As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
TONE SOUND KEEPS REPEATING EVERY 7 SECONDS. GROUNDED - YES. TONE IN QUESTION IS ALT ALERTER. DFCS BITE GRP TEST 11.61 PASS - NO FAULTS. DFCS MCP INSTALL TEST GOOD REF B737-800 AMM 22-11-34. W/ MCP ALT SELECTED ABOVE FIELD ELEV, TONE STOPPED. ETOPS GND VERIFICATION TEST PASS.