The Raman and IR spectra of NH$_4$MnF$_3$, NH$_4$ZnF$_3$ and NH$_4$MnCl$_3$ have been measured in order to study the internal vibration modes of NH$_4^+$ in different surrounding conditions. The internal force constants have been determined and compared to their values in ammonium halides and in the free ion, Their trends have been discussed in terms of the hydrogen bonding and volume effects. The intraionic polarizability parameters have also been obtained and compared to those of CH$_4$.