What is speech recognition or automatic speech recognition ?
Automatic speech recognition can be defined as a process by which spoken words are converted to text. Many people may confuse with voice recognition as speech recognition. Voice recognition is recognising the speaker of the voice, while automatic speech recognition recognise the words spoken. While speech recognition is mainly used for menu selection, voice recognition is used for checking authorised user.

How automatic speech recognition can be used in voice portal ?
Voice portal is a large IVR application which provides many value added services to the voice portal user. Normally, voice portals are operated by telecom operators to provide information of their services, activating deactivating services, utility services like matrimonial, job search, listening to music and download, jokes etc. Since voice portals have large information to be provided to a caller, it needs to give out a long list of options. But the DTMF digits or touch tones on a mobile phone or telephone instrument is limited. So automatic speech recognition is used as an alternative to touch tone or DTMF input for selecting a menu option in the voice portal or IVR.

Advantages of Automatic Speech Recognition over DTMF in Voice Portal:
1. Caller can choose a menu option quickly without having to listen to boring long list of menus. IVR can become truly interactive with its caller using same human voice.
2. Using an IVR was always a problem as one he has to remove it from his ear to look at the keypad and press a key. This can be again quite irritating for a voice portal user. Implementation of ASR completely remove this problem.
3. Change of menu or introduction of new options a menu, or shuffling of options in a menu becomes easier as menu options are the words most commonly used by everybody for a particular option. Using a touchtone or DTMF menu, any option was assigned to a DTMF key or a number. With ASR, it is assigned to the word itself.
4. Not many people are aware of # and * keys as they are hardly used in normal operation while IVR seems to use them for some options for very long menus. ASR does not face this kind of problem.

So, one may find it very useful in a developer point of view to use ASR in voice portal as it gives more flexibility for designing menu and presentation of data. But as user point of view it may not that user friendly as touch tone. This mainly due to lack of 100% accuracy in recognising the word spoken by the caller. Wrong detection of words by ASR may result in very awkward menu options and information fetching. One way of tackling this problem is to confirm a user of his chosen option in the menu with a YES or NO for every menu option. But it would be too irritating for a user! A voice portal is normally a premium service where irritating caller is the biggest crime one can commit!

Problems of Speech recognition
1. Accuracy of recognition
Accuracy of recognition can be thought as converting words spoken by a user accurately to ts corresponding text.
As per information available ( by Googling and visiting ASR engine provider websites), almost all ASR engine has high accuracy for detecting two words, YES and NO. Apart from them, other words like numbers, date of births etc. has lower accuracy in recognising. For example, accuracy of recognition of numbers 1,2,3 etc vary from 87 to 91% depending on ASR engine. Accuracy of recognising other natural English language is fare much worse! As per report, recognising departments in company is maximum 85%!
Though accuracy can be improved by training of ASR, but it is not practical at all and does not serve a voice portal.

2. Different accent
Using ASR in a big country where people speak different languages or same language with different accents,speech recognition accuracy is bound to fare worse.

3. Confirming YES/NO again and again is irritating
People may design IVR very intelligently to confirm for any doubtful word recognition by YES or NO, but it is still irritating for many people and it slows down the time for fetching an information. In a voice portal where caller pays by minute of usage, it may not work in the interest of voice portal users.

Still, automatic speech recognition (ASR) is used widely in voice portal now a days and here are the few services in voice portal where ASR may work well :-

1. Contests
2. Classifieds
3. City wise weather information

I had promised before that I would write about DTMF and pulse dialing in future. Finally I have decided to write about them!

This article may be ignored by IVR professionals as they must be quite bored with these two terminologies! But many users who have to listen to announcements like “If you are in pulse mode, then please come to Tone mode by pressing # ( Hash), thank you”, for them it might be useful!

Many telephone Instruments/Telephone Handsets has a button on either bottom-side of it or side of it which says P And T on either side. It means Pulse or Tone. Depending on the position of that button, your telephone instrument will generate either pulses or DTMF tones on pressing a key on the keypad.

DTMF stands for Dual Tone Multiple Frequency.  It esentially used to depict the 4X4 Matrix keypad used for Telephone Keypad. 1,2,3,4,5,6,7,8,9,*,0,#,A,B,C,D. Many telephone instruments don’t have A B C D keys! DTMF constitutes two frequencies which are combined together for denoting a DTMF digit.

Here is the table :

This tables shows that:

When you press Key 1, it generates two frequencies, 1209Hz and 697Hz.  Now, lets unsrstand the telephone operation

It has two state or situation

Connecting state : Here you lift the phone, hear the dial tone, and press the number you want to dial. And wait for either ring back tone or some busy tone! This state can be called connecting state. In this state, when you press the keys, these keys ( the two frequencies ) are transmitted to the exchange. Exchnage in turns try to connect to the number you have dialed.

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Connected State : In this state, call is connected and you are talking to your friends ( girfriends), relatives, business contacts or IVRS! Now if you press a key, it will still produce the same two frequencies and it will be heard by you as well as the person at other end which can be IVRS too! That is how DTMF is used for selectiing various options in IVRS! The tone duration has minimum period to detect and I think its 40ms ON and 80ms OFF. it means it has to generate the tones for minimum period of 40ms for the other end to detect and minimum 80ms of gap for the next DTMF tone!

TIP : If you a smart person, you can use the above information this way!

Suppose you have a landline phone in your house. And your father has put a lock on the keypads so that you can not make any outgoing calls! But you can still make outgoing calls! All you have to do is, using your mobile phone, press the keys of the number you want to call, and then record those tones! ( How do you do it, I wont tell!) Just record those tones, lift the handset, play the recorded tones in front of the mouthpiece of handset and wow, you made a call to that number! I hope I wont be sued for this piece of information!

If the Telephone handset is in Pulse Mode, then when you press a key, it will connect / disconnect corresponding to the number of the key! Suppose, you press a 1, it will disconnect once and then connect again! You can think this as ON HOOK and OFF HOOK! This cycle is for certain duration and the duration is standardized. Its called Break and Connect too.

In connected state too, you can press keys in pulse dialing! It will produce some sound which corresponds to some frequency only! And if IVR can detect that frequency, IVR can detect pulse dialing too in connection state and IVR will stop asking you to come to Tone mode! But most IVR Systems dont support this!

Last information : Mobile Phones dont have Pulse dialing option.

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