The influence of external conditions on sound pressure in the pistonphone at the infrasound frequency range

2020 ◽  
pp. 67-72
Author(s):  
A. V. Konkov ◽  
D. V. Golovin
Keyword(s):  
Environmental Conditions ◽  
Sound Pressure ◽  
Primary Method ◽  
Frequency Range ◽  
External Conditions ◽  
Numerical Estimations

The influence of environmental conditions on a sound pressure reproduced by the primary method in the measuring chambers of the Pistonphone in the frequency range from 1 mHz to 250 Hz is estimated. Numerical estimations of influence of environmental conditions on sound pressure in pistonphone measuring chambers are given and special requirements to system of maintenance of required external conditions are specified.

The Study of Method for Calculating Geometric Average Sound Intensity in Scattering Field

2010 ◽  
Vol 458 ◽  
pp. 185-191
Author(s):  
Feng Li Luo ◽  
Guang Yu Li
Keyword(s):  
High Frequency ◽  
Sound Pressure ◽  
Computing Time ◽  
Sound Intensity ◽  
Frequency Range ◽  
Average Value ◽  
Geometric Average ◽  
Scattering Field ◽  
Measurement Efficiency ◽  
Frequency Area

When calculating sound intensity by indirectly measuring way, the sound pressures obtained from two microphones should be mathematically averaged as the sound pressure of measured point. The research showed that the method exists lower of allowable value in the high frequency area. Using the geometric average value of two measured points to replace the sound pressure of measured point, studying the measurement of sound intensity in scattering field, the errors from which were compared. The result showed that the error of geometric average sound intensity was more flat than that of mathematic average. So the sound intensity obtained from geometric average sound pressure is more suitable for the measurement of a wider frequency range. And the computing time is short, which can raise the measurement efficiency and the real-time of measurement.

scholarly journals Reducing the harmful effects of noise on the human environment. Sound insulation of industrial skeleton enclosures in the 10–40 kHz frequency range

2020 ◽  
Vol 18 (2) ◽  
pp. 1451-1463
Author(s):  
Witold Mikulski
Keyword(s):  
Sound Pressure Level ◽  
Sound Pressure ◽  
Sheet Steel ◽  
Pressure Level ◽  
Sound Insulation ◽  
Frequency Range ◽  
Noise Sources ◽  
Human Environment ◽  
Absorbing Material ◽  
Acoustic Enclosures

Abstract Purpose The purpose of the research is to work out a method for determining the sound insulation of acoustic enclosures for industrial sources emitting noise in the frequency range of 10–40 kHz and apply the method to measure the sound insulation of acoustic enclosures build of different materials. Methods The method is developed by appropriate adaptation of techniques applicable currently for sound frequencies of up to 10 kHz. The sound insulation of example enclosures is determined with the use of this newly developed method. Results The research results indicate that enclosures (made of polycarbonate, plexiglass, sheet aluminium, sheet steel, plywood, and composite materials) enable reducing the sound pressure level in the environment for the frequency of 10 kHz by 19–25 dB with the reduction increasing to 40–48 dB for the frequency of 40 Hz. The sound insulation of acoustic enclosures with a sound-absorbing material inside reaches about 38 dB for the frequency of 10 kHz and about 63 dB for the frequency of 40 kHz. Conclusion Some pieces of equipment installed in the work environment are sources of noise emitted in the 10–40 kHz frequency range with the intensity which can be high enough to be harmful to humans. The most effective technical reduction of the associated risks are acoustic enclosures for such noise sources. The sound pressure level reduction obtained after provision of an enclosure depends on its design (shape, size, material, and thickness of walls) and the noise source frequency spectrum. Realistically available noise reduction values may exceed 60 dB.

Duration tuning in the inferior colliculus of the mustached bat

2011 ◽  
Vol 106 (6) ◽  
pp. 3119-3128 ◽  
Author(s):  
Silvio Macías ◽  
Emanuel C. Mora ◽  
Julio C. Hechavarría ◽  
Manfred Kössl
Keyword(s):  
Inferior Colliculus ◽  
Sound Pressure ◽  
Frequency Range ◽  
Constant Frequency ◽  
Third Harmonic ◽  
Mustached Bat ◽  
Pteronotus Parnellii ◽  
Sound Levels ◽  
Response Profile ◽  
Band Pass

We studied duration tuning in neurons of the inferior colliculus (IC) of the mustached bat. Duration-tuned neurons in the IC of the mustached bat fall into three main types: short (16 of 136), band (34 of 136), and long (29 of 136) pass. The remaining 51 neurons showed no selectivity for the duration of sounds. The distribution of best durations was double peaked with maxima around 3 and 17 ms, which correlate with the duration of the short frequency-modulated (FM) and the long constant-frequency (CF) signals emitted by Pteronotus parnellii. Since there are no individual neurons with a double-peaked duration response profile, both types of temporal processing seem to be well segregated in the IC. Most short- and band-pass units with best frequency in the CF2 range responded to best durations > 9 ms (66%, 18 of 27 units). However, there is no evidence for a bias toward longer durations as there is for neurons tuned to the frequency range of the FM component of the third harmonic, where 83% (10 of 12 neurons) showed best durations longer than 9 ms. In most duration-tuned neurons, response areas as a function of stimulus duration and intensity showed either V or U shape, with duration tuning retained across the range of sound levels tested. Duration tuning was affected by changes in sound pressure level in only six neurons. In all duration-tuned neurons, latencies measured at the best duration were longer than best durations, suggesting that behavioral decisions based on analysis of the duration of the pulses would not be expected to be complete until well after the stimulus has occurred.

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.

OPTIMAL DESIGN OF A 1-3 PIEZOCOMPOSITE TONPILZ TRANSDUCER BY MEANS OF THE FINITE ELEMENT METHOD

2008 ◽  
Vol 22 (11) ◽  
pp. 1087-1092 ◽  
Author(s):  
DA LIE PEI ◽  
YONGRAE ROH
Keyword(s):  
Finite Element Method ◽  
Sound Pressure ◽  
Optimization Technique ◽  
Pressure Level ◽  
Frequency Bandwidth ◽  
The Finite Element Method ◽  
Frequency Range ◽  
Design Variables ◽  
Structural Variables ◽  
Functional Forms

Underwater Tonpilz transducer is designed with 1-3 piezocomposite materials to overcome the problems with conventional piezoceramic transducers. With the FEM, the variation of the resonance frequency, bandwidth and sound pressure of the transducer are analyzed in relation to the structural variables of the transducer. Through statistical multiple regression analysis of the results, functional forms of the transducer performance are derived in terms of design variables. By applying the constrained optimization technique, SQP-PD, to the derived functions, the optimal structure of the transducer is determined that can provide the highest sound pressure level at a given resonant frequency over a pre-determined frequency range. The validity of the optimized results is confirmed through comparison of the optimal performance with that of the FEA.

Comparison of Seven Systems for High-Frequency Air-Conduction Audiometry

1970 ◽  
Vol 13 (2) ◽  
pp. 254-270 ◽  
Author(s):  
Cecil K. Myers ◽  
J. Donald Harris
Keyword(s):  
High Frequency ◽  
Sound Pressure ◽  
Frequency Noise ◽  
Noise Band ◽  
Frequency Range ◽  
Pure Tones ◽  
Auditory Acuity ◽  
Narrow Bands ◽  
Reference Threshold ◽  
Air Conduction

Seven equipment systems were assembled to examine human auditory acuity from 8 to 20 kHz. Two loudspeakers and two earphones were examined, together with two types of stimulus (pure tones and narrow bands of noise) and two psychometric methods (Limits and Adjustments). All systems were capable of providing usably reliable thresholds on 28 ears throughout the whole frequency range. When carefully calibrated, several systems (those involving loudspeakers, as well as those involving earphones) yielded comparable reference threshold sound-pressure levels at the eardrum. A preference was expressed for a system using Bekesy threshold tracking with a changing-frequency noise band of 300 Hz, and for a discrete-tone system using the Method of Constants.

scholarly journals Measurement and Analysis of Infrasound Signals Generated by Operation of High-Power Wind Turbines

Energies ◽  
2021 ◽  
Vol 14 (20) ◽  
pp. 6544
Author(s):  
Tomasz Malec ◽  
Tomasz Boczar ◽  
Daria Wotzka ◽  
Michał Kozioł
Keyword(s):  
Wind Turbines ◽  
High Power ◽  
Sound Pressure ◽  
Operating Time ◽  
Weather Conditions ◽  
Acoustic Energy ◽  
Working Environment ◽  
Frequency Range ◽  
Noise Levels ◽  
Measurement And Analysis

The development of wind energy and the increasing number of installed wind turbines make it necessary to assess them in terms of the nuisance of the emitted infrasound noise generated by such devices. The article presents the results of measurements and analyses of infrasound emitted during the operation of wind turbines installed in various locations in Poland. Comparative analysis of noise levels in the infrasound and audible range has shown that acoustic energy is mainly in the low and infrasound frequency range, and the measured levels depend significantly on the weighting curves used. On the basis of the results, it was confirmed that the sound pressure level of infrasound signals emitted by the operation of high-power wind turbines, regardless of wind velocity, weather conditions, design solutions of turbines, operating time, rated capacity, does not exceed the criteria specified in the applicable legislation dealing with the assessment of infrasound noise on the working environment.

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