Audibility within and Outside Deposited Snow

AbstractFactors which control the audibility within and outside deposited snow are described and applied to explain the preferential detection of sound by persons buried under avalanche debris as compared to persons on the overlying snow surface. Strong attenuation of acoustic waves in snow and the small acoustic impedance differences between snow and air are responsible for the strong absorption and transmission-loss characteristics that are observed for snow. The absorption and transmission-loss characteristics are independent of the direction of propagation of acoustic signals through the snow. The preferential detection of sound by a person buried under snow can be explained by the relatively higher level of background acoustic noise that exists for persons above the snow surface as compared to an avalanche burial victim. This noise masks sound transmitted to persons on the snow surface, causing a reduction of hearing senstitivity as compared to the burial victim. Additionally, the listening concentration of a buried individual is generally greater than for persons working on the snow surface, increasing their subjective awareness of sound.

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Analysis of Propagation and Distribution Characteristics of Leakage Acoustic Waves in Water Supply Pipelines

Sensors ◽

10.3390/s21165450 ◽

2021 ◽

Vol 21 (16) ◽

pp. 5450

Author(s):

Yunfei Li ◽

Yang Zhou ◽

Ming Fu ◽

Fan Zhou ◽

Zhaozhao Chi ◽

...

Keyword(s):

Acoustic Wave ◽

Water Supply ◽

Acoustic Waves ◽

Simulation Analysis ◽

Acoustic Signals ◽

Detection Methods ◽

Acoustic Analogy ◽

Acoustic Wave Propagation ◽

Source Characteristics ◽

Water Supply Pipeline

Leakage detection methods based on the analysis of leakage acoustic signals provide an effective technical approach for detecting small leaks in water supply pipelines. From a technical perspective, the study of the propagation characteristics of acoustic waves generated by the leakage in the water supply pipeline is necessary for detecting the leak location on the basis of acoustic signals. In this study, a 3D transient leakage acoustic wave propagation equation was derived by combining the principles of fluid dynamics and Lighthill acoustic analogy theory. The propagation of the leakage-induced noise in water supply pipeline was modelled theoretically. We simulated the propagation of a leakage acoustic wave under different conditions for different target scenarios encountered in actual pipeline inspections. Specifically, we analysed the effect of different factors, such as the pipe size and acoustic source characteristics, on acoustic propagation. Finally, the simulated experiments were practically performed using a self-designed simulated water supply pipeline and self-developed spherical water supply pipeline detector to validate the simulation analysis. The results of this study provide a theoretical guidance and basis for the analysis of characteristics of leakage acoustic wave signals and the recognition of leakage conditions in water supply pipelines.

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Development of acoustic mufflers for cabin noise reduction in Orion spacecraft

INTER-NOISE and NOISE-CON Congress and Conference Proceedings ◽

10.3397/in-2021-1568 ◽

2021 ◽

Vol 263 (6) ◽

pp. 568-576

Author(s):

Indranil Dandaroy ◽

S. Reynold Chu ◽

Jeffrey Dornak ◽

Christopher S. Allen

Keyword(s):

Test Performance ◽

Speech Intelligibility ◽

Life Support ◽

Transmission Loss ◽

Complex Geometry ◽

Environmental Control ◽

Acoustic Noise ◽

Primary Source ◽

Broadband Noise ◽

Cabin Noise

Controlling cabin acoustic noise levels in the Crew Module (CM) of the Orion spacecraft is critical for adequate speech intelligibility, avoid fatigue, and prevent any possibility of temporary and permanent hearing loss to the crew. The primary source of cabin noise for the on-orbit phase of the mission is from the Environmental Control and Life Support System (ECLSS) which recycles and conditions breathing air and maintains cabin pressurization through its ducting network and components. Unfortunately, as a side effect, noise from the ECLSS fans propagates through theses ducts and emanate into the cabin habitable volume via the ECLSS inlet and outlets. To mitigate excessive duct-borne noise, two ECLSS mufflers have been designed to provide significant acoustic transmission loss (TL) so that the cabin noise requirements can be met. Each muffler is meant to be installed in the ducting of the ECLSS air inlet and outlet sides, respectively. Packaging constraints and tight volume requirements necessitated the mufflers to be of complex geometry and compatible with the bends of the ECLSS duct layout. To design and characterize the acoustic performance of the inlet and outlet mufflers, computational acoustic models were developed using the Finite Element Method (FEM) with software. Characterization of the acoustic material and perforations in the mufflers were addressed with poro-elastic theory. Once the mufflers were designed on paper and its TL predicted, prototypes of these mufflers were created using additive manufacturing. The muffler prototypes were subsequently tested for acoustic TL in the laboratory with various configurations of acoustic materials. Comparing the analytical predictions to the test performance yielded excellent correlation for acoustic TL and demonstrated significant broadband noise attenuation. The ECLSS mufflers are currently scheduled to be installed on the Artemis II CM of the Orion spacecraft and will provide significant cabin comfort to crew during the mission.

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A variety of surface waves in ocean-bottom DAS records

10.5194/egusphere-egu21-8284 ◽

2021 ◽

Author(s):

Zack Spica ◽

Loïc Viens ◽

Jorge Castillo Castellanos ◽

Takeshi Akuhara ◽

Kiwamu Nishida ◽

...

Keyword(s):

Surface Wave ◽

Acoustic Waves ◽

Fiber Optic ◽

Acoustic Noise ◽

Seismic Exploration ◽

Ocean Bottom ◽

Wide Range ◽

Ocean Layer ◽

Noise Cross Correlation ◽

Low Amplitude

<p>Distributed acoustic sensing (DAS) can transform existing telecommunication fiber-optic cables into arrays of thousands of sensors, enabling meter-scale recordings over tens of kilometers. Recently, DAS has demonstrated its utility for many seismological applications onshore. However, the use of offshore cables for seismic exploration and monitoring is still in its infancy.<br>In this work, we introduce some new results and observations obtained from a fiber-optic cable offshore the coast of Sanriku, Japan. In particular, we focus on surface wave retrieved from various signals and show that ocean-bottom DAS can be used to extract dispersion curves (DC) over a wide range of frequencies. We show that multi-mode DC can be easily extracted from ambient seismo-acoustic noise cross-correlation functions or F-K analysis. Moderate magnitude earthquakes also contain multiple surface-wave packets that are buried within their coda. Fully-coupled 3-D numerical simulations suggest that these low-amplitude signals originate from the continuous reverberations of the acoustic waves in the ocean layer.&#160;</p>

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Predictive Modeling of Acoustic Signals From Thermoacoustic Power Sensors (TAPS)

Volume 1: Operations and Maintenance, Aging Management and Plant Upgrades; Nuclear Fuel, Fuel Cycle, Reactor Physics and Transport Theory; Plant Systems, Structures, Components and Materials; I&C, Digital Controls, and Influence of Human Factors ◽

10.1115/icone24-61034 ◽

2016 ◽

Author(s):

Christopher M. Dumm ◽

Jeffrey S. Vipperman ◽

Jorge V. Carvajal ◽

Melissa M. Walter ◽

Luke Czerniak ◽

...

Keyword(s):

Predictive Modeling ◽

Acoustic Waves ◽

Nuclear Reactor ◽

Reactor Core ◽

Signal Propagation ◽

Acoustic Signals ◽

Operating Conditions ◽

Liquid Sodium ◽

Thermoacoustic Engines ◽

Self Powered

Thermoacoustic Power Sensor (TAPS) technology offers the potential for self-powered, wireless measurement of nuclear reactor core operating conditions. TAPS are based on thermoacoustic engines, which harness thermal energy from fission reactions to generate acoustic waves by virtue of gas motion through a porous stack of thermally nonconductive material. TAPS can be placed in the core, where they generate acoustic waves whose frequency and amplitude are proportional to the local temperature and radiation flux, respectively. TAPS acoustic signals are not measured directly at the TAPS; rather, they propagate wirelessly from an individual TAPS through the reactor, and ultimately to a low-power receiver network on the vessel’s exterior. In order to rely on TAPS as primary instrumentation, reactor-specific models which account for geometric/acoustic complexities in the signal propagation environment must be used to predict the amplitude and frequency of TAPS signals at receiver locations. The reactor state may then be derived by comparing receiver signals to the reference levels established by predictive modeling. In this paper, we develop and experimentally benchmark a methodology for predictive modeling of the signals generated by a TAPS system, with the intent of subsequently extending these efforts to modeling of TAPS in a liquid sodium environment.

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Design and Fabrication of a High Frequency Thin Film Resonator Using Low Acoustic Impedance Reflective Layer

Microelectromechanical Systems ◽

10.1115/imece2003-41416 ◽

2003 ◽

Author(s):

Chung-Hsien Lin ◽

Hong-Ren Chen ◽

Chen-Hsun Du ◽

Weileun Fang

Keyword(s):

Thin Film ◽

Mobile Communication ◽

Acoustic Impedance ◽

Piezoelectric Layer ◽

Acoustic Waves ◽

High Frequency ◽

The Novel ◽

Novel Device ◽

Reflective Layer ◽

Air Interface

A high frequency thin film resonator using single reflective layer is presented. The reflective layer is chosen to have a low acoustic impedance to reflect acoustic waves, which is generated by the piezoelectric layer above it. With an air interface serves as a free boundary at the other end of piezoelectric layer, a high frequency resonator can be formed. Since the fabrication process included no bulk etching and multi-layer, a high manufacturability can be achieved. Moreover, the novel device and its applications can be designed to be suit many mobile communication applications.

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Experimental investigation on the potential of the Feedback Fx-LMS Active Noise Control technology for use in industrial generator sets

E3S Web of Conferences ◽

10.1051/e3sconf/202131208007 ◽

2021 ◽

Vol 312 ◽

pp. 08007

Author(s):

Marco Ciampolini ◽

Lorenzo Bosi ◽

Luca Romani ◽

Andrea Toniutti ◽

Matteo Giglioli ◽

...

Keyword(s):

Acoustic Waves ◽

Noise Control ◽

Noise Source ◽

Acoustic Noise ◽

Active Noise Control ◽

Lms Algorithm ◽

Destructive Interference ◽

Exhaust Pipe ◽

Least Mean Square ◽

Active Noise

Active Noise Control (ANC) has been considered a promising technology for the abatement of acoustic noise from the mid-20th century. Feedback and Feedforward ANC algorithms, based on the destructive interference principle applied to acoustic waves, have been developed for different applications, depending on the spectrum of the noise source. Feedback ANC algorithms make use of a single control microphone to measure an error signal which is then employed by an adaptive filter to estimate the noise source and generate an opposite-phase control signal. The Fx-LMS (Filtered-X Least Mean Square) algorithm is mostly adopted to update the filter. Feedback ANC systems have proven to be effective for the abatement of low-frequency quasi-steady noises; however, different challenges must be overcome to realize an effective and durable system for high-temperature application. This paper aims at experimentally assessing the feasibility of a Feedback Fx-LMS ANC system with off-line Secondary Path estimation to be used in mid-size diesel gensets for the reduction of the exhaust noise. Several solutions are proposed, including the mechanical design, the development of the Fx-LMS algorithm in the LabVIEW FPGA programming language, and the key features required to prevent parts from thermal damage and fouling. The developed prototype was implemented on a 50-kW diesel genset and tested in a semi-anechoic chamber. The noise abatement inside the exhaust pipe and at different measurement points around the machine was evaluated and discussed, showing good potential for improving the acoustic comfort of genset users.

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System and method for characterizing voiced excitations of speech and acoustic signals, removing acoustic noise from speech, and synthesizing speech

The Journal of the Acoustical Society of America ◽

10.1121/1.2756488 ◽

2007 ◽

Vol 122 (1) ◽

pp. 29

Author(s):

Greg C. Burnett

Keyword(s):

Acoustic Noise ◽

Acoustic Signals

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Packets of Capillary and Acoustic Waves of Drop Impact

Herald of the Bauman Moscow State Technical University Series Natural Sciences ◽

10.18698/1812-3368-2021-1-73-91 ◽

2021 ◽

pp. 73-91

Author(s):

Yu.D. Chashechkin

Keyword(s):

Acoustic Waves ◽

High Speed ◽

Large Scale ◽

Video Camera ◽

Acoustic Signals ◽

Capillary Waves ◽

Near Surface ◽

Large Scale Analysis ◽

High Speed Video Camera ◽

Hydro Phone

Flows, capillary waves, and acoustic signals generated by a drop of water falling into a pool of degassed liquid were recorded by a high-speed video camera, hydro-phone, and microphone. A large-scale analysis of the system of equations was performed. The fast conversion of available surface potential energy is traced. The converted energy is stored in a thin layer in the vicinity of the merged free surfaces and creates large perturbations of temperature, pressure and flow velocity. Capillary waves start to radiate simultaneously with the formation of a cavity and the rise of the crown. New groups of capillary waves arise with all changes in the flow structure --- the formation and immersion of a splash, come back of secondary drops, the formation of cavities, the immersion of a streamer and droplets. Simultaneously with the waves, ligaments --- thin near-surface flows are formed that affect the transport and rupture of gas cavities. Thin flows quickly decay and form again when a new group of capillary waves is generated. A comparison of flow patterns and acoustic signals indicates that the generation of resonant sound packets is synchronized with the pinch-off gas fragments from the cavity or their breaking. The duration of the sound depends on the initial heterogeneity of the geometry of the sounding cavity, gradually transforming into a smooth spheroidal form

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Prozessüberwachung beim Laser-Strahlschmelzen mit akustischen Signalen*/Monitoring a laser beam melting process with acoustic signals

wt Werkstattstechnik online ◽

10.37544/1436-4980-2017-11-12-42 ◽

2017 ◽

Vol 107 (11-12) ◽

pp. 818-823

Author(s):

N. Eschner ◽

J. Lingenhöhl ◽

S. Öppling ◽

G. Prof. Lanza

Keyword(s):

Laser Beam ◽

Acoustic Waves ◽

Ultrasonic Inspection ◽

Melting Process ◽

Acoustic Signals ◽

Inspection System ◽

Near Surface ◽

Surface Areas ◽

Melt Pool ◽

Laser Beam Melting

Gegenwärtig ist bei der additiven Fertigung eine prozessbegleitende Überwachung des Bauteils auf das Schmelzbad und oberflächennahe Bereiche limitiert. Mithilfe akustischer Signale lassen sich typische Defekte, die im Rahmen des LBM (laser beam melting – Laserstrahlschmelzen)-Verfahrens auftreten, detektieren. Dies umfasst neben Porosität und Rissen auch Eigenspannungen. In diesem Fachbeitrag werden die Möglichkeit eines in den LBM-Prozess integrierten akustischen Prüfsystems sowie alternative Sensorkonzepte diskutiert und evaluiert.   Current process monitoring techniques for additive manufacturing are limited to the melt pool and near-surface areas. Typical defects that occur within the LBM-process, such as porosity and cracks, as well as residual stress, can be detected by using acoustic waves. In this article, the possibility of an integrated ultrasonic inspection system, as well as various sensor concepts are discussed and evaluated.

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