MAS.632 Conversational Computer Systems - MIT OpenCourseWare

110 VOICE (DMMUNICATION WITH COMPUTERS
Transmit
Signal
Silences
Receive
Signal
Interrupt
Signal
Exceplio Ponundlion
Figure 6.2. A configuration to "look through" transmitted speech to
detect user interruptions.
How should a repetition be spoken? In the case of a menu, it suffices to repeat
the menu items with identical wording as the items are often short and the listener
most likely was just having trouble recalling them all. If output consists of
recorded speech, the application can only replay the recording, possibly doing so
at a slower speed. If the text is a passage of computer-generated discourse, it may
be effective to generate an alternate phrasing of the text in the hopes that this
would help with any pronunciation errors. However, this is also problematic as
the user may be expecting a word-for-word repetition and thus be put off balance.
There is little empirical evidence one way or the other.
In the case of synthesizing human-authored text, however, the problem could
be either a spelling or typographical error, failure of the synthesizer's text-tophoneme
rules, or lack of user attention. One repetition strategy is to speak the
same text again at a slower rate in the hope that this enhances intelligibility.The
system to read electronic mail over the telephone, which will be described as a
case study, chose to repeat more slowly and then to switch to "spell mode" and
pronounce the text letter by letter. Spelling a mail message or almost any other
data is tedious. An alternative strategy involved passing the text passage
through a spelling checker program and during repetition combining a slower
speech rate with letter-by-letter spelling of any words not found in the dictionary.
This technique helps catch text-to-phoneme errors as proper names are likely to
be pronounced poorly but would not be found in the dictionary. Most typographical
errors would also fail the spelling check and thus would be spelled out.
Words may be pronounced incorrectly. Ideally, the programmer should be able to
add to the morpheme dictionary in the synthesizer, but no synthesizer product
currently provides this capability. Some synthesizers allow for alternative pronunciations
of a small set of words to be downloaded into the synthesizer, but
if the synthesizer only uses this list with simple string substitution, it is not a