<p>High-fidelity capture of physiological signals across a broad frequency spectrum requires soft vibration sensors with exceptional performance. However, existing devices fail to achieve uniformly high sensitivity across the full spectrum while maintaining reliable, low-power operation. Here we report a piezoelectric-powered capacitive vibration sensor that overcomes these limitations. In this design, a piezoelectric diaphragm serves as a non-contact power source, generating a stable bias field and actively modulating the signal to enable self-powered operation. To further enhance performance, we implement a device architecture featuring in-plane air ventilation and maximized sensor array density. The resulting sensors exhibit a linear sensitivity of 626 mV <i>g</i>⁻¹, a flat frequency response from 80 to 5,000 Hz, an ultralow detection limit of 0.01 <i>g</i> and a signal-to-noise ratio of 80 dB, representing substantial improvements over conventional devices. We demonstrate that the hyperpacked, piezoelectric-powered sensor array enables high-fidelity detection of music, voice and respiratory signals by capturing subtle mechanical vibrations.</p>