C172 INSTRUCTOR WITH STUDENT INADVERTENTLY CROSS ACTIVE RWY DURING TAXI IN DUE TO NOT HEARING THE HOLD SHORT CLRNC.

Narrative

I WAS CLR TO LAND ON RWY 1 AT FRG ARPT; AN INSTRUCTION FLT WITH STUDENT. I WENT OUT R ON TXWY A. I WAS TOLD TO CONTACT GND FREQ AT THE SAME TIME I HEARD FROM TWR FREQ THE ATIS HAD BEEN CHANGED. I DID CONTACT GND AND REQUESTED TAXI TO HANGAR ON THE N OF THE FIELD. THEN I HEARD FROM THE FREQ THAT TAXI TO HANGAR MEANT ALL THE WAY UP ON TXWY G. I DID MAKE L ON TXWY G AND CROSSED THE RWY 14. THE GND CTLR TOLD ME I WAS NOT SUPPOSED TO DO THAT BECAUSE IT WAS THE ACTIVE RWY 14. THEY DID CHANGE IT TO RWY 14 BECAUSE THEY CHANGED THE ATIS. FROM THE GND FREQ; THEY CLAIMED THEY GAVE ME INSTRUCTION TO HOLD SHORT ON RWY 14; BUT I DID NOT HEAR ANYTHING AND NEITHER DID MY STUDENT. ON THE FREQ; THEY TOLD ME TO CONTACT TWR BY PHONE; AND I SPOKE TO THE SUPVR. I BELIEVE THE PROB WAS CONGESTION ON GND AND TWR FREQS BECAUSE THE ARPT WAS BUSY THAT DAY AND ALSO HAD TO DO WITH THE SWITCH OF RWYS FROM RWY 1 TO RWY 14. ALSO; I THINK BY THE TIME THE GND FREQ INSTRUCTED ME TO HOLD SHORT; SOMEBODY ELSE WAS TALKING AT THE SAME TIME. THAT'S WHY I DID NOT HEAR THE XMISSION.