3D Printed Interactive Speakers
We propose technology for designing and manufacturing interactive 3D printed speakers. With the proposed technology, sound reproduction can easily be integrated into various objects at the design stage and little assembly is required. The speaker can take the shape of anything from an abstract spiral to a rubber duck, opening new opportunities in product design. Furthermore, both audible sound and inaudible ultrasound can be produced with the same design, allowing for identifying and tracking 3D printed objects in space using common integrated microphones. The design of 3D printed speakers is based on electrostatic loudspeaker technology first explored in the early 1930s but not broadly applied until now. These speakers are simpler than common electromagnetic speakers, while allowing for sound reproduction at 60 dB levels with arbitrary directivity ranging from focused to omnidirectional. Our research of 3D printed speakers contributes to the growing body of work exploring functional 3D printing in interactive applications.
The design of 3D printed free-form speakers based on electrostatic sound reproduction principles (ESR). The basic principles of electrostatic sound reproduction are simple and were explored in depth in the 1930s. A thin conductive diaphragm and an electrode plate are separated by insulating material, e.g., air, with the dielectric permittivity ε.
The audio signal is amplified to ~1000 V and applied to the electrode, charging it relative to the ground level that is connected to the diaphragm. As the electrode is charging, an electrostatic attraction force is developed be- tween the electrode and diaphragm. In the ESR speakers reported here we connect the ground to the diaphragm and the audio signal to the electrode (Figure b right). This is contrary to the ESR speaker design pro- posed previously, where the signal was connected to the diaphragm or a two-electrode configuration was used (Figure b left and middle). In designing home audio speakers the choice is irrelevant. However, it becomes important in 3D printed speakers embedded in toys and objects that can be touched by the user. The grounded diaphragm protects the user touching the speaker from the high-voltage audio source, making it safe to handle and manipulate the object with embedded speakers. This becomes particularly important in the interactive applications.