Audible Sound Waves Research Articles

Sound absorption coefficient in the audible and ultrasonic frequency range measured in a reverberation chamber with an omnidirectional parametric loudspeaker

An omnidirectional parametric loudspeaker (OPL) is a sound source that contains hundreds of ultrasonic transducers set on the surface of a sphere. Each transducer emits an ultrasonic collimated beam consisting of an audible exponential sweep sine (ESS) modulated in amplitude. This results in hundreds of ultrasonic sound waves emitted in all directions, but also audible sound waves generated by the parametric acoustic array (PAA) phenomenon, by which a modulated signal returns to the audible range thanks to nonlinear propagation in the air. This work examines how the OPL performs in assessing room acoustics, specifically in determining material sound absorption coefficients within reverberation chambers. The ISO 354 standard requires measuring reverberation times with the chamber empty and with the material sample. These are measured using ESS, which has proven effective for the OPL performance. This signal concentrates all the sound power into a single frequency, which improves ultrasonic power levels and thus the signal-to-noise ratio of the audible sound field. The absorption coefficient is next evaluated following the standard, and the results are compared with those obtained using a standard dodecahedral loudspeaker. Finally, the absorption coefficient in the ultrasonic range is examined to evaluate the OPL performance in this frequency range.

Investigation of heat transfer characteristics in air-to-air heat exchanger with steady flow, oscillating flow and sound waves

A steady flow with a high flow rate, oscillating flow, and audible sound waves can enhance the heat transfer performance in air-to-air heat exchangers, while the comparison of influence mechanisms and degrees of different methods is ignored. This study investigates flow instability and heat transfer characteristics in an air-to-air heat exchanger under steady flow, oscillating flow and sound waves. The results show that steady flow and oscillating flow with different amplitudes have little effect on the distribution characteristics of velocity and vortices. However, the vortices disappear and generate periodically under 140 dB. Moreover, oscillating flow and sound waves exert distinct influences on flow instability. The cold side experiences the highest increase in turbulence kinetic energy when subjected to high-amplitude oscillating flow, while the greatest increase on the hot side occurs under high-amplitude sound waves, and the influence of steady flow on turbulence kinetic energy is relatively low. Additionally, the steady flow enhances the heat transfer performance by increasing flow rate, while the oscillating flow and sound waves promote the heat transfer between the fluid and surface. Under the effect of steady flow, oscillating flow, and sound waves, the values of heat flux are 1.22, 1.24, and 1.31 times that of the initial condition with the amplitude increasing to 0.683 m/s (140 dB). The results demonstrate that with the increase in amplitude acting on the inlet, the sound waves have the greatest impact on heat transfer performance, followed by oscillating flow, and the effect of steady flow is relatively slight. The research can provide guidelines for the development of heat transfer enhancement in air-to-air heat exchangers.

Nondestructive characterization and artificial intelligence recognition of acoustic identifiers of ancient ceramics

Cultural heritage identity management is the most basic and important work in the process of cultural heritage protection. It is of great significance to provide a unique and identifiable digital identity for ancient ceramics. At present, the identification information of ancient ceramics is mainly composed of external visual characteristics, and there is no report on feature identification method that can reflect the properties of ancient ceramics. Audible sound signals not only have advantages in non-destructive testing, but also can be used as voiceprint information to identify, monitor and analyze ancient ceramics. In this paper, seven ancient ceramics and 12 similar modern ceramic cups are taken as research objects, and an acoustic identifier (AID) is constructed. We put forward a reliable acoustic identification method for ancient ceramics, and established a digital code of acoustic characteristics of ancient ceramics. The results show that audible sound waves can reflect the attribute information of ancient ceramics. Sufficient acoustic data combined with deep learning can not only accurately match the identity of ancient ceramics, but also detect the real-time identity information of ancient ceramics, and make a comparative analysis of its cracks and whether it has caused damage. This method can provide a variety of practical applications for audible signal feature recognition technology in the exhibition, protection, trading, recognition and safety management of ancient ceramics and other cultural relics.

Potential effects of audible sound signals including music on plants: A new trigger

Plants are highly sensitive organisms and can indeed benefit from specific sound signals in multi-layered processes. Scientific evidences have shown the potential applications of sound wave treatment in plant biology. However, there are some limitations to sound wave treatment that must be overcome. We still do not understand how do plants initially perceive and recognize sound signals, which is very critical to maximize the effectiveness of the use of sound treatment from practical viewpoint. Proper setup of sound treatment equipment and detailed understanding and evaluation of the effects of selected frequencies and intensities along with sound exposure times are also very crucial during sound treatment. More experimental studies with different models need to be done in a multidisciplinary approach toward establishing suitable mechanism for sound treatment application in agriculture production. The aim of this paper is to provide an overview of findings associated with potential effects of audible sound waves including music on different biological, physiological and biochemical processes in plants.

Investigation of audible sound waves on the heat transfer characteristics of air-to-air heat exchange systems

To reveal the mechanism of the effect of audible sound waves on the heat transfer process, the flow and heat transfer characteristics of an air-to-air heat exchanger were analyzed by incidence of sound waves with different intensities on its cold, hot, and both sides. The results showed that the sound waves incident on the cold side enhanced the heat exchange between the unstable cold flow and hot surface, which decreased the surface temperature of the latter with an increasing sound pressure level (SPL). In contrast, the sound waves incident on the hot side increased the surface temperature, thereby enhancing the heat transfer performance. When the SPL increased to 140 dB, the average surface heat flux increased by 8.22% and 15.19% under the sound waves incident on the cold and hot sides, respectively, whereas the sound energy efficiency was relatively higher with the sound waves incident on the cold side. Additionally, under the synergetic effect of the incidence of sound waves on both sides on the flow characteristics, the average surface heat flux increased by 25.56%. It was higher than the summation of the corresponding fluxes under the incidence of sound waves on single side, while the sound energy efficiency decreased under high SPL. The results indicated that sound waves incident on both sides can effectively enhance the heat transfer performance. This research is significant for the application of sound waves on the heat transfer process of air-to-air heat exchange systems.

Unidirectional Parametric Speaker

One of the most significant ways that people convey information is through sound. The production of directed sound is dramatically increasing in terms of personal privacy in contemporary culture. The Ultrasonic Unidirectional Speaker project aims to design and develop a compact, lightweight, and energy-efficient speaker system that can deliver sound in a specific direction using ultrasonic waves. The system utilises the non-linear properties of air to generate audible sound waves through the use of ultrasonic frequencies, creating a directional sound beam that can be precisely targeted. The work involves designing and fabricating the necessary electronic components, such as the ultrasonic transducer, amplifier, and signal generator, and developing software to control the system. The ultimate goal of this project is to create a high-quality directional speaker system that can be used in a variety of applications, such as public address systems, directional sound for displays, and immersive gaming experiences.

Influence of frequency and intensity of bilateral audible sound waves on heat transfer performance of air-to-air heat exchange systems

To enhance the air heat transfer performance, this study applied the bilateral audible sound waves to an air-to-air heat exchanger. The effect of the frequency and intensity of sound waves on heat transfer performance was investigated from the viewpoint of flow instability and heat flux, and the sound power efficiency was also explored to reveal the efficiency of sound waves on the heat transfer performance. The results showed that the flow instability intensified with the increase in sound pressure level (SPL) and decrease in frequency, which was reflected by the distribution of turbulence kinetic energy. The change in sound waves has different effects on the turbulence kinetic energy at different locations, and the directivity distribution characteristics of the turbulence kinetic energy inside and outside the heat tube caused similar directivity distribution characteristics of the heat flux, in which the maximum value of the heat flux was located perpendicular to the flow direction. Additionally, the heat flux at different locations increased with an increase in SPL and a decrease in frequency. The heat transfer performance was relatively superior when the SPL was higher than 120 dB and the frequency was lower than 100 Hz, and a decrease in frequency could increase the sound power efficiency. This study can guide the application of sound waves in the heat transfer enhancement of air-to-air heat exchange systems.

Measurement of the Elastic Modulus of Cornea, Sclera and Limbus: The Importance of the Corneal-Limbus-Scleral Biomechanical Unit

Energy storage, transmission and dissipation are important considerations of normal mechanical homeostasis. In this paper we present a new technique termed vibrational optical coherence tomography (VOCT) to study the anterior anatomic structures of the pig eye to better understand how energy applied to the cornea is dissipated without delamination occurring. VOCT uses infrared light and an applied sinusoidal audible sound wave to image and measure the resonant frequency and modulus of individual macromolecular components of tissue non-invasively. We have measured the resonant frequencies and calculated the moduli of tissues in the anterior portion of the pig eye using VOCT. While both pig and human eyes have similar resonant frequencies, they do differ in the peak amplitudes near the frequencies of 80, 120, 150 and 250 Hz. It is known that the stroma of pig cornea is much thicker than that of human corneas and these differences may explain the normalized peak height differences. The similarity of the resonant frequency peaks near 80, 120, 150 and 250 Hz of cornea, sclera and limbus suggest that the anatomically described layers in these tissues are connected into a single biomechanical unit that can store external mechanical energy and then transmit it for dissipation. Since the energy stored and dissipated is proportional to the modulus and the ability of the tissue to deform under stress, energy storage in these tissues is related to the stiffness. It is concluded that stored energy is transmitted to the posterior segment of the eye for dissipation through the attachment with the sclera. This mechanism of energy dissipation may protect the cornea from changes in shape, curvature, and refractive power. However, ultimately, energy dissipation through thinning of the sclera may cause globe elongation observed in subjects with myopia and glaucoma.

Under the surface: Pressure-induced planetary-scale waves, volcanic lightning, and gaseous clouds caused by the submarine eruption of Hunga Tonga-Hunga Ha'apai volcano

We present a narrative of the eruptive events culminating in the cataclysmic January 15, 2022 eruption of Hunga Tonga-Hunga Ha'apai Volcano by synthesizing diverse preliminary seismic, volcanological, sound wave, and lightning data available within the first few weeks after the eruption occurred. The first hour of eruptive activity produced fast-propagating tsunami waves, long-period seismic waves, loud audible sound waves, infrasonic waves, exceptionally intense volcanic lightning and an unsteady volcanic plume that transiently reached—at 58 ​km—the Earth's mesosphere. Energetic seismic signals were recorded worldwide and the globally stacked seismogram showed episodic seismic events within the most intense periods of phreatoplinian activity, and they correlated well with the infrasound pressure waveform recorded in Fiji. Gravity wave signals were strong enough to be observed over the entire planet in just the first few hours, with some circling the Earth multiple times subsequently. These large-amplitude, long-wavelength atmospheric disturbances come from the Earth's atmosphere being forced by the magmatic mixture of tephra, melt and gasses emitted by the unsteady but quasi-continuous eruption from 0402±1–1800 UTC on January 15, 2022. Atmospheric forcing lasted much longer than rupturing from large earthquakes recorded on modern instruments, producing a type of shock wave that originated from the interaction between compressed air and ambient (wavy) sea surface. This scenario differs from conventional ideas of earthquake slip, landslides, or caldera collapse-generated tsunami waves because of the enormous (∼1000x) volumetric change due to the supercritical nature of volatiles associated with the hot, volatile-rich phreatoplinian plume. The time series of plume altitude can be translated to volumetric discharge and mass flow rate. For an eruption duration of ∼12 ​h, the eruptive volume and mass are estimated at 1.9 ​km3 and ∼2 900 ​Tg, respectively, corresponding to a VEI of 5–6 for this event. The high frequency and intensity of lightning was enhanced by the production of fine ash due to magma—seawater interaction with concomitant high charge per unit mass and the high pre-eruptive concentration of dissolved volatiles. Analysis of lightning flash frequencies provides a rapid metric for plume activity and eruption magnitude. Many aspects of this eruption await further investigation by multidisciplinary teams. It represents a unique opportunity for fundamental research regarding the complex, non-linear behavior of high energetic volcanic eruptions and attendant phenomena, with critical implications for hazard mitigation, volcano forecasting, and first-response efforts in future disasters.

Highly Stretchable Sound-in-Display Electronics Based on Strain-Insensitive Metallic Nanonetworks.

The growing importance of human–machine interfaces and the rapid expansion of the internet of things (IoT) have inspired the integration of displays with sound generation systems to afford stretchable sound‐in‐display devices and thus establish human‐to‐machine connections via auditory system visualization. Herein, the synchronized generation of sound and color is demonstrated for a stretchable sound‐in‐display device with electrodes of strain‐insensitive silver nanowires (AgNWs) and emissive layers of field‐induced inorganic electroluminescent (EL) phosphors. In this device, EL phosphors embedded in a dielectric elastomer actuator (DEA) emit light under alternating‐current bias, while audible sound waves are simultaneously generated via DEA actuation along with input sound signals. The electroluminescence and sound‐generation performances of the fabricated device are highly robust and reliable, being insensitive to stretch‐release cycling because of the presence of the AgNW stretchable electrodes. The presented principle of integrating light emission and acoustic systems in a single stretchable device can be further expanded to realize sound‐in‐display electronics for IoT and human–machine interface applications.

Specific audible sound waves improve flavonoid contents and antioxidative properties of sprouts

Recent studies have suggested that sound waves regulate the growth, phytochemical contents, and stress responses of plants. Here, we investigated the effect of different frequencies of sound waves (0.25, 0.8, 1 and 1.5 kHz) on the flavonoid contents and antioxidative properties of 1–6 day treated sprouts, including red radish (Raphanus sativus), lettuce (Lactuca sativa), and Chinese cabbage (Brassica rapa subsp. pekinensis). These sprouts were treated with each sound wave for 2 h per day for either consecutive (long term [LT]) or three alternating (1st, 3rd, and 5th) days (short term [ST]). The flavonoid contents of the sprouts were found to vary according to the sound frequency, exposure time, species, and growth conditions. A 25–88% increase in flavonoid content could be induced in the sprouts under specific conditions. Quantitative RT-PCR (qPCR) based analysis showed that the expression patterns of the flavonoid biosynthesis-related genes were correlated with the flavonoid contents observed in each treatment suggesting that sound waves regulate the flavonoid biosynthesis pathway. In addition, DPPH and FRAP assays indicated that the antioxidative effects of the sprouts were significantly higher under certain sound wave treatments. Furthermore, the flavonoid accumulation was positively correlated with the antioxidative properties of the sprouts. Therefore, sound waves with a particular frequency could be used to improve the phytochemical contents of crops for functional products.

Vibrational optical coherence tomography detects unique skin fibrotic states: Preliminary results of animal and human studies

To the Editor: Scleroderma is an autoimmune disease that causes fibrosis of the skin and other organs. A major obstacle to the delivery of clinical care is the ability to objectively quantify fibrosis noninvasively over time. Vibrational optical coherence tomography (VOCT) is an imaging technique in which the skin is vibrated by using audible sound waves, and the maximum displacement of the skin can be determined from the OCT image. The resonant frequency is that at which maximum displacement occurs and is related to tissue stiffness.

Mechano-Vibrational Spectroscopy of Tissues and Materials Using Vibrational Optical Coherence Tomography: A New Non-Invasive and Non-Destructive Technique

Elastic moduli of tissues and synthetic polymeric materials are important design properties needed to develop new implants. In this paper we report the use of vibrational optical coherence tomography (VOCT) to measure the resonant frequency and calculate the modulus of tissues and synthetic polymers non-invasively and non-destructively in vitro and in vivo. Values of tissue and polymer moduli were obtained by applying an audible sinusoidal sound wave to the surface of each specimen. The sound wave travels to the interior of the material and is reflected back to the surface from underlying layers. A spectrum of resonant frequencies and moduli are then obtained. By analyzing the frequencies at which the maximum displacements are observed the resonant frequencies are determined of the material components and the moduli can then be calculated from calibration equations. The characteristic spectrum of resonant frequencies measured is a finger print by which the composition of the underlying tissue components can be determined using VOCT. The resonant frequencies of cells and tissues range from about 40 Hz for fat to about 990 Hz for lamellar bone. The modulus for these tissues ranges from about 1 MPa (cells) to that for extracellular matrix components that range from 2 to 173 MPa (tissue macromolecular components). Measurements reported on synthetic polymers indicate that the resonant frequency ranges from 80 Hz (silicone rubber) to 2800 Hz (acrylonitrile butadiene styrene) and values of the modulus are found to be between 2 MPa and 2120 MPa, respectively. The resonant frequency and modulus are shown to decrease as a result of fatigue in Viton rubber. It is concluded that the width of the resonant frequency peak is related to the molecular weight distribution and that VOCT may serve as method to rapidly determine molecular weight distributions and properties after cyclic loading of uncrosslinked and crosslinked polymers.

Effects of high-amplitude low-frequency structural vibrations and machinery sound waves on ultrasonic guided wave propagation for health monitoring of composite aircraft primary structures

A reliable damage diagnostic by ultrasonic guided wave (GW) based structural health monitoring (SHM) can only be achieved if the physical interactions between wave propagation, the SHM system and environmental factors are fully understood. The purpose of this research was to gain knowledge about the effects of high-amplitude low-frequency structural vibrations (HA-LFV) and audible sound waves (SW) on ultrasonic GW propagation. Measurements were performed on a stiffened panel of a full-scale composite torsion box containing barely visible impact damage. Time-domain analysis of the filtered GW signals revealed that the main effect of HA-LFV was the presence of coherent noise. This was interpreted as the consequence of superposition of multiple dispersive wave groups produced by mode conversion at the moment of reflection on the corrugated panel surfaces during propagation. It was also observed that the coherent noise amplitude depends on the amplitude of the HA-LFV, and on the ratio between the HA-LFV frequency and the ultrasonic excitation frequency. These relationships can potentially be explored for the development of a HA-LFV compensation mechanism to enable in-service GW based damage diagnostics. In contrast, GW signals in the cases with audible SW present were almost unaffected. It was concluded that there is strong evidence supporting the hypothesis that ultrasonic GW propagation with HA-LFV effects can be analysed under the assumption of a permanently corrugated structure.

Broadband low-frequency sound absorption by periodic metamaterial resonators embedded in a porous layer

Broadband absorption of the audible sound wave at low frequency has been achieved by using periodic acoustic metamaterial resonators (AMRs) embedded inside a porous layer. A single AMR embedded in a porous layer could reach perfect absorption (PA) at the resonance frequency, and it can be easily tuned by adjusting the inner radius of AMR. With four AMRs in the porous layer, a high absorption (>80%) is obtained in the frequency range from 180 Hz to 550 Hz, while the thickness of the porous layer is only 1/10 of the relevant wavelength at 300 Hz. The broadband and high absorption performances are due to the interferences of the low-frequency resonances of the AMRs and the energy trapping between the AMRs and the rigid backings. The finite element simulations are experimentally validated. Moreover, the broadband low-frequency absorption is robust under various oblique incidence even at large incident angles. The effects of the acoustic parameters of the porous layer on the absorption properties are also discussed. The absorbers should have high potential for the practical applications in buildings, aircrafts and automobiles due to their ease of fabrication, ultra-thin, and robust high-efficiency.

Dissipation of Ultrasonic and Audible Sound Waves in Liquid Foams

Dissipation of Ultrasonic and Audible Sound Waves in Liquid Foams

Research on the static experiment of super heavy crude oil demulsification and dehydration using ultrasonic wave and audible sound wave at high temperatures

In this paper, the static experiment of super heavy crude oil demulsification and dehydration using ultrasonic irradiation at high temperatures is carried out. How the all factors, such as ultrasonic frequency, sound intensity, ultrasonic power, ultrasonic treatment time, sedimentation time, temperature and water ratio, affect ultrasonic crude oil demulsification and dehydration are summarized though this experiment. In addition, recent progress on ultrasonic demulsification equipment in China are reviewed. The purpose of this paper is to provide equipment and technical support for the extensive application of the technique of ultrasonic demulsification and dehydration.

Perfect absorption of low-frequency sound waves by critically coupled subwavelength resonant system

The perfect absorption (PA) for low-frequency audible sound waves has been achieved by critically coupling the inherent loss factor to the inherent leakage factor of a system, which is constructed by attaching a deep-subwavelength lossy resonant plate (LRP) to a backed rigid wall closely. We have certified it by using the graphical method in the complex frequency plane. By coupling the LRP to an air cavity in front of the rigid wall, the high efficient (>80%) low-frequency broadband absorption is obtained from 99.1 Hz to 294.8 Hz. Here, the thickness of LRP is only 1/13.5 of the relevant wavelength at 294.8 Hz. The impedance analyses further demonstrate that the impedances are perfectly matched between the system and the surrounding background medium at PA.

Vibrational Profiling of Brain Tumors and Cells.

This study reports vibration profiles of neuronal cells and tissues as well as brain tumor and neocortical specimens. A contact-free method and analysis protocol was designed to convert an atomic force microscope into an ultra-sensitive microphone with capacity to record and listen to live biological samples. A frequency of 3.4 Hz was observed for both cultured rat hippocampal neurons and tissues and vibration could be modulated pharmacologically. Malignant astrocytoma tissue samples obtained from operating room, transported in artificial cerebrospinal fluid, and tested within an hour, vibrated with a much different frequency profile and amplitude, compared to meningioma or lateral temporal cortex providing a quantifiable measurement to accurately distinguish the three tissues in real-time. Vibration signals were converted to audible sound waves by frequency modulation, thus demonstrating, acoustic patterns unique to meningioma, malignant astrocytoma and neocortex.

Multimodal Feature-Based Surface Material Classification.

When a tool is tapped on or dragged over an object surface, vibrations are induced in the tool, which can be captured using acceleration sensors. The tool-surface interaction additionally creates audible sound waves, which can be recorded using microphones. Features extracted from camera images provide additional information about the surfaces. We present an approach for tool-mediated surface classification that combines these signals and demonstrate that the proposed method is robust against variable scan-time parameters. We examine freehand recordings of 69 textured surfaces recorded by different users and propose a classification system that uses perception-related features, such as hardness, roughness, and friction; selected features adapted from speech recognition, such as modified cepstral coefficients applied to our acceleration signals; and surface texture-related image features. We focus on mitigating the effect of variable contact force and exploration velocity conditions on these features as a prerequisite for a robust machine-learning-based approach for surface classification. The proposed system works without explicit scan force and velocity measurements. Experimental results show that our proposed approach allows for successful classification of textured surfaces under variable freehand movement conditions, exerted by different human operators. The proposed subset of six features, selected from the described sound, image, friction force, and acceleration features, leads to a classification accuracy of 74 percent in our experiments when combined with a Naive Bayes classifier.