频率调制（FM） [英] Frequency modulation (FM)

问题描述

我试图频率调制的音频信号。我successfuly FM正弦波（载体）通过使用下列公式：Y = COS（FC +罪（FM）），但我不知道其他的正弦波（调制器）如何去FMing的音频信号因为很明显我不能使用上述公式。我的问题是：我如何与调制信号结合输入数据获得一个FM信号

I'm trying to Frequency modulate an audio signal. I can successfuly FM a sine wave (the carrier) with another sine wave (the modulator) by using the following equation y=cos(Fc + sin(Fm)), however I'm not sure how to go about FMing an audio signal because apparently I can't use the aforementioned formula. My question is: How do I combine the input data with the modulating signal to get an FM signal?

推荐答案

可惜我一直没能得到保罗的方法来工作，但我对音频信号的FM合成一个有效的解决方案。我做了很多在Excel测试，实现了怎么办呢。这里的算法

Unfortunately I haven't been able to get Paul's method to work but I have a working solution for FM synthesis of audio signals. I did a lot of testing in Excel and realized how to do it. Here's the algorithm

    for (i = 0; i < N; i++)     {
    // increase the frequency with increasing amlitudes (fc + fm)
    if (input[i] < input[i+1])
        out[i] =   cos(acos(input[i]) + A * sin(2 * pi * mf * i));
    else  //decrease the frequency with decreasing amplitudes (fc - fm)
        out[i] =  cos(acos(input[i]) - A *  sin(2 * pi * mf * i));
                } 

它运作良好，但它确实产生一些不良的谐波（可能是由于舍入误差），所以你可能必须使用某种过滤器（移动平均可以做，以减少那些不需要的谐波一份好工作）。当施加到音频信号，则可能必须采取音频的包络，并与调制信号相乘，以便不对音频等的安静部分申请调频

It works well but it does generate some undesirable harmonics (possibly due to rounding errors) so you may have to use some sort of a filter (a moving average might do a good job at reducing those unwanted harmonics). When applied to an audio signal, you will probably have to take the envelope of the audio and multiply it with the modulating signal so as not to apply FM on the quiet portions of the audio etc.

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