When the content has low energy in the lower frequency part, we can sometime show the apparition of a frequency peak close to 2 kHz. bitstream used : [ltv_STEREO_p9dB_32k.bit.13200](/uploads/b4de4c8c589fca939871093c856ffe17/ltv_STEREO_p9dB_32k.bit.13200) and the problem shown is located at least between 21-23s  This seems to be coming from the high band synthesis as shown in the next figure (spectrogram and shown are from the hb_synth_32_fx).  Most of the time, it is not audible as the input content has enough energy to hide this frequency peak.