There's much more to an internet connection than the average speed per second. If we're talking about downloading files (and loading websites), you're mostly c

There's much more to an internet connection than the average speed per second. If we're talking about downloading files (and loading websites), you're mostly correct. However, temporary slowdowns, disruptions in wireless connectivity and wireless-specific packet loss affect audio quality a lot, while not having much impact on your download speed. Even when streaming audio or video, you don't feel them as much, as your device usually keeps at least 10 seconds of buffer that it can rely on. When in a call, though, 10 seconds of buffer would mean 10 seconds of latency, which is simply unacceptable. You can have a 1.2 mb/s connection that sometimes goes down to 64kb/s for two to three seconds. Even if your download speed is still 1 mb/s, you can't really receive more than 64 kb/s when in a call, or you will get dropouts.