1,720,963 research outputs found
Testing a Model of Stimulus Frequency Otoacoustic Emissions in Humans
No full textIn recent theories of cochlear mechanics, it has been proposed that spontaneous, transiently evoked and stimulus frequency otoacoustic emissions originate from scattering of a "tall and broad" travelling wave (TW) with a random spatial distribution of cochlear inhomogeneities.In the first theory, the periodicity is determined predominantly by the wavelength of the TW near its peak amplitude, whilst in the second it is determined by the spatial period of the corrugations, and is therefore largely independent of TW wavelength. The aim of this thesis is to test these two rival theories in humans by attempting to induce changes in the TW wavelength through ipsilateral acoustic suppression, whilst measuring any accompanying changes in the periodicity of stimulus frequency otoacoustic emissions (SFOAE).For both theories, a one-dimensional longwave model of cochlear mechanics was developed including representations of the two scattering mechanisms and of nonlinear cochlear active processes. Detailed predictions of the changes in SFOAE periodicity under conditions of self-suppression and high-side, two-tone suppression were then made from both models. In the model with random inhomogeneities, the periodicity clearly increased with the extent of self-suppression, and decreased with the extent of two-tone suppression. In sharp contrast, in the model with regular spatial corrugations, no change in periodicity occurred in either case. SFOAE periodicity generally increased with the extent of self-suppression and decreased with the extent of high-side, two-tone suppression. This result was interpreted as strong evidence favouring the theory of spatially random inhomogeneities over the rival theory of regular spatial corrugations, thereby enhancing understanding of the mechanism for generation of otoacoustic emissions.</p
The effect of recreational noise exposure on hearing thresholds, TEOAEs, and DPOAE above 8 kHz
No full textAn asymmetric Duffing oscillator: hysteretic behaviour and jump phenomena
No full textThe primary resonance response of a non-linear oscillatory system that is excited by both a
constant and a harmonic force is investigated in this study. The equation of motion is the
asymmetric Duffing equation with no linear term and with hardening cubic non-linearity. An
approximate solution corresponding to the steady-state response is sought by the harmonic
balance method. Its stability is studied by applying Floquet theory. Numerical simulations are
also given to confirm the analytical results. It is found that the frequency-response curves of
the harmonic response can be single-valued or multi-valued with different shapes depending
on the values of the system parameters. First, when they are single-valued, their shape is
similar to the response of a linear system. Second, if they are multi-valued, they can have a
maximum of three or five steady-state values. In this group, several different shapes can be
distinguished: one in which the peak is bent to the right, as is for a hardening Duffing
oscillator; another, when it is bent to the left, as is for a softening Duffing oscillator; finally,
there exist responses that have a double bend - first towards lower frequencies, and then
towards higher frequencies. The multivaluedness of these curves causes the occurrence of the
multiple jumps in the system. It is possible for the system to exhibit one or two jumps when
increasing frequency and one or two jumps when decreasing frequency. The effects of
different parameters on the system behaviour are analysed. The analogy between the
asymmetric Duffing equation and the Helmoltz-Duffing equation is also discusse
Non-medical bone-conduction devices for management of glue-ear: performance characteristics and the effect of contact force
No full textSome children with otitis media with effusion (OME) are using low-cost bone-conduction (BC)headsets to improve speech intelligibility in classrooms or for use with personal listening devices. The poster presents results on three aspects of the “Hear Glue Ear” device, which comprises a BC headset paired with a blue-tooth microphone. These are:1. The frequency and amplitude responses of the bone-vibrator force as measured on an artificial mastoid,2. The airborne sound emitted from device as measured using an acoustic mannequin,3. The effect of the contact force between the BC transducer and the skull on the speech intelligibility in participants with simulated conducted hearing losses
On the resonance response of an asymmetric Duffing oscillator
No full textThe primary resonance response of an asymmetric Duffing oscillator with no linear stiffness term and with hardening characteristic is investigated in this paper. An approximate solution corresponding to the steady-state response is sought by applying the harmonic balance method. Its stability is also studied. It is found that different shapes of frequency–response curves can exist. Multiple-valued solutions, indicating the occurrence of jump phenomena, are observed analytically and confirmed numerically. The influence of the system parameters on the primary resonance response is also examine
Effect of a static force on the dynamic behaviour of a harmonically excited quasi-zero stiffness system
No full textThis paper concerns the way in which a static force can dramatically change the dynamic behaviour of a harmonically excited quasi-zero stiffness single-dof system. The primary resonance response of the system is considered using the harmonic balance method and the results are verified numerically. It is found that the system changes its characteristic from being purely hardening to a mixed softening and hardening characteristic and finally to a purely softening characteristic as the static force increases from zero. Consequently for certain values of the static force multiple jumps can occur. Five different cases of a possible response are distinguished and related to the values of the static force. It is also found that just one harmonic is required to qualitatively describe the behaviour of the system. The inclusion of a second harmonic in the solution does result in changes to the response, especially the softening behaviour, but overall it has a small effect for the system parameters chosen in this paper, which is representative of a quasi-zero stiffness isolator. The influence of damping is also considered
Age, high-frequency hearing function and speech perception in real-world settings: a cross-sectional study
No full textSensory unpleasantness of very-high frequency sound and audible ultrasound
No full textAudible very-high frequency sound (VHFS) and ultrasound (US) have been rated more unpleasant than lower frequency sounds when presented to listeners at similar sensation levels (SLs). In this study, 17 participants rated the sensory unpleasantness of 14-, 16-, and 18-kHz tones and a 1-kHz reference tone. Tones were presented at equal subjective loudness levels for each individual, corresponding to levels of 10, 20, and 30 dB SL measured at 1 kHz. Participants were categorized as either “symptomatic” or “asymptomatic” based on self-reported previous symptoms that they attributed to exposure to VHFS/US. In both groups, subjective loudness increased more rapidly with sound pressure level for VHFS/US than for the 1-kHz reference tone, which is consistent with a reduced dynamic range at the higher frequencies. For loudness-matched tones, participants rated VHFS/US as more unpleasant than that for the 1-kHz reference. These results suggest that increased sensory unpleasantness and reduced dynamic range at high frequencies should be considered when designing or deploying equipment which emits VHFS/US that could be audible to exposed people.</p
Measuring speech recognition and quality of life in Arabic children with OME using the PAAST SiQ and Arabic OM-6 questionnaire
No full textBackground: otitis media with effusion (OME) is the most common cause for conductive hearing loss in children and is associated with poor quality of life (QoL). The Paediatric Arabic Auditory Speech Test in Quiet (PAAST SiQ) and Arabic OM-6 (AOM-6) are investigated in this study as tools to measure speech recognition threshold (SRT) and QoL, respectively, in Arabic children with OME.Aims and objectives: (1) to investigate the relationship between SRTs, OME condition and PTA Threshold, and (2) to investigate the relationship between the AOM-6 scores and SRTs. Study design: 50 children between the ages 3 and 5.9 years with confirmed OME (unilateral or bilateral) were tested using PAAST SiQ to measure their SRTs for each ear. The child’s main care giver filled the AOM-6 questionnaire.Results and conclusion: preliminary results show a significant positive relationship between PTA threshold and SRT, which may indicates the PAAST SiQ’s potential for predicting hearing threshold. Further analysis will be discussed in the conference
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