The apparatus for symbol boundary synchronization in one embodiment includes on the receive path of a multi-tone modem a window synchronizer, a converter and a symbol boundary component. The ion source includes a plurality of walls defining a chamber in which ions are generated. The plurality of separated signal components are synthesized into a synthesized audio signal, which is then outputted, or alternatively, the plurality of separated signal components are outputted separately as audio signals. It allows rapid processing of impulsive signals.