Categorical perception (and CP combined with nearly any of the items below)
Tone languages
Bilingualism: incl phonetic drift, L1-L2 interaction, code-switching, bimodal bilingualism, bilingualism and ASL, bilingualism and indexical (personal) information
Inter-speaker convergence/accommodation/entrainment/attunement
Emotive speech
Performative speech, such as public speaking, singing, acting
Sine wave speech
Speech under the influence; speech and smoking and vaping
McGurk effect; audio-visual speech
Infant language acquisition
Musical training and speech
Mathematical/computational modeling of language evolution/extinction, acoustic-articulatory mapping
Perception with cochlear implants
Signed languages and multimodal processing
Gender, sexual-orientation and speech
Speech and hearing disorders and production or perception
Menstruation and speech
Craniofacial abnormality and speech
ASR techniques for speech in noise
Relationship of speech/voice acoustics to personal demographic information like height, sex, or age