Frequency modulation (FM)

Question

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=co

Answer 1

Simply replace your carrier equation, cos(t), with an f(t) for your input signal, where t might be scaled by the sample rate for sampled data. Then modulate dt as before.

Note that, for sampled data and depending on the bandwidth of your input signal, to make this f(t) sound "good" you may need to use a higher order interpolation method combined with a low pass filter (such as a windowed Sinc convolution), rather than just using the nearest sample or a linear interpolation between two samples, which could alias rather badly in the frequency domain.