I was curious and went to look at the raw to see if I could find anything about sound. I found this: "バレたらしゃれにならない教えといたげるわ神殺鎗の延びる速さ・・・届いた?今の五百倍や"
Literal translation without contexts: "If I were discovered, it wouldn’t be funny at all. I’ll teach you, the speed of Kamishini no Yari’s extension... Did it reach you? Now it’s 500 times."
There is no explicit "faster" and no "you hear that? so "500 times" of what? well, with the context we can find out. Gin in the first frame says: "I'll teach you, the speed of Kamishini no Yari's extension..." in other words, he's talking about speed, so it would be "500 times faster". However, "500 times faster" than what? Well, Gin doesn't say it directly, but he claps his hands and asks Ichigo if something reached him, he didn't threw anything at Ichigo, and also did not extend the bankai again, the only thing that could have gone from him to Ichigo was the sound of his handclap. So, discovering the entire context, the most accurate translation would be: "If I were discovered, it wouldn’t be funny at all. I’ll teach you, the speed of Kamishini no Yari’s extension... You hear that?it’s 500 times faster than that."
I think the only way remove this is to argue that there are more feats about this speed than anti-feats.