Seashell Effect Pre-Touch Sensing is a new form of sensing used to help robots sense the shape and material of objects before they grasp. ''Pretouch'' refers to sensing modalities that are intermediate in range between tactile sensing and vision. The novel pretouch technique is effective on materials for which prior pretouch techniques fail. Seashell effect pretouch is inspired by the phenomenon of ''hearing the sea'' when a seashell is held to the ear and relies on the observation that the ''sound of the sea'' changes as the distance from the seashell to the head varies. To turn the familiar seashell effect into a sensor for robotic manipulation, a cavity and microphone was built into a robot finger. The sensor detects changes in the spectrum of ambient noise that occur when the finger approaches an object. Environmental noise is amplified most (attenuated least) at the cavity's resonant frequency, which changes as the cavity approaches an object.