Vibration sensors

A vibration sensor, comprising:

• a housing structure;
• an acoustic transducer physically connected to the housing structure, wherein an acoustic cavity is formed at least partially by the housing structure and the acoustic transducer;
• and
• a vibration unit configured to divide the acoustic cavity into a plurality of acoustic cavities, the plurality of acoustic cavities including a first acoustic cavity, the first acoustic cavity being in acoustic communication with the acoustic transducer, wherein
• the vibration unit includes an elastic element and a mass element, the elastic element and the mass element being located in the acoustic cavity, and the mass element being connected to the housing structure or the acoustic transducer through the elastic element;
• the housing structure is configured to generate vibrations based on an external vibration signal, the vibration unit causes a volume change of the first acoustic cavity in response to the vibrations of the housing structure, and the acoustic transducer generates an electrical signal based on the volume change of the first acoustic cavity;
• the elastic element includes a first elastic element and a second elastic element, the first elastic element and the second elastic element being respectively connected to the mass element and distributed at intervals along a vibration direction of the vibration unit, the vibration direction including a first direction and a second direction, and a ratio of a resonant frequency of vibrations of the vibration unit in the second direction to a resonant frequency of vibrations of the vibration unit in the first direction being larger than or equal to 2.