Detected Noise Level Research Articles

Supercontinuum intensity noise coupling in Fourier transform photoacoustic spectroscopy.

We investigate the noise transfer mechanism from the light source intensity fluctuations to the acoustic signal in Fourier transform photoacoustic spectroscopy (FT-PAS). This noise coupling is expected to be reduced in FT-PAS compared with conventional Fourier transform spectroscopy, as only the specific spectral components that are absorbed by the probed sample contribute to the noise level. We employ an incoherent supercontinuum (SC) light source in our experiments and observe a linear relation between the sample gas concentration and the detected noise level, which significantly reduces the influence of the SC noise on the detection limit. Based on our experimental results, we derive a model for the noise level, which establishes the foundation for practical sensitive implementation of FT-PAS.

Force detection sensitivity spectrum calibration of levitated nanomechanical sensor using harmonic coulomb force

Oscillators based on levitated particles are promising for the development of ultrasensitive force detectors. The theoretical performance of levitated nanomechanical sensors is usually characterized by the so-called thermal noise limit force detection sensitivity, which does not exhibit spectral specificity in practical measurements. To characterize the actual detection performance, we propose a method for the force detection sensitivity calibration of a levitated nanomechanical sensor based on the harmonic Coulomb force. Utilizing the measured transfer function, we obtained the force detection sensitivity spectrum from the position spectrum. Although the thermal noise limit force detection sensitivity of the system reached (4.39±0.62)×10−20N/Hz1/2 at 2.4×10−6mbar with feedback cooling, the measured sensitivity away from the resonance was of the order of 10−17N/Hz1/2 based on the existing detection noise level. The calibration method established in our study is applicable to the performance evaluation of any optical levitation system for high-sensitivity force measurements.

Fuzzy C-Means Algorithm-Based Adoption of Obturator Nerve Block under Adaptive Ultrasound Imaging for Bladder Tumor

This work aimed to study the adoption of obturator nerve block (ONB) based on adaptive medical ultrasound imaging under C-means algorithm in transurethral resection of bladder tumor (TURBT). 120 patients with bladder tumors were diagnosed by C-means algorithm-based ultrasound imaging and were enrolled into group A (epidural anesthesia + resection), group B (general anesthesia), and group C (epidural anesthesia + ONB), each with 40 cases. The accuracy of the detection method, noise level, and complications before and after the operation were compared. All patients received TURBT for treatment. There was no significant difference in the general information of patients in each group ( P > 0.05 ). As a result, the correct segmentation rate of the tumor region segmented by ultrasound imaging by C-means algorithm reached 95.6%. The incidence of obturator nerve reflex (ONR) in group A (7.5%) was greatly inferior to groups B and C ( P < 0.05 ). The length of hospital stay in group A was (4.01 ± 1.43) days, which was notably different from groups B and C, with considerable difference among the three ( P < 0.05 ). In short, the adaptive medical ultrasound imaging under C-means algorithm was more accurate in the diagnosis of bladder tumors. Moreover, ONB can effectively reduce the ONR and the incidence of complications in patients.

18F-NaF PET/CT of Obese Patients on a Lutetium-Yttrium Oxyorthosilicate PET/CT System: Patient Dosimetry, Optimization of Injected Activity, and Acquisition Time.

18F-NaF PET/CT has a rapid single-pass extraction and fast clearance from soft tissues, resulting in a good target-to-background ratio. This study aimed to establish the optimum acquisition time and dosimetry for 18F-NaF PET/CT to evaluate bone metastases in obese patients. A secondary objective was to evaluate the impact of acquisition time on image quality, lesion detection rate, noise level, and radiation burden in this patient group. Methods: In total, 60 patients were included in the study (20 patients with a body mass index (BMI) of 30.0-34.9 kg/m2, 20 with a BMI of 35-39.9 kg/m2, and 20 with a BMI of >40 kg/m2). Images were acquired after intravenous injection of a 2.2 MBq/kg (0.06 mCi/kg) dose of 18F-NaF. Data were acquired in list mode using ordered-subset expectation maximization reconstruction. The raw data were rebinned to simulate scans with acquisition times of 2, 2.5, and 3 min per bed position. The scans were visually analyzed by 2 observers and scored by rank against a panel of parameters (overall image quality, noise level, background soft tissue, and lesion detectability), and the contrast-to-noise ratio (CNR) was calculated. Results: The mean CNR was 20.19 ± 8.39 for a 2-min acquisition, 21.03 ± 8.35 for 2.5 min, and 22.16 ± 8.37 for 3 min. There were no statistically significant differences in CNR among the 3 different acquisition durations (P > 0.05). Lesion delineation was excellent and independent of the acquisition time. All relevant lesions could be identified with all 3 acquisition times. A mean activity of 215.4 ± 31.3 MBq was injected, with estimated mean effective absorbed doses of 4.09 ± 0.59 mSv for 18F-NaF PET and 7.88 ± 1.66 mSv for CT alone. Conclusion: 18F-NaF PET/CT can be beneficial in obese patients because of its good pharmacokinetics. Optimal osseous staging can be achieved with relatively low doses and radiation burden. Lesion delineation was excellent regardless of acquisition time. However, it is recommended that an acquisition of 3 min per bed position be used in patients with a BMI of more than 40.

Pendeteksi Tingkat Kebisingan berbasis Internet of Things sebagai Media Kontrol Kenyamanan Ruangan Perpustakaan

The library is a place that is used as a study and reading room, so that a comfortable place is needed from disturbances in the library building. Based on the decision of the Minister of Environment in 1996, the standard noise for library environments ranged from 45 to 55 dB. but in fact there is often a commotion caused by visitors. in this study a noise level detection system was created where the noise detection system is expected to be used as a media for comfort control in the library room. The noise level detector uses a sound sensor that is connected to Arduino.The system will be equipped with a warning system in the form of Buzzer and Warning Text sounds that will be displayed on the P10 LED Panel and equipped with Internet of Things technology that allows the supervisor or guard of the library to monitor the noise of the library room real time via Web Server. The test results show that this tool can detect noise levels in the range of at least 41 dB and a maximum of 69 dB with a deviation of 0.6 and an average error of 1.0%. the average sound intensity measured in the library room is 56.24 dB. The average percentage of the success of the system against Buzzer and Warning text warnings is equal to 97.3% and the average percentage of the success of sending data to the web server in the noise level detector is 95%

On the design of an energy-harvesting noise-sensing WSN mote

Wireless sensor networks (WSNs) could potentially help in the measurement and monitoring of noise levels, an important step in mitigating and fighting noise pollution. Unfortunately, the high energy required by the noise measurement process and the reliance of sensor motes on batteries make the management of noise-sensing WSNs cumbersome. Giving motes energy harvesting (EH) capabilities could alleviate such a problem, and several EH-WSNs have already been demonstrated. Nevertheless, the high-frequency nature of the data required to measure noise places significant additional challenges to the design of EH-WSNs. In this paper, we present a design and prototype for a mote extension which enables the mote to detect noise levels while being powered by energy harvesting. The noise level detection carried out by the system relies primarily on the concept of peak detection. Results of performance testing are presented. Aside from the hardware design and prototype, we also discuss methods of assigning charge times for application scenarios where there are multiple pulse loads. We also propose a new opportunistic method for charge time determination. Experiments demonstrate that the new method could improve analytically-derived duty cycles by at least 350%.

Integrated fluorescence detection of labeled biomolecules using a prism-like PDMS microfluidic chip and lateral light excitation

Microfabricated amorphous silicon photodiodes were integrated with prism-like PDMS microfluidics for the detection and quantification of fluorescence signals. The PDMS device was fabricated with optical quality surfaces and beveled sides. A 405 nm laser beam perpendicular to the lateral sides of the microfluidic device excites the fluorophores in the microchannel at an angle of 70° to the normal to the microchannel/photodiode surface. This configuration, which makes use of the total internal reflection of the excitation beam and the isotropy of the fluorescence emission, minimizes the intensity of excitation light that reaches the integrated photodetector. A difference of two orders of magnitude was achieved in the reduction of the detection noise level as compared with a normally incident excitation configuration. A limit-of-detection of 5.6 × 10(10) antibodies per square centimeter was achieved using antibodies labeled with a model organic fluorophore. Furthermore, the results using the lateral excitation scheme are in good proportionality agreement with those by fluorescence quantification using wide-field fluorescence microscopy.

Wa-LiD: A New LiDAR Simulator for Waters

A simulator (Wa-LiD) was developed to simulate the reflection of LiDAR waveforms from water across visible wavelengths. The specific features of the simulator include 1) a geometrical representation of the water surface properties; 2) the use of laws of radiative transfer in water adjusted for wavelength and the water's physical properties; and 3) modeling of detection noise and signal level due to solar radiation. A set of simulated waveforms was compared with observed LiDAR waveforms acquired by the HawkEye airborne and Geoscience Laser Altimeter System (GLAS) satellite systems in the near infrared or green wavelengths and across inland or coastal waters. Signal-to-noise ratio (SNR) distributions for the water surface and bottom waveform peaks are compared with simulated and observed waveforms. For both systems (GLAS and HawkEye), Wa-LiD simulated SNR conform to the observed SNR distributions. Moreover, Wa-LiD showed a good ability to reproduce observed waveforms according to some realistic water parameters fitting.

Comparisons of spectral characteristics of wind noise between omnidirectional and directional microphones

Wind noise reduction is a topic of ongoing research and development for hearing aids and cochlear implants. The purposes of this study were to examine spectral characteristics of wind noise generated by directional (DIR) and omnidirectional (OMNI) microphones on different styles of hearing aids and to derive wind noise reduction strategies. Three digital hearing aids (BTE, ITE, and ITC) were fitted to Knowles Electronic Manikin for Acoustic Research. They were programmed to have linear amplification and matching frequency responses between the DIR and OMNI modes. Flow noise recordings were made from 0° to 360° azimuths at flow velocities of 4.5, 9.0, and 13.5 m/s in a quiet wind tunnel. Noise levels were analyzed in one-third octave bands from 100 to 8000 Hz. Comparison of wind noise revealed that DIR generally produced higher noise levels than OMNI for all hearing aids, but it could result in lower levels than OMNI at some frequencies and head angles. Wind noise reduction algorithms can be designed to detect noise levels of DIR and OMNI outputs in each frequency channel, remove the constraint to switch to OMNI in low-frequency channel(s) only, and adopt the microphone mode with lower noise levels to take advantage of the microphone differences.

Experimental comparison of autodyne and heterodyne laser interferometry using an Nd:YVO_4 microchip laser

Using an Nd:YVO₄ microchip laser with a relaxation frequency in the megahertz range, we have experimentally compared a heterodyne interferometer based on a Michelson configuration with an autodyne interferometer based on the laser optical feedback imaging (LOFI) method regarding their signal-to-noise ratios. In the heterodyne configuration, the beating between the reference beam and the signal beam is realized outside the laser cavity, while in the autodyne configuration, the wave beating takes place inside the laser cavity, and the relaxation oscillations of the laser intensity then play an important part. For a given laser output power, object under investigation, and detection noise level, we have determined the amplification gain of the LOFI interferometer compared to the heterodyne interferometer. LOFI interferometry is demonstrated to show higher performance than heterodyne interferometry for a wide range of laser powers and detection levels of noise. The experimental results are in good agreement with the theoretical predictions.

Influence of laser sources with different spectral properties on the performance of vapor cell atomic clocks based on lin‖lin CPT

We evaluate the influence of 2 types of laser sources with different spectral profiles on the performance of vapor cell atomic clocks based on lin||lin coherent population trapping (CPT) resonances. We show that a short-term stability of 1-2 x 10(-11) tau(-1/2) may be reached in a compact system using a modulated vertical cavity surface-emitting laser. Here the stability is limited by the detection noise level and can be improved up to a factor of 4 by increasing the lock-in detection frequency to several tens of kilohertz, which is not possible in standard double resonance atomic clocks. We compare these results with CPT prepared under the same experimental conditions, using 2 phase-locked extended cavity diode lasers, with which we predict a challenging short-term stability of 1-3 x 10(-13) tau(-1/2), comparable to the state-of-the-art laser-pumped Rb-clocks.

Exposure to noise in orthopaedic theatres - do we need protection?

To detect noise levels, generated by high-powered tools in orthopaedic theatres at varying distances from the operating site, and its impact on hearing in staff and patients. Sound-level meter was used to measure the sound level generated by various high-powered tools in routine orthopaedic procedures, at varying distances from the operating site. These recorded noise levels were compared against the UK noise safety guidelines. We found that the noise generated was often significantly higher than the safety guidelines. Noise levels in orthopaedic theatres can be at unacceptable levels, which could potentially lead to hearing problems in the staff and patients. We believe that all patients, especially the elderly patients, (who are more prone to hearing problems) should have hearing protection during orthopaedic operations that use high-powered tools. Surgeons and scrubbed theatre staff should take precautions.

System and method of noise-dependent classification

A noise-dependent classifier for a speech recognition system includes a recognizer ( 15 ) that provides scores and score differences of two closest in-vocabulary words from a received utterance. A noise detector ( 17 ) detects the noise level of a pre-speech portion of the utterance. A classifier ( 19 ) is responsive to the detected noise level and scores and noise dependent model for making decisions for accepting or rejecting the utterance as a recognized word depending on the noise-dependent model and the scores.

Correlation spectrum analyzer for direct measurement of device current noise

This article analyzes the realization and the performance of a correlation spectrum analyzer specifically conceived to directly measure the current noise produced by electronic devices with maximum sensitivity. The text describes in detail and gives the design rules of the instrument input amplifiers taking into consideration noise, dynamic range, stability, and bandwidth, together with the effects that a device under test (DUT) having complex impedance introduce. This article shows that the proposed scheme may allow current noise measurements with a sensitivity improved by few orders of magnitude with respect to a standard spectrum analyzer and to a correlation analyzer in voltage scheme whenever the DUT has an impedance larger than few 10 kΩ. Such a sensitivity makes the proposed instrument ideal for the characterization of advanced devices, such as ultrashort channel metal-oxide-semiconductor field effect transistors, mesoscopic junctions, or spin dependent electron transfer devices where it may be necessary to detect noise levels as low as fA/Hz.

Power Ratio Estimation in Incoherent Backscatter Lidar: Heterodyne Receiver with Square Law Detection

Abstract Comparative return irradiance estimation in a two channel heterodyne lidar receiver should be facilitated by processing finite data samples obtained in a period short compared with that of atmospheric fluctuations affecting beam propagation. Here the performance is compared of two ratio or log-ratio estimators with the assumptions of square law detection, uncorrelated speckle and arbitrary background noise level and sample size. In both cases storage of the sample logarithm is usually advantageous regarding short-term bias and variance especially where the sample size is small and the ratio near unity. Implications for control of overall measurement bias and optimized processing speed are briefly discussed.

Noise monitoring apparatus

An apparatus for monitoring the noise which impinges a human ear and for generating a signal representing the noise level accumulated over a period of time. Typically, the apparatus can be located in a hearing protector worn by a worker in a noisy environment. A microphone generates a signal having a magnitude representing the detected noise level of the ear which signal is processed by an absolute value circuit and a root mean square circuit to generate a signal having a magnitude proportional to the logarithm of the detected noise level. This logarithmic signal is converted by a voltage to frequency converter and a counter accumulates a count total proportional to the noise level over a period of time. The apparatus includes visual and aural alarms to indicate a maximum allowed noise level and dosage. The apparatus can also be inserted into a storage unit for reading the data, calibrating the noise monitor circuitry and recharging the batteries in the apparatus.