What Is Reverb in Audio and Music?

When a sound is made in a room, you first hear the sound that travels straight to your ears. A moment later come reflections from the nearest surfaces, then reflections of those reflections, more and more of them, each a little quieter as the walls, furniture and air absorb energy. Wikipedia describes reverberation as the persistence of sound after it is produced: it builds up and then decays as surfaces absorb it. In music production, "reverb" usually means the effect that adds this persistence on purpose. A dry vocal recorded in a treated booth can be placed in a virtual room, hall or church with a reverb plugin, so it sounds as if it was performed there.

No, although both come from reflections. The difference is timing. An echo is a reflection that arrives late enough to be heard as a separate repeat; Wikipedia puts the threshold at roughly 50 to 100 milliseconds after the original sound. Reverb is made of reflections that arrive in quick succession, less than about 50 ms apart, so the ear hears them as one continuous tail rather than distinct repeats. That is why shouting across a canyon gives you an echo (one clear "hello" coming back) while singing in a stairwell gives you reverb (a smooth wash). Delay effects in audio software imitate echo; reverb effects imitate the wash.

Acousticians measure reverb with reverberation time, written RT60 or T60: the time it takes for the sound level to drop by 60 dB after the source stops. Big, hard rooms have long RT60 times; small rooms full of soft furnishings have short ones. Reverberation time also changes with frequency, so it is often measured in octave bands. In the late 1890s, Wallace Sabine worked out an equation that links reverberation time to a room's volume and how much sound its surfaces absorb. It is the basis of room acoustics: more volume means a longer tail, more absorption a shorter one. Reverb plugins borrow the idea: their decay or RT60 control sets how long the tail lasts.

Most reverb effects break the sound into three parts. Pre-delay is the short gap between the dry sound and the first reflections. Large spaces have longer pre-delays because the walls are further away. In a mix, a pre-delay of a few tens of milliseconds lets the start of each word or note come through clearly before the reverb arrives. Early reflections are the first few bounces off nearby surfaces. They tell the ear how big the space is and where the sound sits in it. The tail, or late reverberation, is the dense wash that follows and fades out over the decay time.

A little reverb makes a sound feel natural and alive, as if it was played in a real room rather than inside your headphones. A short room reverb adds body without an obvious tail. A plate gives vocals and snares a smooth, bright shine. A long hall makes strings and pads sound wide and distant, with a tail you can hear fading after each phrase. Too much reverb pushes a sound back in the mix and blurs words, which is why spoken audio such as podcasts usually has little or none. One way to hear reverb clearly is to compare the end of a phrase: a dry recording stops instantly, while a reverberant one keeps ringing for a moment after the singer or instrument stops.

Every audio editor and DAW has a reverb effect. In the free editor Audacity, for example: 1. Select the part of the track you want to treat. Add a few seconds of silence at the end first, or the reverb tail will be cut off abruptly, as Audacity's manual warns. 2. Open the Reverb effect from the Effect menu (it sits under Delay and Reverb in recent versions). 3. Set Room Size: Audacity describes 0% as a closet and 100% as a large auditorium or cathedral. 4. Set Pre-delay (up to 200 ms in Audacity) and Reverberance, which controls the length of the tail. 5. Keep Dry Gain below 0 dB, because reverb adds level and can push the result into clipping. 6. Preview, adjust, apply, then export. In a full DAW, put the reverb on a separate bus instead, as described below, so you can change it later without touching the original recording.

These controls appear on almost every reverb plugin: 1. Decay (or RT60, or time): how long the tail lasts, from a few hundred milliseconds for a small room to several seconds for a large hall. 2. Pre-delay: the gap before reflections start. 3. Size: how large the virtual space is; on many plugins it also changes pre-delay and decay together. 4. Diffusion: how dense the reflections are. Low diffusion can sound grainy or fluttery; high diffusion sounds smooth. 5. Damping or high cut: how quickly high frequencies fade in the tail. More damping sounds darker and more natural, because real rooms absorb treble faster. 6. Low cut: removes low frequencies from the reverb so the bass and kick stay clean. 7. Wet/dry or mix: the balance between the original sound and the reverb.

Room, hall and chamber reverbs imitate spaces of different sizes, from a small room with a short, tight sound to a concert hall with a long, smooth tail. Early studios used real echo chambers: by the 1930s, engineers were playing recordings through a loudspeaker into a reverberant room and recording the result. Spring reverb sends the signal through metal springs. Laurens Hammond patented a spring reverb system in 1939, and it became a staple of guitar amplifiers, surf music and dub reggae. Plate reverb vibrates a large metal sheet. Elektromesstechnik introduced the famous EMT 140 in the late 1950s, and its smooth, bright sound is still copied on vocals and snare drums. Digital reverb simulates reflections with delay lines and filters. EMT introduced the EMT 250 in 1976, and digital units spread through the 1980s, along with effects like gated reverb, the abrupt drum reverb of 1980s pop. Convolution reverb uses a recording of a real space, called an impulse response, to recreate how that exact room or hall reverberates. Sony announced the first real-time convolution reverb processor, the DRE S777, in 1999.

Use a send, not an insert, for most reverb. Put the reverb on an auxiliary or bus channel set to 100% wet and send each instrument to it in the amount you want. Several sounds then share one space, which makes the mix feel coherent, and you can process the reverb on its own. Cut the lows and highs of the reverb. A common starting point is to filter out content below roughly 200 Hz and above roughly 8 kHz in the reverb return, so the tail does not cloud the bass or add hiss. Many engineers leave the kick drum out of the reverb entirely. Match the decay to the tempo and style. Fast, busy songs need short decays, or the tails overlap into mud. Slow ballads and ambient music can take long halls. Use pre-delay to keep vocals upfront. A longer pre-delay separates the dry voice from its reverb, so it sounds big without being pushed back. Check in mono. Wide stereo reverbs can partly cancel when a mix is summed to mono; our guide to audio phase explains why.

When people talk about reverb on a mic, they usually mean one of two things. The first is room sound picked up by the microphone itself: a mic in a bare room records the reflections along with your voice, which can make speech sound distant and hollow. Recording closer to the mic, using a more directional microphone, or adding soft furnishings and acoustic panels reduces it. The second is a reverb effect applied to a live microphone, such as on a karaoke machine, a streaming setup or a live sound desk, to make a voice sound fuller. That reverb is added after the mic and can be turned down or off.

Reverb recorded into a track is hard to remove, because it is mixed into the same audio as the voice or instrument. Dedicated de-reverb tools, such as the de-reverb modules in audio repair suites like iZotope RX, can reduce it, and some AI-based voice enhancers do the same for speech. Results vary: a little reduction often sounds natural, while heavy processing can make audio sound watery. The best fix is to record in a drier space in the first place. Gating or noise reduction can also tidy the gaps between phrases, and our remove silence tool shortens long pauses, which makes trailing room sound less noticeable in spoken recordings.

Reverse reverb is a classic effect in which a swelling wash leads into a word or note instead of trailing after it. The usual method: reverse the clip, add reverb, render it, then reverse it again so the reverb tail now builds up before the sound. Our reverse audio tool handles the reversing steps in the browser, and any audio editor can add the reverb in between. Other creative uses include long "shimmer" reverbs that add an octave-up glow, which Wikipedia credits Brian Eno with pioneering, and very short room reverbs that make dry, close-miked instruments sound as if they were played in a real space.

Reverb tails are quiet and detailed, so they are among the first things to suffer from heavy lossy compression. At low MP3 or AAC bitrates, long tails can sound grainy or smeared. Keep mixes with long reverbs at 256–320 kbps for MP3, or deliver lossless WAV or FLAC when a platform accepts it. Our WAV to MP3 converter defaults to 320 kbps, and WAV to FLAC keeps every sample.