Some low‐frequency effects in propagation loss models

1978 ◽  
Vol 64 (S1) ◽  
pp. S44-S44
Author(s):  
Charles L. Bartberger
Keyword(s):  
Low Frequency ◽  
Propagation Loss ◽  
Frequency Effects ◽  
Loss Models

Real Ear Sound Pressure Levels Developed by Three Portable Stereo System Earphones

1992 ◽  
Vol 1 (4) ◽  
pp. 52-55 ◽  
Author(s):  
Gail L. MacLean ◽  
Andrew Stuart ◽  
Robert Stenstrom
Keyword(s):  
High Frequency ◽  
Sound Pressure ◽  
Low Frequency ◽  
Test System ◽  
Output Frequency ◽  
Frequency Effects ◽  
Adult Men ◽  
Frequency Responses ◽  
Significant Difference ◽  
Sound Pressure Levels

Differences in real ear sound pressure levels (SPLs) with three portable stereo system (PSS) earphones (supraaural [Sony Model MDR-44], semiaural [Sony Model MDR-A15L], and insert [Sony Model MDR-E225]) were investigated. Twelve adult men served as subjects. Frequency response, high frequency average (HFA) output, peak output, peak output frequency, and overall RMS output for each PSS earphone were obtained with a probe tube microphone system (Fonix 6500 Hearing Aid Test System). Results indicated a significant difference in mean RMS outputs with nonsignificant differences in mean HFA outputs, peak outputs, and peak output frequencies among PSS earphones. Differences in mean overall RMS outputs were attributed to differences in low-frequency effects that were observed among the frequency responses of the three PSS earphones. It is suggested that one cannot assume equivalent real ear SPLs, with equivalent inputs, among different styles of PSS earphones.

The driving frequency effects on the atmospheric pressure corona jet plasmas from low frequency to radio frequency

2011 ◽  
Vol 18 (4) ◽  
pp. 043503 ◽  
Author(s):  
Dan Bee Kim ◽  
H. Jung ◽  
B. Gweon ◽  
S. Y. Moon ◽  
J. K. Rhee ◽  
...  
Keyword(s):  
Radio Frequency ◽  
Atmospheric Pressure ◽  
Low Frequency ◽  
Driving Frequency ◽  
Frequency Effects

Prediction on operating range of passive troposcatter detection system

2018 ◽  
Vol 11 (1) ◽  
pp. 22-26 ◽  
Author(s):  
Zan Liu ◽  
Xihong Chen
Keyword(s):  
Electromagnetic Wave ◽  
Analytical Study ◽  
Detection System ◽  
Rain Attenuation ◽  
Propagation Loss ◽  
Line Of Sight ◽  
Time Model ◽  
Operating Range ◽  
Statistic Model ◽  
Loss Models

AbstractElectromagnetic wave of enemy radar propagated by troposcatter is a valuable candidate for beyond line-of-sight detection. There is no analytical study considering the operating range of passive troposcatter detection system. In this paper, we study the way to predict the operating range, which is dominated by propagation loss. The key propagation loss models including statistic model and real-time model are analyzed. During deducing the latter loss model, Hopfield model is introduced to precisely describe the tropospheric refractivity. Meanwhile, rain attenuation is also taken into consideration. Several examples demonstrate the feasibility of predicting operating range through the proposed method.

Studies on the interaction of low‐frequency acoustic signals with the ocean bottom

Geophysics ◽  
1979 ◽  
Vol 44 (12) ◽  
pp. 1922-1940 ◽  
Author(s):  
Salvatore R. Santaniello ◽  
Frederick R. DiNapoli ◽  
Robert K. Dullea ◽  
Peter D. Herstein
Keyword(s):  
Acoustic Waves ◽  
Grazing Angle ◽  
Low Frequency ◽  
Propagation Loss ◽  
Ocean Bottom ◽  
Computer Technique ◽  
Quantitative Evidence ◽  
Ocean Sediment ◽  
Wave Models ◽  
Processing Techniques

Understanding the mechanisms by which the ocean sediment redirects impinging sound back into the ocean is necessary in developing propagation models for sonar performance prediction. The Naval Underwater Systems Center (NUSC) has (1) conducted controlled, self‐calibrating acoustic measurements where the ocean bottom interacted signal is isolated in time for analysis, (2) developed deconvolution processing techniques to aid in describing the impulse response of the ocean sediment, and (3) performed modeling to study the interaction of acoustic waves at the ocean bottom. This paper presents a synopsis of studies showing the necessity of considering the refraction of sound by the ocean sediment when predicting low‐frequency propagation loss. Constructive interference between nonplanar wave sediment refracted sound and sound reflected by the ocean‐sediment interface and subbottom layering can cause negative values of bottom loss when using plane‐wave models to interpret measured data. These models cannot account for all possible acoustic arrivals at a receiver. In addition, for a given frequency and constant ocean bottom grazing angle, bottom loss can be dependent upon both processing bandwidth and source/receiver depth. Deconvolution has aided in time resolution of signals that make up the bottom‐interacted signals. Resolution of these signals aids in interpreting results. A modeling effort utilizing the Fast Field Program (a computer technique for evaluating the field integral by the fast Fourier transform) provides quantitative evidence for the necessity of accounting for the refraction of sound by subocean sediments to interpret properly low‐frequency propagation loss measurements.

The Frequency Effects on Fatigue Threshold of PVC-M and PVC-U in Air and Water Medium

2008 ◽  
Vol 41-42 ◽  
pp. 183-187
Author(s):  
N. Samat ◽  
Alan Whittle ◽  
Mark Hoffman
Keyword(s):  
Stress Ratio ◽  
Low Frequency ◽  
Threshold Value ◽  
Cyclic Fatigue ◽  
Fatigue Threshold ◽  
Water Medium ◽  
Chlorinated Polyethylene ◽  
Frequency Effects ◽  
Testing Environment ◽  
Impact Modifier

The cyclic fatigue threshold value (Kth) of PVC materials with (PVC-M) and without (PVC-U) impact modifier was determined and compared in air and water environments. The PVCM specimens contain 6 pphr of chlorinated polyethylene (CPE) impact modifier. The testing was undertaken at a stress ratio of R=0.1 and fatigue threshold was evaluated at 3 different frequencies: 1Hz, 7Hz and 20Hz. Frequency noticeably affected the fatigue threshold value; regardless of the testing environment; at low frequency the fatigue threshold of PVC-M was below PVC-U, however, this difference gradually decreased with increasing frequency as Kth of PVC-M increased but Kth of PVC-U remained constant. This trend was accelerated in water where a higher of fatigue threshold, Kth, was also observed. A lower fatigue threshold of PVC-M than PVC-U is associated with the presence of CPE particles. The absorption of water into the PVC matrix was evident with the formation of nodular structures observed on the fracture surface. The presence of the nodular structures (at regions close to the threshold) has retarded the fibrillation of crazes, which then blunted the crack propagation.

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