Most of the author's points about sound come down to hand waving and weasel wording. He says hearing loss is "coming up fast on the list" of public health problems (a meaningless assertion), and then he never presents evidence that leaf blowers are a significant cause of this. He started with the conclusion (leaf blowers make an annoying sound), and then did his best to argue the sound that annoys him should be illegal.
On the other hand, he's right that 2 stroke engines are dirty as hell, and his statistics to that ends are a bit more convincing.