What would an IPA narrow transcription be for Finnish /d/?

Question

From Finnish Sound Structure (Suomi, Toivonen, Ylitalo):

The Finnish /d/ is apical alveolar, and the duration of its occlusion is very short, about half of that of /t̪/, ceteris paribus, see e.g. Lehtonen (1970: 71), Suomi (1980: 103). During the occlusion, the location of the apical contact with the alveoli moves forward also in vowel contexts that are in principle unfavourable to such a movement (Suomi 1998). Thus in pseudowords of the type [V1dV2], in which V1 is a front vowel and V2 is a back vowel, coarticulation would predict that the location of the contact would be retracted rather than fronted, and yet it moves forward (as it does, more expectedly, when V1 is back and V2 is front). That is, the fronting of the place of alveolar contact during the occlusion seems to be a special property of the Finnish /d/, which overrides the coarticulation due to vocalic context. Presumably this fronting, together with the short duration of the occlusion, contributes to /d/ being voiced: the fronting increases the volume of the cavity between the closure and the glottis, and maintains a sufficiently large transglottal pressure difference to enable voicing to continue during the brief occlusion. The fronting of the apex is reminiscent of a flap, but at the same time it is clear that the Finnish /d/ is not a flap; the fronting of the apex is not as extensive and as fast as that in a flap, and the duration of the occlusion is longer. Rather, the Finnish /d/ appears to be something half-way between a plosive (and hence obstruent) and a flap-like resonant.

What would be an appropriate narrow transcription for this sound?

Answer 1

A narrow transcription of /d/ in Finnish at least includes [d], and could contain other diacritics, depending on how narrow one wants to go. Narrow transcription is about actual pronunciation, not phonemic analysis, so it depends on what specific words (context) you are interested in, and what level of detail you are hoping to add. This requires specific recordings, which we don't have. However, it is generally agreed that the voiceless lingual stop is [t̪] whereas the voiced one is [d], alveolar, not dental. Suomi et al suggests a possible micro-differentiation in [d] (not [d̪]) related to vowel sequence, but this conjecture has not been validated articulatorily, and certainly not to the level of perceptibility so that it might enter into narrow phonetic transcriptions. The shortness of [d] compared to [t̪] might be transcribed with a breve diacritic, but half-length on [t̪] would be more appropriate (it's not that /d/ is specially-short, it's that /t/ is a bit long).