On a CCTV 9 show shot in Shanghai, a couple of people who were certainly speaking Putonghua have made comparisons and if I heard right they were pronouncing 比较 as "biao." Am I wrong? Is that a common contraction? Is it typical of Shanghai?
When someone is speaking fast, or speaking casually,
bijiao may become something like
jiao are pronounced too weak to be heard. The first initial
b and the last final
iao are left to form a
biao. However, this newly formed
biao is definitely different form the single syllable
biao. I'm not a linguist and cannot describe this difference in detail.
I don't know in which area this usually happens. Native Chinese can "correct" this pronunciation variation automatically and may not even notice this.
This kind of weakening of sounds happens in every language. In Chinese, it may happen in a syllable or in a word, or even among a phrase. Usually, this kind of weakened syllables are auxiliary words which help construct the sentence.
There is coarticulation which means that adjacent syllables would affect the pronunciation of each other, and they all sound differently from when they are pronounced alone.
An interesting result of this is that if you cut out a single syllable from a spontaneous sentence, there is high probability that even natives cannot figure out what it is, although they would have no problem understanding the full sentence.