You wouldn't have heard of it.你应该没听说过

hear of:听说

I rejoice to hear of your promotion.

听说你高升我非常高兴。

相关短语：not hear of不答应(拒绝考虑)

I will not hear of you making a trip to that place.

我不允许你去那个地方旅行。

She said you wanted to turn something in?她说你有东西要上交

turn in:上缴

Only a few guns have been turned in so far.

时至今日只上缴了少数几支枪。

We'll return it to you as soon as we can.我们会尽快把它还给你的

as soon as:一 ... 就

I'll write you as soon as I get there.

我一到那儿，就给你写信。

Let us start as soon as he comes.

等他一来我们就动身。

词义辨析：once，as soon as两者均为从属连词，引导时间状语从句，都表示主句的动作紧跟在从句的动作之后发生。

once除表时间外，还表示条件，一般译作“一旦......就......”。

as soon as强调的只是时间，译作“刚......就......”或“一......就......”。