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1.
We present a high-sensitivity fiber Bragg grating(FBG)-based microphone with a flat response and static pressure equalization. A very high dynamic sensitivity of the microphone is achieved by a pressure sensing structure based on a carbon fiber diaphragm. Static pressure equalization is realized by a balance structure with a capillary glass tube. The resonances of the sensor are suppressed by air damping structures, and a broadened flat response is achieved. An acoustic-solid interaction model was used to analyze the response characteristics of the microphone. An experimental prototype was produced and tested, and the results are well consistent with the design.The tested sensitivity was-10 d B re 1 pm/Pa from 10 Hz to 2.5 kHz with a fluctuation of less than ±1.5 dB.Combined with the phase-generated-carrier-based coherent detection scheme, the microphone can achieve a sound resolution of the milli-pascal level. The static pressure sensitivity is measured to be-0.27 pm/atm, which is 100 dB lower than the dynamic sensitivity.  相似文献   

2.
Some results from the study of the physiological effects of high level broad-band noise fields(165-173 dB)on guinea-pigs are presented in this paper.The lethal time for guinea-pigs undervarious sound pressure levels was determined.The logarithm of exposure time and the sound pres-sure level had good linear correlation.The experimental results showed that lethal time was decreasedby half if the sound pressure level was increased by 3 dB.These results agreed with the law ofequal energy and showed the death of guinea-pigs depended on the noise-dose,i.e.the noise in-tensity times the exposure duration.The average value of the lethal noise-dose is a constant,about33 J/mm~2.  相似文献   

3.
Using an audiometer,the effect of the noise level upon temporarythreshold shift(TTS)for five trained normal subjects(left ear only)was studied.The measurements were carried out after 6 min exposure(in third octave band)for different sound pressure levels ranging between 75-105 dB at three test fre-quencies 2,3,and 4 kHz.The results indicated that at exposure to noise of soundpressure level(SPL)above 85 dB,TTS increases linearly with ths SPL for all thetest frequencies.The work had extended to study the recovery curves for the sameears.The results indicated that the reduction in TTS on doubling the recoverytimes,for the two sound pressure levels 95 dB and 105 dB,occurs at a rate of near-ly 3 dB.The comparison of the recovery curve at 3 kHz with that calculated usingWard's general equation for recovery was made.Finally,to study the values ofTTS produced by exposure to certain noise at different test frequencies,distribu-tion curves for two recovery times were plotted representing TTS values,for anexposure  相似文献   

4.
Experiments of the temperature effect on single bubble sonoluminescence (SBSL) are performed with a mixture of water and anti-freeze.Since experiments of constant pressure (keeping sound pressure constant) are not feasible for a wide temperature range,experiments of constant luminance (keeping light intensity stable),which reflect pure sensitivity of SBSL to temperature,are investigated.The results show that lower temperature needs less pressure to obtain the same light intensity,which means that lower temperature is better for SBSL.Numerical calculations show a qualitative agreement with experiments.  相似文献   

5.
The energy response calibration of the commonly used high pressure ionization chamber is very difficult to obtain when the gamma-ray energy is more than 3 MeV. In order to get the calibration of the higher part of the high pressure ionization chamber, we use the Fluka Monte Carlo program to perform the energy response in both the spherical and the cylindrical high pressure ionization chamber which are full of argon gas. The results compared with prior study when the gamma-ray energy is less than 1.25 MeV. Our result of Monte Carlo calculation shows agreement with those obtained by measurement within the uncertainty of the respective methods. The calculation of this study is significant for the high pressure ionization chamber to measure the high energy gamma-ray.  相似文献   

6.
The acoustical quality of an ordinary hall,namely the reverberation time and the spatial nonuni-formity of sound pressure level in audience area,was simulated on a microcomputer.Comparisonbetween calculation,measurement and simulation of reverberation time shows that the reverberationtime from simulation is closer to measurement than from calculation,if the absorption of the audience isproperly chosen,in the frequency range from l25 to 4000 Hz;the average deviation is less than 10%.For the spatial nonuniformity of sound pressure level,there is a good correspondency botween thesimulation and the measurement.In addition,some details in simulation were discussed.  相似文献   

7.
The electro-pneumatic loudspeaker has been used widely as a sound source of high intensity noise.Investigation in this paper shows that by suitably increasing the upper limit frequency of the soundsource it can be used as a broadcasting sound source to reproduce speech and music.The acousticpower output of the sound source developed is 2000W;the power output at l000Hz deviates less than4 dB from the highest power output in its frequency range.The intelligibility of sentences recordedword for word at 5.8 km distance from the single sound source is 56%.And for an array of foursources,the intelligibility of sentences recorded word for word is 58% at 8.7 km from the soundsource,and 32% at l0.2 km from the sound source.The subjective rating for short passages isnearly intelligible at 8.7 km from the sound source,and less intelligible at 10.2 km from the soundsource.The experimental results show that the obtained intelligibility is dependent on the educa-tional level and the sense of responsibility of the list  相似文献   

8.
A truncated broadband parametric array with a primary frequency of 500 kHz and difference frequency range of 1 kHz to 30 kHz was designed as a sound source of the underwater acoustic material measurement system.By analyzing the theoretical calculation and actual measurement results in array directivity of the truncated broadband parametric source at typical frequencies,we observed that the curves of the two results were basically consistent,which proved that the calculation model was correct.Application of bell-shaped short-duration pulse to achieve broadband measurement for characteristics of underwater acoustic materials was beneficial to reduce the effects of diffraction from the panel edges.The measurement system was established for measuring the sound pressure reflection coefficients,sound pressure transmission coefficients and absorption coefficients of the large panel sample in the pressure vessel.The size of this tank is φ4 m×12 m,the maximum hydrostatic pressure is 4.5 MPa,and the corresponding measuring frequency range is from 1 kHz to 30 kHz.The measured curves had a good agreement with theoretical curves,which verified that the parametric source measurement method was feasible.Then,the sound absorption properties of the rubber plate sample were measured under different hydrostatic pressures.The studying results could show that the parametric source measurement method had the potential application in the limited space water,such as the pressure vessel.  相似文献   

9.
We present a new method for detecting near-infrared, mid-infrared, and far-infrared photons with an ultrahigh sensitivity. The infrared photon detection was carried out by monitoring the displacement change of a vibrating microcantilever under light pressure using a laser Doppler vibrometer. Ultrathin silicon cantilevers with high sensitivity were produced using micro/nano-fabrication technology. The photon detection system was set up. The response of the microcantilever to the photon illumination is theoretically estimated, and a nanowatt resolution for the infrared photon detection is expected at room temperature with this method.  相似文献   

10.
董必春  张润梅  袁彬  俞传阳 《中国物理 B》2022,31(2):24303-024303
Nearfield acoustic holography in a moving medium is a technique which is typically suitable for sound sources identification in a flow.In the process of sound field reconstruction,sound pressure is usually used as the input,but it may contain considerable background noise due to the interactions between microphones and flow moving at a high velocity.To avoid this problem,particle velocity is an alternative input,which can be obtained by using laser Doppler velocimetry in a non-intrusive way.However,there is a singular problem in the conventional propagator relating the particle velocity to the pressure,and it could lead to significant errors or even false results.In view of this,in this paper,nonsingular propagators are deduced to realize accurate reconstruction in both cases that the hologram is parallel to and perpendicular to the flow direction.The advantages of the proposed method are analyzed,and simulations are conducted to verify the validation.The results show that the method can overcome the singular problem effectively,and the reconstruction errors are at a low level for different flow velocities,frequencies,and signal-to-noise ratios.  相似文献   

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