4 Pics 1 Word Level 444

Answer:
Volume
Hint
What is the answer to the 4 Pics 1 Word level with Speaker volume , Stereo adjustments and knobs , Control levels , and Speakers and sound system ?

Hint
What is the answer to the 4 Pics 1 Word level with Speaker volume , Stereo adjustments and knobs , Control levels , and Speakers and sound system ?