ACR X UNAUTH DSCNT BELOW ASSIGNED ALT BECAUSE OF COPYING WRONG ALT SETTING.

Narrative

AS FO; I HANDLED COMS WITH ATC ON ACR X. W OF PROVIDENCE; ATC INSTRUCTED US TO DSND TO 11000 FT; AND STATED THE LCL ALTIMETER. I READ BACK THE CLRNC; UNDERSTANDING THE ALTIMETER TO BE 30.37. AT THIS TIME; I ATTEMPTED TO LISTEN TO BOS ATIS ON THE SECOND RADIO. NO XMISSION WAS RECEIVED WHICH I ATTRIBUTED TO THE ATIS BEING IN THE PROCESS OF BEING CHANGED. THE PRELIMINARY CHKLIST WAS ACCOMPLISHED; USING 30.37 AS THE ALTIMETER SETTING. ABOUT 5 MINS LATER; THE NEW ATIS WAS BEING BROADCAST. AS I COPIED IT; WE WERE DSNDING THROUGH 12000 FT. ALMOST SIMULTANEOUSLY; I FINISHED COPYING THE ATIS; WE LEVELED AT 11000 FT; AND ATC CALLED TELLING US TO CHK OUR ALT AND ALTIMETER AT 29.37. WE CORRECTED OUR ALTIMETERS; AND CLBED BACK TO 11000 FT. THERE WAS NO OTHER TFC IN THE AREA. FACTORS IN THIS INCIDENT INCLUDE MY HEARING '.37' AND ASSUMING IT WAS THE MORE NORMAL 30.37 RATHER THAN THE LOW READING OF 29.37; THE DELAY IN RECEIVING ATIS INFO THAT WOULD HAVE CORRECTED THE ERROR; AND THE XMISSION BY ATC IN 1 CALL OF A SERIES OF MULTI-DIGIT NUMBERS.