And that means testing. Network equipment manufacturers are facing increasing pressure from both customers and management to deliver public network voice quality and to deliver it quickly. Today's public network is the ultimate benchmark for voice quality in communications networks. The Internet's audio transport capabilities are still far below the benchmark set by public-network standards. Traditional telephone networks are designed for a time-sensitive application like voice and to ensure with low delay and jitter.
Telephone networks are good at reliably providing constant but low bandwidth services.
Two major network components that can impair public network voice quality are the phone itself, which can influence clarity, loudness and echo through the quality of the loudspeaker and microphone, and digital transmission equipment for greater efficiency on the backbone can also hurt quality. IP network equipment also influences voice transmission and quality. For instance, although VoIP gateway components such as speech codecs, silence suppression and comfort noise generators are designed to increase the performance of VoIP, they can hurt clarity if not properly tuned. Using a model of the human auditory system allows engineers to code speech but not the inaudible sounds or the bandwidth it takes to transport that information. The coder must choose the parts of speech that, if reproduced, the human brain would not perceive.