As shown in FIG. 17D, the low pass filter 1752 transmits the low frequency components 1756 (components with a frequency lower than a certain threshold frequency) of the rectified signals 1750 to the actuator signal generator 1776 and attenuates (filters out) high frequency components of the rectified signals 1750 with frequencies higher than the threshold frequency. The low pass filter 1752 may be implemented in the form of a hiss filter, an anti-aliasing filter for conditioning signals prior to analog-to-digital conversion, or a digital filter. In one embodiment, the low pass filter 1752 generates the temporal envelope 1754 of the speech signals 1706 by filtering out filtering out frequency components of the rectified signals 1750 that are higher than a threshold frequency. By filtering out these high frequency components, the remaining signals consist of slowly varying components that track the temporal envelope 1754 of the rectified signals 1750. As shown in FIG. 17D, the low pass filter 1752 may also directly receive the speech signals 1706 and transmit low frequency components 1756 of the speech signals 1706 to the actuator signal generator 1776 by filtering out filtering out frequency components of the speech signals 1706 that are higher than a threshold frequency. These low frequency components 1756 of the speech signals 1706 are used by the actuator signal generator 1776 to determine a low frequency signal power of the low frequency components 1756 of the speech signals 1706 and generate the actuator signals 1718, as described below with respect to the actuator signal generator 1776.
