Naturalist Thomas Herbert, who encountered dodos on Mauritius in the 17th century, described their vocalizations as resembling the lowing of an ox or cow, particularly when several were calling together. Some researchers suggest that this description might be exaggerated or influenced by cultural perceptions.
Another account by François Leguat, another 17th-century observer, indicated that the dodo produced a kind of hoarse grunt. Based on comparisons with the vocalizations of pigeons and doves, which are close relatives of the dodo, it's possible that the species used similar sounds of cooing, gurgling, or low grunts for various communication purposes.
It's important to note that these descriptions are limited and open to interpretation, so the exact vocalizations of the dodo remain unknown.