Japa has three divisions: mānasika (in the mind), upāṁśu (chanting very softly), and vācika (audible).
Bhakti-rasāmṛta Sindhu mentions the second one, upāṁśu.
When japa is done in the mind, it falls into the category of smaraṇa. If japa is mānasika it comes under the category of smaraṇa. Thus, sometimes the word nāma-smaraṇa is also used for nāma-japa.
When it is done loudly, it may fall into the category of kīrtana, and there, in the definition of japa, only the second type has been included (upāṁśu or sulaghūccāram).
Hari-bhakti Vilāsa mentions all three divisions of japa.
Vinod baba