Use appropriate troubleshooting methods to determine and solve QoS issues in complex IP Telephony networks

Questions derived from the 642-425 – IP Telephony Troubleshooting Exam Cisco Self-Test Software Practice Test.

Objective: Use appropriate troubleshooting methods to determine and solve QoS issues in complex IP Telephony networks
SubObjective: Identify common problems associated with voice echo

Item Number: 642-425.5.3.12
Multiple Answer, Multiple Choice

Which of the following statements are TRUE regarding listener echo? (Choose two.)

1. The listener hears the talker’s voice twice.
   
2. Listener echo is due to inadequate loss of echo signal.
   
3. Listener echo is caused by an acoustic echo produced by the listener’s phone.
   
4. Listener echo is generally caused by a device known as hybrid.
   
5. Listener echo takes place when acoustic energy from a device such as a handset enters the microphone of the same device.

Answer:
A. The listener hears the talker’s voice twice.
B. Listener echo is due to inadequate loss of echo signal.

Tutorial:
In listener echo, the signal leaks through the near-end hybrid and comes back to the listener. The following statements are true regarding listener echo:

• The listener hears the talker’s voice twice.
  
• Listener echo is caused by inadequate loss of the echo signal.

The following are the causes of listener echo:

• Inadequate loss of the echo signal.
  
• Long echo tail.
  
• Inactive echo cancellers in the gateway nearby the near-end hybrid.

The option stating that listener echo is caused by acoustic echo produced by a listener’s phone is incorrect because this is a cause of talker echo.

The option stating that listener echo is generally caused by a device known as hybrid is incorrect because this is a cause of electrical echo, not listener echo.

The option stating that listener echo takes place when acoustic energy from a device such as a handset enters the microphone of the same device is incorrect because this is a cause of acoustic echo, not listener echo.

Reference:
http://cisco.com/en/US/tech/tk652/tk698/technologies_white_paper09186a00801545e4.shtml#echoed

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