This isn’t really an eye test but it provides a visual explanation of the issue of voice packet sizing and the impact on voice QOS.  According to Cisco, Voice bandwidth = (Payload + L3 + L2 overhead) * 8 * PPS-Packets Per Second (50 default)

There are three examples:

1 – Voice Payload is 80 bytes in 10 ms-millisecond packet which means little delay proportionally higher overhead or 72% overhead premium 20-IP + 8-UDP + 16-RTP + 14-Ethernet = 58 bytes overhead.

2 – Voice Payload is 160 bytes using G.711 and 20 bytes using G.729 in 20 ms-millisecond packet which means potentially higher delay but lower overhead of 36% (160/58 overhead).

3 – Voice Payload is 240 bytes in 10 ms-millisecond packet which means higher performance and even lower overhead 24% but potentially higher impact of loss due to delays.

Like any testing, YMMV-your mileage may vary, however, this is designed to help you in your SIP/VoIP planning and design.

Click here for “eye test.”