Every now and then I hear someone call a radio station using a landline phone -in good repair-. The difference in quality (despite the LL bandwidth filtering) c

Every now and then I hear someone call a radio station using a landline phone -in good repair-. The difference in quality (despite the LL bandwidth filtering) compared to mobile-phone callers is often unmistakable. For one thing, the mobile artifactual garbling and missing audio segments stand out. So it's helpful to stipulate what kind of 'phone audio' you're trying to mangle into 'fidelity'.