B737-300
Air Traffic Control Fully Certified
Communication Breakdown
ATC Issue All Types; Aircraft Equipment Problem Critical
Air Traffic Control Issued New Clearance
Aircraft; Human Factors
A B737 level at FL340 on route requested lower in a muffled tone. I advised traffic on an E145 at FL320; descended him to FL330; and turned 15 degrees left. At that time I could not understand the reason the pilot stated he needed to change altitude. Traffic was moderate to busy so I began to issue other clearances until vector took effect and I could further descend the B737. It did not appear that the B737 took the turn when he again made a transmission requesting lower altitude. The aircraft sounded in distress and advised he needed to descend now due to a cracked windshield. During the entire situation it was very difficult to understand transmissions from the B737. Although the aircraft did not declare an emergency; I felt the situation was extremely serious; borderline emergency situation. I turned the B737 from about a 260 heading to a 180 heading away from the E145; and descended the B737 to FL290. I also turned the E145 to a 280 to get additional separation. Declare an emergency for the aircraft experiencing difficulty; since he did not declare an emergency himself.
Enroute Controller provided a descent to an aircraft experiencing a cracked windshield; the reporter noting he should have declared an ATC emergency for the aircraft and provided an immediate descent.