关于加噪声问题，高手帮忙

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The noisy FRFs referred to as ‘measured’ in this section are simulated by numerically adding additive white noise or multiplicative noise to the real and imaginary parts of the exact (noise-free) FRFs.
The additive white noise is scaled such that its mean deviation is the stated percentage of the mean magnitude of the individual FRF.
On the other hand, multiplicative noise is simulated by multiplying the real and imaginary parts of each
FRF with random numbers, the mean deviation of which is the stated percentage of the mean
magnitude of the noise-free FRF.
上面这段文字是怎么加噪声的呢？谢谢！

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