Is there a real distinction in say, a spectrogram, between unaspirated voiceless stops and their voiced counterparts before a (voiced) vowel? For example, /ka/ and /ga/. Are they actually different phonetically? And if so, how different.... picoseconds of voicelessness? Or is it significant?
My question comes from noticing that in Zulu, an aspirated /k/ often becomes non-aspirated when there's a nasal preceding it I believe (e.g., inkukhu (chicken) instead of inkhukhu), and it sounds very close to a /g/.... particularly when followed by a vowel. So, my hypothesis is that the two sounds become so similar, that they probably lose their ability to be distinct in that environment. Anyone know any specifics?