Swept Sine Wave Research Articles

A Goertzel Filter-Based System for Fast Simultaneous Multi-Frequency EIS

Bioimpedance measurement is a non-invasive, radiation-free, and inexpensive method for measuring the electrical properties of biological tissues. In applications where transients occur, the commonly used swept sinewave is replaced with broadband signals such as multisine. This makes the signal generation and the extraction of the real and imaginary parts of the impedance challenging. In this brief, an alternative to traditional fast Fourier transform (FFT) or coherent demodulation is presented. Based on the Goertzel filter, this alternative is simpler and requires very few digital resources. Its robustness to the harmonic fold back phenomenon, enables simple ternary current pulses to be used for excitation. The developed digital architecture is capable of simultaneous demodulation of 16 frequencies with an accuracy of 97% and 96% on the magnitude and phase measurement respectively. Employing a ternary sequence allows the use of a low power H-bridge current driver. The analog front-end and demodulation algorithm were implemented in an ASIC using a 180-nm CMOS technology. The system was tested on an isolated pig heart distinguishing edema from non-edema tissue by impedance changes.

Implementation and application of digitally controlled piezoelectric vibration absorbers to truss structures

The aim of this study involves implementing adaptive PVAs by adjusting their characteristics in orbit. Specifically, the results of the study focus on the implementation of digitally controlled PVAs and demonstrate their performance in vibration control. Digital potentiometers are used to improve the ease of tuning the PVA characteristics. We derived empirical formulae to estimate the characteristics of PVAs and implemented PVAs in which natural frequency and damping ratio are designated in the microcomputer. The formulae corresponded well with the theoretical values. Additionally, we simulated the transmission of vibration to the observation equipment with the truss structure and performed vibration control experiments. The truss structure was composed of five bays. Two electromagnets fixed on the uppermost nodes excited the truss structure with a swept sine wave. Four PVAs were equipped on the lowermost nodes for vibration. We measured the mode shapes and obtained a natural frequency of 16.38 Hz corresponding to a fundamental mode such as beam bending. Based on the results, we conducted vibration control experiments under the condition with a natural frequency of 16.38 Hz and optimum damping ratio of 0.07530. The results confirmed that PVAs could reduce the peak value of frequency response at least by 2 dB. Furthermore, we derived the transfer function from the mode and natural frequency and compared this function with the experimental results. The results clearly indicated that digitally controlled PVA worked effectively and suppressed the vibration of truss structures.

Contact and non-contact approaches in load monitoring applications using surface response to excitation method

Surface response to excitation (SuRE) method is a low-cost alternative to electromechanical impedance based structural health monitoring (SHM) technique. The SuRE method uses one piezoelectric transducer to excite the surface of a structure with a sweep sine wave. Piezoelectric sensors or scanning laser vibrometer can be used to monitor the dynamic response of structure.In this study, the performance of the SuRE method was evaluated with the conventional piezoelectric elements and scanning laser vibrometer used as contact and non-contact sensors, respectively, for monitoring the presence of loads on the surface. In order to determine the accuracy and reliability of both monitoring approaches in detecting changes in level of applied load, three different experimental setups were studied. Response of a system in the presence of a single ​load applying and multiple loads applying and its performance in detecting tightness in a nut and bolt system were investigated. The spectrum of the dynamic response is collected at the optimal operating condition. Any significant change of the spectral characteristics may indicate defects, improper loading or loose fasteners. The performance of the SuRE method using contact and non-contact sensors indicated that both variations of the method could be successfully used in load monitoring applications.

Damping performance of metal swarfs in a horizontal hollow structure

The scope of this paper is to investigate the damping performance of metal swarfs in hollow structures and to compare its vibration suppression performance with existing granular damping technologies. The effectiveness in suppressing vibrations in a hollow aluminum beam using aluminum, mild steel and stainless steel swarfs is compared to that of rubber spheres. Performance is compared using swept sine wave across a range of amplitudes from 0.1 g to 10 g for both first and the second modes of the beam. Considerable vibration suppression is observed for both modes, and the effect of filler type on damping and natural frequency variation is presented.

Very early age concrete hydration characterization monitoring using piezoceramic based smart aggregates

Very early age (0–20 h) concrete hydration is a complicated chemical reaction. During the very early age period, the concrete condition dramatically changes from liquid state to solid state. This paper presents the authors’ recent research on monitoring very early age concrete hydration characterization by using piezoceramic based smart aggregates. The smart aggregate (SA) transducer is designed as a sandwich structure using two marble blocks and a pre-soldered lead zirconate titanate (PZT) patch. Based on the electromechanical property of piezo materials, the PZT patches function as both actuators and sensors. In addition, the marble blocks provide reliable protection to the fragile PZT patch and develop the SA into a robust embedded actuator or sensor in the structure. The active-sensing approach, which involved a pair of smart aggregates with one as an actuator and the other one as a sensor, was applied in this paper’s experimental investigation of concrete hydration characterization monitoring. In order to completely understand the hydration condition of the inhomogeneous, over-cluttering, high-scattering characteristics of concrete (specifically of very early concrete), a swept sine wave and several constant frequency sine waves were chosen and produced by a function generator to excite the embedded actuating smart aggregate. The PZT vibration induced ultrasonic wave propagated through the concrete and was sent to the other smart aggregate sensor. The electrical signal transferred from the smart aggregate sensor was recorded during the test. As the concrete hydration reaction was occurring, the characteristic of the electrical signal continuously changed. This paper describes the successful investigation of the three states (the fluid state, the transition state, and the hardened state) of very early age concrete hydration based on classification of the received electrical signal. Specifically, the amplitude and frequency response of the electrical signal were of main interest. Both the swept sine wave and the constant frequency sine wave excitation methods presented the same conclusion on the three concrete states during the hydration, which enhances the reliability of the active-sensing approach for very early age concrete hydration monitoring.

Effect of internal pressure on the vibrational response of a fluid‐filled spherical shell: Experiment.

The resonance frequencies of a spherical aluminum shell (radius 3.0 in., thickness 1/8 in.) filled with water have been measured for several different values of static water pressure. It is found that a pressure increase of 100 psi causes resonance frequencies associated with axisymmetric bending modes to shift higher by about 0.15%, consistent with predictions of elastic shell theory [DiGiovanni and Dugundji, Air Force Office of Scientific Research Report No. 65‐0640 (1965). The shell is suspended by elastic cords attached to an inlet valve and is excited acoustically with a swept sine wave; the vibrational response is measured with small accelerometers mounted on the shell surface. Techniques for identifying frequency shifts associated with very small pressure changes (less than 1 psi) will be discussed. The effect reported here may have an application in the development of noninvasive methods for measuring intracranial pressure changes. [Work supported by National Science Foundation STEM program and Central Washington University.]

Temporary hearing threshold shifts and recovery in a harbor porpoise (Phocoena phocoena) and harbor seals (Phoca vitulina) exposed to white noise in a 1/1‐octave band around 4 kHz.

To set safety criteria for levels of sounds produced during pile driving for offshore wind parks, temporary hearing threshold shifts (TTSs) were studied in a harbor porpoise and two harbor seals. A psychoacoustic behavioral technique was used to quantify TTS and hearing recovery in the animals exposed to underwater sounds (white noise in a 1/1‐octave band around 4 kHz). Hearing thresholds were determined once a day for a narrow‐band frequency swept sine wave (3.9–4.1 kHz) before and after exposure to the fatiguing noise, which was offered at two sound pressure levels (131 and 119 dB re 1 μPa for the porpoise and 151 and 139 dB re 1 μPa for the seals) each at four durations (15, 30, 60, and 120 min). Recovery was quantified by measuring hearing thresholds at 4, 8, 12, and 48 min after the noise exposure. The results show that TTS in harbor porpoises occurred at a sound exposure level threshold approximately 20 dB below the threshold for which TTS occurred in harbor seals.

Tse'Biinaholts'a Yalti (Curved Rock That Speaks)

A large performance space attached to a natural amphitheater in a cliff face has recently been identified at the geometric center of the precolumbian (“Anasazi”) architectural complex in Chaco Canyon, New Mexico. The Amphitheater is a semicircular arc of sandstone measuring approximately 167m wide by 30m high. Sound recordings of computer-generated tones and swept sine waves, classical flute, Native American flute, conch shell trumpet, and prerecorded music were made in the amphitheater. Recording equipment included an analog tape deck, digital minidisk, and direct digital recording to a laptop computer hard drive utilizing stage-performance-quality microphones. The arc is in an overhanging cliff face and brings distant sounds to a line focus. Along this line there are unusual acoustic effects at conjugate foci. Time history analysis showed that a 60 dB reverberation decay lasted from 1.8 to 2 seconds, nearly ideal for the public performance of music. The acoustical properties of the Amphitheater are recognized by Navajo people (Diné). It has been given a special place name and is still used by Navajo ceremonial practitioners, utilizing shell trumpets, eagle bone whistles, and reed flutes.

Experiments and simulations on ultrasonically assisted drilling

Ultrasonically assisted drilling (UAD) has received great interest in the past few years by both academia and industry. The technology has already demonstrated a multitude of advantages over conventional drilling technology although its use has been mainly thwarted by inconsistent results. In order to aid the further development of UAD, a better understanding of the underlying dynamical process is required. In this work, an investigation into UAD is performed. Longitudinal vibration is used to excite standard 8 mm high-speed steel drill bits and mild steel samples are used for cutting tests. A swept sine wave is used to excite the system whilst the cutting forces that result are acquired. Clearly optimal regions are revealed and these are discussed. Subsequent to the experimental investigation, three-dimensional finite element drill bit models are employed to further understand the drill bit's vibrational characteristic. The simulation results show new areas of interest in which further work is necessitated.

DEVELOPMENT OF SELF-SENSITIVE PIEZOELECTRIC CANTILEVER UTILIZING PZT THIN FILM DEPOSITED ON SOI WAFER

ABSTRACT Piezoelectric micro cantilevers were applied to a resonant type mass sensor, biosensor, vapor sensor and probe for scanning force microscopes. These devices utilize impedance, phase, and charge as output signals. However, the measurement system could be greatly simplified if an output voltage were utilized. Therefore, a self-sensitive piezoelectric cantilever with separated electrode for actuation and sensing was developed. The self-sensitive piezoelectric cantilever was fabricated from a multilayer of Pt/Ti/PZT/Pt/Ti/SiO2/SOI through MEMS bulk micromachining. The cantilever was oscillated by a sweep sine wave and the output voltage was measured as a function of the input frequency. The resonant frequency determined from the output voltage spectrum agrees well with that measured by a laser Doppler vibrometer.

Liquid and moisture sensing by ultra-wideband pseudo-noise sequence signals

The use of ultra-wideband signals for moisture sensing by electromagnetic wave interaction provides more information on the material under test compared to single tone or narrowband approaches, regarding spatial and frequency dependent phenomena. Current activities to regulate the emission of electromagnetic waves in the spectral band up to 10 GHz for sensor applications open new perspectives for microwave moisture sensing. Therefore, improved and cost effective ultra-wideband measurement principles will become more and more interesting. The use of short pulses or swept sine waves are classic approaches to cover a large spectral band. However, this paper deals with some variants of an alternative method, which applies pseudo-random codes, namely M-sequences, to stimulate the test objects. The method permits monolithic integration of the RF-electronics in SiGe technology. The signal generation and data capturing are referred to a common stable single tone clock and they are controlled by steep trigger signals. This provides for very stable operation, which allows for measurements in both time and frequency domain. Two versions of an M-sequence approach will be considered and their functioning will be demonstrated by means of simple measurement examples.

Computer analysis of sound recordings from two Anasazi sites in northwestern New Mexico

Sound recordings were made at a natural outdoor amphitheater in Chaco Canyon and in a reconstructed great kiva at Aztec Ruins. Recordings included computer-generated tones and swept sine waves, classical concert flute, Native American flute, conch shell trumpet, and prerecorded music. Recording equipment included analog tape deck, digital minidisk recorder, and direct digital recording to a laptop computer disk. Microphones and geophones were used as transducers. The natural amphitheater lies between the ruins of Pueblo Bonito and Chetro Ketl. It is a semicircular arc in a sandstone cliff measuring 500 ft. wide and 75 ft. high. The radius of the arc was verified with aerial photography, and an acoustic ray trace was generated using cad software. The arc is in an overhanging cliff face and brings distant sounds to a line focus. Along this line, there are unusual acoustic effects at conjugate foci. Time history analysis of recordings from both sites showed that a 60-dB reverb decay lasted from 1.8 to 2.0 s, nearly ideal for public performances of music. Echoes from the amphitheater were perceived to be upshifted in pitch, but this was not seen in FFT analysis. Geophones placed on the floor of the great kiva showed a resonance at 95 Hz.

Milacron sells Widia industrial magnets business to Magnequench

Surface response to excitation (SuRE) method is a low-cost alternative to electromechanical impedance based structural health monitoring (SHM) technique. The SuRE method uses one piezoelectric transducer to excite the surface of a structure with a sweep sine wave. Piezoelectric sensors or scanning laser vibrometer can be used to monitor the dynamic response of structure.In this study, the performance of the SuRE method was evaluated with the conventional piezoelectric elements and scanning laser vibrometer used as contact and non-contact sensors, respectively, for monitoring the presence of loads on the surface. In order to determine the accuracy and reliability of both monitoring approaches in detecting changes in level of applied load, three different experimental setups were studied. Response of a system in the presence of a single ​load applying and multiple loads applying and its performance in detecting tightness in a nut and bolt system were investigated. The spectrum of the dynamic response is collected at the optimal operating condition. Any significant change of the spectral characteristics may indicate defects, improper loading or loose fasteners. The performance of the SuRE method using contact and non-contact sensors indicated that both variations of the method could be successfully used in load monitoring applications.

Manufacture of iron aluminide sheet by PM technology : M.Hajaligol et al. (P.Morris (USA), Virginia, USA.)

Surface response to excitation (SuRE) method is a low-cost alternative to electromechanical impedance based structural health monitoring (SHM) technique. The SuRE method uses one piezoelectric transducer to excite the surface of a structure with a sweep sine wave. Piezoelectric sensors or scanning laser vibrometer can be used to monitor the dynamic response of structure.In this study, the performance of the SuRE method was evaluated with the conventional piezoelectric elements and scanning laser vibrometer used as contact and non-contact sensors, respectively, for monitoring the presence of loads on the surface. In order to determine the accuracy and reliability of both monitoring approaches in detecting changes in level of applied load, three different experimental setups were studied. Response of a system in the presence of a single ​load applying and multiple loads applying and its performance in detecting tightness in a nut and bolt system were investigated. The spectrum of the dynamic response is collected at the optimal operating condition. Any significant change of the spectral characteristics may indicate defects, improper loading or loose fasteners. The performance of the SuRE method using contact and non-contact sensors indicated that both variations of the method could be successfully used in load monitoring applications.

Evaluation of the dewaxing process : S.Andersson, A.Ahlqvst. (Höganäs AB, Höganäs, Sweden.)

Surface response to excitation (SuRE) method is a low-cost alternative to electromechanical impedance based structural health monitoring (SHM) technique. The SuRE method uses one piezoelectric transducer to excite the surface of a structure with a sweep sine wave. Piezoelectric sensors or scanning laser vibrometer can be used to monitor the dynamic response of structure.In this study, the performance of the SuRE method was evaluated with the conventional piezoelectric elements and scanning laser vibrometer used as contact and non-contact sensors, respectively, for monitoring the presence of loads on the surface. In order to determine the accuracy and reliability of both monitoring approaches in detecting changes in level of applied load, three different experimental setups were studied. Response of a system in the presence of a single ​load applying and multiple loads applying and its performance in detecting tightness in a nut and bolt system were investigated. The spectrum of the dynamic response is collected at the optimal operating condition. Any significant change of the spectral characteristics may indicate defects, improper loading or loose fasteners. The performance of the SuRE method using contact and non-contact sensors indicated that both variations of the method could be successfully used in load monitoring applications.

Room acoustic parameters in a physical scale model of the new Music Centre in Eindhoven: Measurement method and results

A physical model with a scale of 1:10 has been constructed to aid in the design of the new Music Centre in Eindhoven, The Netherlands. This paper discusses the measurement method that has been used to acquire impulse responses in this model and to obtain important room acoustic parameters. As a model source a special high-frequency omni-directional sound source was used, fed by a swept sine wave. The microphone signal was deconvolved to obtain the impulse responses. From these impulse responses we calculated the reverberation time, the early decay time, the clarity, the Schwerpunktzeit (centre time) and the lateral efficiency. For the lateral efficiency a velocity-type microphone response is needed, which was obtained from a two-channel intensity probe. The paper concludes with a summary of the results that were obtained, indicating that the hall will sound very bright and spacious.

The characteristics of dynamic systems via the swept sine wave technique

The characteristics of dynamic systems via the swept sine wave technique

Use of swept sine wave in physiological systems analysis.

The use of a swept sine wave as a transient forcing function for measuring the frequency response characteristics of a physiological system is suggested. The spectral characteristics of a linear frequency swept sine wave are illuistrated and it is shown that, with relatively short sweep sine wave excitations, one can obtain almost rectangular modulus spectra with relatively good frequency selectivity. Such a transient method may be of potential use in physiological systems analysis.

Sweep sine wave simulation of random vibration and its effect on design with particular reference to space rockets

Rockets, aircraft and other vehicles experience random vibrations. Although random vibration test facilities have become widely available they have not totally superseded sine wave vibration tests, which continue to be specified. This is because sine tests retain diagnostic advantages, although they are likely to overtest some elements of an equipment, and to lead to unrepresentative patterns of damage. The paper discusses formulae for the level and duration of a sine wave test and how the uncertainties surrounding the assumptions made will lead to weight penalties if random vibration is not used for proof of design.