A range of smartphone models are used., page-14

Enough with the hollow rhetoric @piggywig ! If you believe that the hardware in different devices makes such an enormous difference in the captured cough that the algorithms would be unable to extract or recognise the signature then say so. What are the bandwidth limitations/differences you're concerned about? What is the frequency envelope of a cough? Which are the critical frequencies that fall within the brand-variable parts of the hardware capabilities?

And if you believe that there are problems dealing with the FDA using a range of hardware or operating systems, what are those problems? Can you cite examples of other applications that failed because they didn't standardise on a single platform? Can you cite examples of failed submissions that were repeated successfully where the only change in the second submission was to standardise on a single platform?

If not, you're wasting everybody's time with useless, rhetorical one-liners.