What should I do in order to prevent Oracle writes to the operating system audit file.

Regardless of whether database auditing is enabled, Oracle always audits certain database-related operations and writes them to the operating system audit file.

What should I do in order to prevent Oracle writes to the operating system audit file <...>.aud.

Aud. parameters in the database are

audit_sys_operations	FALSE	TRUE
audit_file_dest	/u01/app/oracle/adump	FALSE
audit_syslog_level		TRUE
audit_trail	NONE	TRUE

Thanks