BZ-5828

VoIP phone testing interface

Software for simulating a VoIP network phone and handling analogue input and output via a high-quality sound card, for speech performance evaluation

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This interface software establishes an audio connection to a VoIP (voice over Internet protocol) phone. By simulating the phone’s VoIP network, it allows you to test the phone’s acoustical performance during a call using PULSE test software. The interface works by establishing a call between itself and the phone. Then it reassembles the packetized data in the network into a continuous signal stream. This is presented to the test system in a usable and calibrated analogue format, using a high-quality sound card.

USE SCENARIOS

  • Verification of acoustic design of IP phone systems that use a LAN (local area network) or the Internet during R&D in the research lab
  • Evaluation and refinement of speech processing for VoIP phones, such as echo cancellers, voice activity detection and multiband compression
  • Objective and subjective evaluation of phone components such as noise suppressors, microphone input filters and receiver output filters
  • Calibrating the audio interface used with the VoIP terminal
  • Quality assurance and sample testing of VoIP terminals from the production line

IN USE

The interface – or network simulator – allows you to set up relevant VoIP terminal parameters, before a dedicated calibration procedure allows accurate compensation for the gain (or attenuation) presented by the sound card. Calibration uses a built-in generator to output a sinusoidal signal. During testing, the two level meters provide analogue displays of the input and output, with small digital readouts in dBm. 

We recommend using Brüel & Kjær’s USB Audio Interface ZE-0948 as the sound card.

CAPABILITIES

  • Implements SIP (session initiation protocol) and RTP (real-time transport protocol) for transfer of audio 
  • Stable delay that is known, and free from jitter or dropouts
  • Codec encodes and decodes the audio
  • Acts as a telephone exchange for VoIP terminals
  • Monitors digital input and digital output level