I have a single instance database, version 10gR2 on linux, with the following settings for the audit trials
SQL> show parameter aud

audit_file_dest string /u/p3/admin/DB1/audit
audit_sys_operations boolean FALSE
audit_syslog_level string
audit_trail string NONE

The minimal audits that get generated with audit_trial = none are going to the proper destination "/u/p3/admin/DB1/audit".

The problem is that in addition to going to "/u/p3/admin/DB1/audit", some of the audit files (specifically those that get generated when i startup the database)
are also getting created in $ORACLE_HOME/rdbms/audit/ directory.

What can be the reason for this and is there a way I can prevent this from happening?