This morning's discussion on Alphanumeric Reco was great. Here are the slides for anyone who is interested. Thanks to all for sharing their experiences!

1. © 2002 – 2012 Versay Solutions, LLC. All rights reserved.
Alphanumeric Speech
Recognition
SpeechTek
August 19, 2013
Crispin Reedy

2. “The fault, dear Brutus, is not in
our stars, but in ourselves”
-- Julius Caesar, Act I, scene ii
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The ProblemWithAlphanumerics

3. © 2002 – 2012 Versay Solutions, LLC. All rights reserved.
The Need
• Account Numbers
• Policy Numbers
• Spelling out names and addresses
• Special cases
– VIN, Canadian Postal Code
• And more…
3

4. © 2002 – 2012 Versay Solutions, LLC. All rights reserved.
Methods for Addressing
• Project Tactics
• Limit the grammar
– Constraint List
– N-Best + Back-End Data Validation
• Confirmation
• Prefiller
4

5. © 2002 – 2012 Versay Solutions, LLC. All rights reserved.
Project Tactics
• Can you avoid it?
– Phone number / SSN / Zip / DOB?
• Set expectations
– Not always easy!
• Describe the problem
• What tools do you have available?
– Constraints / patterns?
– Back-end data source available?
• Can you run a proof of concept / experiment?
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6. © 2002 – 2012 Versay Solutions, LLC. All rights reserved.
Constraints and Patterns
• Does the number have any known pattern
that can be used to limit possible values (and
thereby improve recognition)
– For example:
• First character is always A
• First three characters are always numbers
• Last characters are always C, G or T.
• If the answer is “no,” consider doing your own
analysis.
– Even if you don’t think there is a pattern, there
may be one.
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7. © 2002 – 2012 Versay Solutions, LLC. All rights reserved.
Applying Constraints
• Writing grammar specifically for the pattern
– How complicated is it?
• Applying a constraint list.
– How big is it?
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8. © 2002 – 2012 Versay Solutions, LLC. All rights reserved.
Using nBest + Back-End Data
• Collect using an unconstrained grammar
• Set your recognizer to return an nBest list.
• Use a webservice / back end data dip to
determine which ones are “real.”
• Confirm the first “real” one on the list
– Throw out the ones that are not real.
• If no, confirm the second “real” one on the
list.
– Potentially collect again after that.
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9. © 2002 – 2012 Versay Solutions, LLC. All rights reserved.
Confirmation Strategy
• PROTIP: Phonemes that are difficult for the
recognizer to hear … are also difficult for
humans to hear when they are spoken back.
• Confirm using letter names for easily
confusable alphanumerics.
– “You said 8, 2, 7 G as in George, B as in Boy, 9. Is
that right?”
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10. © 2002 – 2012 Versay Solutions, LLC. All rights reserved.
What About Letter Names?
• Yes with caveats:
– Do you have a special domain that would allow
you to teach the caller letter names?
– Letter names invented by the caller will be quite
variable.
• Some of the “oddballs” will never be recognized
– If letter names are used during confirmation, and
the utterance is re-collected, the caller may tend
to use those letter names during the second
collection.
• So add them.
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11. © 2002 – 2012 Versay Solutions, LLC. All rights reserved.
What About Letter Names?
• Yes, because:
– Longer utterances “B as in Boy” are not likely to
generate false acceptance between shorter
utterances such as “G” “T” etc.
• Make them separate rules so they can be
weighted
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12. © 2002 – 2012 Versay Solutions, LLC. All rights reserved.
Using Prefiller
• “The account number is… B Z 3 9 0”
– Noticeable improvement in recognition of first
letter
– Caller may spontaneously offer
– Consider teaching the caller to say the prefiller
• Especially if you have repeat callers
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13. © 2002 – 2012 Versay Solutions, LLC. All rights reserved.
Other Suggestions
• Look at speech recognition parameters that
are not directly related to alphanumeric
– Are callers calling from a very noisy environment?
• Adjust overall speech threshold
– Timing of utterance collection?
• Listen to recording of utterances to make sure
everything is getting collected
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14. © 2002 – 2012 Versay Solutions, LLC. All rights reserved.
Specific Cases
• VIN
– Has specific pattern, but different for each
manufacturer
– 16 digits: nobody will want to re-enter if you get it
wrong.
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15. IT DEPENDS!
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but which way is “the best?”