Abstract:
A method of authentication is disclosed. When a user registers with an enterprise, the enterprise instructs the user to select sounds from a selection of sounds. Any sound that the user selects is designated as a “type-A” sound and any sound that is not so designated is deemed a “type-B” sound. To authenticate the user, the enterprise combines type-A sounds and type-B sounds into a temporal series of sounds and constructs questions about the series that can only be answered by someone who can recognize and distinguish type-A sounds from type-B sounds. The series of sounds and the questions are then transmitted to the user. If the user is able to answer the questions, then he or she is authenticated, and if not, then he or she is not authenticated.

Description:
FIELD OF THE INVENTION 
     The present to telecommunications in general, and, more particularly, to telecommunications enterprises. 
     BACKGROUND OF THE INVENTION 
     When a user contacts a bank or other enterprise via the telephone, the bank might require the user to orally provide his or her password to authenticate his identity. This type of authentication is particularly vulnerable to eavesdroppers, and, therefore, the need exists for a better method of authenticating a user via telephone. 
     SUMMARY OF THE INVENTION 
     The present invention provides a method of authenticating a user via telephone in a way that avoids some of the costs and disadvantages for doing so in the prior art. When a user registers with an enterprise for the first time, the enterprise instructs the user to select one or more sounds from a selection of sounds. The selection of sounds can include anything—spoken words, music, noise, a friend or family&#39;s member&#39;s voice, etc. The user can also record and select one or more sounds. 
     Any sound that the user selects is designated as a “type-A” sound. Any sound that is not designated by the user as “type-A” is—automatically and by definition—designated as a “type-B” sound. There is nothing inherent in a sound that makes it either “type-A” or “type-B,” and the designation of any given sound as type-A by the user should appear to an eavesdropper as arbitrary. In other words, it should be impossible—or at least improbable—for an eavesdropper to predict whether a user would designate a given sound as type-A or not. 
     After registration is complete and a set of type-A sounds have been designated, the user can begin to authenticate himself or herself to the enterprise by asserting his or her identity and a request for authentication. The enterprise then selects a random number of type-A sounds and a random number of type-B sounds and combines them, in random order, to form a temporal series of sounds. The enterprise also constructs a question about the series of sounds that can only be answered by someone who is able to recognize type-A sounds and distinguish them from type-B sounds. For example, the question might be “Does the series of 7 sounds contain exactly 3 type-A sounds?” or “Does the series of sounds comprise 2 type-A sounds in succession?” 
     The series of sounds and the question is then transmitted by the enterprise to the user via telephone. If the user is able to answer the question, then he or she is authenticated, and if the user is unable to answer the question, then he or she is not authenticated. 
     An advantage of the illustrative embodiment is that even if an eavesdropper hears the series of sounds, the question, and the correct answer, it can be difficult for the eavesdropper to deduce which are the type-A sounds. This makes it difficult for the eavesdropper to later impersonate the user. 
     The illustrative embodiment of the present invention comprises: (i) transmitting a series of X(t 1 )+Y(t 1 ) sounds to a client, wherein the series of X(t 1 )+Y(t 1 ) sounds comprises X(t 1 ) type-A sounds and Y(t 1 ) type-B sounds, and (ii) authenticating the client when and only when a user demonstrates an ability to distinguish a type-A sound from a type-B sound in the X(t 1 )+Y(t 1 ) sounds, wherein X(t 1 ) and Y(t 1 ) are positive integers. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  depicts a schematic diagram of the salient components of telecommunications systems  100  in accordance with the illustrative embodiment of the present invention. 
         FIG. 2  depicts a flowchart of the salient tasks associated with the operation of the illustrative embodiment of the present invention. 
         FIG. 3  depicts a flowchart of the salient tasks associated with the operation of task  201  in accordance with the illustrative embodiment of the present invention. 
         FIG. 4  depicts a flowchart of the salient tasks associated with the operation of task  301  in accordance with the illustrative embodiment of the present invention. 
         FIG. 5  depicts a flowchart of the salient task associated with the operation of task  302  in accordance with the illustrative embodiment of the present invention. 
         FIG. 6  depicts a flowchart of the salient task associated with the operation of task  202  in accordance with the illustrative embodiment of the present invention. 
         FIG. 7  depicts a flowchart of the salient task associated with the operation of task  602  in accordance with the illustrative embodiment of the present invention. 
         FIG. 8  depicts a flowchart of the salient task associated with the operation of task  604  in accordance with the illustrative embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  depicts a schematic diagram of the salient components of telecommunications systems  100  in accordance with the illustrative embodiment of the present invention. Telecommunications system  100  comprises: client telecommunications terminal  101 , telecommunications network  102 , and enterprise  103 , which comprises call-processing switch  104 , and agent telecommunications terminal  105 . 
     Although the illustrative embodiment comprises one client terminal, it will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention that comprise any number of client terminals. 
     Although the illustrative embodiment comprises one telecommunications network, it will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention that comprises any number or any combination of telecommunications networks. 
     Although the illustrative embodiment comprises one enterprise, it will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention that comprises any number of enterprises. 
     Although the illustrative embodiment comprises one call-processing switch, it will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention that comprises any number or any combination of call-processing switches. 
     Although the illustrative embodiment comprises one agent terminal, it will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention that comprises any number of agent terminals. 
     Caller terminal  101  comprises hardware and software that enables a user to contact and interact with enterprise  103  via sounds. In accordance with the illustrative embodiment, client terminal  101  is a wireless terminal (e.g., a cell phone, a personal digital assistant, a smart-phone, etc.), but it will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention in which some or all of the client terminals connect to telecommunications network  102  via wireline. In any case, it will be clear to those skilled in the art how to make and use client terminal  101 . 
     Telecommunications network  102  is the Public Switched Telephone Network (PSTN), but it will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention in which telecommunications network  102  is a different network or a combination of different networks, for example, and without limitation, the Internet, a private data network, a satellite network, etc. 
     Enterprise  103  is a building for housing call-processing switch  104 , agent terminal  105  and an agent associated with agent terminal  105 . In accordance with the illustrative embodiment, agent terminal  105  and the agent are co-located with call-processing switch  104  in enterprise  103 , but it will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention in which some or all of the agent terminals and agents are not co-located with call-processing switch  104 . 
     Call-processing switch  104  comprises hardware and software that enables it to store sounds, authenticate a client, retrieve and transmit information requested by the client, connect the client to an agent, etc. In particular, call-processing switch  104  is capable of performing the tasks described below and in the accompanying figures. 
     Agent terminal  105  comprises hardware and software that enables an agent to interact with client terminal  101 , in well-known fashion. 
       FIG. 2  depicts a flowchart of the salient tasks associated with the operation of the illustrative embodiment of the present invention. 
     At task  201 , the user of client terminal  101  contacts enterprise  103  and registers with call-processing switch  104 . As part of task  201 , the user and enterprise  103  agree upon:
         i. a user-identifier, and   ii. a non-empty set of “type-A” sounds that are associated with the user-identifier, and   iii. a non-empty set of “type-B” sounds that are associated with the user-identifier.
 
In accordance with the illustrative embodiment, sounds are designated as one of two types, but it will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention in which the sounds are designated as:
   i. any one of M types (e.g., type-A, type-B, type-C, etc.), wherein M is a positive integer greater than 1 (e.g., 2, 3, 4, 5, 6, etc.), or   ii. any N of M types (e.g., Sound # 1  is type-A and type-B, Sound # 2  is both type-A and type-C, Sound # 3  is type-C, Sound # 4  is type-B and type-C and type-D, etc.), wherein N is a positive integer greater than 1 (e.g., 2, 3, 4, 5, 6, etc.) and N&lt;M, or   iii. any combination of i and ii.
 
Task  201  is described in detail below and with respect to  FIG. 3 .
       

     At task  202 , enterprise  103  uses the type-A and type-B sounds to authenticate the user. Task  202  is described in detail below and with respect to  FIG. 6 . 
       FIG. 3  depicts a flowchart of the salient tasks associated with the operation of task  201 . 
     It will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention in which tasks  301  and  302  are performed in a different order or are performed concurrently. Furthermore, it will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention that omit task  302 . 
     At task  301 , the user records and designates a plurality of sounds that are designated as “type-A,” and call-processing switch  104  associates them with the user-identifier. Task  301  is described in detail below and in the figures. 
     At task  302 , the user records and designates a plurality of sounds that are designated as “type-B,” and call-processing switch  104  associates them with the user-identifier. Task  302  is described in detail below and in the figures. In embodiments where task  302  is omitted, enterprise  103  designates a plurality of sounds as “type-B”—unilaterally and without input from the user—at any time up to, and including, at task  602  as described below. 
       FIG. 4  depicts a flowchart of the salient tasks associated with the operation of task  301  in accordance with the illustrative embodiment. 
     It will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention in which tasks  401  and  402  are performed in a different order or are performed concurrently. Furthermore, it will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention that omit exactly one of tasks  401  and  402 . 
     At task  401 , call-processing switch  104  records X R  type-A sounds, wherein X R  is a positive integer. In accordance with the illustrative embodiment, X R =10, but it will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention in which X R  is any positive integer. 
     As part of task  401 , call-processing switch  104  directs the user to produce or provide X R  sounds, one at a time, to constitute the X R  type-A signals. Once this is done, call-processing switch  104  associates the X R  type-A signals with the user-identifier. 
     In accordance with the illustrative embodiment, each sound produced by the user is a word spoken by the user, but it will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention in which a sound is:
         i. a spoken word, or   ii. music, or   iii. noise, or   iv. any combination of i, ii, and iii.       

     At task  402 , call-processing switch  104  directs the user to designate X S  sounds from a plurality of sounds presented to the user as “type-A,” wherein X S  is a positive integer. Once the user has designated the sounds, call-processing switch  104  associates them with the user&#39;s identifier. In accordance with the illustrative embodiment, X S =10, but it will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention in which X S  is any positive integer. 
       FIG. 5  depicts a flowchart of the salient tasks associated with the operation of task  302  in accordance with the illustrative embodiment. 
     It will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention in which tasks  501  and  502  are performed in a different order or are performed concurrently. Furthermore, it will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention in which either task  501  is omitted or task  502  is omitted or both tasks  501  and  502  are omitted. 
     At task  501 , call-processing switch  104  records Y R  type-B sounds, wherein Y R  is a positive integer. In accordance with the illustrative embodiment, Y R =10, but it will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention in which Y R  is any positive integer. 
     As part of task  501 , call-processing switch  104  directs the user to produce or provide Y R  sounds, one at a time, to constitute the Y R  type-B signals. Once this is done, call-processing switch  104  associates the Y R  type-B signals with the user-identifier. 
     In accordance with the illustrative embodiment, each sound produced by the user is a word spoken by the user, but it will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention in which a sound is:
         i. a spoken word, or   ii. music, or   iii. noise, or   iv. any combination of i, ii, and iii.       

     At task  502 , call-processing switch  104  directs the user to designate Y S  sounds from a plurality of sounds presented to the user as “type-B,” wherein Y S  is a positive integer. Once the user has designated the sounds, call-processing switch  104  associates them with the user&#39;s identifier. In accordance with the illustrative embodiment, Y S =10, but it will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention in which Y S  is any positive integer. 
       FIG. 6  depicts a flowchart of the salient tasks associated with the operation of task  202 . It will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention in which some or all of the tasks associated with task  202  are performed in a different order than represented or in which some or all of the tasks are performed concurrently. Furthermore, it will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention that omit one or more of the tasks associated with task  202 . 
     At task  601 , the user seeks to authenticate himself or herself to enterprise  103  and provides his or her user-identifier to via client terminal  101 . 
     At task  602 , call-processing switch  104  transmits a first temporal series of type-A and type-B sounds and two questions about the series of sounds to the user. It will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention in which any number of questions is asked about a series of sounds. Task  602  is described in detail below and with respect to  FIG. 7 . 
     At task  603 , call-processing switch  104  receives the user&#39;s answers to the two questions and determines whether the user answered them correctly. When the user answers the questions correctly, then control moves to a second level of authentication; otherwise, the user&#39;s attempt at authentication fails and task  202  ends. 
     At task  604 , call-processing switch  104  transmits a second temporal series of type-A and type-B sounds and two questions about the series of sounds to the user. Task  604  is described in detail below and with respect to  FIG. 9 . 
     At task  605 , call-processing switch  104  receives the user&#39;s answers to the two questions and determines whether the user answered them correctly. When the user answers the questions correctly, then call-processing switch  104  deems the authentication successful; otherwise, the user&#39;s attempt at authentication fails and task  202  ends. 
     Although the illustrative embodiment comprises two levels of authentication, it will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention that comprise any number of levels of authentication. 
       FIG. 7  depicts a flowchart of the salient task associated with the operation of task  602  in accordance with the illustrative embodiment of the present invention. It will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention in which some or all of the tasks associated with task  602  are performed in a different order than represented or in which some or all of the tasks are performed concurrently. Furthermore, it will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention that omit one or more of the tasks associated with task  602 . 
     At task  701 , call-processing switch  104  randomly chooses X(t 1 ) type-A sounds from the set of X R +X S  type-A sounds, based on a contextual factor, where X(t 1 ) is a positive integer equal to 5. It will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention in which X(t 1 ) has any value. 
     In accordance with the illustrative embodiment, the contextual factor is the calendrical time, but it will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention in which the contextual factor is:
         i. the calendrical time (e.g., time of day, day of week, day or month, month of year, holiday, etc.), or   ii. an environmental factor (e.g., the weather, when it&#39;s daylight, etc.)   iii. a state in an Interactive Voice Response (IVR) menu, or   iv. a trait of the client terminal used by the user, or   v. the geographic location of client terminal  101 , or   vi. any combination of i, ii, iii, iv, and v.       

     At task  702 , call-processing switch  104  randomly chooses Y(t 1 ) type-B sounds from the set of Y R +Y S  type-B sounds, based on a contextual factor, where Y(t 1 ) is a positive integer equal to 5. It will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention in which Y(t 1 ) has any value. 
     In accordance with the illustrative embodiment, the contextual factor is the calendrical time, but it will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention in which the contextual factor is:
         i. the calendrical time (e.g., time of day, day of week, day or month, month of year, holiday, etc.), or   ii. an environmental factor (e.g., the weather, when it&#39;s daylight, etc.)   iii. a state in an Interactive Voice Response (IVR) menu, or   iv. a trait of the client terminal used by the user, or   v. the geographic location of client terminal  101 , or   vi. any combination of i, ii, iii, iv, and v.       

     At task  703 , call-processing switch  104  arranges the X(t 1 ) type-A sounds and the Y(t 1 ) type-B in random order into temporal series of X(t 1 )+Y(t 1 ) sounds. Table 1 depicts a illustrative temporal series of X(t 1 )+Y(t 1 )=10 sounds. 
     
       
         
               
             
               
               
               
             
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Illustrative Temporal Series of 
               
               
                 X(t 1 ) + Y(t 1 ) = 10 Sounds 
               
             
          
           
               
                   
                   
                 Sound 
               
               
                   
                 Order 
                 Type 
               
               
                   
                   
               
             
          
           
               
                   
                 1 
                 A 
               
               
                   
                 2 
                 B 
               
               
                   
                 3 
                 B 
               
               
                   
                 4 
                 A 
               
               
                   
                 5 
                 A 
               
               
                   
                 6 
                 B 
               
               
                   
                 7 
                 B 
               
               
                   
                 8 
                 A 
               
               
                   
                 9 
                 B 
               
               
                   
                 10 
                 A 
               
               
                   
                   
               
             
          
         
       
     
     At task  704 , call-processing switch  104  constructs Q 1  questions about the series of X(t 1 )+Y(t 1 ) sounds, where Q 1  is a positive integer. In accordance with the illustrative embodiment, Q 1 =3, but it will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention in which Q 1  has any value (e.g., 1, 2, 3, 4, 5, 6, 7, etc.). 
     In accordance with the illustrative embodiment, the Q 1  questions require the user to demonstrate the ability to distinguish a type-A sound from a type-B sound in the X(t 1 )+Y(t 1 ) sounds by;
         i. counting the number of type-A sounds in the series, or   ii. counting the number of type-B sounds in the series, or   iii. determining whether the series comprises one or more sequences of type-A and type-B sounds, or   iv. identifying one or more type-A sounds in the series, or   v. identifying one or more type-B sounds in the series, or   vi. any combination of i, ii, iii, iv, and v.       

     In accordance with the illustrative embodiment, the Q 1 =3 questions are:
         (1) Does the series of sounds contain 5 type-A sounds?” (Answer: Yes)   (2) Does the series of sounds contain three type-B sounds in succession? (Answer: No)   (3) Are there more than 2, but less than 5 type-B sounds? (Answer: No)
 
It will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention that use any questions that user demonstrates an ability to distinguish a type-A sound from a type-B sound in the X(t 1 )+Y(t 1 ) sounds.
       

     At task  705 , call-processing switch  104  transmits the series of X(t 1 )+Y(t 1 ) sounds and the Q 1  questions to the user via to client terminal  101 . 
     At task  706 , call-processing switch  104  receives the user&#39;s Q 1  answers and determines whether the answers are correct. 
       FIG. 8  depicts a flowchart of the salient task associated with the operation of task  604  in accordance with the illustrative embodiment of the present invention. It will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention in which some or all of the tasks associated with task  604  are performed in a different order than represented or in which some or all of the tasks are performed concurrently. Furthermore, it will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention that omit one or more of the tasks associated with task  604 . 
     At task  801 , call-processing switch  104  randomly chooses X(t 2 ) type-A sounds from the set of X R +X S  type-A sounds, based on a contextual factor, where X(t 2 ) is a positive integer equal to 4. It will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention in which X(t 2 ) has any value. 
     In accordance with the illustrative embodiment, the contextual factor is the calendrical time, but it will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention in which the contextual factor is:
         i. the calendrical time (e.g., time of day, day of week, day or month, month of year, holiday, etc.), or   ii. an environmental factor (e.g., the weather, when it&#39;s daylight, etc.)   iii. a state in an Interactive Voice Response (IVR) menu, or   iv. a trait of the client terminal used by the user, or   v. the geographic location of client terminal  101 , or   vi. any combination of i, ii, iii, iv, and v.       

     At task  802 , call-processing switch  104  randomly chooses Y(t 2 ) type-B sounds from the set of Y R +Y S  type-B sounds, based on a contextual factor, where Y(t 2 ) is a positive integer equal to 7. It will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention in which Y(t 2 ) has any value. 
     In accordance with the illustrative embodiment, the contextual factor is the calendrical time, but it will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention in which the contextual factor is:
         i. the calendrical time (e.g., time of day, day of week, day or month, month of year, holiday, etc.), or   ii. an environmental factor (e.g., the weather, when it&#39;s daylight, etc.)   iii. a state in an Interactive Voice Response (IVR) menu, or   iv. a trait of the client terminal used by the user, or   v. the geographic location of client terminal  101 , or   vi. any combination of i, ii, iii, iv, and v.       

     At task  803 , call-processing switch  104  arranges the X(t 2 ) type-A sounds and the Y(t 2 ) type-B in random order into temporal series of X(t 2 )+Y(t 2 ) sounds. Table 2 depicts a illustrative temporal series of X(t 2 )+Y(t 2 )=11 sounds. 
     
       
         
               
             
               
               
               
             
               
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 Illustrative Temporal Series of 
               
               
                 X(t 2 ) + Y(t 2 ) = 11 Sounds 
               
             
          
           
               
                   
                   
                 Sound 
               
               
                   
                 Order 
                 Type 
               
               
                   
                   
               
             
          
           
               
                   
                 1 
                 A 
               
               
                   
                 2 
                 B 
               
               
                   
                 3 
                 B 
               
               
                   
                 4 
                 A 
               
               
                   
                 5 
                 B 
               
               
                   
                 6 
                 B 
               
               
                   
                 7 
                 B 
               
               
                   
                 8 
                 A 
               
               
                   
                 9 
                 B 
               
               
                   
                 10 
                 A 
               
               
                   
                 11 
                 B 
               
               
                   
                   
               
             
          
         
       
     
     At task  804 , call-processing switch  104  constructs Q 2  questions about the series of X(t 2 )+Y(t 2 ) sounds, where Q 2  is a positive integer. In accordance with the illustrative embodiment, Q 2 =1, but it will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention in which Q 2  has any value (e.g., 1, 2, 3, 4, 5, 6, 7, etc.). 
     In accordance with the illustrative embodiment, the Q 2  questions require the user demonstrates an ability to distinguish a type-A sound from a type-B sound in the X(t 2 )+Y(t 2 ) sounds by;
         i. counting the number of type-A sounds in the series, or   ii. counting the number of type-B sounds in the series, or   iii. determining whether the series comprises one or more sequences of type-A and type-B sounds, or   iv. identifying one or more type-A sounds in the series, or   v. identifying one or more type-B sounds in the series, or   vi. any combination of i, ii, iii, iv, and v.       

     In accordance with the illustrative embodiment, the Q 2 =3 questions are:
         (1) Does the series of sounds contain 6 type-A sounds?” (Answer: No)   (2) Does the series of sounds contain three type-B sounds in succession? (Answer: Yes)
 
It will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention that use any questions that user demonstrates an ability to distinguish a type-A sound from a type-B sound in the X(t 2 )+Y(t 2 ) sounds.
       

     At task  805 , call-processing switch  104  transmits the series of X(t 2 )+Y(t 2 ) sounds and the Q 2  questions to the user via to client terminal  101 . 
     At task  806 , call-processing switch  104  receives the user&#39;s Q 2  answers and determines whether the answers are correct. 
     It is to be understood that the disclosure teaches just one example of the illustrative embodiment and that many variations of the invention can easily be devised by those skilled in the art after reading this disclosure and that the scope of the present invention is to be determined by the following claims.