Interdental approximant

This research project was spearheaded by Ken Olson. As a collaborator with him I focused on the historical linguistics status of the interdental approximant in Philippine languages. I also did a lot of library resources discovery and acquisition.

In this project description I have listed more than my contribution because I am not sure there is anywhere else that has pulled together the combined research on this topic.

Results & Significance:

  • Ultrasound Study on the articulation of the interdental approximant.
  • Published phonetic descriptions of the interdental approximant.

Academic Output:


  • Mielke, Jeff, Kenneth S. Olson, Adam Baker & Diana Archangeli. 2011. Articulation of the Kagayanen interdental approximant: An ultrasound study. Journal of Phonetics 39(3). 403–412. DOI: 10.1016/j.wocn.2011.02.008

  • Olson, Kenneth S., Emy T. Ballenas & Nilo M. Borromeo. 2009. Buhi’non (Bikol) digital wordlist: Presentation form. Language Documentation & Conservation 3(2). 213–225. URI:

  • Olson, Kenneth S., Glenn Machlan & Nelson Amangao. 2008. Minangali (Kalinga) digital wordlist: Presentation form. Language Documentation & Conservation 2(1). 141–156. URI

  • Olson, Kenneth S. & Jeff Mielke. 2008. Acoustic properties of the interdental approximant in Kagayanen. Journal of the Acoustical Society of America 123(5). 3460. DOI: 10.1121/1.2934307

Related Academic Work:

  • Matthew Harley (2012) Unusual sounds in Nigerian languages. In Advances in Minority Language Research in Nigeria Part I (eds.) Roger M. Blench and Stuart McGill. Kay Williamson Educational Foundation African languages Monographs No. 5. pages: 38-65. Rüdiger Köppe Verlag: Köln

Follow-up work:

It seems that the interdental approximant [ð̞] in Austronesian languages should challenge linguists in three important areas and thus deserves more thought and perhaps application in our theories. These categories are:

  • The phonological status and interactions that happen with the segment.
  • The phonetic contrast of the segment.
  • The Historical status of the segment and the impact of its recognition in the Austronesian historical linguistic narrative.

Publications to date have focused on two relevant aspects of the interdental approximant:

  • ð̞ is important in descriptive linguistics.
  • ð̞ is different phonetically from other described segments.

The following remain to be shown clearly in appropriate publications.

Phonetic contrast

  • What is the duration of the sound and what are the boarders?
  • Measure the stable section?
  • Where does it stop and where does it begin?
  • What is the acoustical (in terms of both production and perception) difference between /l/ and /ð̞ /?

The ulturasound study does provide a good starting point to answer these questions.

  • ð̞ it has a unique spectrograph when compared with other liquids, vowels, and interdentals - especially within the same language.

  • ð̞ is different from the native sounds of { l, a, ɐ, n, ʔ, d, g, r, s, h, x} which occur in Philippine languages.

    • This has been done in small phonology descriptions but not full scale acoustically reference-able phonetic descriptions across the entire set of languages discussed in the JIPA article.
  • ð̞ is different from the borrowed sounds of { l, a, ɐ, n, ʔ, d, g, θ, ð, r, s, h, x, ɣ}

  • In terms of psycholinguistics the question remains,: What are the unique properties of this sound as they are culturally defined? or to put this another way: What are the acustic cues, what are the visual cues, and what are the cultural constraints that those cues may violate?

  • My research position suggests that there has been change. Change involves a variety of cognitive processes. Re-analysis is one such process. If I hypothesize that re-analysis has occurred, then what is the Cognitive load of this segment? How has that load shifted or why can it shift?

  • What are the unique properties that users attribute to this segment as cross-linguistically defined (but keeping within Austronesian or the Austro-Tai hypotheses).

  • What are those unique properties as Universally or empirically defined?

Historical Narrative

  • There is an open question with relationship to historical Austronesian as to what the metrical structure of the language was. If we posit some change in the metical structrue what relevance does that have on the interdental approximant? Does the concept of Phonetic Gemination apply?

  • In some theories of Austro-Tai there is some relevance to constructing suprasegmental features and genisis or de-genesis processes for these features. In that contexts: Is it possible that ð̞ is a tone bearing unit? (TBU).

  • Interdental is contrastive with dental in Place in the IPA Chart ð̞ is important to PAn Historical Phonology Theory

  • ð̞ is related to several mergers and splits

  • ð̞ is PAn *R

  • ð̞ Shows that [+Nasal], historically, is, or is/and a super-segmental feature in Austronesian languages.

  • ð̞ shows that there are fewer proto-phonemes than necessary in current models of PAn.

  • ð̞ helps us to understand the PAn foot.

  • ð̞ was represented in the baybin original orthography.

ð̞ is relevant enough to be represented consistently in orthographies in the languages it occurs in.


There are several open phonological questions. Some of these have answers in the cited materials, but the data is not always clear for all languages which also have interdental approximants.

  • What are the claimed Phonemes of kangayen?

  • It would be all the more the claim that ð̞ is phonemic not due to a split. If it is a retention then this perspective has more weight.

  • What is the ð̞ pattern concerning natural classes.

  • In a feature geometry perspective, what features does ð̞ have.

  • Some Austornesian language have Metathesis. Is this metathesis process triggered in any way by the ð̞?

  • ð̞ has moraic value - what is it?

  • What is the affect of ð̞ on vowel quality?

  • In what ways can we measure the impact that ð̞ has on cognitive load?

  • Does the ð̞ occur in multiple areas of the lexicon

  • To do this a survey of the texts should be used to evaluated the location of ð̞ in the lexicon. One resource for texts could be:

  • Grayden, Bruce. 1978. “Southern Kalinga [language text].” In Evan L. Antworth (ed.), Folktale texts, 13-23. Studies in Philippine Linguistics, 2(2). Manila: Linguistic Society of the Philippines and Summer Institute of Linguistics.

  • What do I want to research?

  • Why is it important?

  • How do I want to research it?

  • What is the Problem?

  • What is the Solution?

  • What do I want to Say?

  • What is the continued importance of a feature analysis to the field of descriptive linguistics and to the field of historical linguistics and to the field of Phonology?

Hugh Paterson III
Hugh Paterson III
Collaborative Scholar

I specialize in bespoke research at the intersection of Linguistics, Law, Languages, and Technology; specifically utility and life-cycle management for information products in these spaces.

Kenneth S Olson
Kenneth S Olson
Field Linguist / Phonetician

My research interests include phonetics, phonology, translation, and orthography.