Time-delay spectrometry measurement of magnitude and phase of hydrophone response

Wear, Keith A.; Gammell, Paul M.; Maruvada, Subha; Liu, Yunbo; Harris, Gerald R.

doi:10.1109/tuffc.2011.2090

Cited by 35 publications

(33 citation statements)

References 18 publications

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“…The complex sensitivity of the fiber optic hydrophone was obtained from the Fourier transform of the impulse response provided by the manufacturer. Complex sensitivities for the three needle hydrophones were measured using a digital time-delay spectrometry (TDS) system previously described [27, 53]. (There are many methods for measuring sensitivity magnitude but fewer methods for measuring sensitivity phase [53–57], with some TDS methods extending to frequencies as high as 40 MHz [27, 56] and a nonlinear method providing phase measurements at harmonic frequencies up to 100 MHz [55] Some methods have shown that common hydrophone measurement systems can be accurately modeled as minimum phase systems [27, 53, 56]. )…”

Section: Experimental Methodsmentioning

confidence: 99%

Pressure Pulse Distortion by Needle and Fiber-Optic Hydrophones due to Nonuniform Sensitivity

Wear

Liu

Harris

2018

IEEE Trans. Ultrason., Ferroelect., Freq. Contr.

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Needle and fiber optic hydrophones have frequency-dependent sensitivity, which can result in substantial distortion of nonlinear or broadband pressure pulses. A rigid cylinder model for needle and fiber optic hydrophones was used to predict this distortion. The model was compared with measurements of complex sensitivity for a fiber optic hydrophone and 3 needle hydrophones with sensitive element sizes (d) of 100, 200, 400, and 600 μm. Theoretical and experimental sensitivities agreed to within 12 ± 3% (RMS normalized magnitude ratio) and 8 ± 3 degrees (RMS phase difference) for the four hydrophones over the range from 1 – 10 MHz. The model predicts that distortions in peak positive pressure can exceed 20% when d/λ0 < 0.5 and SI > 7% and can exceed 40% when d/λ0 < 0.5 and SI > 14%, where λ0 is the wavelength of the fundamental component and SI (spectral index) is the fraction of power spectral density contained in harmonics. The model predicts that distortions in peak negative pressure can exceed 15% when d/λ0 < 1. Measurements of pulse distortion using a 2.25 MHz source and needle hydrophones with d = 200, 400 and 600 μm agreed with the model to within a few percent on the average for SI values up to 14%. This work 1) identifies conditions for which needle and fiber optic hydrophones produce substantial distortions in acoustic pressure pulse measurements and 2) offers a practical deconvolution method to suppress these distortions.

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Section: Experimental Methodsmentioning

confidence: 99%

Pressure Pulse Distortion by Needle and Fiber-Optic Hydrophones due to Nonuniform Sensitivity

Wear

Liu

Harris

2018

IEEE Trans. Ultrason., Ferroelect., Freq. Contr.

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“…Unlike membrane hydrophones, they do not present big planar interfaces that can produce reflections that possibly could interfere with measurements, especially for long-pulse or continuous-wave operation. Needle hydrophones are often used for cavitation detection [1], transcranial ultrasound system characterization [2–9], high-intensity therapeutic ultrasound system characterization [10–12], gene-delivery system characterization [13], high-frequency transducer characterization [14], and other medical applications [15, 16]. …”

Section: Introductionmentioning

confidence: 99%

Directivity and Frequency-Dependent Effective Sensitive Element Size of Needle Hydrophones: Predictions From Four Theoretical Forms Compared With Measurements

Wear

Baker

Miloro

2018

IEEE Trans. Ultrason., Ferroelect., Freq. Contr.

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Directivity is a hydrophone specification that describes response as a function of angle of incidence. The goal of this study was to compare, in the context of needle hydrophones, the commonly-used rigid baffle (RB) model for hydrophone directivity to three alternative models: soft baffle (SB), unbaffled (UB), and rigid piston (RP). Directivity measurements were performed at 1, 2, 3, 4, 6, 8, and 10 MHz from ±70° in two orthogonal planes for two ceramic and two polymer needle hydrophones with nominal geometrical sensitive element diameters of 200, 400, 600, and 1000 μm. Effective hydrophone sensitive element radius was estimated by least-squares fitting the four models to directivity measurement data using the sensitive element radius (a) as an adjustable parameter. For ka < 4 (where k = 2π/λ and λ = wavelength), the RP model outperformed the other three models. For ka = 1, the average error in estimated sensitive element radius was 7% (95% Confidence Interval: 3% - 12%) for the RP model while the lowest average error by the other three models was 46% (95% CI: 38% - 54%) for the UB model.

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“…The complex pressure reciprocity parameter, J, must be calculated for a small rigid-walled cavity in order to obtain the hydrophone sensitivity from the voltage and current measurements in (8). The crux of the primary calibration is that the reciprocity parameter is derived in terms of the acoustic properties of the fluid medium.…”

Section: Reciprocity Parametermentioning

confidence: 99%

“…The type H48 reference is used well below it first resonance, but the low end of the frequency range can be affected by the low-frequency cutoff, problematic when secondary references are needed to measure frequencies below 5 Hz. Extending the coupler reciprocity calibration measurement to include phase is important to provide traceability for secondary references and to reduce Driven by the needs of the ultrasound community, calibrations can now include phase measurement using non-linear acoustic wave propagation [5,6], time-delay spectrometry [7,8], and pulse excitation [9,10] methods. Lower frequency, underwater calibrations are also using phase [11].…”

Section: Introductionmentioning

confidence: 99%

A primary method for the complex calibration of a hydrophone from 1 Hz to 2 kHz

2017

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Considerations for a new high-accuracy transfer-coupler reciprocity system for absolute electro-acoustic calibration J F Zalesak IntroductionPrimary calibrations of hydrophones at frequencies less than about 1 kHz are typically performed in a coupler reciprocity chamber ('coupler'). The closed and controlled environment in the coupler allows for the performance of primary calibrations over the temperature and hydrostatic pressure range found in the ocean. The coupler reciprocity chamber is designed together with a primary reference standard hydrophone and two other reciprocal transducers because the volume and stiffness of the closed coupler system must be known precisely.The Underwater Sound Reference Division (USRD), a laboratory within the US Navy's (USN) research and development enterprise, provides metrology services related to underwater sound in the United States, including device calibration and leasing of underwater transducers, hydrophones, and projectors. Primary standards are maintained in-house. A coupler reciprocity system provides the primary standard calibration for frequencies less than 2 kHz [1]. The primary reference standard hydrophone is the USRD type H48 [2].To completely reproduce the acoustic waveform measured with a hydrophone, magnitude and phase information are required. Coupler reciprocity calibrations are historically performed measuring only magnitude [1, 3], and [4]. Phase response is more difficult to measure accurately and can be assumed constant when hydrophones are operating well below their resonance frequencies and, for hydrophones with preamplifiers, above their low-frequency cutoff. The type H48 reference is used well below it first resonance, but the low end of the frequency range can be affected by the low-frequency cutoff, problematic when secondary references are needed to measure frequencies below 5 Hz. Extending the coupler reciprocity calibration measurement to include phase is important to provide traceability for secondary references and to reduce AbstractA primary calibration method is demonstrated to obtain the magnitude and phase of the complex sensitivity for a hydrophone at frequencies between 1 Hz and 2 kHz. The measurement is performed in a coupler reciprocity chamber ('coupler'); a closed test chamber where time harmonic oscillations in pressure can be achieved and the reciprocity conditions required for a primary calibration can be realized. Relevant theory is reviewed and the reciprocity parameter updated for the complex measurement. Systematic errors and corrections for magnitude are reviewed and more added for phase. The combined expanded uncertainties of the magnitude and phase of the complex sensitivity at 1 Hz were 0.1 dB re 1 V µPa −1 and ±1• , respectively. Complex sensitivity, sensitivity magnitude, and phase measurements are presented on an example primary reference hydrophone.

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Time-delay spectrometry measurement of magnitude and phase of hydrophone response

Cited by 35 publications

References 18 publications

Pressure Pulse Distortion by Needle and Fiber-Optic Hydrophones due to Nonuniform Sensitivity

Pressure Pulse Distortion by Needle and Fiber-Optic Hydrophones due to Nonuniform Sensitivity

Directivity and Frequency-Dependent Effective Sensitive Element Size of Needle Hydrophones: Predictions From Four Theoretical Forms Compared With Measurements

A primary method for the complex calibration of a hydrophone from 1 Hz to 2 kHz

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