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I am a native speaker from Mexico and I just noticed that the word "toalla" when pronounced sounds as if it has an "u" instead of an "o" as if you were pronouncing "tualla". This also happens with "Oaxaca" which sounds like "Uaxaca".

  • Could it be that when "o" and "a" are combined the "o" sound changes to "u"?
  • Why is that?

You can see their pronunciation here:

You will see that some of the examples are pronounced with "u" and others with "o". At least here in Mexico most of the times in daily conversation sounds like "u".

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I have never heard the word "toalla" pronounced as "Tualla" in Spain. And in the link you give I hear clearly "toalla" (not "tualla") in the 6 recordings. – Javi Feb 29 '12 at 15:53
@Javi In the recordings it is pronounced so slow that you can notice "oa" but when pronounced quickly, as you will do on daily conversation, it sounds like "ua". – Alfredo Osorio Feb 29 '12 at 15:55
Mmmm, I have always pronounced toalla as toalla, but yes, it sounds like an u sometimes – César Feb 29 '12 at 15:58
@Alfredo O OK, maybe it's something regional or I have never noticed that in Spain. – Javi Feb 29 '12 at 15:59
Quizás al pronunciarlo rápido la posición de los labio y la lengua al prepararte para la "a" queda más próxima a la "u" que a la "o" y, diría, que este fenómeno tiene nombre en la fonología pero no me acuerdo. – Laura Feb 29 '12 at 16:18
up vote 5 down vote accepted

In a book I have on Spanish phonetics and phonology (Fonética y fonología españolas by Armin Schwegler and Juergen Kempff), this is classified as la conversión de hiatos en diptongos (interior de palabras). Some excerpts (note that not all linguistic symbols are exact, emphasis on toalla mine):

Como ya hemos explicado en el capítulo anterior, en el habla normal (rápida), la vocal [-o] final de palabra se realiza como semivocal [u] cuando entra en contacto con otra vocal (por ej., lo es = [lues]).

Este mismo cambio también puede aplicarse en el interior de palabra... Pero allí es menos frecuente que entre palabras, aun cuando la articulación sea rápida.

La tendencia a la reducción de dos vocales en contacto a una sola sílaba en el habla rápida es tan fuerte que las combinaciones "[e] + vocal acentuada" y "[o] + vocal acentuada" pueden convertirse en diptongos. En el habla informal de algunos hispanohablantes, el grupo vocálico "ea" es realiza a veces como [ia]... De igual modo, peor se articula [pior], y toalla = ['tua-ja]. Obsérvese, sin embargo, que este tipo de cambio articulatorio se produce sólo cuando la segunda vocal del grupo (y no la primera) es tónica.

In other words, this is a linguistic phenomenon that occurs in the informal, rapid speech of some Spanish speakers in cases where the vowels e or o followed by a stressed vowel can become diphthongs instead of hiatuses. It is more common at the boundary of words (like lo es), but can also happen inside a single word (like toalla).

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+1 Yeha, sometimes I've seen how parents correct their kids telling them "No se dice pior, se dice peor". – Alfredo Osorio Mar 1 '12 at 15:13

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