Perceiving speech in non-laboratory environments is challenging for both native and non-native listeners, even if they are able to perform well in laboratory (quiet) environment. The difficulty of speech perception by non-native listeners is caused by the differences in the phonological systems of the listener's native and target languages. This difficulty is magnified with the presence of background noise and reverberation, both of which are often present in real-life listening environments. Additionally, accurate perception of non-native speech sounds remains difficult regardless of the listeners' proficiency in the target language. This paper states an overview of the difficulty of non-native speech perception, focusing on consonants, and how its research results could be implemented to the development of perceptual training materials.