The acoustic output characterization of medical ultrasonic equipment requires regular calibration of the hydrophones used to ensure the reliability of measurements. Such hydrophone calibration is offered as a service by several institutions. Various calibration techniques using a variety of ultrasonic excitation pressure waveforms comprising different pressure amplitude ranges and frequency compositions as well as different reference measurement systems have been proposed and applied over the past decades. Currently, four different setups for hydrophone calibration are available at the Physikalisch-Technische Bundesanstalt (PTB). This internal comparison study addresses the consistency of all four methods, including direct primary calibration and substitution calibration using reference hydrophones. The methods apply single-frequency tonebursts and swept tonebursts in the kPa amplitude range of quasi-linear acoustics as well as impulse excitation including nonlinear propagation. In recent years, a new primary calibration setup using a high-frequency vibrometer has been implemented at PTB, enabling the characterization of hydrophone frequency responses in modulus and phase and extending the upper frequency limit to up to 100 MHz. For the comparison in the frequency range from 0.5 MHz to 60 MHz, two passive membrane hydrophones with well-known characteristics gained from many years of measurements were used. Another membrane hydrophone with a nominal diameter of 0.2 mm and an integrated preamplifier was applied to address the frequency range up to 100 MHz. The results obtained with the different setups showed good agreement with average root-mean-square (rms) deviations of 3% (primary calibrations, 1–60 MHz) and 4% (1–100 MHz). The consistency of the implementations was thus verified in this comparison.

中文翻译：

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医用超声场测量中水听器不同校准技术的比较

医用超声设备的声学输出特性要求定期校准所使用的水听器，以确保测量的可靠性。这种水听器校准是由多个机构提供的服务。在过去的几十年中，已经提出并应用了使用包括不同的压力幅度范围和频率组成的各种超声激励压力波形以及不同的参考测量系统的各种校准技术。当前，Physikalisch-Technische Bundesanstalt（PTB）提供了四种不同的水听器校准设置。这项内部比较研究解决了所有四种方法的一致性，包括直接初级校准和使用参考水听器的替代校准。该方法在准线性声学的kPa幅度范围内应用单频音爆和扫频音爆以及包括非线性传播在内的脉冲激励。近年来，PTB已使用高频测振仪进行了新的一次校准设置，从而能够以模数和相位表征水听器的频率响应，并将上限频率扩展至高达100 MHz。为了在0.5 MHz到60 MHz的频率范围内进行比较，使用了两台无声膜水听器，这些无声水听器具有从多年的测量中获得的著名特性。另一个标称直径为0.2 mm的膜式水听器和一个集成的前置放大器被用于处理高达100 MHz的频率范围。在不同设置下获得的结果表明，均方根（rms）偏差分别为3％（主校准，1-60 MHz）和4％（1-100 MHz），具有很好的一致性。因此，在此比较中验证了实现的一致性。