[t] is just the voiceless version of [d] and vice versa. The more lazily you pronounce the [t] between two vowels, the closer to [d] it becomes because it's les

[t] is just the voiceless version of [d] and vice versa. The more lazily you pronounce the [t] between two vowels, the closer to [d] it becomes because it's less work to just keep the vocal chords vibrating.