modified Bessel function for Speech enhancement Using MMSE in matlab I am trying to implement an algorithm proposed in an old research paper by Ephraim and Malah for my DSP course project. I hope someone can help me with this difficult question. For the clean signal Amplitude Estimator, they used the following equation: 



I understand most of the variables in the equation except the Bessel function stuff. Why did they use a Bessel function in here? 
and most importantly, how can I implement it in Matlab?
The Bessel function just turns up as a result of the MMSE estimation problem given the assumed statistical model (cf. Appendix A of the paper). This modified Bessel function is implemented in Matlab as besseli.