用VHDL中描述减法，简单，易懂，可轻松理解-Described using VHDL subtraction, simple, easy to understand and can be easily understood

采用谱减法的语音降噪实现代码，适用于语音和音频系统中，可直接调用。-Speech noise reduction using spectral subtraction implementation code, for voice and audio systems, can be called directly.

通过向源码中添加指令：RSUB_INT_LIT8 （既逆减法指令）对抗dex2jar等反编译工具。(By adding instructions to the source code, RSUB_INT_LIT8 (anti subtractive instruction) against dex2jar and other decompile tools.)