Qol means voice, sound, or noise. It appears about 505 times. It describes the human voice, God's voice (thunder, revelation), animal sounds, and musical instruments.
The 'voice of the LORD' is powerful and majestic (Psalm 29). God's voice created the world, gave the law at Sinai, and speaks through prophets. Hearing and obeying God's voice is the essence of faith. 'Today, if you hear his voice, do not harden your hearts' (Psalm 95:7-8).