其一噪声是否按指定的信噪比叠加，其二怎么样检验带噪信号中信噪比满足指定的信噪比。-First noise is superimposed specified signal-to-noise ratio, and the second is how to test signal with noise in the signal-to-noise ratio to meet the specified signal-to-noise ratio.

信号处理中段式叠加的一个例子程序，希望大家借鉴。-Signal processing stage superimposed an example program, we hope to learn from.