Search results for "Acoustic impedance"
showing 10 items of 12 documents
On the variations of acoustic absorption peak with particle velocity in micro-perforated panels at high level of excitation.
2010
The acoustic behavior of micro-perforated panels (MPP) is studied theoretically and experimentally at high level of pressure excitation. A model based on Forcheimer's regime of flow velocity in the perforations is proposed. This model is valid at relatively high Reynolds numbers and low Mach numbers. The experimental method consists in measuring the acoustical pressure at three different positions in an impedance tube, the two measurement positions usually considered in an impedance tube and one measurement in the vicinity of the rear surface of the MPP. The impedance tube is equipped with a pressure driver instead of the usual loudspeaker and capable of delivering a high sound pressure lev…
Acoustic characterization of Silica aerogel clamped plates for perfect absorption purpose
2017
International audience; Silica aerogel has been widely studied as bulk material for its extremely low density and thermal conductivity. Plates or membranes made of this extremely soft materials exhibits interesting properties for sound absorption. A novel signal processing method for the characterization of an acoustic metamaterial made of silica aerogel clamped plates is presented. The acoustic impedance of a silica aerogel clamped plate is derived from the elastic theory for the flexural waves, while the transfer matrix method is used to model reflection and transmission coefficients of a single plate. Experimental results are obtained by using an acoustic impedance tube. The difference b…
Assessing audiological, pathophysiological and psychological variables in tinnitus patients with or without hearing loss
2010
The aim of this work is to study the characteristics of tinnitus both in normal hearing subjects and in patients with hearing loss. The study considered tinnitus sufferers, ranging from 21 to 83 years of age, who were referred to the Audiology Section of Palermo University in the years 2006–2008. The following parameters were considered: age, sex, hearing threshold, tinnitus laterality, tinnitus duration, tinnitus measurements and subjective disturbance caused by tinnitus. The sample was divided into Group1 (G1), 115 subjects with normal hearing, and Group2 (G2), 197 subjects with hearing loss. Especially for G2, there was a predominance of males compared to females (P = 0.011); the highest…
Acoustic Airway Profiles in Unilateral Cleft Palate Patients
1999
Objective: This study investigates the nasal airway in unilateral cleft palate patients by means of a noninvasive, objective diagnostic method that provides topographic information about the airway profile. Design: A consecutive sample of patients was measured. Setting: Cleft palate rehabilitation center of the University of Mainz, Germany. Patients: Forty-nine subjects were investigated: 34 full-grown patients with complete unilateral cleft lip and palate and 15 controls with subjective normal nasal patency. Intervention: A transnasal series of three acoustic measurements of nasal volume was performed per nostril; measurements were taken both before and after decongestion with 0.3 mg xylom…
Eustachian Tube Function Assessment after Radiofrequency Turbinate Reduction in Atopic and Non-Atopic Patients.
2021
(1) Background: Inferior turbinates&rsquo
Risk factors for otitis media with effusion: Case–control study in Sicilian schoolchildren
2011
Objective To identify the prevalence and demographic, maternal and child risk factors for otitis media with effusion (OME) in Sicilian schoolchildren and analyse the results with reference to the review of the literature. Methods Associations of possible risk factors with prevalence of otitis media with effusion (OME) were studied in a cohort of 2097 children, aged 5–14 years. In order to determine OME, otoscopy and tympanometry were performed at 3-monthly intervals beginning at term date. Sixteen epidemiologically relevant features were inventoried by means of standardized questionnaires and skin tests were performed. Univariate analysis was performed to examine the association between det…
The role of atopy in otitis media with effusion among primary school children: audiological investigation
2010
The objective of this study was to evaluate the role of atopy in otitis media with effusion (OME) in children attending primary school in western Sicily focusing on the audiological characteristics among atopic and non-atopic subjects suffering from OME. A total of 310 children (5-6 years old) were screened by skin tests and divided into atopics (G1) and non-atopics (G2). The samples were evaluated for OME by pneumatic otoscopy, tympanogram and acoustic reflex tests. The parameters considered were: documented persistent middle ear effusion by otoscopic examination for a minimum of 3 months; presence of B or C tympanogram; absence of ipsilateral acoustic reflex and a conductive hearing loss …
Prelingual sensorineural hearing loss and infants at risk: Western Sicily report.
2013
Objective: To evaluate independent etiologic factor associated with sensorineural hearing loss (SNHL) in newborn at risk; to study the role of their interaction especially in NICU infants who present often multiple risk factors for SNHL. Methods: The main risk factors for SNHL reported by JCIH 2007 were evaluated on 508 infant at risk ranging from 4 to 20 weeks of life, transferred to the Audiology Department of Palermo from the main births centers of Western Sicily. After a global audiological assessment, performed with TEOAE, tympanometry and ABR, the prevalence and the effect of risk factors was statistically studied through univariate and multivariate analysis on the total population (n…
Reverberation reduction in capacitive micromachined ultrasonic transducers (CMUTs) by front-face reflectivity minimization
2015
Abstract Front-face acoustic reflectivity of ultrasonic imaging transducers, due to acoustic impedance mismatch with the propagation medium, may cause reverberation phenomena during wideband pulse-echo operation. Front-face reflectivity may be reduced by promoting the transmission of the echoes, received from the medium, to the transducer backing, and by maximizing the mechanical-to-electrical energy conversion and dissipation by tuning the electrical load impedance connected to the transducer. In Capacitive Micromachined Ultrasonic Transducers (CMUTs), the energy transfer from the medium to the backing is very low due to the large impedance mismatch between the medium and the transducer su…
Long Lived Acoustic Vibrational Modes of an Embedded Nanoparticle
2004
Classical continuum elastic calculations show that the acoustic vibrational modes of an embedded nanoparticle can be lightly damped even when the longitudinal plane wave acoustic impedances $Z_o=\rho v_L$ of the nanoparticle and the matrix are the same. It is not necessary for the matrix to be less dense or softer than the nanoparticle in order to have long lived vibrational modes. Continuum boundary conditions do not always accurately reflect the microscropic nature of the interface between nanoparticle and matrix, and a multi-layer model of the interface reveals the possibility of additional reduction of mode damping.