B737-800
Flight Crew Air Transport Pilot (ATP)
Flight Crew Type 519
Time Pressure; Situational Awareness; Distraction; Communication Breakdown
ATC Issue All Types; Deviation - Speed All Types; Deviation / Discrepancy - Procedural Clearance
Air Traffic Control Issued Advisory / Alert; Flight Crew Requested ATC Assistance / Clarification
Airspace Structure; Airport; Company Policy; Procedure; Human Factors
We were on downwind at an assigned speed of 210 knots while in the descent to 7;000 feet. Speed brake was already out. ATC asked for best rate of descent. We slowed to 200 knots and put out flaps 10. Speed fluctuation was too close to flaps 10 limit for me; so I slowed to 190 for flap 10 speed buffer. At the same time; we are hearing on the busy radios of Precision Runway Monitoring (PRM) Approaches being conducted. We hadn't previously briefed PRM Approaches and confirmed that wasn't on the ATIS; so we were working on that now as well. Passing somewhere around 5;000 feet; we were queried on what the airspeed was. We responded with speed of 185 and were subsequently scolded for slowing down without permission and given a phone number to call.I think the combination of busy radios; probable PRM Approach clearance coming; slow to 210 knots; and go down faster resulted in non-compliance with speed clearance. Upon landing I called the company FAA representative who called ATL ATC and said he had talked to the Controller about the above situation who understood our concern.
[Report narrative contained no additional information.]
B737-800 flight crew reported they did not comply with an ATC assigned speed.