Sound-induced Vibrations Research Articles

Analysis of low frequency sound and sound induced vibration in a Norwegian wooden building

Low frequency sound, in addition to the effects of audible sound, contributes to human annoyance and building damage by inducing building vibration. This involves whole body vibration sensing of humans, and therefore frequencies down to a few Hz become important. Here, the results of a study of low frequency sound and its generation of building vibration and induced indoor sound is presented. The study is conducted by combining both full scale field tests and numerical simulations. It is shown that the low frequency sound interaction with the fundamental frequencies of the building components combined with air leaks in the building envelope are the main factors that govern transmission of sound into the building. Furthermore, radiation from vibrating ceiling and walls seems to be the dominant source of the low frequency indoor sound, and floor vibration is acoustically driven by the indoor sound pressure in the room. Due to the low frequencies in question, tools to predict sound and vibration, and design mitigation measures at low frequencies noise and vibration in building structures are virtually non-existent. To this end, a finite element model combining acoustic wave propagation and structural dynamics presented in this paper provides a first step. Using this model, a number of countermeasures has been tested and some proven effective in this low frequency range.

Acoustic-induced motion of the bushcricket (Mecopoda elongata, Tettigoniidae) tympanum

Bushcrickets have a tonotopically organised hearing organ, the so-called crista acustica, in the tibia of the forelegs. This organ responds to a frequency range of about 5-80 kHz and lies behind the anterior tympanum on top of a trachea branch. We analyzed the sound-induced vibration pattern of the anterior tympanum, using a Laser-Doppler-Vibrometer Scanning microscope system, in order to identify frequency-dependent amplitude and phase of displacement. The vibration pattern evoked by a frequency sweep (4-79 kHz) showed an amplitude maximum which would correspond to the resonance frequency of an open tube system. At higher frequencies of about 30 kHz a difference in the amplitude and phase response between the distal and the proximal part of the tympanum was detected. The inner plate of the tympanum starts to wobble at this frequency. This higher mode in the motion pattern is not explained by purely acoustic characteristics of the tracheal space below the tympanum but may depend on the mechanical impedance of the tympanum plate. In accordance with a previous hypothesis, the tympanum moves over the whole tested frequency range in the dorso-ventral direction like a hinged flap with the largest displacement in its ventral part and no higher modes of vibration.

Spectroscopic visualization of sound-induced liquid vibrations using a supramolecular nanofibre

The question of whether sound vibration of a medium can bring about any kind of molecular or macromolecular events is a long-standing scientific controversy. Although it is known that ultrasonic vibrations with frequencies of more than 1 MHz are able to align certain macromolecules in solution, no effect has yet been reported with audible sound, the frequency of which is much lower (20-20,000 Hz). Here, we report on the design of a supramolecular nanofibre that in solution becomes preferentially aligned parallel to the propagation direction of audible sound. This phenomenon can be used to spectroscopically visualize sound-induced vibrations in liquids and may find application in a wide range of vibration sensing technologies.

The cell biology of hearing

Mammals have an astonishing ability to sense and discriminate sounds of different frequencies and intensities. Fundamental for this process are mechanosensory hair cells in the inner ear that convert sound-induced vibrations into electrical signals. The study of genes that are linked to deafness has provided insights into the cell biological mechanisms that control hair cell development and their function as mechanosensors.

Mechanical feedback amplification in Drosophila hearing is independent of synaptic transmission

Vertebrate inner-ear hair cells use mechanical feedback to amplify sound-induced vibrations. The gain of this 'cochlear amplifier' is centrally controlled via efferent fibres that, making synaptic contacts with the hair cells, modulate the feedback gain. The sensory neurons of the Drosophila ear likewise employ mechanical feedback to assist sound-evoked vibrations, yet whether this neuron-based feedback is also subject to efferent control has remained uncertain. We show here that the function of Drosophila auditory neurons is independent of efferent modulation, and that no synaptic transmission is needed to control the gain of mechanical feedback amplification. Immunohistochemical, mechanical and electrophysiological analyses revealed that the Drosophila auditory organ lacks peripheral synapses and efferent innervations, and that blocking synaptic transmission in a pan-neural manner does not affect the afferent electrical activity of the sensory neurons or the mechanical feedback gain. Hence, unlike the cochlear amplifier of vertebrates, mechanical feedback amplification in Drosophila is not associated with an efferent control system but seems to be a purely local process that is solely controlled peripherally within the ear itself.

Relationship between Helmholtz-resonance absorption and panel-type absorption in finite flexible microperforated-panel absorbers

Microperforated panels (MPPs) can provide wide-band absorption without fibrous and porous materials and are recognized as next-generation absorption materials. Although the fundamental absorbing mechanism of an MPP absorber is Helmholtz-resonance absorption, sound-induced vibration of an MPP itself can affects the absorption characteristics. There have been some studies considering the effects of the sound-induced vibration and there even is a proposal to widen the absorption bandwidth by positively utilizing the vibration of an MPP itself. On the other hand, in a previous study, the relationship between MPP absorbers and panel-type absorbers was investigated with infinite theory. However, the relationship between Helmholtz-resonance absorption and panel-type absorption in finite flexible MPP absorbers has not been clarified. Herein, from the viewpoint of an absorption-characteristics transition with the perforation ratio, the relationship between Helmholtz-resonance absorption and panel-type absorption including the effects of eigen-mode vibrations of the panel is theoretically and experimentally investigated. The analytical model considers a finite flexible MPP supported in a circular duct, and the predicted data for the absorption coefficient under normal incidence is validated by an experiment using an acoustic tube. From this investigation, it is found that panel-type absorption due to eigen-mode vibrations of the panel occurs independently from Helmholtz-resonance absorption, while panel-type absorption due to a mass–spring resonance of a panel and a back cavity has a trade-off relationship with Helmholtz-resonance absorption with respect to the perforation ratio.

A study of sound shielding control of curved piezoelectric sheets connected to negative capacitance circuits

A study is conducted on the control of the sound-induced vibrations of a curved piezoelectric composite sheet connected to a negative capacitance circuit. The amplitudes of the sound-induced vibrations of the sheet are measured using a laser Doppler vibrometer. The piezoelectric voltage generated by the sound and the control voltage of the circuit are also measured. When a normal capacitor is used as a circuit element, the vibration of the sheet over a limited frequency band is selectively attenuated by circuit control. The frequency band is controlled by varying the values of the circuit elements. The effective frequency band is increased over a broad frequency range of 40–200 Hz by installing another composite sheet as a capacitor in the circuit. The frequency characteristics of both the ratio of the amplitude of the control voltage of the circuit to that of the piezoelectric voltage of the sheet and the vibration control level of the circuit are expressed as functions of the absolute value of the complex capacitance ratio and the difference between the loss factors of the circuit and the sheet. A vibration amplitude attenuation of up to 27 dB is achieved when the absolute value is matched with the constant depending on the electromechanical coupling factor of the sheet, and the difference between the loss factors is 0.003.

Power Amplification in the Mammalian Cochlea

It was first suggested by Gold in 1948 [1] that the exquisite sensitivity and frequency selectivity of the mammalian cochlea is due to an active process referred to as the cochlear amplifier. It is thought that this process works by pumping energy to augment the otherwise damped sound-induced vibrations of the basilar membrane [2-4], a mechanism known as negative damping. The existence of the cochlear amplifier has been inferred from comparing responses of sensitive and compromised cochleae [5] and observations of acoustic emissions [6, 7] and through mathematical modeling [8, 9]. However, power amplification has yet to be demonstrated directly. Here, we prove that energy is indeed produced in the cochlea on a cycle-by-cycle basis. By using laser interferometry [10], we show that the nonlinear component of basilar-membrane responses to sound stimulation leads the forces acting on the membrane. This is possible only in active systems with negative damping [11]. Our finding provides the first direct evidence for power amplification in the mammalian cochlea. The finding also makes redundant current hypotheses of cochlear frequency sharpening and sensitization that are not based on negative damping.

Computer modeling and seismic performance assessment of historic Aspendos theatre in Antalya, Turkey

Computer modeling and earthquake simulation of historic structures and monuments is important for understanding their behavior and for predicting their response for preservation and strengthening studies. This paper focuses on analytical and experimental studies conducted on the historic Aspendos theatre, which is a 2200-year-old structure located in Antalya, Turkey. Concerts and performances are still presented at the Aspendos theatre and the recent usage of high decibel amplifiers during concerts generates an increasing amount of concern about the structural safety of the theatre. A detailed 3D-FE model and on-site dynamic acceleration measurements were used to evaluate seismic performance by response-spectrum and time-history analyses. The same model was utilized to evaluate the resonance conditions of slender and lightly damped theatre walls under sound-induced vibrations by equivalent static loading. The maximum tensile stresses calculated for the earthquake loading were several times the assumed tensile capacity of the material and dead load generated compressive stresses, especially at the base and upper corners of the walls. The building is expected to experience heavy structural damage during a possible large earthquake and it may be assumed that the theatre must have been repaired many times during its lifetime. Sound-induced resonance state stresses were relatively less critical but might still pose danger under rare and unfavorable conditions. Vertical reinforcement placement inside the slender walls would improve the out-of-bending capacity while connecting inner and outer walls by two levels of slab would enhance load transfer mechanisms to the perpendicular side walls and improve the theatre’s structural performance.

Vibration Control of Curved Piezoelectric Sheets Using Negative Capacitance Circuits

Sound-induced vibrations of a curved PZT fiber composite sheet have been controlled by a negative capacitance circuit. A laser Doppler vibrometer was used to measure the vibration amplitude. The estimated value of the sound transmission loss was increased up to 85 dB by operating this circuit from 60 dB. The controllable frequency range was increased by using another composite sheet as a capacitor. When compared with the case of a curved PVDF film, the required voltage amplification was reduced to 1/20 because the electromechanical coupling factor was five times greater.

Mechanical Signatures of Transducer Gating in the Drosophila Ear

Hearing relies on dedicated mechanotransducer channels that convert sound-induced vibrations into electrical signals [1]. Linking this transduction to identified proteins has proven difficult because of the scarcity of native auditory transducers and their tight functional integration into ears [2-4]. We describe an in vivo paradigm for the noninvasive study of auditory transduction. By investigating displacement responses of the Drosophila sound receiver, we identify mechanical signatures that are consistent with a direct mechanotransducer gating in the fly's ear. These signatures include a nonlinear compliance that correlates with electrical nerve responses, shifts with adaptation, and conforms to the gating-spring model of vertebrate auditory transduction. Analyzing this gating compliance in terms of the gating-spring model reveals striking parallels between the transducer mechanisms for hearing in vertebrates and flies. Our findings provide first insights into the mechanical workings of invertebrate mechanotransducer channels and set the stage for using Drosophila to specifically search for, and probe the roles of, auditory transducer components.

2523 圧電素子による能動的な音響加振の抑制と遮音(J10-5 振動・音響抑制,J10 知的材料・構造システム)

This paper propose a actuator method of sound-induced vibration control and noise isolation by using a piezo-electric devices-In this research, a hardware experiment has been made for investigate the effectiveness of the proposed controller. The control system is designed by using a mixed H2/H ∞ control, where the weighting functions in frequency domain are designed considering the dynamic characteristics of the smart board.

638 圧電素子による能動的な音響遮音の抑制と遮音

This paper investigates a method of active acoustic vibration control and noise isolation by using a smart board equipped with the piezoelectric actuator. The smart board is designed as a separation wall for preventing the sound propagation through the wall and suppressing the sound-induced vibration. In this research, a hardware experiment has been made for evaluating the effectiveness of the smart board and the proposed controller. The control system is designed by using a mixed H2/H ∞ control, where the weighting functions in frequency domain are designed considering the dynamic characteristics of the smart board.

Regulation of electromotility in the cochlear outer hair cell

Mechanosensory outer hair cells play an essential role in the amplification of sound-induced vibrations within the mammalian cochlea due to their ability to contract or elongate following changes of the intracellular potential. This unique property of outer hair cells is known as electromotility. Selective efferent innervation of these cells within the organ of Corti suggests that regulation of outer hair cell electromotility may be the primary function of the efferent control in the cochlea. A number of studies demonstrate that outer hair cell electromotility is indeed modulated by the efferent neurotransmitter, acetylcholine. The effects of acetylcholine on outer hair cells include cell hyperpolarization and a decrease of the axial stiffness, both mediated by intracellular Ca(2+). This article reviews these results and considers other potential mechanisms that may regulate electromotility, such as direct modification of the plasma membrane molecular motors, alteration of intracellular pressure, and modification of intracellular chloride concentration.

Physical and Functional Interaction between Protocadherin 15 and Myosin VIIa in Mechanosensory Hair Cells

Hair cells of the mammalian inner ear are the mechanoreceptors that convert sound-induced vibrations into electrical signals. The molecular mechanisms that regulate the development and function of the mechanically sensitive organelle of hair cells, the hair bundle, are poorly defined. We link here two gene products that have been associated with deafness and hair bundle defects, protocadherin 15 (PCDH15) and myosin VIIa (MYO7A), into a common pathway. We show that PCDH15 binds to MYO7A and that both proteins are expressed in an overlapping pattern in hair bundles. PCDH15 localization is perturbed in MYO7A-deficient mice, whereas MYO7A localization is perturbed in PCDH15-deficient mice. Like MYO7A, PCDH15 is critical for the development of hair bundles in cochlear and vestibular hair cells, controlling hair bundle morphogenesis and polarity. Cochlear and vestibular hair cells from PCDH15-deficient mice also show defects in mechanotransduction. Together, our findings suggest that PCDH15 and MYO7A cooperate to regulate the development and function of the mechanically sensitive hair bundle.

The Transduction Channel Filter in Auditory Hair Cells

In the first step in auditory transduction, sound-induced vibrations of the stereociliary bundles on the sensory hair cells are converted into electrical signals by opening of mechanotransducer channels. Faithful transduction and hence auditory performance will be limited by the kinetic properties of these channels. We have measured the time course of mechanotransducer currents in turtle and rat auditory hair cells during rapid deflections of the hair bundle. Current activation in the turtle had a time constant that decreased 10-fold with stimulus amplitude to a limiting value of approximately 50 micros. Lowering the external Ca2+ concentration slowed both activation and adaptation time constants. Similar effects were seen in hair cells tuned to low and high frequencies, but the overall kinetics was slower in low-frequency cells. In rat outer hair cells, the time courses of both activation and adaptation were at least 10-fold faster. Although activation kinetics was too fast to characterize accurately, the adaptation time constants in the rat, like the turtle, were Ca2+ dependent and faster in hair cells tuned to higher frequencies. The results imply that mechanotransducer channels operate similarly in turtle and rat but are faster in the mammal to accommodate its higher frequency range of hearing. We suggest that the kinetics of channel activation and adaptation imposes a bandpass filter on transduction, with a center frequency matched to the frequencies detected by the hair cell, which may improve the signal-to-noise ratio near threshold.

Effects of coiling on the micromechanics of the mammalian cochlea

The cochlea transduces sound-induced vibrations in the inner ear into electrical signals in the auditory nerve via complex fluid-structure interactions. The mammalian cochlea is a spiral-shaped organ, which is often uncoiled for cochlear modelling. In those few studies where coiling has been considered, the cochlear partition was often reduced to the basilar membrane only. Here, we extend our recently developed hybrid analytical/numerical micromechanics model to include curvature effects, which were previously ignored. We also use a realistic cross-section geometry, including the tectorial membrane and cellular structures of the organ of Corti, to model the apical and basal regions of a guinea-pig cochlea. We formulate the governing equations of the fluid and solid domains in a curvilinear coordinate system. The WKB perturbation method is used to treat the propagation of travelling waves along the coiled cochlear duct, and the O(1) system of the governing equations is solved in the transverse plane using finite-element analysis. We find that the curvature of the cochlear geometry has an important functional significance; at the apex, it greatly increases the shear gain of the cochlear partition, which is a measure of the bending efficiency of the outer hair cell stereocilia.

Tuning of host plants with vibratory songs ofNezara viridulaL(Heteroptera: Pentatomidae)

Songs of the southern green stink bug Nezara viridula L, recorded on a non-resonant loudspeaker membrane, reflect frequency characteristics of body vibrations. The song dominant frequency directly depends on the repetition rate of potentials recorded from synchronously contracting muscles that vibrate the abdomen during singing. Spectra of naturally emitted signals recorded on the pronotum of a singing bug or on a plant contain peaks characteristic of plant resonant spectra. The dominant resonant frequency of sound-induced vibrations in bean and other stink bug host plants ranges between 160 and 215 Hz and subdominant peaks do not exceed 600 Hz. There is no correlation between spectral peak positions and recording points on a plant. The dominant resonance peak corresponds to the best frequency sensitivity of N. viridula middle frequency subgenual receptor cell. Subdominant peaks around and below 100 Hz lie close to the dominant frequency of body vibrations during singing and to the range of best frequency sensitivity of low frequency receptor cells. Tuning of plant resonant frequencies with spectral properties of songs and frequency sensitivity of sensory organs is discussed in the context of stink bug substrate-borne communication.

Sound-induced differential motion within the hearing organ

Hearing depends on the transformation of sound-induced basilar membrane vibration into deflection of stereocilia1 on the sensory hair cells, but the nature of these mechanical transformations is unclear. Using new techniques to visualize and measure sound-induced vibration deep inside the moving organ of Corti, we found that two functionally crucial structures, the basilar membrane and the reticular lamina, have different centers of rotation, leading to shearing motion and rapid deformation for the mechanoreceptive outer hair cells. Structural relations within the organ of Corti are much more dynamic than previously thought, which clarifies how outer hair cell molecular motors can have such a powerful effect.

Motion generation by Drosophila mechanosensory neurons.

In Drosophila melanogaster, hearing is supported by mechanosensory neurons transducing sound-induced vibrations of the antenna. It is shown here that these neurons additionally generate motions that mechanically drive the antenna and tune it to relevant sounds. Motion generation in the Drosophila auditory system is betrayed by the auditory mechanics; the antenna of the fly nonlinearly alters its tuning as stimulus intensity declines and oscillates spontaneously in the absence of sound. The susceptibility of auditory motion generation to mechanosensory mutations shows that motion is generated by mechanosensory neurons. Motion generation depends on molecular components of the mechanosensory transduction machinery (NompA, NompC, Btv, and TilB), apparently involving mechanical activity of ciliated dendrites and microtubule-dependent motors. Hence, in analogy to vertebrate hair cells, the mechanosensory neurons of the fly serve dual, transducing, and actuating roles, documenting a striking functional parallel between the vertebrate cochlea and the ears of Drosophila.