Mouse models are key tools for studying cochlear alterations in noise-induced hearing loss (NIHL) and for evaluating new therapies. Stimuli used to induce deafness in mice are usually white and octave band noises that include very low frequencies, considering the large mouse auditory range. We designed different sound stimuli, enriched in frequencies up to 20 kHz (“violet” noises) to examine their impact on hearing thresholds and cochlear cytoarchitecture after short exposure. In addition, we developed a cytocochleogram to quantitatively assess the ensuing structural degeneration and its functional correlation. Finally, we used this mouse model and cochleogram procedure to evaluate the potential therapeutic effect of transforming growth factor β1 (TGF-β1) inhibitors P17 and P144 on NIHL. CBA mice were exposed to violet swept-sine noise (VS) with different frequency ranges (2–20 or 9–13 kHz) and levels (105 or 120 dB SPL) for 30 min. Mice were evaluated by auditory brainstem response (ABR) and otoacoustic emission tests prior to and 2, 14 and 28 days after noise exposure. Cochlear pathology was assessed with gross histology; hair cell number was estimated by a stereological counting method. Our results indicate that functional and morphological changes induced by VS depend on the sound level and frequency composition. Partial hearing recovery followed the exposure to 105 dB SPL, whereas permanent cochlear damage resulted from the exposure to 120 dB SPL. Exposure to 9–13 kHz noise caused an auditory threshold shift (TS) in those frequencies that correlated with hair cell loss in the corresponding areas of the cochlea that were spotted on the cytocochleogram. In summary, we present mouse models of NIHL, which depending on the sound properties of the noise, cause different degrees of cochlear damage, and could therefore be used to study molecules which are potential players in hearing loss protection and repair.

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A theoretical and experimental study of a proposed hybrid passive–active plane-wave system to provide broadband acoustic absorption is presented. The passive absorber consists of a microperforated panel (MPP), used in place of conventional fibrous materials, in front of an air layer. The active system uses an active transducer (a loudspeaker), an error sensor (a microphone), and an adaptive controller. MPPs are thinner than fibrous materials and provide a better solution in hygienic environments. For two such systems, the dependence of performance on MPP parameters is studied for two control strategies: impedance matching and pressure release. The first condition is found to be better for cases where the acoustic impedance of the system approaches that of air. Otherwise, the pressure-release condition is better, and a wideband solution is the implementation of the active control system up to a frequency where the natural band of the passive system provides higher absorption. Therefore, the use of a low-pass filter in the error signal is implemented to afford hybrid passive–active wideband absorption. The control effort of active system is also considered. Experimental verification shows good agreement with theory, and an average absorption coefficient of 0.82 in the frequency bandwidth 100 to 1600 Hz was achieved.

Scientific evidence has proved reorganisation processes in the auditory cortex after sensorineural hearing loss and overstimulation of certain tonotopic cortical areas, as we see in auditory conditioning techniques. Acoustic rehabilitation reduces the impact of these reorganisation changes. Recent theories explain tinnitus mechanisms as a negative consequence of neural plasticity in the central nervous system after a peripheral aggression. Auditory discrimination training (ADT) could partially reverse the wrong changes in tonotopic representation and improve tinnitus. We discuss different studies and their efficacy on tinnitus perception and annoyance. Indications, method, dose and sound strategy need to be implemented.

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Bloch-like surface waves associated with a quasiperiodic structure are observed in a classic wave propagation experiment which consists of pulse propagation with a shallow fluid covering a quasiperiodically drilled bottom. We show that a transversal pulse propagates as a plane wave with quasiperiodic modulation, displaying the characteristic undulatory propagation in this quasiperiodic system and reinforcing the idea that analogous concepts to Bloch functions can be applied to quasicrystals under certain circumstances.PACS numbers: 47.35.+i, 47.54.+r, 71.23.Ft The main difficulty towards the development of a systematic analytic approach to the transport properties of quasiperiodic systems has been the absence of an analogous Bloch theorem approach as used in the periodic case. In the first efforts to apply a modified version of the Bloch theorem, it was noticed that the dense spectrum of quasiperiodic systems is dominated by only a few special reciprocal lattice points that may be taken to construct a quasi-Brillouin zone [1]. Thus, by considering only the dominant Fourier components, the atomic distribution can be expanded in terms of a discrete aperiodic lattice. Wave functions of the form Ψ k = u k (r)e ik·r will therefore solve the Schrodinger equation. In this case u k is quasiperiodic and should formally be defined on a countable dense set of reciprocal lattice vectors. But, by the above considerations, this expansion is useful since the Fourier development of the modulation function u k can be restricted to the few special reciprocal vectors that dominate the spectra. Thus, Bloch-like states could describe the plane wave propagation in so schematized quasicrystals and free-electron-like bands are expected. Recently this idea was experimentally tested showing that analogous concepts to Bloch functions can be applied to quasicrystals [2].The classic wave propagation in quasicrystalline systems was addressed in a first seminal acoustic experiment of He and Maynard [3] by the feature that acoustical waves are ideal tools to investigate formally similar * Electronic address: manolo@iec.csic.es † Electronic address: aragon@fata.unam.mx quantum propagation effects [4]. On the other hand, appearance of the quasicrystalline symmetry in fluids dynamics was firstly predicted theoretically by Zaslavsky and co-workers [5] and a simulation similar to the conditions of the present experiments was reported in Ref. [6]. Finally, compressible quasisymmetric flows were considered in Ref. [7], whereas a general outlook on order and disorder in fluid motion can be found in the experiments of Gollub [8].In this letter we shall see that a discrete restricted spectral scenario can be displayed by means of impulsive waves in hydrodynamic quasicrystals, where we observe Bloch-like surface waves. The waves are generated at the frequencies corresponding to the Fourier components of the quasiperiodic structure at the dominant diffraction spots. The observed Bloch-like waves are plane waves with quasiperiodic modulation generated ...

A hybrid model describing the acoustic properties of plates with macroperforations that can be unevenly distributed on the plate surface and backed by woven or precision woven meshes with microscopic perforations is proposed. The plate perforations may be of circular or rectangular shapes.Since the perforated plate may not necessarily be considered as an equivalent fluid, its surface impedance is calculated by the Maa model [Noise Control Eng. J. 29, 77-84 (1987)], whereas the Johnson-Champoux-Allard model [J. Appl. Phys. 70, 1975-1979(1991] is used for the mesh, considered as an equivalent fluid. A simple model for the elementary cell of the mesh structure is proposed in order to calculate a parameter that can be considered as the thermal length. It is shown that, this thermal length can be smaller than the length considered as the viscous length. An effective airflow resistivity is introduced to account for the increase of particle velocity through the mesh placed behind the carrying macroperforated plate and is used in the transfer matrix approach to obtain the impedance of the whole multilayer system. The hybrid model seems to represent a good approach of this multilayer system. The theoretical predictions are compared with experimental measurements.