Apparatus for unified audio tactile feedback

A method for controlling a unified tactile and audio output from a touch interface device comprising:

• combining both a haptic and an audio content into a single bipolar controlling signal;
• applying a DC bias to the combined signal;
• and
• feeding the combined signal to one or more electrodes coupled to a touch surface of the touch interface device, wherein the combined signal modulates a friction between a surface of the touch interface device and an appendage of a user which causes a skin of the appendage to vibrate as the appendage is moved across the surface, wherein the vibration of the skin is tactilely perceptible to the user, and wherein the vibration of the skin causes a vibration in the surrounding air that is audible to the user, and that is based on the audio content.

A touch interface device that produces tactile and audio output comprising:

• a touch surface;
• a first electrode coupled to the touch surface that receives a first haptic/audio output potential;
• a second electrode coupled to a low impedance return path to the device;
• the first and second electrodes being configured such that when both the first and second electrodes are touched by an appendage of a user, a current flows between the first and second electrodes and the appendage;
• wherein the current creates an electric field that imparts a controlled electrostatic force at an interface of the first electrode and the appendage, wherein the controlled electrostatic force modulates a friction between the touch surface and the appendage;
• and
• wherein when the appendage slides long the touch surface, the modulation of friction causes a skin of the appendage to vibrate, wherein the vibration of the skin is tactilely perceptible to the user;
• and
• wherein the vibration of the skin causes a vibration in the surrounding air that is audible to the user, and that is based on the first haptic/audio output potential.