How one can demonstrate that microphone is a nonlinear device?

[Hafiz Malik <hafiz.malik@xxxxxxxxx>]

Hi Every 1, 

Microphone is generally modeled using a second-order nonlinear function, that is, y(n) = ax(n) + b x(n)^{2} where x(n) is the microphone input. 

How can one demonstrate this non-linearity?

Any suggestions/comments/literature in this regard. 

Thanks,
-- 
Hafiz Malik
Assistant Professor
Electrical and Computer Engineering Department,
University of Michigan - Dearborn
Dearborn, MI 48128
RN: 220 ELB
Tel: (313)5935677
Fax: (313)5836336
http://www-personal.engin.umd.umich.edu/~hafiz