Dynamic Level Control to Reduce Noise in Long Distance Phonemail Networking
Original Publication Date: 1989-May-01
Included in the Prior Art Database: 2005-Jan-28
One of the major forms of distortion of voice message transmitted over the public network (analog transmission between voice messaging equipment) is additive noise. The effect of additive noise can be reduced by increasing the amplitude of the transmittal signal; however, government regulations and practical considerations do not allow transmission of signals above a certain level. This article describes the use of dynamic range compression to increase the amplitude of low amplitude parts of a message without increasing the peak amplitude of the signal in the environment described. The figure shows a diagram of the system. Target is the target message power. Alpha is a filter constant which is required to maintain stability with an imperfect transmission media (alpha is near 1).