The extracted temporal envelope 1728 is used to activate the cutaneous actuators 1722 using the carrier signals 1734. The carrier signals 1734 have a periodic waveform (e.g., sinusoidal) that is altered using features of the temporal envelope 1728 for the purpose of conveying the speech information via the actuator signals 1718. Features of the temporal envelope 1728 may include amplitude, frequency, phase, periodicity, wavelength, etc. In one embodiment shown in FIG. 17B, the carrier signals 1734 may be sinusoidal signals describing a smooth repetitive oscillation. In other embodiments, the carrier signals 1734 may be a pulse wave or pulse train, any non-sinusoidal periodic waveform, or a square wave train having a regular duty cycle. The carrier signals 1734 typically have a higher frequency than the temporal envelope 1728. In one embodiment, the cutaneous actuators 1722 are oscillated using carrier signals 1734 having a periodic (e.g., sinusoidal or pulse wave train waveform) whose frequency is advantageous for human perception, e.g., between 10 Hz to 300 Hz. The carrier signals 1734 may be altered using frequency modulation (FM) or amplitude modulation (AM) to generate the actuator signals 1718.
