Laser Heterodyne System for Measurement and Analysis of Vibration

Eberhardt, F. J.; Andrews, F. A.

doi:10.1121/1.1912183

Cited by 79 publications

(11 citation statements)

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“…The vibration measurement set-up consists of a custom-built LDV (SI Text) employing a conventional heterodyne interferometer (43), for which all optical and electronic parts were tailored to the problem of measuring picometer-sized vibrations in the presence of large, extraneous movements in the order of 0.1 mm (e.g., heart beat, breathing, or swallowing). The LDV, including the custom-built demodulator, achieves a maximum sensitivity of 0.3 pm/ ͌ Hz for acoustic frequencies of Ͼ1.5 kHz when measured on a mirror, the ¶ The model in ref.…”

Section: Methodsmentioning

confidence: 99%

Distortion product otoacoustic emissions measured as vibration on the eardrum of human subjects

Dalhoff

Ţurcanu

Zenner

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

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It has previously not been possible to measure eardrum vibration of human subjects in the region of auditory threshold. It is proposed that such measurements should provide information about the status of the mechanical amplifier in the cochlea. It is this amplifier that is responsible for our extraordinary hearing sensitivity. Here, we present results from a laser Doppler vibrometer that we designed to noninvasively probe cochlear mechanics near auditory threshold. This device enables picometer-sized vibration measurements of the human eardrum in vivo. With this sensitivity, we found the eardrum frequency response to be linear down to at least a 20-dB sound pressure level (SPL). Nonlinear cochlear amplification was evaluated with the cubic distortion product of the otoacoustic emissions (DPOAEs) in response to sound stimulation with two tones. DPOAEs originate from mechanical nonlinearity in the cochlea. For stimulus frequencies, f 1 and f2, with f2/f1 ‫؍‬ 1.2 and f 2 ‫؍‬ 4 -9.5 kHz, and intensities L1 and L2, with L1 ‫؍‬ 0.4L2 ؉ 39 dB and L 2 ‫؍‬ 20 -65 dB SPL, the DPOAE displacement amplitudes were no more than 8 pm across subjects (n ‫؍‬ 20), with hearing loss up to 16 dB. DPOAE vibration was nonlinearly dependent on vibration at f 2. The dependence allowed the hearing threshold to be estimated objectively with high accuracy; the standard deviation of the threshold estimate was only 8.6 dB SPL. This device promises to be a powerful tool for differentially characterizing the mechanical condition of the cochlea and middle ear with high accuracy.cochlea ͉ hearing loss ͉ laser interferometer ͉ middle ear

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Section: Methodsmentioning

confidence: 99%

Distortion product otoacoustic emissions measured as vibration on the eardrum of human subjects

Dalhoff

Ţurcanu

Zenner

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

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“…The nanometer-level displacement amplitude of an oscillating surface may be quantified based on the time-dependent interference between a constant-frequency reference beam and a frequency-modulated object beam (Eberhardt and Andrews, 1970;Thalhammer, 1993). The experimental apparatus used is depicted in Figure 2.…”

Section: Sur$ace-velocity Amplitude Measurementmentioning

confidence: 99%

Acoustic force distribution in resonators for ultrasonic particle separation

et al. 1998

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The effectiveness of particle -liquid separation by ultrasonic radiation forces depends on the acoustic energy density distribution in the standing-wavefield. The energy distribution in an ultrasonic particle-separation device was analyzed to assist continued optimization and design efforts. Measurements of the energy-density distribution in the liquid using a microscope-based imaging system were compared to laser inteferometer measurements of the velocity-amplitude distribution on the transducer and rejlector sur- introductionThe capabilities of ultrasonic radiation forces for manipulating suspended particles have engendered a broad spectrum of experimental investigations. Ultrasonic aggregation has been exploited to improve the sensitivity of medical latex agglutination tests for detecting immunogenic agents (Grundy et al., 1994; Gualano et al., 19951, to fuse different cell types in combination with electric-field pulses (Vienken et al., 19851, and to enhance the recovery of two cell populations by phase partitioning (Allman and Coakley, 1994). The potential for continuous separation of particles from fluid suspensions was demonstrated by Tolt and Feke (1993). Continuous cell separation has been achieved for mammalian cells Correspondence concerning this article should be addressrd to S. M. Woodside. (Doblhoff-Dier et al., 1994; Trampler et al., 19941, yeast (Hawkes and Coakley, 1996), and bacteria (Hawkes et al., 1997). Fractionation according to particle size (Mandralis et al., 1994), continuous fractionation of mixed-particulate suspensions based on the compressibility of the solid phase (Gupta et al., 19951, and the selective retention of generally larger viable mammalian cells over nonviable cells and cell debris (Gaida et al., 1996) have been reported.Particle separation by ultrasonic forces exhibits innate advantages relative to conventional methods, particularly in the area of biotechnology. Cross-flow membrane filtration and spin-filter separators suffer from fouling; continuous centrifuges are susceptible to mechanical failure; conventional sedimentation systems require long holdup times. For ultrasonic separation, no physical barrier is required, there are no 1976September 1998 Vol. 44, No. 9 AIChE Journal moving mechanical parts, holdup times are low, and chemical flocculants are not necessary. Trampler et al. (1994) demonstrated the advantages of ultrasonic separation, running a continuous mammalian-cell perfusion culture for more than one month at cell concentrations up to 6X107/mL, with no decline in separation performance. In continuous separation systems, particles collect at the nodal planes of the standing-wave field due to the axial primary radiation force (PRF). Fluid flow is generally parallel to the nodal planes. The transverse PFR aggregates the particles within the nodal planes and retains them in the field against the flow-induced drag. The retention performance of these devices is therefore particularly dependent on the magnitude of the transverse PRF. The axial and transverse pri...

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“…Since it was not feasible to utilize mirror-like surfaces, laser heterodyne techniques [1][2][3][4] were not deemed appropriate and an approach was· taken that utilized the frequency stabilization scheme of a low power helium-neon laser. Tests with this laser system had shown a great sensitivity to even the small amounts of light backscattered from the black tile surface.…”

Section: A Noncontacting Acousto-optic Sensormentioning

confidence: 99%

Laser optic vibration sensing for the inspection of bonds in the orbiter thermal protection tiles

1991

NDT & E International

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Laser Heterodyne System for Measurement and Analysis of Vibration

Cited by 79 publications

References 0 publications

Distortion product otoacoustic emissions measured as vibration on the eardrum of human subjects

Distortion product otoacoustic emissions measured as vibration on the eardrum of human subjects

Acoustic force distribution in resonators for ultrasonic particle separation

Laser optic vibration sensing for the inspection of bonds in the orbiter thermal protection tiles

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