Batak Simalungun language
Simalungun, or Batak Simalungun, is an Austronesian language of Sumatra. It is spoken mainly in Simalungun Regency and Pematang Siantar, North Sumatra, Indonesia. Phonology 

/b, d/ can also have implosive allophones [ɓ, ɗ]. Sounds /i, u, ɛ, ɔ, a/ can have allophones [ɪ, ʊ, e, o, ɑ]. References

External links 
 Indonesian-Simalungun Dictionary
 David Goldsworthy's collection of Music of Indonesia and Malaysia archived with Paradisec includes open access recordings in Batak Simalungun. Batak languages
Languages of Indonesia