Why do sonorants not voice in Hungarian?: And why do they voice in Slovak?

This paper investigates the acoustic aspects of voicing assimilation in Hungarian and Slovak, paying special attention to the position before the sonorant consonants /m/ and /l/. With the help of acoustic experiments, we enumerate and compare the acoustic phonetic correlates of laryngeal contrast for the obstruents /t d s z/ in various contexts in the two languages, presenting acoustic evidence of why voiceless obstruents are voiced before sonorants in Slovak but remain voiceless in Hungarian. We show that regressive voicing assimilation — including pre-sonorant voicing and inal devoicing in Slovak — is close to be a completely phonologised process in both languages