In one embodiment, the actuator signal generator 1776 encodes features of the temporal envelope 1728 into the carrier signals 1774 by increasing or decreases the frequency of the carrier signals 1774 proportional to the amplitude (e.g., 1732) of the speech signals 1706. The carrier signals 1774 are altered such that the frequency of the carrier signals 1774 varies in line with the variations in intensity of the speech signals 1706. When features of the temporal envelope 1728 are encoded into the carrier signals 1774 to generate the actuator signals (e.g., signals 1743 in