noun
sexual moan; cries of pleasure
Refers to vocal expressions of pleasure during sexual activity; often used in erotic contexts.
隣の部屋からよがり声が聞こえてきた。
I could hear sexual moans coming from the next room.
彼女は恥ずかしそうによがり声を漏らした。
She let out a cry of pleasure, looking embarrassed.
Ateji spelling using 良; rarely used in modern writing.
喘ぎ声 refers to panting or gasping sounds, which may or may not be sexual; よがり声 specifically denotes moans of sexual pleasure.
Compound of よがり (continuative form of よがる 'to moan in pleasure') + 声 (voice). The kanji 善 and 良 are ateji.