OT but what do you mean by "English speaker with no accent"? Clearly every person has an accent, and every system that understands language must be able to understand the various accents that people have.
I've lived here in the US for 25 years and I notice the phrase every single time. :-)
More importantly, I was distinguishing because while Siri should be able to to understand various accents, it's struggled with that. When it launched, there were only two English variants (US and UK), so if you were a native Indian or Australian English speaker (for example) your experience would suffer. Now, Siri has support for 9 different English variants so they've clearly come a long way, but I remember it wasn't always the case.
Obviously that's "no accent."