Why is conversational speech recognition much more difficult than read speech (such as Broadcast News, Wall Street Journal, etc)? Simply put, there are many more factors that come into play when humans converse naturally than when a person is reading prepared text. Added to this is the effect of telephone bandwidth and line noise. To demonstrate this, we have prepared a set of examples illustrating the varying difficulty levels of speech recognition tasks.

The main factors contributing to the difficulty of SWITCHBOARD recognition are: