Is it normal that my voice changes when i'm horny?

I never noticed it before I started having a sexual relationship with one of my friends, but I've realized that my voice gets higher when I'm aroused. Like, very noticeably higher. She and I were starting to get physical while her sister was just separated from us by a curtain, and I was doing my very best to stay silent, but my voice apparently changed enough that her sister thought we were role playing two of our characters we use in writing instead of actually having sex.