Pit TRACON controller reported missing a read back resulting in an aircraft flying below the MVA.

Narrative:

Aircraft X inbound to pit from southeast already had checked in. Frequencies were combined and aircraft Y was departing airspace to the north. Aircraft Y was already handed off to yng approach and requested a lower altitude. Aircraft Y was issued 3;000 and I immediately coordinated with yng. While on the line I missed the partial read back of what turned out to by aircraft X. I noticed aircraft X descending and asked to confirm assigned altitude. Aircraft responded 3;000. Aircraft was still inside jst approach control airspace and our MVA (minimum vectoring altitude) in the area is 3;400. Aircraft was descending through 3;300 and about 1 mile from pit. I took no further action.hearback/readback prior to coordination with adjacent approach control. I should have stopped aircraft descent.

Original NASA ASRS Text

Title: PIT TRACON Controller reported missing a read back resulting in an aircraft flying below the MVA.

Narrative: Aircraft X inbound to PIT from southeast already had checked in. Frequencies were combined and Aircraft Y was departing airspace to the north. Aircraft Y was already handed off to YNG Approach and requested a lower altitude. Aircraft Y was issued 3;000 and I immediately coordinated with YNG. While on the line I missed the partial read back of what turned out to by Aircraft X. I noticed Aircraft X descending and asked to confirm assigned altitude. Aircraft responded 3;000. Aircraft was still inside JST Approach Control airspace and our MVA (Minimum Vectoring Altitude) in the area is 3;400. Aircraft was descending through 3;300 and about 1 mile from PIT. I took no further action.Hearback/readback prior to coordination with adjacent Approach Control. I should have stopped aircraft descent.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.

Attributes
ACN	1622696
Time
Date	201902
Local Time Of Day	1201-1800
Place
Locale Reference	PIT.Airport
State Reference	PA
Environment
Light	Daylight
Aircraft 1
Make Model Name	PC-12
Flight Phase	Cruise
Route In Use	Vectors
Flight Plan	IFR
Person 1
Function	Other / Unknown
Qualification	Air Traffic Control Fully Certified
Experience	Air Traffic Control Time Certified In Pos 1 (yrs) 13
Events
Anomaly	ATC Issue All Types Deviation - Procedural Clearance Inflight Event / Encounter CFTT / CFIT