We live in a noisy world, so it is no wonder that most species have evolved ways to send and receive vibrations. In general, vibrations come in two flavors, substrate- and air-borne. Both forms are similar in that they involve waves (moving particles) traveling through a medium. Substrate-borne vibrations are torsional waves carried through a solid surface and perceived by specialized organs that are in contact with the vibrated medium. Air-borne vibrations are pressure variations received by a different suite of organs. Interestingly, a mechanical signal sent by an organism can involve both forms. Take a stridulating beetle on a plant for example. A potential mate on a nearby plant might be receiving the air-borne portion of the signal, however, a predatory spider might be receiving the substrate vibrations through the same plant.
Nick Aflitto 