Tajudeen Mamadou Y., Huteng Dai, Yair Haendler, and Mariapaola D’Imperio recently presented a poster titled ”The Role of Global and Local Pitch Levels in the Perception of Questions in Ede Chaabe” at the 2021 Phonetics and Phonology in Europe (PaPE2021).
Here’s an excerpt from the abstract :
Low-pitched ‘Lax prosody’ [5,6] is an areal feature found along the Sudanic Belt, presenting
some or all of the following intonational cues for polar questions: final L% tone or falling
intonation, final polar or mid tone, final lengthening, breathy termination and/or cancellation
of penultimate lengthening [6, 5, 2, 1]. In particular,  added a raised register level (i.e.
‘expanded pitch range’) to these characteristics, which would counteract the effect of the
presence of a final L% in questions, in line with Frequency Code predictions . In Ede Chaabe
(Niger-Congo), however, yes/no questions are systematically realized at a lower global
pitch level than statements, as well as with a local final F0 fall (L%), as illustrated in Figure 1.
This goes counter to Ede Yoruba with which it shares the same sub-family and which is an
established non-lax-prosody language . These production findings put into question the
predictions of the Frequency Code, given that neither global pitch differences nor boundary
tone marking would go towards a higher pitch level (Register) specification in questions. The
aim of this study was hence to perceptually test the combined role of the terminal contour
(presence vs absence of a fall) and global pitch level manipulation on the perception of polar
questions in Ede Chaabe.
The complete abstract can be found here.