The noise youre hearing is called ground loop, because the faster you go, the faster youre alternator goes, and the more interference youre hearing. Try getting one of these:
http://cgi.ebay.com/ebaymotors/alternator-kit-noise-Capacitor-Honda-Isuzu-Toyota_W0QQcmdZViewItemQQ_trksidZp1638Q2em118Q2el1247QQcategoryZ33576QQihZ011QQitemZ320305321171QQrdZ1QQsspagenameZWD1V
http://cgi.ebay.com/ebaymotors/alternator-kit-noise-Capacitor-Honda-Isuzu-Toyota_W0QQcmdZViewItemQQ_trksidZp1638Q2em118Q2el1247QQcategoryZ33576QQihZ011QQitemZ320305321171QQrdZ1QQsspagenameZWD1V
Just find the ones that go with your car. You can get them on ebay or best buy. These should kill all the noise. Good Luck!