Fig. 1. PCI calibration using sound waves launched by a loudspeaker.

Fig. 2. Signals caught by two detection channels in four independent tests.

Fig. 3. Power spectra of detected signals in different channels with a 20 kHz sound wave modulation.

Fig. 4. Power spectra of detected signals with different sound wave modulations in Ch9.

Fig. 5. Raw signals from five detecting channels with a modulating sound wave frequency of 20 kHz.

Fig. 6. Time slices of signals from detecting channels after filtering and absolute magnitude calibration.

Fig. 7. Phase shifts between nearby channels.

Fig. 8. Frequency-wavenumber spectrum of the signals from the 32 channel detector array after calibration.

Fig. 9. (a) Voltage amplitudes in detection array; (b) conversion relations of detection array.

Fig. 10. Raw data of PCI detector element during plasma discharge on HL-2A tokamak; shot number, 34299.