Noise detection

References

1. ^ abIn Metal Gear Solid Integral (SLPM-86247), a noise is a power, a length, and a position (GM_SetNoise), and a noise replaces the current one only if its power is higher, or equal with a length at least as long. A guard whose field_BA3 bit 1 is set (its setup sets it) hears the current noise by its power (s00a_command_800C9930): 5 within 1,500 units, 200 within COM_NOISEMODE_DIS (8,000 by default; a stage script's y option sets it), 255 at any distance, and 100 only if it is the guard the commander picked; for every power but 255 the guard must be on Snake's map, and 255 has its own test on GM_ClaymoreMap. Other powers aren't heard, such as the 4 of Snake's kick. For a 100, the commander (s00a_command_800CF9A0), outside mode 1, picks the guard within COM_NOISEMODE_DIS of the noise whose HZD_ZoneDistance to it is under 300 and least; that guard hears it and clears it, so one guard answers. Knocking on a wall makes a 100: sna_knock_80054D68 probes the wall beside Snake and, when the surface's attribute code is under 4, starts NewAfterSe, which 6 frames later plays the knock and calls GM_SetNoise(100, 16) at Snake's position. A footstep makes a 100 when Snake isn't in a duct (PLAYER_INTRUDE) and the stage script's n list gives the floor under him a nonzero noise flag. Explosions (blast.c) and stun grenades (stngrnd.c) make a 255. A patrolling guard (think2 0, s00a_command_800CD210) answers a heard noise (field_BA1 bit 1) after bits 4 and 2 and before footprints (bit 16) and sight; for a 255 it goes to the same reaction state as a sighting (think2 7), which after 21 updates (computed) sets its alert_level to 255.CodeFoxdieTeam/mgs_reversingrevised
   How we know

   74static inline void GM_SetNoise( int power, int length, SVECTOR *pos )
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   76    int old ;
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   78    old = GM_NoisePower ;
   79    if ( power < old ) return ;
   80    if ( power == old && length < GM_NoiseLength ) return ;
   81    GM_NoisePower = power ;
   82    GM_NoiseLength = length ;
   83    GM_NoisePosition = *pos ;
   

   62void s00a_command_800C9930( WatcherWork* work )
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   64    CONTROL *ctrl;
   65    if ( !( work->field_BA3 & 1 ) )
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   67        return;
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   72        return;
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   78        return;
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   83    if ( GM_NoisePower == 0xFF )
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   86        if ( !( ctrl->map->index & GM_ClaymoreMap ) &&
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   90            return;
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   93    else
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   95        if ( !( ctrl->map->index & GM_PlayerMap ) )
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   97            return;
   ⋮
   

   677    work->field_BA3 =  7;
   

   1190    COM_NOISEMODE_DIS = 0x1F40;
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   1192    ops = GCL_GetOption( 'y' );
   1193    if ( ops )
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   1195        COM_NOISEMODE_DIS = GCL_StrToInt( ops );
   

   714int s00a_command_800CF9A0( WatcherWork *work, int dis, int idx )
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   721    if ( TOPCOMMAND.mode == 1 )
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   723        goto exit;
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   726    if ( GM_NoisePower != 0x64 )
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   728        goto exit;
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   733       goto exit;
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   736    if ( GV_DiffVec3( &GM_NoisePosition, &ctrl->mov ) >= COM_NOISEMODE_DIS )
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   738        goto exit;
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   741    x = s00a_command_800CF940( ctrl->map->hzd, &ctrl->mov, &GM_NoisePosition );
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   743    if ( x < 300 && x < dis )
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   745        COM_NoiseMinDisID = idx;
   746        dis = x;
   

   697int s00a_command_800CF940( HZD_HDL *hzd, SVECTOR *pos, SVECTOR *pos2 )
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   702    from = HZD_GetAddress( hzd, pos, -1 );
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   707        to = HZD_GetAddress( hzd, pos2, -1 );
   708        do {
   709            return HZD_ZoneDistance( hzd, from & 0xFF, to & 0xFF );
   

   4128        if (sna_8004F628(work, &vec, -250, HZD_CHK_D_SEGMENT | HZD_CHK_F_SEGMENT, SEGMENT_ATR, var_t0))
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   4130            temp_v0 = HZD_GetOnlineHazardAtr();
   4131            code = (temp_v0 >> 8) & 7;
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   4133            if (code < 4)
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   4135                temp_v0 = GM_GetNoiseSound(temp_v0, 0);
   4136                noise = temp_v0;
   4137                NewAfterSe(noise, 6);
   

   14static void Act(Work *work)
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   16    if ( --work->time == 0 )
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   18        // Play the sound
   19        GM_SeSetMode(&GM_PlayerPosition, work->sound, GM_SEMODE_BOMB);
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   21        // Allow soliders/chavs/whatever to hear it
   22        GM_SetNoise(100, 16, &GM_PlayerPosition);
   

   104        else
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   106            index = asioto_800C396C(work);
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   112            bank2 = asioto_800C392C(work);
   113            if (bank2 >= 0)
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   115                GM_SeSet(&GM_PlayerPosition, work->se[bank2][index]);
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   117                if (work->noise[bank2] != 0)
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   119                    GM_SetNoise(100, 4, &GM_PlayerPosition);
   

   90        if (GM_PlayerStatus & PLAYER_INTRUDE)
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   92            if (GM_PlayerStatus & PLAYER_MOVE)
   

   193    if (GCL_GetOption('n'))
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   202            work->noise[i] = GCL_StrToInt(GCL_NextStr());
   

   6847        sound = SE_KICK_SWING;
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   6854        GM_SetNoise(4, 2, &work->control.mov);
   

   170        GM_SetNoise(255, 32, &work->pos);
   

   224        GM_SetNoise(255, 32, &work->field_E0);
   

   1939    if ( work->field_BA1 & 4 )
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   1941        s00a_command_800CB3F0( work );
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   1943    else if ( work->field_BA1 & 2)
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   1945        s00a_command_800CB610( work );
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   1947    else if ( work->field_BA1 & 1)
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   1949        s00a_command_800CB504( work );
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   1951    else if ( work->field_BA1 & 16 )
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   1953        s00a_command_800CB628( work );
   

   558    case 255:
   559        s00a_command_800CAB74( work );
   560        s00a_command_800CEB54();
   561        work->think2 = 7;
   562        work->think3 = 16;
   

   2344        case 16:
   2345        if ( s00a_command_800CBE90( work ) )
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   2356            work->alert_level = 255;
   

   953int s00a_command_800CBE90( WatcherWork* work )
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   962    if ( work->count3 > 20 )
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   964        return 1;
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   967    work->count3++;
   

   Checked against the evidence by its author, an AI model, 2026-10-22.

   Revised after a check by a second AI model, 2026-10-22.

   In the claim ledger