Live person detection in an automated calling system

Abstract

A method of operating a telephony system for determining whether a telephone call made to a call destination terminal is a live call which is answered by a live person and not by an answering machine, the system performing steps comprising detecting that the telephone call has been answered and that the call is in progress transmitting one or more voice messages in a transmitted signal to the call destination terminal analyzing a received signal from the call destination terminal to detect voice signals, and determining whether or not the telephone call is a live call by applying test criteria to relative timing of events in the received signal and transmitted signal, the test criteria being based on an expected pattern of speech and silence representative of normal conversation.

What is claimed is: 
     
         1 . A method of operating a telephony system for determining whether a telephone call made to a call destination terminal is a live call which is answered by a live person and not by an answering machine, the method comprising:
 detecting that the telephone call has been answered and that the call is in progress;   transmitting one or more voice messages in a transmitted signal to the call destination terminal;   analyzing a received signal from the call destination terminal to detect voice signals; and   determining whether or not the telephone call is a live call by applying test criteria to relative timing of events in the received signal and transmitted signal, the test criteria being based on an expected pattern of speech and silence representative of normal conversation.   
     
     
         2 . A method as claimed in  claim 1  wherein the call is determined to be a live call according to the test criteria if:
 one of the voice messages is an uninterrupted voice message during which no voice signal in the received signal is detected; and 
 a voice signal is then detected in the received signal within a predetermined listening period, P 2 , after the uninterrupted voice message has ended. 
 
     
     
         3 . A method as claimed in  claim 2  wherein, if no voice signal is detected within an initial listening period P 1  at an initial part of the call, a prompt voice message is transmitted, and if voice signal is detected in the received signal after transmission of the prompt voice message has ended, one or more further voice messages are then transmitted and the criteria applied. 
     
     
         4 . A method as claimed in  claim 2  wherein, if one of the voice messages is interrupted by the occurrence of voice signal detected in the received signal, a clarification voice message is transmitted to request clarification, and if a subsequent voice signal is detected in the received signal, another of the voice messages is then transmitted and the criteria applied. 
     
     
         5 . A method as claimed in  claim 1  wherein the voice signals are detected by applying a threshold to a signal amplitude in the received signal. 
     
     
         6 . A method as claimed in  claim 1  wherein a call is determined to not be a live call if a tone of single frequency is detected in the received signal having an amplitude greater than a predetermined tone amplitude threshold and a duration greater than a predetermined tone length threshold. 
     
     
         7 . A method as claimed in  claim 2  further comprising controlling operation of a predictive dialer dependent upon the determination of whether the call is a live call. 
     
     
         8 . A method as claimed in  claim 7  wherein the predictive dialer assigns the call to an agent selected from a plurality of agents manning the telephony system and wherein the transmitted voice messages are thereafter generated from recordings of the voice of the assigned agent. 
     
     
         9 . A telephony system for determining whether a telephone call made to a call destination terminal over a communication network is a live call which is answered by a live person and not by an answering machine, the system comprising:
 an interface unit coupled to the communication network; and   a server configured to:   detect that the telephone call has been answered and that the call is in progress,   transmit one or more voice messages in a transmitted signal to the call destination terminal,   analyze a received signal from the call destination terminal to detect voice signals, and   determine whether or not the telephone call is a live call by applying test criteria to relative timing of events in the received signal and transmitted signal, the test criteria being based on an expected pattern of speech and silence representative of normal conversation.   
     
     
         10 . A system as claimed in  claim 9  wherein the call is determined to be a live call according to the test criteria if:
 one of the voice messages is an uninterrupted voice message during which no voice signal in the received signal is detected; and 
 a voice signal is then detected in the received signal within a predetermined listening period, P 2 , after the uninterrupted voice message has ended. 
 
     
     
         11 . A system as claimed in  claim 10  wherein, if no voice signal is detected within an initial listening period P 1  at an initial part of the call, a prompt voice message is transmitted, and if voice signal in the received signal is detected after transmission of the prompt voice message has ended, one or more further voice messages are then transmitted and the criteria applied. 
     
     
         12 . A system as claimed in  claim 11  wherein, if one of the voice messages is interrupted by the occurrence of voice signal detected in the received signal, a clarification voice message is transmitted to request clarification, and if a subsequent voice signal is detected in the received signal, another of the voice messages is then transmitted and the criteria applied. 
     
     
         13 . A system as claimed in  claim 9  wherein the voice signals are detected by applying a threshold to signal amplitude in the received signal. 
     
     
         14 . A system as claimed in  claim 9  wherein a call is determined to not be a live call if a tone of a single frequency is detected in the received signal having an amplitude greater than a predetermined tone amplitude threshold and a duration greater than a predetermined tone length threshold. 
     
     
         15 . A system as claimed in  claim 9  further configured to control operation of a predictive dialer dependent upon the determination of whether the call is a live call. 
     
     
         16 . A system as claimed in  claim 15  wherein the predictive dialer is adapted to assign the call to an agent selected from a plurality of agents manning the telephony system and wherein the transmitted voice messages are thereafter generated from recordings of the voice of the assigned agent. 
     
     
         17 . A system as claimed in  claim 9 , wherein the server comprises a computer and the interface unit comprises a telephony card having a digital signal processor connected to an expansion port of the computer. 
     
     
         18 . A system as claimed in  claim 17  wherein the system is configured to determine whether the call is a live call by execution of program code in the computer interacting with execution of code in the telephone card via an application programming interface. 
     
     
         19 . As system as claimed in  claim 17  wherein the system is configured to determine whether the call is a live call by execution of program code executed in the telephony card. 
     
     
         20 . A computer program comprising instructions which when executed in a computer system causes the system to carry out all of the steps of a method as claimed in  claim 1 . 
     
     
         21 . A storage medium storing a computer program as claimed in  claim 20 . 
     
     
         22 . A signal carrying a computer program as claimed in  claim 20 .