The Flaps

• In a sense we should not even be talking about the flaps, because they are not considered to be phonemes, but rather allophones of the alveolar phonemes /th/, /d/, and /n/ which occur in American English when the alveolar is found between a stressed syllable and an unstressed syllable as in the words ``latter, ladder, tanner." There is little difference between the voiceless and voiced flaps; the nasal flap is accompanied by a lowered velum.
• The reasons for looking at this particular set of allophones is that they can differ so markedly from the parent phoneme and occur so frequently that it is very useful to be able to recognize them.
• Ladefoged seems to prefer the term tap, which he defines as a sound ``in which the tongue makes a single tap against the alveolar ridge." He states that other books contrast the alveolar tap with the retroflex flap. We will continue to use the word flap for the three Worldbet symbols /t_(/, /d_(/, and /n_(/, since it seems to be the preferred term at OGI.
• In all of these cases, the flap replaces a /th/, /d/, or /n/ which occurs between a stressed vowel and an unstressed vowel. Although normal American English pronunciation almost always substitutes a flap in this context, the full phoneme /th/, /d/, or /n/ does occur infrequently - for example, in more formal contexts or for emphasis. In British English the flap does not exist as an allophone for the alveolars, although as Ladefoged points out, regional varieties of English such as Scottish use a flap for the phoneme /9r/, so that the word `petal' as pronounced in American English sounds very much like the word `pearl' in Scottish English.
• The reason for the flap is gestural economy - it is much easier, and takes less time, to flap the tongue briefly against the roof of the mouth as compared with the normal closure, release, and optional aspiration cycle of the plosive, or the full lowering and reraising of the velum to produce the nasal. Since the flap is against the alveolar ridge, the alveolar quality of the sound is preserved.
• A flap is among the shortest lasting phonemes in English -- as short as two or three pitch periods, which assuming a 125 Hz would occupy only 16 to 24 milliseconds. There is often a V-shaped falloff in total energy, with the alveolar flags and a mini-plosion just before the resumption of the full vowel after the flap. The mini-plosion occurs when the tongue leaves the alveolar ridge. See Figure 4 for two examples of flaps.

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