Dispersion of phase of narrow-band acoustic signals at near-surface paths

2016 ◽  
Keyword(s):  
Narrow Band ◽  
Acoustic Signals ◽  
Near Surface

Phase variance of narrow-band acoustic signals on near-surface paths

2017 ◽  
Vol 30 (3) ◽  
pp. 236-242 ◽  
Author(s):  
V. P. Mamyshev ◽  
S. L. Odintsov
Keyword(s):  
Narrow Band ◽  
Acoustic Signals ◽  
Near Surface ◽  
Phase Variance

scholarly journals Simultaneous lithospheric-atmospheric signals of acoustic emission at “Karymshina” site in Kamchatka

2021 ◽  
Vol 254 ◽  
pp. 02013
Author(s):  
Igor Larionov ◽  
Yuriy Marapulets ◽  
Mikhail Mishchenko
Keyword(s):  
Acoustic Emission ◽  
Active Region ◽  
Ground Surface ◽  
Wide Band ◽  
Kamchatka Peninsula ◽  
Acoustic Signals ◽  
Rock Deformation ◽  
Acoustic System ◽  
Near Surface ◽  
Atmosphere Interaction

We present the results of complex lithospheric-atmospheric investigations of acoustic emission in a seismically active region (Kamchatka peninsula). A laser strainmeter-interferometer, a geophone, a wide-band acoustic system and a microbarometer, installed at Karymshina site (IKIR FEB RAS), are used in the monitoring. Rock deformation, acoustic emission in the near-surface rocks and in the atmosphere by the ground surface are under the consideration. Moreover, we suggest a method to detect acoustic signals recorded simultaneously in the near-surface rocks and in the atmosphere by the ground surface. The method consists in filtration of acoustic signals from the sensors at different frequency sub-ranges from fractions to the first hundreds of hertz followed by detection and accumulation of on 1-second interval. We analyze the data from September 2016 to December 2020. Examples of records of simultaneous acoustic signals in rocks and in the atmosphere are illustrated. The investigation is topical for the construction of a model of lithosphere-atmosphere interaction in a seismically active region.

Relationships between acoustic reflex patterns elicited by unfiltered white noise and narrow band white noise stimuli of different duration but of the same intensity

1985 ◽  
Vol 99 (9) ◽  
pp. 857-863 ◽  
Author(s):  
Giovanni Rossi ◽  
Paolo Solero ◽  
M. Rolando
Keyword(s):  
White Noise ◽  
Narrow Band ◽  
Acoustic Signals ◽  
The Other ◽  
Acoustic Reflex ◽  
Other Hand ◽  
Recruitment Time

AbstractFor the purpose of this study, acoustic signals were generated by an Amplaid MK VI. An Amplaid 702 impedence meter was connected to its averaging section and to its computer. The stimuli were bursts of unfiltered white noise (UWN) and of narrow band white noise (NBWN; 30 db./oct/slope; central frequencies 1,000, 2,000, 4,000 Hz.) lasting 3–1,000 msec, at intensity of 105 db. SPL p.e. The following parameters were evaluated: stapedius contraction latency, amplitude, duration and recruitment time. It was found that latency was independent of the spectrum of the stimulus and its duration. Amplitude and recruitment time, on the other hand, were related to spectrum and duration, while duration of contraction was directly related to the duration of the stimulus only.

Temporal coherence of acoustic signals propagating through the near surface bubble layer

2002 ◽  
Vol 112 (5) ◽  
pp. 2424-2424
Author(s):  
R. Lee Culver ◽  
David Bradley ◽  
Jon Reeves
Keyword(s):  
Acoustic Signals ◽  
Temporal Coherence ◽  
Near Surface ◽  
Bubble Layer ◽  
Surface Bubble

scholarly journals Ventilation Induced in an Isolated Subsurface Structure by Natural Forces: Method Development and Application

2019 ◽  
Vol 4 (4) ◽  
pp. 68
Author(s):  
Thomas Neil McManus ◽  
Assed Haddad
Keyword(s):  
Vertical Profile ◽  
Method Development ◽  
Narrow Band ◽  
Operating Time ◽  
Gas Transfer ◽  
Tracer Gas ◽  
Engine Exhaust ◽  
Near Surface ◽  
Subsurface Structures ◽  
Development And Utilization

It is believed that isolated subsurface structures of an infrastructure do not ventilate through opening(s) in manhole covers. The literature has almost no information on this topic. This study reports on considerations involved in the development and utilization of a method to study this question. Carbon monoxide (CO) is readily obtainable in engine exhaust, easily detectable at very low concentration, and is relatively safe to handle, which makes it ideal for use as a tracer gas. Transfer into the airspace of the structure was carried out using metal tubing. This study examined the engine operating time and the number of openings in a manhole cover. CO was measured using four instruments in the vertical profile. It was found to generally decrease in a narrow band, initially linearly through a curvilinear region and a linear tail. Clearance of most of the contaminant occurred rapidly during the first part of the process. A decrease to 25 ppm required from 439 min (7 openings) to 1118 min (1 opening). Ambient temperature and near-surface air flow likely influenced these values. The measurement profiles strongly suggest that the atmosphere in the airspace was rapidly and thoroughly well-mixed. The methodology developed and reported here is suitable for a more expanded investigation, the intent being to identify modifications of the design to optimize the process.

Packets of Capillary and Acoustic Waves of Drop Impact

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

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

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.

Optimization of the spectral signal processing for narrow‐band stochastic acoustic signals

1996 ◽  
Vol 100 (4) ◽  
pp. 2832-2832
Author(s):  
Leonid M. Gelman ◽  
Yuri V. Burau ◽  
Vladimir I. Krytsyn
Keyword(s):  
Signal Processing ◽  
Narrow Band ◽  
Acoustic Signals ◽  
Spectral Signal
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