Burmese has four tones. Each tonal contrasts involve not only differences in pitch and vowel length but also differences in voice quality.
The presence or absence of a glottal stop at the end of a syllable is considered to be part of the tonal system.
And consonants are divided into four classes [low (long, low, clear voice), high (long, high, sometimes breathy voice), creaky (short, high, creaky voice), checked (very short, mid-high, clear voice with final glottal stop)]