scholarly journals DEVELOPMENT OF SMALL-SIZE LOW-FREQUENCY PRESSURE GRADIENT SENSORS

2020 ◽  
Author(s):  
В.И. Коренбаум ◽  
С.В. Горовой ◽  
А.А. Тагильцев ◽  
А.Е. Бородин
Keyword(s):  
Pressure Gradient ◽  
Sound Pressure ◽  
Dynamic Range ◽  
Linear Array ◽  
Low Frequency ◽  
Directivity Pattern ◽  
Differential Pressure ◽  
Effective Pressure ◽  
Frequency Range

Проанализированы проблемы создания приемников градиента давления различных типов для использования в низкочастотном диапазоне, определяемые необходимостью достижения достаточной чувствительности к звуковому давлению в плоской волне, коэффициента деления дипольной характеристики направленности не хуже 26 дБ, динамического диапазона не менее 80–100 дБ. Теоретически оценены пределы применимости ПГД 2-гидрофонного (разностного) типов по волновым размерам. Разработаны высоко- эффективные ПГД инерционного и силового типов. Предложено комбинирование ПГД инерционного/силового и 2-гидрофонного типов в линейной антенне. The problems of development of pressure gradient sensors of various types for usage in low-frequency range are analyzed, which are connected to a necessity to provide acceptable sensitivity to sound pressure in a flat wave, minima of the dipole directivity pattern being nor less 26 dB, dynamic range being nor less 80–100 dB. The wavelength limits of acceptability of 2-hydrophone (differential) pressure gradient sensors are theoretically predicted. High effective pressure gradient sensors of inertial and force types are designed. It is suggested to combine a pressure gradient sensor of inertial or force type with the pressure gradient sensor of 2-hydrophone type in linear array.

scholarly journals Photodetector resistant to background light noise with extended dynamic range of input signals

2021 ◽  
pp. 3-8
Author(s):  
V. M. Lipka ◽  
V. V. Ryukhtin ◽  
Yu. G. Dobrovolsky
Keyword(s):  
Dynamic Range ◽  
Automatic Gain Control ◽  
Modulation Frequency ◽  
Low Frequency ◽  
Gain Control ◽  
Ambient Air ◽  
Frequency Range ◽  
Background Light ◽  
Useful Signal ◽  
Extended Dynamic

Measurement of periodic optical information signals in the background light noise with a photodetector with extended dynamic range is an urgent task of modern electronics and thus has become the aim of this study. To increase the dynamic range of the photodetector, a new version of the automatic gain control (AGC) circuit has been developed, which consists of an AGC controller, an output photodetector amplifier and an AGC detector. The authors measured the dynamic range of the photodetector when receiving optical radiation with a wavelength of 1064 nm in the power range from 2.10–8 to 2.10–5 W at a modulation frequency of 20 kHz with the AGC on. Under these conditions, the dynamic range of the photodetector was found to be up to 67 dB. If the AGC was off, the dynamic range did not exceed 30 dB. Thus, the study made it possible to create a photodetector with an extended dynamic range up to 67 dB based on a new version of the AGC circuit. The design of the photodetector allowed choosing a useful signal of a particular modulation frequency in the frequency range from 3 to 45 kHz and effectively suppresses the frequencies caused by optical interference in the low frequency range from the frequency of the input signal of constant amplitude up to 3 kHz inclusive. This compensates the current up to 15 mA, which is equivalent to the power of light interference of about 15 mW. Further research should address the issues of reliability of the proposed photodetector design and optimization of its optical system. The photodetector can be used in geodesy and ambient air quality monitoring.

scholarly journals Noise-silencing technology for upright venting pipe jet noise

2018 ◽  
Vol 10 (8) ◽  
pp. 168781401879481 ◽  
Author(s):  
Enbin Liu ◽  
Shanbi Peng ◽  
Tiaowei Yang
Keyword(s):  
Natural Gas ◽  
Sound Pressure Level ◽  
Sound Pressure ◽  
Low Frequency ◽  
Jet Noise ◽  
Pressure Level ◽  
Living Environment ◽  
Frequency Noise ◽  
Frequency Range ◽  
Expansion Chamber

When a natural gas transmission and distribution station performs a planned or emergency venting operation, the jet noise produced by the natural gas venting pipe can have an intensity as high as 110 dB, thereby severely affecting the production and living environment. Jet noise produced by venting pipes is a type of aerodynamic noise. This study investigates the mechanism that produces the jet noise and the radiative characteristics of jet noise using a computational fluid dynamics method that combines large eddy simulation with the Ffowcs Williams–Hawkings acoustic analogy theory. The analysis results show that the sound pressure level of jet noise is relatively high, with a maximum level of 115 dB in the low-frequency range (0–1000 Hz), and the sound pressure level is approximately the average level in the frequency range of 1000–4000 Hz. In addition, the maximum and average sound pressure levels of the noise at the same monitoring point both slightly decrease, and the frequency of the occurrence of a maximum sound pressure level decreases as the Mach number at the outlet of the venting pipe increases. An increase in the flow rate can result in a shift from low-frequency to high-frequency noise. Subsequently, this study includes a design of an expansion-chamber muffler that reduces the jet noise produced by venting pipes and an analysis of its effectiveness in reducing noise. The results show that the expansion-chamber muffler designed in this study can effectively reduce jet noise by 10–40 dB and, thus, achieve effective noise prevention and control.

Effects of Very Low Frequency Tones on Auditory Thresholds

1966 ◽  
Vol 9 (1) ◽  
pp. 150-160 ◽  
Author(s):  
J. Jerger ◽  
B. Alford ◽  
A. Coats ◽  
B. French
Keyword(s):  
Adverse Effects ◽  
Sound Pressure ◽  
Human Subjects ◽  
Low Frequency ◽  
Pressure Level ◽  
Variable Speed ◽  
Frequency Range ◽  
Auditory Thresholds ◽  
Very Low Frequency ◽  
Piston Cylinder

Nineteen human subjects were exposed to repeated three-minute tones in the sound pressure level range from 119 to 144 dB and the frequency range from 2–22 cps. The tones were produced in an acoustic test booth by a piston-cylinder arrangement, driven by a variable speed direct current motor. Eight subjects showed no adverse effects. Temporary threshold shifts (TTS) of 10 to 22 dB in the frequency range from 3 000 to 8 000 cps were observed in the remaining 11 subjects. In addition, the 7 and 12 cps signals produced considerable masking over the frequency range from 100 to 4 000 cps.

Reverberant Chamber Enhancement

2015 ◽  
Vol 58 (1) ◽  
pp. 24-36
Author(s):  
Daniel Hayes
Keyword(s):  
Fundamental Mode ◽  
Research Laboratory ◽  
Sound Pressure ◽  
Low Frequency ◽  
Naval Research ◽  
Frequency Range ◽  
Testing Frequency ◽  
Acoustic Testing ◽  
High Sound ◽  
High Pass

Typical reverberant chambers used for High Intensity Acoustic Testing (HIAT) can achieve high sound pressure levels (SPL) across most of the applicable frequency range (20 Hz to 10 kHz), but they have limitations. Depending on the size of the chamber, low frequency chamber modes may be limited in the testing frequency range. In addition, reverberant chambers that use conventional 1/3-Octave controllers are not able to control low frequency chamber modes as effectively as the higher frequencies. A typical response to this inability to control the chamber modes is to high pass the frequency range of the excitation in the chamber to prevent exciting the low frequency modes. This method protects the test article from over-testing, although it also might under-test an article that has a fundamental mode below the high-pass frequency of the chamber. Recently, Maryland Sound International conducted a test at the Naval Research Laboratory (NRL) to determine if Direct Field Acoustic Testing (DFAT) technology could be applied to conventional reverberant chambers.

Low Frequency Electrochemical Accelerometer with Low Noise Based on MEMS

2012 ◽  
Vol 503 ◽  
pp. 75-80 ◽  
Author(s):  
Wen Tao He ◽  
De Yong Chen ◽  
Guang Bei Li ◽  
Jun Bo Wang
Keyword(s):  
Early Warning ◽  
Dynamic Range ◽  
Low Frequency ◽  
Inertial Mass ◽  
Low Noise ◽  
Fabrication Process ◽  
Frequency Range ◽  
Wide Dynamic Range ◽  
Geological Disaster ◽  
Excellent Property

Petroleum prospecting and early warning of some geological disaster increasingly depend on the accelerometers which can detect vibrate of frequency below 1Hz, but it’s embarrassing that accelerometers based on Si or SiO2 structure make an awful performance in this frequency range. Electrochemical accelerometers were developed in 1990s. With fluidics to be inertial mass, electrochemical accelerometer not only show an excellent property in low frequency, but also has a wide dynamic range. However, traditional fabrication process of electrochemical accelerometer is rather complex and can’t eliminate the noise due to the inconsistency and asymmetry of electrodes. To solve these problems, a scheme based on MEMS is proposed here, including design, fabrication and package. Properties of electrochemical accelerometer (EAM) are tested in two conditions at last.

Procedure for determination of sound power levels of direct-radiator loudspeakers in the low-frequency range using the sound pressure within the system enclosure

2015 ◽  
Vol 96 ◽  
pp. 75-82 ◽  
Author(s):  
José Luis Sánchez Bote ◽  
Juan Sancho Gil ◽  
Francisco Aznar Ballesta ◽  
Lino Pedro García Morales
Keyword(s):  
Sound Pressure ◽  
Low Frequency ◽  
Sound Power ◽  
Frequency Range

scholarly journals A New Method for Sound Generation Based on Digital Sound Reconstruction

2021 ◽  
Vol 29 (04) ◽  
Author(s):  
Dominik Mayrhofer ◽  
Manfred Kaltenbacher
Keyword(s):  
Sound Pressure ◽  
Low Frequency ◽  
New Method ◽  
General Idea ◽  
Sound Generation ◽  
Frequency Range ◽  
Numerical Investigations ◽  
Multiple Array ◽  
Depth View ◽  
Digital Sound

In this paper, we consider the general idea of Digital Sound Reconstruction (DSR) and analyze its inherent limitations. Based on this discussion, a new method which we call Advanced Digital Sound Reconstruction (ADSR) is introduced and analyzed in detail. This method aims to overcome the problems of classical DSR by introducing shutter gates and focuses on sound generation in the low-frequency domain. Combining the idea of classical DSR with a redirection mechanism leads to a gain of 20[Formula: see text]dB per decade regarding the sound pressure for decreasing frequency values. We present multiple array designs and possible embodiments for ADSR as well as an in depth view of excitation and optimization approaches. Finally, numerical investigations are used in order to demonstrate the potential of ADSR especially in the mid- to low-frequency range.

scholarly journals The Sound of Gas-Turbine Installations

1970 ◽  
Author(s):  
Robert M. Hoover
Keyword(s):  
Control Problem ◽  
Gas Turbine ◽  
Sound Pressure ◽  
Noise Control ◽  
Low Frequency ◽  
Frequency Range ◽  
Level Data ◽  
Industry Performance ◽  
Noise Measurements ◽  
Control Criteria

In this overall review of gas-turbine sound and its control, the author discusses the variety of installations, the scope of the noise control problem, criteria, industry performance, noise specifications, and noise measurements. In particular, the magnitude of the noise control problem is indicated by discussion of the sound of an unmuffled 20 Mw turbine. Typical sound pressure level data on current installations are given, and suggestions are made for noise control criteria in the low frequency range.

A High-Precision Marine Ambient Noise Sound Pressure Monitoring System

2013 ◽  
Vol 321-324 ◽  
pp. 724-727
Author(s):  
Lei Li ◽  
Jun Li Liu ◽  
Cheng Xing Lv
Keyword(s):  
Monitoring System ◽  
High Precision ◽  
Ambient Noise ◽  
Sound Pressure ◽  
Measurement Accuracy ◽  
Dynamic Range ◽  
Low Frequency ◽  
Signal Modulation ◽  
Pressure Monitoring ◽  
Wide Dynamic Range

A high-precision marine ambient noise sound pressure monitoring system is developed based on the Michelson interference, a method of improving the measurement accuracy is presented by signal modulation and compensation. Experiments show that the monitoring system has a wide dynamic range and high accuracy especially in low-frequency.

scholarly journals Annoyance of Audible Infrasound

1987 ◽  
Vol 6 (1) ◽  
pp. 1-17 ◽  
Author(s):  
Henrik Møller
Keyword(s):  
Sound Pressure Level ◽  
Sound Pressure ◽  
Dynamic Range ◽  
Pressure Level ◽  
Frequency Range ◽  
Low Frequencies ◽  
Pure Tones ◽  
The Individual

Contours of equal annoyance were determined for pure tones in the frequency range 4 – 31.5 Hz. The curves show a narrowing of the dynamic range of the ear at low frequencies. The same pattern is seen for equal loudness curves, and the results support the theory that the annoyance of infrasound is closely related to the loudness sensation. Annoyance ratings of 1/3 octave noise did not deviate from ratings of pure tones with the same sound pressure level. Combinations of audio and infrasonic noise were in general given a rating close to or slightly above the rating of the most annoying of the individual noise conditions. For infrasound the proposed G1-weighting curve is shown to give values that correlate well with subjective annoyance rating. Values obtained with the G2-curve do not correlate as well. Low audio frequencies are not covered by the G-curves, and it is shown that these are insufficiently covered by the A-curve. Further research is needed in this area.

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