My main problem with the later Chrysalis Audiobooks

The sound effect Jeff Hays does for the Gravity Bomb.

For context I'm half way through book 7 and since Anthony has been using the spell it's been sounding worse and weaker like a gent breaze now.

The Gravity Bomb in book 1 sounded impressive and scary but each book beyond it grew in power yet sounded weaker and less impressive.

No I'm unsure if it's too much of a strain on the voice and that's why it changed but I just miss the more guttural sounds for the first couple times it was used.