The voiced consonant one hears in American English (among other varieties of English) between vowels post-tonically (= after the stress) in words like bitter and bidder is called an alveolar flap, a sound articulated with the tip of the tongue placed against the alveolar ridge and the vocal bands vibrating. This allophone (phonetic variant) of the phonemes /t/ and /d/, symbolized [ᴅ], is also heard after the post-vocalic nasal /n/, so that international is typically pronounced [-nᴅ-].
The identical intervocalic pronunciation of orthographic t and d can create an unintended comic effect when the words in question belong to two stylistically quite incompatible sectors of the lexicon. Thus, the recent frequency in the news of the Swiss name Blatter (the surname of the FIFA president, Sepp Blatter), which Americans understandably pronounce with an alveolar flap, makes the man sound like a component of human anatomy.
What has not been remarked elsewhere, however, is the stylistic restriction on such a neutralization of the difference between /t/ and /d/, namely in formal speech. But less-than-careful speakers, even radio announcers, do allow themselves to carry over their informal phonetic habits into formal diction, with noticeable effect. Thus the male radio voice one hears announcing the name of the organization, Public Radio International, after its programs habitually fails to articulate the appropriate formal variant [t]––i.e., the dental stop––in the third word, substituting the alveolar flap instead, which makes him sound less than sober.