Decibels readings for a roadburner

[Nanook]

I was wondering is someone as a set of roadburner pipes on a drifter 800 ? and if so, if it would posiible to get a few decibels reading with an iphone or similar? The reading must be taken on a warm engine at an angle of about 45 degree, 2 feets from the tip of the exhaust, one reading at idle and the other at 2500rpm.

Thanks in advance.

Robert