Reverb and delay

What is reverb and what is the difference between reverb and delay?

Well, to over simplify it (almost to the extent of being close to lie), you could see it as reverb being room reflections and delay being echoes.

Before we dive into the components. Let’s imagine a large hall. There is nothing in it, just you. Clap your hands, a single hard clap. The most likely thing that happens is that the sound from your clap bounces off the walls and comes back to you. Echo. The closer you stand to a wall, the faster the sound bounces back to you. The further away, the longer it takes. And the lounder your clap is, the sound is able to travel longer through the air. Because just like when you move around, the sound looses energy when moving through the air. The more energy (louder) the longer it travels. Which can easily be tested. Same hall, your clap echoes back to you, but if you whisper the word “Hello”, you will most likely not receive any echo back. But yell all you can, and the hall will reward you with a reply. The mechanics behind an echo is that the sound moves in a direction, hits a hard surface and bounces. Depending on the direction of the sound compared to the surface, it might bounce back to where it originated from, or in a completely different direction, kind of like a ball on a snooker-table. One surface gives one echo, several surfaces may generate several echoes. To get this effect, delay can be used, and depending on the settings of the delay, you can get the sound to bounce one or more times, with various timesettings for the echo to return. As the name suggests, the delay is moving the sound backwards in the timeline, delaying the sound. If you take a signal direct to the delay, and then into your mix, you just put the sound backwards in time, delaying it, but if you play the source in your mix, and simultaneously send it to a delay, it will be played in the mix first, and then return via the delay according to the settings on the delay.

Now, let’s make the same fictional experiment, but with reverb. Reverb is in a way just like delay, only that it is not only one reflection, it is multiple reflections from multiple directions. Imagine yourself in a church instead of a large hall. Plenty of hard flat surfaces close to you, all around you, even in the high roof. Now imaginary clap again. This time the sound travels from your hands in all directions and are getting bounced back towards you from many directions at the same time, both direct bounces and bounces of bounces where the sound has bounced of one surface, to the next, and perhaps a few more, before getting back to you. Now, you do not hear each individual bounce returning to you, but a collective bounce reaching your ears. The energy in the sound is also important here. A whisper might bounce back to you, but will not “stay in the air” for as long as the clap does. You will get a (non-mathematical) formula like this:

  • Low sound close by – strong direct sound, some or no reflections
  • Low sound further away – low direct sound, almost no or no reflections
  • Strong sound close by – strong direct sound, strong reflections
  • Strong sound further away – low direct sound, strong reflections

Please note that above statements are also oversimplifying hugely. Point being that a sound is a mix between its direct trajectory and the reflections. The closer you are to the source, the stronger the direct sound is. The stronger the sound is, the more reflections will hit you, and the lower the sound is, fewer reflections will hit you.

Now, why do I spend time writing about this?

Well, in my opinion, knowing this will help you place your sound in the mix. Moving it back and forth as you wish, create a large room or a small room, taking sounds to the same room or separating them into different rooms. Forging sounds together or dividing them. Like panning, but with several more dimensions.

All rooms have a ”reverb profile” with sound reflections. Unless it is designed specifically to not have any reflection at all. And most rooms are filled with stuff that effects the “reverb profile” of the room. The more stuff, the less reflections. Then there is designing a “reverb profile” (like cinemas, offices, shopping malls etc) where you actively put up different kinds of dampeners in well chosen places to reduce unwanted reflections.

This is something you should be observant about when you record something with a microphone. The closer the mic is to the sound source, the less of the room acoustics you get in your recorded sound signal, the further away, the more of the room acoustics you get. Here is nothing right or wrong, just be aware so you can make a conscious decision on how you want to use the signal you record. In some studios, the room acoustics are so good that you really want to have it with your recorded sound signal, and sometimes, it is highly unwanted to have extra room acoustics along with your sound signal. It all depends on how you want to use it and what you are after.

As always, stay curious and play around!