Add Reverb & Echo to Audio Online

Reverb, almost certainly. It is the sound of a space — hundreds of reflections arriving too close together to be heard separately — so it puts the voice in a room instead of against a wall. Echo is a different thing: distinct repeats you can count, which read as an effect rather than as a place. Reach for echo when you want the effect to be noticed, and for reverb when you want the recording to stop sounding like a bedroom.

Yes. Drag the handles on the waveform to select a region, then switch to "Selection Only" mode. The effect will only be applied within that region, with optional fade-in/out at the boundaries.

Room Size controls the duration of the reverb tail. Decay sets how quickly reflections fade. Brightness filters high frequencies. Pre-delay adds a gap before the reverb starts. Wet/Dry controls the effect balance. Stereo Width separates the left and right reverb channels.

Two controls do most of the work. Mix decides how much of the wet signal you hear against the dry one — a voice usually wants far less than feels right while you are dragging the slider. Pre-delay keeps the first few milliseconds dry, so the start of each word arrives before the space does, which is what lets a heavy hall sit behind speech without turning it to mush. Decay is the third: a long tail on a fast delivery smears one word into the next.