This attribute specifies the time after the end of speech before
silence suppression starts. It applies only to voice traffic. It is not
used unless Vsr Svs Framer negotiatedSilenceSuppression is on,
congested or slowAndCongested.
Higher values of speechHangoverTime reduce undesirable clipping
but increase bandwidth usage.
speechHangoverTime is not used on DS1V, E1V, 1pDS1V, 1pE1V
and J2MV cards.