Hello,
I checked it, and it seems that you didn't setup encoder correctly (e.g. using 24 kbit with 44100 sample rate freq). To use 24 kbit you should change sample rate to either: 8000, 12000, 11025, 16000, 24000, 22050 Hz.
The table below shows other possible combinations of bitrate/sample rate.
MPEG-1 layer III sample frequencies (kHz): 32 48 44.1
bitrates (kbps): 32 40 48 56 64 80 96 112 128 160 192 224 256 320
MPEG-2 layer III sample frequencies (kHz): 16 24 22.05
bitrates (kbps): 8 16 24 32 40 48 56 64 80 96 112 128 144 160
MPEG-2.5 layer III sample frequencies (kHz): 8 12 11.025
bitrates (kbps): 8 16 24 32 40 48 56 64 80 96 112 128 144 160