nicer ration to db20

src/ITANumericUtils.cpp

@@ -132,9 +132,15 @@ double db20_to_ratio(double db) {
 	return (db == DECIBEL_MINUS_INFINITY ? 0 : pow(10, db/20.0));
 }
 
-double ratio_to_db20(double r) {
-	if (r < 0) ITA_EXCEPT0(INVALID_PARAMETER);
-	return (r == 0 ? DECIBEL_MINUS_INFINITY : 20*log10(r));
+double ratio_to_db20( double r )
+{
+	if( r < 0.0f )
+		ITA_EXCEPT1( INVALID_PARAMETER, "Conversion to decibel not possible for negative values" );
+
+	if( r == 0.0f )
+		return DECIBEL_MINUS_INFINITY;
+	else
+		return 20.0f * log10( r );
 }
 
 /* +------------------------------------+