Passive Attenuation Research Articles

Seismic isolation systems for next-generation gravitational wave detectors

Gravitational Wave (GW) Astronomy is becoming a revolutionary method for studying the Universe and understanding its evolution, opening a new frontier in the exploration of cosmic phenomena. Third-generation ground-based gravitational wave interferometers, expected to be built around 2035, will be an order of magnitude more sensitive than the current detectors. Their low frequency sensitivity will allow the detection of binary compact coalescences up to high red-shift improving the capability to study intermediate-mass black holes and enhancing early alerts of binary neutron star coalescences. Within this scientific contest an important effort is being made to increase the detection capabilities in a frequency range down to 3 Hz and mitigating low-frequency noise. The Superattenuator is the mechanical device designed to isolate the optical components of the Advanced VIRGO (AdV) interferometer from seismic noise and local disturbances, relying on the passive and active action of the elements. In this short note, we summarize the design activity around new generation of seismic attenuation systems with the intent to improve the sensitivity in the low frequencies region. The optimization of prototypes and their passive attenuation performance is also considered in view of the Einstein Telescope with the possibility to decrease the size of the mechanical structure and minimizing the impact on the civil works for the construction of the underground laboratory.

X‐Band 130‐nm CMOS transceiver front‐end with a broadband attenuator design for phased‐array systems

AbstractThis letter demonstrates an X‐band transceiver front‐end in 130‐nm CMOS technology for phased‐array systems. To solve the problem that passive attenuator performance deteriorates significantly in wideband systems, a 6‐bit attenuator with source follower and common‐gate amplifier is proposed. Besides, an 8‐bit vector‐summing phase shifter is implemented in common path to realize the phase coverage of 360° with the least significant bit of 5.625°. In the frequency range of 8–12 GHz, the measured root‐mean‐square (rms) amplitude and phase errors of the attenuator in the transceiver are less than 0.36 dB and 2.2°, respectively. The rms phase and amplitude errors of the phase shifter in the transceiver are less than 4.8° and 0.56 dB, respectively. The whole chip area including pads is 3 × 2.3 mm2.

A 5–6-GHz CMOS Beamforming Transceiver Front-End for Fiber-to-the-Room All-Optical Wi-Fi Solution

This letter presents a 5–6-GHz CMOS beamforming transceiver front-end with high linearity and low power consumption for fiber-to-the-room (FTTR) all-optical Wi-Fi solution, which can greatly reduce the transmission power and eliminate signal mutual interference among access points compared with traditional architecture, by aggregating beams of multichannel. The transmitter (TX) employs a high-linearity power amplifier, a variable-gain amplifier, a 5-bit passive attenuator (ATT), and a 4-bit passive phase shifter (PS). The receiver (RX) is composed of a single-to-differential variable gain low-noise amplifier (LNA), frequency-tuning buffers, a 5-bit ATT, and a 4-bit PS. Implemented in a 55-nm CMOS technology, the measured output power 1dB compression point (OP1dB) of TX is better than 12.1 dBm. The error vector magnitudes (EVMs) of the TX at 0-dBm output power with 80-MHz 256-quadrature amplitude modulation (QAM) orthogonal frequency division multiplexing (OFDM) signal are better than −36.3 dB, and the EVMs of the RX at −40 dBm input power are better than −37.8 dB. The noise figure is 4.3 dB in high-gain mode.

Cabin noise analysis of an H120 B helicopter for active noise control applications

Helicopter pilots are exposed to high noise levels during flight induced by the rotor, engine and airflow. To reduce this noise exposure, headsets with active noise control functions are increasingly being used. In addition to the passive noise reduction these systems reduce low frequency noise by local destructive interference of the sound waves. The development of active noise control systems requires detailed analysis of the acoustic environment, which is rarely available for helicopters. For this reason, sound measurements were taken for different flight parameters on board an H120 B helicopter. Multiple microphones were placed at the crew and passenger positions and in the center of the cabin. In addition, a head and torso simulator (HATS) was placed in the copilot seat to measure the passive attenuation and the ANC performance of a commonly used commercial ANC headset in flight. The results of the analysis provide useful information about the noise characteristics for different flight conditions of the H120 B and identify the most critical noise components.

Analysis of an Adaptive Periodic Low-Frequency Wave Filter Featuring Magnetorheological Elastomers.

This study aims to enhance and tune wave-propagation properties (Bandgaps) of periodic structures featuring magnetorheological elastomers (MREs). For this purpose, first, a basic model of periodic structures (square unit cell with cross-shaped arms), which does not possess noise filtering properties in the conventional configuration, is considered. A passive attenuation zone is then proposed by adding a cylindrical core mass to the center of the conventional geometry and changing arm angles, which permitted new bandgap areas. It was shown that better wave-filtering performance may be achieved by introducing a large radius of the cylindrical core as well as low negative cross-arm angles. The modified configuration of the unit cell was subsequently utilized as the basic model for the development of magnetoactive metamaterial using a MRE capable of varying the bandgaps areas upon application of an external magnetic field. The finite element model of the proposed MRE-based periodic unit cell was developed, and the Bloch theorem was employed to systematically investigate the ability of the proposed adaptive periotic structure to attenuate low-frequency noise and vibration. Results show that the proposed MRE-based periodic wave filter can provide wide bandgap areas which can be adaptively changed and tuned using the applied magnetic field. The findings in this study can provide an essential guide for the development of novel adaptive periodic structures to filter low-frequency noises in the wide frequency band.

Instability Regions of a laminated Sandwich Plate with MRE Core Under Parametric Excitation Using Finite Element Method

This paper is concerned with the instability regions of a laminated sandwich plate with magneto-rheological elastomer (MRE) core under periodic axial loads. Structures operating under this unstable region cause large response even if the excitation force is small in magnitude. The governing equations of motion of the system are obtained by using finite element method [FEM].The parametric stable and unstable regions of the MRE cored composite sandwich plate for different system parameters and end constraints are found using modified Hsu method for simple parametric resonance condition. This analysis will help to design passive attenuation by using sandwich plates of varied dimensions, material parameters of both skin and core. Further active vibration reduction is possible by applying suitable magnetic field and operating the system outside of the instability region.

Vibration control systems in a building prototype: Application of SMA coil springs in diagonal bracing and TMD

The growing concern with the efficiency and reliability of civil structures that are slim, flexible and highly vulnerable to earthquakes, side winds and impacts can be addressed with the use of smart materials. Among the available techniques, passive control stands out due to its low cost, low maintenance, and no need for an external energy source. In this sense, this work proposes the incorporation of NiTi superelastic SMA springs in a diagonal bracing arrangement and as a secondary device in a Tuned Mass Damper (TMD) to improve the passive vibration control of a 3-DOF building prototype. The study compares the efficiency of the proposed control systems through the modal analysis of the structure under scenarios combining different control types (diagonal bracing or TMD), vibration types (impulse excited or base-forced) and passive attenuation (with or without SMA springs). It was concluded that the length of the SMA spring attenuators has a direct influence on the control capacity, with the shorter springs providing a higher attenuation efficiency, as they generate greater mechanical hysteresis and dissipate more mechanical energy, while adding less mass to the structure. In terms of the amplitudes reached in the experimental modal analysis, the TMD with the SMA springs as a secondary device was the most efficient technique, allowing reductions of up to 74% in impulse excitation and 44% in forced vibration. In terms of added mass, TMD also proved to be more effective, reducing about 63% of NiTi SMA material in impulse excitation and 73% in forced vibration, when compared to diagonal bracing.

Nonlinear vibratory energy exchanges in a meta-cell

Meta-materials are utilized for bringing passive attenuation solution especially in the acoustics and vibration domains. Generally speaking, they are composed of an array or a chain of meta-cells. Here the vibratory energy exchanges between particles of a nonlinear meta-cell are studied. The meta-cell is composed of an outer mass which houses an inner mass with a compound nonlinear restoring forcing term. It is globally non-smooth, containing pure cubic and piece-wise linear terms, which constitutes a new type of nonlinearity for such mass-in-mass cells. The complexified form of system equations is treated by the multiple time scale method to find out its fast and slow dynamics, leading to determination of the slow invariant manifold as well as the singular and equilibrium points of the system. The compound nonlinear restoring forcing function of the inner mass makes the global geometry of the slow invariant manifold to be different from those of systems with pure cubic nonlinearities, for example, including four singular lines and two distinct unstable zones. Amplitude dependency of the frequency of such a nonlinear system in the conservative form is represented by the backbone curves. Furthermore, detected equilibrium points for different external forcing amplitudes are represented by three-dimensional frequency response curves. Finally, analytical predictions are confronted with numerical results obtained by direct time integration of the system equations. An application of such system can be the passive control of main systems via embedding another nonlinear oscillator inside it. Moreover, such system can also be extended in the form of an array to create meta-materials.

An improved lumped parameter model predicting attenuation of earmuff with air leakage

Since air leakage is inevitable when earmuffs are worn improperly or together with safety glasses in factory or military, it is required to be considered to accurately predict earmuff attenuation. Besides unwanted air leakage, under controlled air leakage is introduced to earmuff to achieve adjustable attenuations in different signal-to-noise ratios (SNRs) and balance between attenuation and speech intelligibility. This work is to develop an improved lumped parameter model (LPM) to predict earmuff attenuation with consideration of air leakage. Air leakage paths are introduced into conventional LPM without air leakage, and air leakage path impedance is analytically described by Maa’s microperforated tube impedance. Earmuff passive attenuation behavior can be analytically described and analyzed with the improved LPM. Finally, the validity of improved LPM is verified experimentally. The results indicate that the improved LPM can predict earmuff attenuation with air leakage, and air leakage deteriorates earmuff attenuation and turns resonance frequency higher.

Passive Attenuation of Mechanical Vibrations with a Superelastic SMA Bending Springs: An Experimental Investigation

This work presents an experimental study related to the mechanical performance of a special design spring fabricated with a superelastic shape memory alloy (SMA-SE). For the experimental testing, the spring was coupled in a rotor machine, aiming to attenuate the mechanical vibration when the system went through a natural frequency without any external power source. It was verified that the reduction in instabilities stemmed from the better distribution of vibration force in the proposed device, as well as the damping capacity of the spring material. These findings showed that the application of the M-Shape device of SMA-SE for three different cases could reduce vibration up to 23 dB when compared to the situations without, and with, 1.5 mm of preload. The M-Shape device was shown to be efficient in reducing the mechanical vibration in a rotor system. This was due to the damping capacity of the SMA-SE material, and because the application did not require any external source of energy to generate phase transformation.

Improvements to the standards for the testing of noise protection equipment

This paper will suggest improvements to the applicable testing standards for the testing of hearing protection units. The units can be over the ear or in the ear units. These suggestions will make the tests more objective and less about using people as test objects. We will discuss when sound is hazardous and what time has to do with the level of danger. We will discuss passive attenuation and active attenuation as well as amplification applications to aid in communications between users of such devices.

Detection thresholds with active hearing protection devices in quiet and noise

The Real-Ear Attenuation at Threshold (REAT) method is a standardized (ANSI/ASA S12.6) method of assessing the passive attenuation of hearing protection devices (HPD), including electronic HPDs with the electronics turned off. Characterizing HPDs with electronics turned on is performed with the Microphone in Real Ear (MIRE) method, or with an acoustic test fixture, as described in ANSI/ASA S12.42. It has been proposed that the REAT method may be useful for characterizing the effect of HPDs on detection of ambient sounds for HPDs with hear-through microphones, including the effects of electronics noise from the HPD. In this study, detection thresholds were measured with three electronic earmuff-type HPDs using a method similar to the REAT method. Detection thresholds were obtained for warble tones presented from a loudspeaker placed in front of the subject in a sound treated room. Thresholds were measured with unoccluded ears and with three HPDs with hear-through capability in quiet and in noise. In addition, thresholds were measured with one of the HPDs with foam earplugs inserted into both ears to simulate a conductive hearing loss. The results point to the interaction between device noise, ambient noise, and human absolute thresholds as limitations on the detectability of ambient sounds.

A 32–40 GHz 4-Channel transceiver with 6-bit amplitude and phase control

This paper presents a Ka band 4-Channel transceiver with 6-bit amplitude and phase control using a 0.13-μm SiGe BiCMOS process. The transmit/receive (TX/RX) channel consists of single-pole double-throw (SPDT) switch, 6-bit passive phase shifter (PS), 6-bit passive attenuator (ATT), low noise amplifier (LNA), power amplifier (PA), and driver amplifier (AMP). Through the virtual negative voltage bias and transmission-line based phase shifter, an RMS phase error less than 3° is achieved with 5.6° steps at 32–40 GHz. The amplitude control operates with 0.5 dB steps while maintaining an RMS gain error of 0.4 dB. The transceiver also integrates serial peripheral interface (SPI), power manager and temperature sensor. The transmitter consumes 28 mA from a 3.3 V supply, and the receiver consumes 16 mA from a 3.3 V supply, 35 mA from a 5 V supply. The chip occupies an area of 5.8 × 2.7 mm2.

Wavenumber domain analysis of full-band energy harvesting and damping dissipation characteristics of plate embedded with heterogeneous ABH array

The Acoustic Black Hole (ABH) structure has been developed as a promising approach for passive vibration attenuation and noise control. The basic theory of ABH effect hinges on the geometry thickness gradual decreasing according to the power law. This feature of structure reduces flexural wave speed, resulting in "trapping" flexural wave into ABH indentation to achieve energy focalizing. In this work, the FE model of a plate embedded with ABH indentation and damp structure is established and excited by a series of harmonic forces respectively. The characteristics of energy distribution in this plate in full frequency band are investigated by the power flow method and wavenumber domain analysis. By transforming the spatial vibratory energy into wavenumber domain, the ABH effect is analyzed and compared with a uniform panel. Meanwhile, the dissipation effect of vibration and sound radiation energy has been studied with addition of damping material. Furthermore, the energy harvesting and dissipation performances of a plate embedded with heterogeneous ABH array are investigated in order to demonstrate the influence of ABH structure parameters and configuration. The research will be beneficial for the vibration energy control in full frequency band.

Design and fabrication of a novel passive hand tremor attenuator

Parkinson’s disease is most highly recognised by tremors of the hands that occur in those afflicted with the disease. Though the symptoms of Parkinson’s disease involving motor function begin with very slight tremors of the hands, they further develop into issues such as difficulty swallowing, severe postural problems and extremely limited mobility. In this study, a method of reducing these tremors that appear during the early stages of the disease is developed by creating a wearable passive device that reduces vibrations of the hand and arm through the use of magnetic actuators. The proposed wearable technology has surpassed other known alternatives in selected testing scenarios while possessing a light weight of only 120 grams.

A DC–Ka-Band 7-Bit Passive Attenuator With Capacitive-Compensation-Based Bandwidth Extension Technique in 55-nm CMOS

This article presents a 7-bit wideband passive attenuator with low insertion loss (IL) and high attenuation accuracy in 55-nm CMOS technology. The π-type and bridge-T-type attenuation units utilize an effective capacitive compensation technique, whose bandwidth extension mechanism is detailed in a single-unit pole-zero analysis. The matching-induced performance deterioration is investigated to minimize amplitude and phase errors at the chip level. The fabricated attenuator demonstrates a 32.4-dB attenuation range with a 0.255-dB resolution and a 3.5-8.4-dB IL from dc to 32 GHz. The measured root-mean-square (rms) amplitude and phase errors are below 0.32 dB and 5.33°, respectively. The attenuator occupies a 0.054-mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> core area and consumes negligible power.

Attenuation characteristics of an extended-wear hearing aid: Impulse and continuous noise.

The extended-wear hearing aid (EWHA) is a hearing assistive device that combines a low-power analog amplification circuit with a soft biocompatible foam plug that allows it to remain in the ear canal for several months at a time without replacement. EWHAs fit snugly in the ear canal and are not vented and so produce insertion losses comparable to a passive earplug when inserted into the ear canal with the active circuitry turned off. However, EWHAs are not marketed as hearing protection devices, and other than a general warning to users that the device will have impaired auditory awareness when the device is inserted in the "off" mode, relatively little has been reported about the attenuation characteristics of EWHAs. In this study, commercially-available EWHAs were evaluated using the ANSI standard procedures for measuring hearing protector attenuation in impulse noise [ANSI (2010). S1242-2010, Methods for the Measurement of Insertion Loss of Hearing Protective Devices in Continuous or Impulsive Noise Using Microphone-In-Real-Ear or Acoustic Text Fixture Procedures (American National Standards Institute, New York)] and in continuous noise [ANSI (2006). S12.6, Methods for Measuring the Real-Ear Attenuation of Hearing Protectors (American National Standards Institute, New York)]. Attenuation values were also measured in double and triple protection conditions that combined EWHAs with traditional earplugs and earmuffs. The results show that properly-fit EWHAs can provide passive attenuation comparable to conventional passive earplugs, which may make it possible to use them to provide persistent protection from intermittent noise sources.

Active cancellation of periodic EMI of power electronic systems by injecting artificially synthesized signals

Active EMI cancellation is an interesting solution to reduce the size of passive filter components. In this work, the already established active EMI filter types are summarized. The systematic limitations are elaborated that result from the feedback or feedforward approach for cancellation signal generation. Afterward, a new method is presented in which the cancellation signal is artificially synthesized and injected into the system. This method is especially well suited for the suppression of periodic EMI since the anti-EMI can conveniently be synthesized from cancelling sine waves. Bothersome effects, like complex frequency characteristics or delays, can be compensated by appropriate amplitudes and phases. By doing so, systematic limitations of active EMI filters can be resolved. In this work, the fundamental concept and possible variants are depicted. Although many limitations of active EMI filters are resolved, also the new method has its limits. These are described and discussed. Furthermore, different methods for determining the cancelling sine waves are summarized. Last, a prototype cancellation system is presented and discussed to suppress the EMI of a GaN-based 48 V/12 V DC-to-DC converter with a switching frequency of 300 kHz. The disturbances are actively suppressed below the strictest limit (class 5) of the automotive standard CISPR 25 in the frequency range from 150 kHz to 30 MHz. The active suppression of the cancellation system and the passive attenuation of the coupling circuits are individually investigated to elaborate the performance of the active cancellation strategy. The power of the generated cancellation signal is estimated.

Hearing Screening in the Community.

Adults typically wait 7-10 yr after noticing hearing problems before seeking help, possibly because they are unaware of the extent of their impairment. Hearing screenings, frequently conducted at health fairs, community events, and retirement centers can increase this awareness. To our knowledge, there are no published studies in which testing conditions and outcomes have been examined for multiple "typical screening events." The purpose of this article is to report hearing screening outcomes for pure tones and self-report screening tests and to examine their relationship with ambient noise levels in various screening environments. One thousand nine hundred fifty-four individuals who completed a hearing screening at one of 191 community-based screening events that took place in the Portland, OR, and Tampa, FL, metro areas. The data were collected during the recruitment phase of a large multisite study. All participants received a hearing screening that consisted of otoscopy, pure-tone screening, and completion of the Hearing Handicap Inventory-Screening Version (HHI-S). In addition, ambient sound pressure levels were measured just before pure-tone testing. Many more individuals failed the pure-tone screening (n = 1,238) and then failed the HHI-S (n = 796). The percentage of individuals who failed the pure-tone screening increased linearly with age from <20% for ages <45 yr to almost 100% for individuals aged ≥85 yr. On the other hand, the percentage of individuals who failed the HHI-S remained unchanged at approximately 40% for individuals aged ≥55 yr. Ambient noise levels varied considerably across the hearing screening locations. They impacted the pure-tone screen failure rate but not the HHI-S failure rate. It is important to select screening locations with a quiet space for pure-tone screening, use headphones with good passive attenuation, measure sound levels regularly during hearing screening events, halt testing if ambient noise levels are high, and/or alert individuals to the possibility of a false-positive screening failure. The data substantiate prior findings that the relationship between pure-tone sensitivity and reported hearing loss changes with age. Although it might be possible to develop age-specific HHI-S failure criteria to adjust for this, such an endeavor is not recommended because perceived difficulties are the best predictor of hearing health behaviors. Instead, it is proposed that a public health focus on education about hearing and hearing loss would be more effective.

Amblyopic Suppression: Passive Attenuation, Enhanced Dichoptic Masking by the Fellow Eye or Reduced Dichoptic Masking by the Amblyopic Eye?

To test the amblyopic suppression at mid to low spatial frequencies when compensating for signal attenuation. Eight amblyopes with (n = 5) or without (n = 3) strabismus and 10 normal controls with normal or corrected to normal visual acuity (≥20/20) and normal stereopsis (≤40 arcseconds) participated. Using a quick contrast sensitivity function approach, we measured individuals' monocular contrast sensitivity functions when the untested eye saw a mean luminance background and when the untested eye saw a bandpass filtered noise whose peak spatial frequency was matched to that of the test grating. Interocular suppression was quantified by the difference in thresholds occurring between these two conditions for each eye. The contrast of the noise mask was set at five times the threshold of the untested eye. Selected spatial frequencies (0.67-1.31 cyc/deg) were identified where neither ceiling (five times the mask contrast threshold in the amblyopic eye <100%) nor floor (threshold of the amblyopic eye when there was a noise mask in the fellow eye <100%) effects occurred for all observers. Within this frequency range, we found no interocular suppressive imbalance in normal observers. However, in amblyopes, the amblyopic eye exerted significantly less suppression than the fellow eye, while the suppression from the fellow eye to the amblyopic eye was similar to that found in the normal controls. We conclude that the reduced dichoptic masking by the amblyopic eye, within the context of normally balanced interocular inhibition, produces the amblyopic suppression at mid to low frequencies.