If it contains no iron there should be no sound. I think it is just an attempt to baffle the user into thinking he is really getting something cool when it is an algorithm to make it sound different from conductive sounds. I like the conductive sounds and I am used to it. I cross save all metal to coin jewelry so I can readily check the numbers match. The lower numbers with actual iron content may have a ferrous sound component though and I pay attention to that when verifying.