Audible Frequency Range Research Articles

Determination of Coupling Loss Factors Between Two Plates Joined at a Right Angle Using the Wave Approach

Abstract Vibration transmission through two homogenous isotropic plates, joined at a right angle to each other, is studied using a wave approach in the audible frequency range. In this study, a generalized mathematical model is developed for the right-angled joint using a spring and dashpot model, which represents welded, riveted, and bolted joints. The energy transfer for the spring-dashpot model is determined in terms of transmission and reflection efficiencies of the aforementioned joints. The effect of variation of stiffness and damping of the joints on the transmission and reflection efficiencies is studied for variation in the coupled plate thickness and density ratio. The transmission efficiency is used to theoretically determine the coupling loss factor (CLF), which is an important parameter of statistical energy analysis (SEA) models. It is observed that with an increase in the mass of the second plate, it acts as a blocking mass to energy transfer. Experiments were performed on two mild steel plates connected using weld, rivet, and bolt joints to determine the CLFs for the joints and to verify the theoretical model. The CLFs determined from experiments and predicted using the wave approach were compared with those determined from the power injection method (PIM).

Sensitivity and Performances Analysis of a Dynamic Pressure Narrow-Band Electrodynamic Micro-Sensor

This paper presents analytic and numerical modelling of a MEMS electrodynamic micro-sensor of dynamic pressure. Two coaxial planar inductors of different diameters are used in the proposed micro-sensor design. Using finite element analysis, the diaphragm resonant frequency and dynamic displacements are evaluated for different diaphragm thicknesses. Then, the total sensitivity is deduced by coupling different physical domains which contribute in the micro-sensor operation. A lumped element model is built in order to study the micro-sensor sensitivity and define the dynamic performance for different resonant frequencies. This model shows that the best sensitivity, within the mV/Pa range, is obtained around the resonant frequency when operation in the audible frequency range, and decreases to the uV/Pa range for ultrasonic frequencies. The obtained sensitivity curves prove that the undamped inductive micro-sensor can offer high pressure sensitivity within a narrow frequency bandwidth.

Nonlinear optical re-orientation and photoacoustic properties of indium tin oxide nanoparticles

Abstract The nonlinear optical Kerr effect of indium tin oxide (ITO) nanoparticles (NPs) was investigated using continuous wave laser beams. ITO NPs were synthesized using the sol-gel method and were prepared as a colloid and a thin film. The structural and optical properties of the synthesized particles were characterized by X-ray diffraction analysis, transmission electron microscopy and UV–visible spectroscopy. The energy band gap was found to be 3.45 eV. The nonlinear optical properties of these NPs were measured by two sources: one He–Ne laser beam and a diode laser beam at wavelengths of 632.8 nm and 450 nm, respectively. For the He–Ne laser beam, the obtained nonlinear refractive index was found to be n 2 = + 1.7 × 10 − 7 c m 2 W , which its plus sign indicates that the main nonlinear refractive phenomenon involved was the optical re-orientation effect due to the electric dipole moment of the particles. The high nonlinear absorption of the particles at both wavelengths leads to the creation of intensity-dependent photoacoustic (PA) signals that are mainly in the audible range of sound frequencies. The sonic waves were within a frequency interval of 2–19 KHz. The ITO particles were present as NPs, which simultaneously show optical re-orientation and PA responses under continue wave (CW) laser irradiations. This research thus finds that ITO NPs are a good candidate for electro-optical sensors and applications.

Evolution of Low-Frequency Band Gaps Using X-Shapes and Single-Sided Stubbed Phononic Crystals

In this work, the evolution of dispersion relations of 2D asymmetric phononic crystals in the low-frequency range is introduced and discussed. Two phononic crystal structures are proposed and calculated using Finite Element method. The first one is a thin plate from PDMS with a circular one-side stubbed from tungsten and the other is a thin plate in the X-shape from rubber and tungsten. The effects of some parameters such as stub height and diameter on the phononic band gap value are studied. Low-frequency band gaps can be found in both structures with frequencies corresponding to the audible sound frequency range. The symmetry and shape of the stub has a remarkable influence on the band structures. Where, the proposed one-side stubbed exhibits a phononic band gap in a lower frequency range compared with the published studies about the double side stubbed. Furthermore, with the same thickness value the band gap value was reduced in the X-shape phononic stub compared with the one-side stubbed. These results may be useful for the low-frequency and noise suppression devices.

Feasibility Study of GaN-based MEMS capacitive microphone using Finite Element Method

Gallium nitride (GaN) is an excellent choice of semiconductor material due to its optoelectronic, mechanical and wide bandgap properties which are highly demanded by high-power and radio-frequency (RF) electronics but also widely employed for the fabrication of Light Emitting Diode (LED). In this paper, we explored the advantage of GaN as an electromechanical material to be used in microelectromechanical systems (MEMS) microphone as a thin film membrane through a theoretical study performed using the finite element method. We consider also the anisotropy and symmetry structural of GaN to be employed as microphone membrane. In addition, we compared also its performance in terms of sensitivity, C-V measurement and pull-in voltage with several conventional membrane materials such as silicon, nickel, and silicon nitride. The result shows that GaN-based MEMS capacitive microphone has sensitivity -57 dBV/Pa which is 4% higher than silicon nitride-based microphone and resonance frequency of 19 kHz which is higher 11.3% than nickel-based microphone. Hence, this theoretical study could pave a way for GaN to be developed especially for MEMS microphone applications and boasted also by the recent advancement of GaN related fabrication. The advantages of GaN compared to other conventional semiconductor material could be useful for the development of ultrasonic MEMS microphone for utilize detection of sound beyond audible frequency range.

A multimodal auditory equal-loudness comparison of air and bone conducted sounds

The term ‘multimodal’ typically refers to the combination of two or more sensory modalities; however, through the advancement of technology, modality variations within specific sensory systems are being discovered and compared in regards to physiological perception and response. The ongoing evaluation of air vs bone conduction auditory perception modalities is one such comparison. Despite an increased awareness of the potential benefits of utilizing bone conduction pathways, a complete understanding of the human auditory system, more specifically, the relationship between air conducted and bone conducted sound remains a critical deficiency hindering the development of advanced multimodal auditory displays. Conduction equivalency ratios (CERs), which were defined as the difference in sound intensity levels (in dB) between equally loud signals transmitted in air conduction (AC) (sound field) and bone conduction (BC) modes provided a link between these two modes of hearing by determining the relationship between spectral content of AC and BC sound. The current report aims to describe, in depth, the establishment of such CERs at three BC transducer contact locations on a listener’s head over a range of audible frequencies presented over three signal intensities within a controlled free-field listening environment. Results indicated the AC–BC relationship is not unique and depends on sound intensity, frequency, and BC transducer location. In addition, in terms of head sensitivity, results support similar findings which indicate that the Mastoid and Condyle locations can be considered interchangeable in terms of their frequency-related sensitivity while the Forehead was found to be considerably less sensitive compared to the other locations.

Preparation and Characterization of Freely-Suspended Graphene Nanomechanical Membrane Devices with Quantum Dots for Point-of-Care Applications.

We demonstrate freely suspended graphene-based nanomechanical membranes (NMMs) as acoustic sensors in the audible frequency range. Simple and low-cost procedures are used to fabricate NMMs with various thicknesses based on graphene layers grown by graphite exfoliation and solution processed graphene oxide. In addition, NMMs are grafted with quantum dots (QDs) for characterizing mass sensitive vibrational properties. Thickness, roughness, deformation, deflection and emissions of NMMs with attached QDs are experimented and analyzed by utilizing atomic force microscopy, Raman spectroscopy, laser induced deflection analyzer and spectrophotometers. Förster resonance energy transfer (FRET) is experimentally achieved between the QDs attached on NMMs and nearby glass surfaces for illustrating acousto-optic utilization in future experimental implementations combining vibrational properties of NMMs with optical emission properties of QDs. This property denoted as vibrating FRET (VFRET) is previously introduced in theoretical studies while important experimental steps are for the first time achieved in this study for future VFRET implementations. The proposed modeling and experimental methodology are promising for future novel applications such as NMM based biosensing, photonics and VFRET based point-of-care (PoC) devices.

Analysis and classification of acoustic scenes with wavelet transform-based mel-scaled features

Analysis of audio from real-life environments and their categorization into different acoustic scenes can make context-aware devices and applications more efficient. Unlike speech, such signals have overlapping frequency content while spanning a much larger audible frequency range. Also, they are less structured than speech/music signals. Wavelet transform has good time-frequency localization ability owing to its variable-length basis functions. Consequently, it facilitates the extraction of more characteristic information from environmental audio. This paper attempts to classify acoustic scenes by a novel use of wavelet-based mel-scaled features. The design of the proposed framework is based on the experiments conducted on two datasets which have same scene classes but differ with regard to sample length and amount of data (in hours). It outperformed two benchmark systems, one based on mel-frequency cepstral coefficients and Gaussian mixture models and the other based on log mel-band energies and multi-layer perceptron. We also present an investigation on the use of different train and test sample duration for acoustic scene classification.

A laboratory study for occupational safety and health on the structure of airborne ultrasound fields

While exposure to airborne ultrasound is increasing in occupational contexts and in public and private spaces, existing demand for reliable and traceable determination of exposure to sound with frequencies above 16 kHz cannot currently be satisfied due to a lack of adequate measurement devices and procedures adapted to the specifics of airborne ultrasound. So that this study may serve as a first step for the development of a novel measurement procedure, its aim is to create a comprehensive database of the structures of airborne ultrasound fields present in occupational contexts. Based on this, the limitations of measurement procedures commonly used in the audible frequency range are clarified and the structural characteristics of airborne ultrasound fields investigated. This paper presents a laboratory study of the structure of the airborne ultrasound field of an ultrasonic welding machine, which can be considered a representative occupational source of airborne ultrasound. For this study, the technical and procedural requirements of a measuring system are derived and used to set up and calibrate a measuring system for three-dimensional, high spatial resolution scans of sound pressure levels in the laboratory. The measurement results reveal complex, extensive and very fine-structured interference patterns, some of which have sound pressure levels of up to 138 dB (re 20 μPa).

2Pa1-1 Characteristics of Wave Propagation on Honeycomb Sandwich Panel in Audible Frequency Range

2Pa1-1 Characteristics of Wave Propagation on Honeycomb Sandwich Panel in Audible Frequency Range

Comparative analysis of mechanical characteristics of different topologies of the cantilever beam to mimic the function of the cochlea

According to the World Health Organization (WHO), approximately 5% of the world’s population has a hearing loss disability caused by various reasons. The cochlea is a spiral-shaped bone found in the inner ear that is capable of doing exceptional sound analysis, in terms of both frequency and intensity which allows the perception of sound frequency in the range of 20 Hz to 20 kHz. An artificial basilar membrane having various shapes has been developed but none of those covers the whole human audible frequency range. This paper compares the mechanical characteristics of the rectangular and taper piezoelectric cantilever to develop an artificial basilar membrane that mimics the human cochlea with high sensitivity. The cantilever beam is made up of molybdenum (Mo), aluminum nitride (AlN), tungsten (W) and the desired frequency range is obtained by varying the length and thickness of the cantilever beams. The 3D design and simulations were performed by COMSOL Multiphysics to study the Eigen frequency, displacement, and stress measurements of the cantilever. The Eigen frequency is observed to be increased with an increase in the thickness and decrease in the length for both rectangular and taper cantilever beam. The rectangular beam showed higher sensitivity and lower stresses compared to the taper beam. Therefore, the rectangular cantilever beam is more suitable to mimic the basilar membrane of the human cochlea.

Ultrasensitive Anti-Interference Voice Recognition by Bio-Inspired Skin-Attachable Self-Cleaning Acoustic Sensors.

Human voice recognition systems (VRSs) are a prerequisite for voice-controlled human-machine interfaces (HMIs). In order to avoid interference from unexpected background noises, skin-attachable VRSs are proposed to directly detect physiological mechanoacoustic signals based on the vibrations of vocal cords. However, the sensitivity and response time of existing VRSs are bottlenecks for efficient HMIs. In addition, water-based contaminants in our daily lives, such as skin moisture and raindrops, normally result in performance degradation or even functional failure of VRSs. Herein, we present a skin-attachable self-cleaning ultrasensitive and ultrafast acoustic sensor based on a reduced graphene oxide/polydimethylsiloxane composite film with bioinspired microcracks and hierarchical surface textures. Benefitting from the synergetic effect of the spider-slit-organ-like multiscale jagged microcracks and the lotus-leaf-like hierarchical structures, our superhydrophobic VRS exhibits an ultrahigh sensitivity (gauge factor, GF = 8699), an ultralow detection limit (ε = 0.000 064%), an ultrafast response/recovery behavior, an excellent device durability (>10 000 cycles), and reliable detection of acoustic vibrations over the audible frequency range (20-20 000 Hz) with high signal-to-noise ratios. These superb performances endow our skin-attachable VRS with anti-interference perception of human voices with high precision even in noisy environments, which will expedite the voice-controlled HMIs.

Developing smart multi-sensor monitoring for tool wear in stamping process

Tool wear and galling are of significant concern in the automotive stamping industry, due to the increase in use of higher strength sheet steels in automotive structures and reduced lubrication during stamping production. There are many methods explored in the literature and applied in industry to combat wear in stamping, including new die materials and coatings, alternative lubrication systems and better predictive models. However, smart condition monitoring will continue to be relevant in conjunction with these methods because it can provide further opportunities for production quality and cost improvements, despite the advancements of these other methods. This paper explores the use of multiple sensors and multiple signal processing techniques, aimed at developing a smart multi-sensor method to monitor galling wear. The three main sensors and corresponding signal processing techniques examined are: (i) measurement of punch force signatures analyzed via Principal Component Analysis (PCA); (ii) acoustic emissions signals measured via wideband sensors and examined using time and frequency domain features; (iii) measurement of audio signals in the audible frequency range analyzed via blind signal separation techniques. For all techniques, a semi-industrial stamping test was used to provide realistic production-type conditions, albeit with accelerated wear rates. The relationship between the key outputs from the three sensor/analysis methods were directly compared to a new quantitative measure of galling wear severity. Based on these results, it was observed that a multi-sensor approach for wear condition monitoring provides an opportunity for the development of a smart monitoring tool that can actively track the progression of wear.

Relationship between biosonar click emissions, age, and hearing bandwidth in bottlenose dolphins, Tursiops truncatus

Previous studies have reported changes in biosonar emissions in a few odontocete subjects as audible frequency range is reduced with increasing age (i.e., presbycusis). For example, some animals have been observed to lower the dominant frequencies of their biosonar clicks to better match their reduced audible frequency range. In the present study, relationships between age, biosonar click emissions, auditory evoked potentials, and hearing bandwidth were studied in 10 bottlenose dolphins (Tursiops truncatus) of various ages and hearing capabilities. Underwater hearing thresholds were estimated by measuring steady-state auditory evoked potentials to sinusoidal amplitude modulated tones at frequencies from 20 to 160 kHz. Input-output functions were generated at each tested frequency and used to calculate frequency-specific thresholds and the upper cut-off frequency of hearing for each subject. Click emissions were measured during a physical target aspect change detection task at a fixed range of 10 m. Relationships between hearing thresholds and the acoustic parameters of biosonar signals will be presented and compared to previous experiments with fewer subjects. [Work supported by the Office of Naval Research.]

Selective remote excitation of complex structures using time reversal in audible frequency range.

Generation of elastic waves is a major issue in nondestructive testing. Structural health monitoring of a thin element can be achieved through the analysis of its resonance spectrum. A time reversal mirror (TRM) operating in the audible frequency range (1-10 kHz) is used to remotely excite thin resonant elastic elements. The generation of elastic waves is studied with respect to the geometry of the TRM. It is observed that the quality of focusing only weakly depends on the number of loudspeakers (LS) in the TRM. When the air/plate coupling is at its maximum, the energetic efficiency of the TRM is estimated to be about 0.02%. The TRM is shown to efficiently and selectively excite a small structure embedded in a complex environment such as a hollow cylinder. Finally, the results are discussed in light of the DORT method (French acronym for "decomposition of the time reversal operator"). In particular, the optimal LS placement and emission signals in this configuration to excite individual eigenmodes of a plate is determined.

A cellular sound-absorbing metasurface with subwavelength thickness

The sound absorbing metasurface efficient in the audible frequency range is proposed. The metasurface has a cellular structure, each cell having a hexagonal shape with a hollow tunnel inside. The wall of the hexagonal cell is sub-divided into six hollow chambers connected to the central tunnel via the six thinner channels of different diameters. The hollow chambers act as Helmholtz resonators providing six different resonant frequencies for each cell. The negative effective bulk modulus property of the metasurface allows full adsorption at the resonant frequencies. By carefully designing the size of the connecting channels we can manipulate the desired sound adsorption frequency range. The thickness of the metasurface is in the range of 0.03–0.1 wavelengths for the sound frequency range between 300 and 1000 Hz. Six absorption peaks are achieved for each unit cell providing broader range of absorption. The hexagonal shape of the unit cell allows full utilization of the metasurface volume by a standard honeycomb tessellation of the cells. By designing a metasurface containing individual cells with different inner channel diameters, the absorption peaks can be multiplied or overlapped and further broaden the frequency range with the absorption coefficient higher than the desired value.

Experimental and analytical evaluation of the acoustic radiation of femtosecond laser plasma filament sound sources in air.

Plasma filaments in air induced by femtosecond laser pulses lead to the generation of strong shock waves. This letter presents a systematic study, both experimental and theoretical, of the acoustic radiation by femtosecond laser-generated filaments. A theoretical model is developed based on the experimental results and is used to evaluate the directivity of the filament's acoustic radiation within and beyond the audible frequency range. It is shown that the acoustic directivity of plasma filaments can be derived from the model of a weighted acoustic line source, consisting of elementary point sources with N-shaped excitation.

Characterization of embedded membrane in corrugated silicon microphones for high-frequency resonance applications

PurposeThe purpose of this paper is to propose an alternative approach to improve the performance of microelectromechanical systems (MEMSs) silicon (Si) condenser microphones in terms of operating frequency and sensitivity through the introduction of a secondary material with a contrast of mechanical properties in the corrugated membrane.Design/methodology/approachFinite element method from COMSOL is used to analyze the MEMS microphones performance consisting of solid mechanic, electrostatic and thermoviscous acoustic interfaces. Hence, the simulated results could described the physical mechanism of the MEMS microphones, especially in the case of microphones with complex geometry. A 2-D model was used to simplify computation by applying axis symmetry condition.FindingsThe simulation results have suggested that the operating frequency range of the microphone could be extended to be operated beyond 20 kHz in the audible frequency range. The data showed that the frequency resonance of the microphone using a corrugated Si membrane with SiC as the embedded membrane is increased up to 70 kHz compared with 63 kHz for the plane Si membrane, whereas the microphone’s sensitivity is slightly decreased to −79 from −76 dB. Furthermore, the frequency resonance of a corrugated membrane microphone could be improved from 26 to 70 kHz by embedding the SiC material. Last, the sensitivity and frequency resonance value of the microphones could be modified by adjusting the height of the embedded material.Originality/valueBased on these theoretical results, the proposed modification highlighted the advantages of simultaneous modifications of frequency and sensitivity that could extend the applications of sound and acoustic detections in the ultrasonic spectrum with an acceptable performance compared with the typical state-of-the-art Si condenser microphones.

Illusory Conjunctions in Speech Perception as a Lens into the Characteristics of Hearing Loss

This study explores the formation of a complex illusory conjunction in simulated speech perception that has yet to see a parallel in visual cognition. The illusory conjunction dealt with in this paper is confounded by 2 disparate spatial modalities – a) spatialization of competing formant features across high and low frequency bands on one hand and b) high-level expectation of speech content competing with the low level processing of auditory objects (such as speechmodulated noise). This paper has extended on a previous initial study around this topic, by controlling for the illusory conjunctions in one of the spatial dimensions (formant space) to then account for specific individual differences as possible correlations with individual hearing abilities across the audible frequency range. The results are an encouraging direction towards a better understanding of audition through the controlled perception of illusory conjunctions.

Are earthquake swarms in South Gujarat, northwestern Deccan Volcanic Province of India monsoon induced?

South Gujarat, a part of the northwestern Deccan Volcanic Province of India has been experiencing episodic swarm activity with reports of sounds, whose association remains unclear. After the Indian monsoon period, during the month of September 2016, a swarm activity occurred around the Keliya dam in the Navsari district of South Gujarat and nearby villages in the Dadra and Nagar Haveli (DNH), which continued for about 4 months. Again, the swarm activity recurred during the month of August 2017 and continued for about 5 months till January 2018. Many of these events were accompanied by audible sounds, like blasting, that caused severe panic among local occupants. A local network of four stations was installed to monitor the swarm activity, in addition to the Gujarat state seismic network. A total of 1048 earthquakes were located around the Keliya dam and 229 events in the DNH region from September 2016 to June 2018. In the present study, we performed a spectrogram analysis of the events with associated sounds. The analysis revealed significant energy at frequencies ≥ 20 Hz, in the audible frequency range. The relocated earthquake distribution shows that seismicity in the Navsari district follows a ~ NW–SE trend, confined to an area of 13 km × 2 km with a depth extent of 3 km. The trend is similar in the DNH region, confined to an area of 15 km × 2 km, down to a depth of 6 km. The determined focal mechanism in DNH region shows strike-slip faulting. The seismicity patterns seem to corroborate with the trends of the lineaments/dykes in the region. In general, the swarm-type earthquake sequences seem to occur when the annual rainfall exceeds the mean annual rainfall. We speculate that the present swarm activity, noticed with some delay after the Indian summer monsoon season, may be due to the phenomenon of hydro-seismicity.