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The best acoustic treatment for vocals would be a combination of absorbent and diffusive materials. You should aim to reduce echo and background noise by treating bare walls and corners with acoustic panels, absorbers, or blankets. These will soak up the sound waves and prevent them from reflecting off the hard surfaces. For the ceiling, you could use a more thickly padded acoustic cloud or canopy to capture higher frequencies.

However, completely absorbing all sound waves can make a room sound too dead and interfere with the natural sound and resonance of the voice. This is where diffusers come in. They scatter and reflect sound waves, creating a sense of openness and space in the room, and allowing the singer to hear their own voice more accurately.

You could also consider a vocal booth, which is a small, enclosed space within a room that provides excellent acoustic treatment and privacy. These are more expensive, but provide a professional-