Commercial Hydrophone Research Articles

Broadband hydrophone calibration below 1 MHz

Recent calibration efforts for miniature hydrophones used to measure medical diagnostic ultrasound fields have been devoted to increasing the upper frequency range of calibration (≳10–15 MHz). However, a bandwidth extending to at least 10 times below the diagnostic pulse center frequency is needed for accurate (error ≊5%) measurement of the peak rarefactional pressure and mechanical index, both important quantities. Since at present no commercial hydrophones for medical ultrasound use provide sensitivity information below 1 MHz, a study was undertaken to determine these low frequency sensitivities. The technique uses broadband, plane‐wave pressure pulses generated by electrical shock excitation of a thick piezoceramic disk. The hydrophone response is calculated from measurements of the source transducer and hydrophone voltage waveforms. The frequency responses of both needle and membrane polymer hydrophones were measured using this technique. The membrane hydrophones studied had bandwidths extending below...

Spectral response of miniature ultrasonic hydrophones

Miniature hydrophones can be used to determine the temporal and spatial characteristics of pulsed ultrasonic fields produced by diagnostic ultrasound equipment. Before temporal parameters, such as peak pressure or intensity, may be accurately known, however, the spectral response of the hydrophone and its effect on the incident broadband pulse must be determined. Commercial hydrophones presently in use consist of a piezoelectric ceramic disk with diameters ranging from 0.25 to 1 mm and resonant frequencies of from 10 to 20 MHz. Measurements have been made of the frequency response of several hydrophones over a 1–10‐MHz range using both a continuous‐wave and pulse technique. In the continuous‐wave technique, a hydrophone is scanned across an ultrasonic beam in the far‐field. The voltage output is squared and integrated to obtain a result proportional to power. This value is then compared to the measured beam power. The pulse techniques utilizes a broadband pulse whose spectral content is determined using a...