strip the first byte

dd if=<inputfile.silk> of="outputfile.silk" bs=1 skip=1

Download Silk Codec

https://github.com/gaozehua/SILKCodec

compile it and using decoder to decode it

usage: ./decoder in.bit out.pcm [settings]

in.bit       : Bitstream input to decoder
out.pcm      : Speech output from decoder
   settings:
-Fs_API <Hz> : Sampling rate of output signal in Hz; default: 24000
-loss <perc> : Simulated packet loss percentage (0-100); default: 0
-quiet       : Print out just some basic values

using audacity to import this raw data

The default sample rate is 24K as shown above.