Fig. 1. HIFU sound pressure measuring device based on laser interferometry

Fig. 2. Spectra of different interference signals under linear and nonlinear sound fields

Fig. 3. ε versus Bsig

Fig. 4. HIFU sound pressure measured by optical fiber hydrophone. (a) Time domain waveform; (b) frequency domain waveform

Fig. 5. Simulation results of interference signal bandwidths under linear and nonlinear sound fields. (a) Spectrum under linear sound field; (b) spectrum under nonlinear sound field; (c) ε versus Bsig

Fig. 6. Influence of bandwidth variation of heterodyne interference system on interference signal and sound pressure measurement result. (a) Time domain curve of interference signal; (b) frequency domain curve of interference signal; (c) measured sound pressure curves

Fig. 7. Relative error of sound pressure measurement versus bandwidth of heterodyne interference system. (a) Nonlinear sound field; (b) linear sound field

Fig. 8. Bandwidth of heterodyne interference system versus peak-to-peak value of measured sound pressure. (a) When relative error of sound pressure is less than 2%; (b) quadratic fitting curves with different relative error requirements under nonlinear sound field