Loud Voice, Big Voice
Noun and の adjective
おおごえ
そんな大声を出さないでください。
Please don’t use such a loud voice.
おもわず大声を出してわらってしまった。
I couldn't help laughing out loud.
クリスティーナは大声の持ち主で、残念なことにそれを使うのを全くはばからない。
Christina has a loud voice, and unfortunately, she’s not afraid to use it.
A large voice is probably pretty large. Maybe even annoying, too. That's why this is a large voice or a loud voice.
The reading for 声 is ごえ (rendaku'd version of the reading you know: こえ). The reading for 大 is the kun'yomi reading, like with the word 大きい (おおきい). Just imagine a loud voice saying "おお！."