Noise burst during silence in ISM 2 at 48 kbps

with 1670c2bf and this bitstream Inp_conc_ism_20240912_-ism_2_-dtx_48000_48.zip

command line IVAS_dec BINAURAL 48 bit syn

looks simialar to #873 (closed), except that the noise is never fading out

In the first figure, it's the worst case that happen at around 40s. The second figure show another example at around 11s. It is happening at many places on that long file. This is not happening if "-dtx" is not used.

@norvell, @multrus, @venkateshsa, Just for your information, the concatenated file as well as the file alone were both having a MLD score < 3.0