I don't doubt that tire noise dominates on average, but engine noise from big trucks is far louder at peak. At least for the roads near my house, typical traffic is a steady ignorable hum, but when big trucks go by uphill or start moving from a stoplight, they make so much noise I can barely hear myself think.
Cars are similar, usually much smaller in magnitude. Every so often you get some silly person who thinks a bad muffler makes his car fast and compete with the big trucks.
Electrification may not bring down average noise levels much, but it'll still make it a lot more pleasant to be near a busy road.