diff --git a/lib_dec/fd_cng_dec_fx.c b/lib_dec/fd_cng_dec_fx.c
index e2379c7cfb4bd14cc7f6e0a9822a102bce9ca6a9..48c91b684170274247d10dea73fccefd0b1c891b 100644
--- a/lib_dec/fd_cng_dec_fx.c
+++ b/lib_dec/fd_cng_dec_fx.c
@@ -2468,15 +2468,15 @@ void perform_noise_estimation_dec_ivas_fx(
         SWITCH( hFdCngDec->hFdCngCom->fftlen )
         {
             case 640:
-                rescale_fac = 20972; // 4/(640 * 640) in Q31
+                rescale_fac = 83886; // 4/(640 * 640) in Q33
                 move32();
                 BREAK;
             case 512:
-                rescale_fac = 32768; // 4/(512 * 512) in Q31
+                rescale_fac = 131072; // 4/(512 * 512) in Q33
                 move32();
                 BREAK;
             case 320:
-                rescale_fac = 83886; // 4/(320 * 320) in Q31
+                rescale_fac = 335544; // 4/(320 * 320) in Q33
                 move32();
                 BREAK;
             default:
@@ -2486,10 +2486,11 @@ void perform_noise_estimation_dec_ivas_fx(
         IF( startBand == 0 )
         {
             W_tmp = W_mult0_32_32( fftBuffer[0], fftBuffer[0] );
-            min_q = 2;
+            tmp_s = W_norm( W_tmp );
+            ( *ptr_per ) = W_extract_h( W_shl( W_tmp, tmp_s ) );
+            tmp_q = sub( add( i_mult( sub( 31, fftBuffer_exp ), 2 ), tmp_s ), 32 );
+            min_q = tmp_q;
             move16();
-            ( *ptr_per ) = W_extract_l( W_shr( W_tmp, sub( i_mult( sub( 31, fftBuffer_exp ), 2 ), min_q ) ) );
-            move32();
             ptr_per++;
             ptr_r = fftBuffer + 2;
         }
@@ -2530,11 +2531,11 @@ void perform_noise_estimation_dec_ivas_fx(
                     *reIter = L_shr( *reIter, diff );
                     move32();
                 }
-                IF( GE_16( tmp_q, 0 ) )
+                IF( tmp_q >= 0 )
                 {
                     min_q = tmp_q;
                 }
-                ELSE IF( LT_16( tmp_q, 0 ) )
+                ELSE IF( tmp_q < 0 )
                 {
                     min_q = 0;
                 }
@@ -2544,10 +2545,10 @@ void perform_noise_estimation_dec_ivas_fx(
             move32();
 
             /* Rescale to get energy/sample: it should be 2*(1/N)*(2/N), parseval relation with 1/N,*2 for nrg computed till Nyquist only, 2/N as windowed samples correspond to half a frame*/
-            ( *ptr_per ) = Mpy_32_32_r( ( *ptr_per ), rescale_fac ); // Q = min_q
+            ( *ptr_per ) = Mpy_32_32_r( ( *ptr_per ), rescale_fac ); // Q = min_q+2
             move32();
 
-            IF( LT_16( tmp_q, 0 ) )
+            IF( tmp_q < 0 )
             {
                 ( *ptr_per ) = L_shl( ( *ptr_per ), negate( tmp_q ) );
                 move32();
@@ -2557,7 +2558,7 @@ void perform_noise_estimation_dec_ivas_fx(
             ptr_i += 2;
         }
 
-        hFdCngDec->hFdCngCom->periodog_exp = sub( 31, min_q );
+        hFdCngDec->hFdCngCom->periodog_exp = sub( 31 - 2, min_q );
         hFdCngDec->hFdCngCom->fftBuffer_exp = fftBuffer_exp;
         move16();
         move16();
@@ -2635,9 +2636,9 @@ void perform_noise_estimation_dec_ivas_fx(
                 msPeriodog[p] = L_add( msPeriodog[p], L_tmp );
                 move32();
 
-                if ( LT_32( msPeriodog[p], 0 ) )
+                IF( LT_32( msPeriodog[p], L_shr( 21474, hFdCngDec->msPeriodog_exp ) ) )
                 {
-                    msPeriodog[p] = 0;
+                    msPeriodog[p] = L_shr( 21474, hFdCngDec->msPeriodog_exp );
                     move32();
                 }
             }