Sound-focusing package for MEMS vector hydrophone

To address the challenge of acoustic wave attenuation in traditional Micro-Electro-Mechanical Systems (MEMS) vector hydrophone packaging, this study proposes a sound-focusing package with tapered apertures (TA) and a nylon sound-focusing cap (NSC). Theoretical analysis and COMSOL simulations reveal that the tapered geometry (wider external and narrower internal apertures) concentrates acoustic energy, enhancing particle acceleration at sensitive elements. Experimental results show that the NSC achieves a sensitivity of -186.4 dB at 100 Hz, representing improvements of 7.9 dB and 6.1 dB compared with the steel mesh sound-transmitting cap (SMC) and non-encapsulated bare cilia (NC), respectively. The directivity null depth of the NSC-encapsulated hydrophone reaches 40.98 dB at 315 Hz, outperforming SMC and NC by 7.35 dB and 5.49 dB. The low Young's modulus and density of nylon ensure a natural frequency in water (942.07 Hz) that exceeds the operating band (20-500 Hz), avoiding structural resonance and ensuring high signal-to-noise ratio output. The sound-focusing design, validated by standing wave tube tests, provides an effective solution for high-sensitivity and high-directivity underwater acoustic detection.Index Terms-MEMS vector hydrophone, sound-focusing package, tapered aperture, bionic cilia, sensitivity, directivity, low-frequency acoustic detection, nylon material.