, and that soft tissue conduction is not an alternative hearing mechanism. Moreover, the simulations indicated that the CSF sound pressure is not an important pathway for BC hearing and that the CSF pressure is generated by the local skull bone vibrations. (c) 2022 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license ( http://creativecommons.org/licenses/by/4.0/ )Funding Agencies|Swedish Research CouncilSwedish Research CouncilEuropean Commission [VR 2017-06092]</p
Review of Whole Head Experimental Cochlear Promontory Vibration with Bone Conduction Stimulation and Investigation of Experimental Setup Effects
No full textBone conduction sound transmission in humans has been extensively studied using cochlear promontory vibrations. These studies use vibration data collected from measurements in live humans, whole cadavers, and severed cadaver heads, with stimulation applied either at an implant in the skull bone or directly on the skin. Experimental protocols, methods, and preparation of cadavers or cadaver heads vary among the studies, and it is currently unknown to what extent the aforementioned variables affect the outcome of those studies. The current study has two aims. The first aim is to review and compare available experimental data and assess the effects of the experimental protocol and methods. The second aim is to investigate similarities and differences found between the experimental studies based on simulations in a finite element model, the LiUHead. With implant stimulation, the average cochlear promontory vibration levels were within 10 dB, independent of the experimental setup and preparations of the cadavers or cadaver heads. With on-skin stimulation, the results were consistent between cadaver heads and living humans. Partial or complete replacement of the brain with air does not affect the cochlear promontory vibration, whereas replacing the brain with liquid reduces the vibration level by up to 5 dB. An intact head-neck connection affects the vibration of the head at frequencies below 300-400 Hz with a significant vibration reduction at frequencies below 200 Hz. Removing all soft tissue, brain tissue, and intracranial fluid from the head increases the overall cochlear promontory vibration level by around 5 dB
Consequences of Mastoidectomy on Bone Conducted Sound Based on Simulations in a Whole Human Head
No full textHypothesis: The aim of this study is to investigate how a mastoidectomy surgery affects bone conduction (BC) sound transmission using a whole head finite element model. Background: Air conduction (AC) and BC hearing thresholds are normally used to evaluate the effect of an ear surgery. It is then assumed that the BC hearing thresholds are unaffected by the surgery. Moreover, BC hearing aids are used in cases of unilateral or conductive hearing loss in heads that have undergone a mastoidectomy surgery. Given the invasiveness of the surgery, the BC hearing sensitivity may be altered by the surgery itself. Methods: Two types of mastoid surgery, canal wall up and canal wall down, with and without obliteration, were simulated in a whole head finite element model for BC stimulation, the LiUHead. The evaluations were conducted for two different methods of applying the BC sound, at the skin surface (B71 transducer) and directly at the bone (BC hearing aid). Results: The results showed that a mastoidectomy surgery increased the cochlear vibration responses with BC stimulation. The increase was less than 5 dB, except for a canal wall down surgery which gave an increase of up to 8 dB at frequencies close to 10 kHz. The increase was greater at the ipsilateral cochlea compared with the contralateral cochlea. Conclusion: A mastoidectomy surgery increases the vibration at both cochleae for BC stimulation and the increase generally improved with frequency. Obliteration of the surgical cavity does not influence BC sound transmission.Funding Agencies|Swedish hearing research foundation [2017-557]</p
Hearing Through Bone Conduction Headsets
No full textBone conduction (BC) stimulation has mainly been used for clinical hearing assessment and hearing aids where stimulation is applied at the mastoid behind the ear. Recently, BC has become popular for communication headsets where the stimulation position often is close to the anterior part of the ear canal opening. The BC sound transmission for this stimulation position is here investigated in 21 participants by ear canal sound pressure measurements and hearing threshold assessment as well as simulations in the LiUHead. The results indicated that a stimulation position close to the ear canal opening improves the sensitivity for BC sound by around 20 dB but by up to 40 dB at some frequencies. The transcranial transmission ranges typically between -40 and -25 dB. This decreased transcranial transmission facilitates saliency of binaural cues and implies that BC headsets are suitable for virtual and augmented reality applications. The findings suggest that with BC stimulation close to the ear canal opening, the sound pressure in the ear canal dominates the perception of BC sound. With this stimulation, the ear canal pathway was estimated to be around 25 dB greater than other contributors, like skull bone vibrations, for hearing BC sound in a healthy ear. This increased contribution from the ear canal sound pressure to BC hearing means that a position close to the ear canal is not appropriate for clinical use since, in such case, a conductive hearing loss affects BC and air conduction thresholds by a similar amount.Funding Agencies|Meta Reality Labs Research</p
Power Dissipation in the Mammalian Cochlea and Consequences on the Frequency Selectivity
No full textThesis (Ph. D.)--University of Rochester. Department of Mechanical Engineering, 2017.The dimensions of the structures in the cochlea, vibrating in viscous fluid, range from
a few hundred micrometers to just a few micrometers. Flow on such a small scale is expected
to be dominated by the viscosity. Because the viscous dissipation is considered
to be detrimental to the function of sound amplification and frequency tuning, the
cochlea is believed to use cellular actuators to overcome the dissipation. Compared
to the extensive investigations on the cellular actuators, the dissipating mechanisms
have not been given appropriate attention. Many theoretical studies used an inviscid
fluid approximation, and lumped the viscous effect to viscous damping of the cochlear
partition. Others completely neglected viscous dissipation in the cochlear partition,
but considered fluid viscosity. In this work, power dissipation in the mammalian
cochlea was investigated at a tissue and a whole-cochlear level. Tissue level investigation
was performed using a two-dimensional fluid-structure interaction model of the
subtectorial space. The inner hair cell hair bundle stiffness and the size of the gap
between the inner hair cell stereocilia tip and the tectorial membrane were identified
as two main parameters affecting the power dissipation. A closed-form equation for
the hydrodynamic forces from the subtectorial space was suggested to facilitate implementation
into a full cochlear model. Whole-cochlear level power dissipation was
investigated using a computational model of the cochlea incorporating viscous fluid
dynamics, organ of Corti detailed micro-structural mechanics, and electro-physiology
of the outer hair cells. The modelling results suggest that the major energy dissipation
occurs within the organ of Corti complex, as opposed to within the viscous fluid
in the cochlear scalae. A novel claim resulting from the investigation is that power
dissipation in the cochlea can be beneficial for high quality tuning. The dissipation
enhances the tuning quality by limiting the spread of energy from the amplification
site in the cochlear partition
AGRICULTURAL COOPERATIVES AND RURAL DEVELOPMENT
No full textIn this paper the author firstly talks about numerous prejudices that still
exist about cooperatives. The source of these prejudices is the historical period in
which the state fully controlled cooperative movement, compromising and
impeding it. A cooperative, including an agricultural cooperative, is an institution
of a modern society, by which social actor are trying to increase their power at the
market. Agricultural cooperatives exist among farmers both the in the USA and in
the EU.
Each society has been trying to increase its power, which can be seen,
besides other forms, as a quantity of resources that a society possesses. These
resources can be called economic, cultural and social capital. Agricultural
cooperatives represent a lever of rural development, i.e. one of the institutions that
can be used to increase economic, cultural and social capital in an area. The
influence of agricultural cooperatives to employment has two forms: first, they
stimulate self-employment (those who want to engage themselves in agricultural
production know they can join or establish an organization); second, when
agricultural cooperatives invest in industrial plants, the demand for hired labor
increases
Creating New Representations of Yugoslav National Territory
No full textIn the following I will discuss symphonic poem Beograd (»Belgrade«) composed by Serbian author Dragutin Gostuški in 1951, and afterwards used for аmusical »documentary television film« in 1969, in the context of the processes of building new representations of the state territory of socialist Yugoslavia. I will firstly discuss the particular political and social issues of territorial trans-formation in the early socialist Yugoslavia, reflecting on the theoretical issues of nation-state territorial authority and space representations. I will then specifically point out how the new territorial narratives of partisan warfare and rebuilding and development featured in the most poignant and all-pervading musical genre of the time, the mass song. Analysing Gostuški’s symphonic poem, I will show how the topoi established in the mass songs penetrated his symphonic idiom, positioning this work as a part and parcel of the representations of space in the socialist Yugoslavia. Finally, referring to the two versions of the ›script‹ for the documentary film from 1969, I will discuss how the cult of labour and the rising cult of enjoyment were portrayed as parallel to the narrative of partisan warfare and positioned as a part of lived experience of the new socialist urban utopia
The Reading of Rotated Text - An Embodied Account
No full textabstract: Individuals engaged in perceptual tasks often use their bodies to lighten the cognitive load, that is, they replace internal (mental) processing with external (body-based) processing. The present investigation explores how the body is used in the task of reading rotated text. The experimental design allowed the participants to exhibit spontaneous behavior and choose what strategies to use in order to efficiently complete the task. The results demonstrate that the use of external strategies can benefit performance by offloading internal processing.Dissertation/ThesisM.S. Psychology 201
ISMS Core Processes: A Study
No full textAbstractAdjustment and cost-effectiveness are key elements of a successful Information Security Management System (ISMS). ISMS-Processes, as basic elements of every ISMS, need to be aligned to the organization and their mission. Actually a specific ISMS process framework which clearly differentiates between ISMS processes and security measures controlled by ISMS-processes does not exist. ISMS processes itself are not focused in current research. This article will fill this research gap while containing the results of a study to identify criteria for ISMS core processes as well as to identify relevant ISMS core processes
Security Management Standards: A Mapping
No full textAbstractAdjustment and cost-effectiveness are key elements of a successful Information Security Management System (ISMS). ISMS-Processes, as basic elements of every ISMS, need to be aligned to the organization and its mission. As of today, a specific ISMS process framework does not exist. ISMS processes are not in focus of current research. This article aims to fill this research gap by presenting results of a process mapping study regarding ISMS processes in the most important and widely accepted international standards for Information Security Management. Authors propose a set of ISMS processes within an ISMS process framework which should be implemented at an individually appropriate maturity level
