B737-900 FO COMPLAINS OF THE AUDIO PANEL DESIGN WHEREIN THE GPWS AND ALT ALERT SIGNALS ARE CHANNELED THROUGH THE PANEL TO THE CREW'S HEADSETS; THEREBY POSSIBLY CREATING A LOSS OF COM WITH ATC.

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CERTAIN ACFT WITHIN THE B737-900 FLEET SOUND THE ALT ALERTER/EGPWS SYS ALERTS THROUGH THE AUDIO PANEL; AND THUS THE PLT'S HEADSET. I BELIEVE THIS TO BE A HAZARDOUS CONFIGN DUE TO THE POSSIBILITY (AND PROBABILITY) OF MISSING AN IMPORTANT ATC INSTRUCTION DUE TO AN ALT ALERT. AT VARIOUS POINTS DURING THESE FLTS; ATC INSTRUCTIONS WERE BLOCKED BY THE ALT ALERTER'S TONE SOUNDING AT AN INOPPORTUNE MOMENT. LUCKILY; IT DID NOT CAUSE US TO DEVIATE FROM ATC INSTRUCTIONS ON THESE 2 PARTICULAR FLTS. BUT; IT HAS CAUSED ME TO ASK ATC TO REPEAT THEIR INSTRUCTIONS TO US; ON PREVIOUS FLTS -- ONE WHEN WE WERE ABOUT TO INTERCEPT A LOC COURSE TO AN ARPT WITH PARALLEL RWYS. I AM CONCERNED BY THE POSSIBILITY THAT A CTL TWR COULD ISSUE 'GO AROUND' INSTRUCTIONS TO AN ACFT (PERHAPS DUE TO A RWY INCURSION); JUST WHEN THE EGPWS IS COUNTING DOWN (100-50-30-20-10); AND THE FLT CREW'S INABILITY TO HEAR THOSE INSTRUCTIONS DUE TO THE VOLUME LEVEL OF THE ALERTS. I HOPE THAT THIS SIT CAN BE RESOLVED AS THE -900 ACFT ARE CYCLED THROUGH MAINT.