outsig = gaindb(insig,gn);
gaindb(insig,gn) increases the energy level of the signal by gn dB.
If gn is a scalar, the whole input signal is scaled.
If gn is a vector, each column is scaled by the entries in gn. The length of gn must match the number of columns.
gaindb(insig,gn,dim) scales the signal along dimension dim.