Position two clothes-rails opposite one another, but not parallel, to create an improvized acoustically-dead vocal-booth. Drape sheets over the top and sides. Position large cushions against the inside "walls." By creating a small space with soft walls, you minimize sound-reflections. Sound reflects more readily against parallel surfaces, especially if those surface are already reflective, like tiles or glass.
Flat surfaces reflect sound. The sound wave hits your wall and bounces off in another direction. For every "bounce," the quality of your sound diminishes. You can trap the sound and stop it from reflecting by hanging egg cartons on your walls. The peaks and dips in the egg carton material stop the sound from reflecting. If you visit any professional recording studio, their live-spaces all have walls with irregular surfaces. You don't need to cover every inch of your wall with egg cartons; just cover the space around "sound height" for the relevant application. For example, if recording a singer, "sound height" is the height of his mouth. If recording a guitarist, it is the height of her amplifier.
At the very least, draw the curtains when recording. Glass not only reflects sound, but when volumes are really high, glass even vibrates and causes resonance of its own. Drape an old sheet over the entire window to stop the sound from reaching the reflective surface.
A noise gate is an audio effect. You can either use it live or in post production. It functions by muting all signals below a certain volume threshold. Only when the volume threshold is breached does the noise gate unmute the signal path, allowing sound to reach the mixing desk or tape recorder. Gating is a convenient technique for muting out extraneous noise. For example, to isolate a singer's voice from her breathing, set the volume threshold to a level between the loudest breath and the quietest singing.