Typically, the only analog connection between your modem and Texas. Net is the one between your home and the phone's switching office. The X2, K56Flex, and v.90 protocols depend on high quality phone lines between your modem and the local phone company's digital switch. Any noise on this portion of the lines will result in deteriorated performance. This 'noise' is not necessarily audible sound.
All phone lines carry some degree of 'noise'.
Unfortunately, local telephone companies offer no guarantee of line quality, where data communications are involved. The 'official' policy, depending on who you talk to at the phone company, is that they only support something between 2.4K and 9.6K connections. Other customers have requested this and been told it doesn't exist. If you suspect that line noise might be giving you problems with your connection, Texas. Net recommends that you do try contacting your local telephone company.