Is speech perceived as set of phonemes by human?
Phonemes are the smallest units of speech sound, usually about 20 to 60 in number, and different for each language (1). They are what letter are to words, actually  alphabetic writing systems are derived from phonemes (2). A group of phonemes together form a chunk, that represent a word. These chunks are arbitrary and are created by culture, and are learned by humans from very early age. Furthermore these chunks point to specific concepts that are stored in our semantic memory.


  Concepts arise as abstractions or generalisations from experience;
  from the result of a transformation of existing ideas; or from innate
  properties. A concept is instantiated by all of its
  actual or potential instances, whether these are things in the real
  world or other ideas.
  
  Semantic memory refers to general world knowledge that we have
  accumulated throughout our lives. This general knowledge (facts,
  ideas, meaning and concepts) is intertwined in experience and
  dependent on culture.