# echo var (sound)

Source: https://ref.dm-lang.org/sound/var/echo

### Default value
> null

If set to an 18-element list, this value customizes reverbration settings for this sound only. A null or non-numeric value for any setting will select its default. Please see the EAX2 documentation at http://developer.creative.com/ for indepth information about these settings.

Here's a rundown of some of the terms: **Direct** refers to the amount of effect when the sound is on a direct path to the listener. **Obstruction** is when an object is blocking the direct path but there are other ways for the sound to reach the listener. **Occlusion** means the sound is on the other side of a wall, and mostly blocked. **Exclusion** means the sound is on the other side of a wall, but a doorway or window is allowing it to pass through to the listener. You can use a little of each of these effects to increase realism.

**1 Direct (-10,000 to 1,000) default = 0**

> direct path level (at low and mid frequencies)

**2 DirectHF (-10,000 to 0) default = 0**

> relative direct path level at high frequencies

**3 Room (-10,000 to 1,000) default = 0**

> room effect level (at low and mid frequencies)

**4 Room HF (-10,000 to 0) default = 0**

> relative room effect level at high frequencies

**5 Obstruction (-10,000 to 0) default = 0**

> main obstruction control (attenuation at high frequencies)

**6 ObstructionLFRatio (0.0 to 1.0) default = 0.0**

> obstruction low-frequency level re. main control

**7 Occlusion (-10,000 to 0) default = 0**

> main occlusion control (attenuation at high frequencies)

**8 OcclusionLFRatio (0.0 to 1.0) default = 0.25**

> occlusion low-frequency level re. main control

**9 OcclusionRoomRatio (0.0 to 10.0) default = 1.5**

> relative occlusion control for room effect

**10 OcclusionDirectRatio (0.0 to 10.0) default = 1.0**

> relative occlusion control for direct path

**11 Exclusion (-10,000 to 0) default = 0**

> main exlusion control (attenuation at high frequencies)

**12 ExclusionLFRatio (0.0 to 1.0) default = 1.0**

> exclusion low-frequency level re. main control

**13 OutsideVolumeHF (-10,000 to 0) default = 0**

> outside sound cone level at high frequencies

**14 DopplerFactor (0.0 to 10.0) default = 0.0**

> like DS3D flDopplerFactor but per source

**15 RolloffFactor (0.0 to 10.0) default = 0.0**

> like DS3D flRolloffFactor but per source

**16 RoomRolloffFactor (0.0 to 10.0) default = 0.0**

> like DS3D flRolloffFactor but for room effect

**17 AirAbsorptionFactor (0.0 to 10.0) default = 1.0**

> multiplies AirAbsorptionHF member of environment reverb properties.

**18 Flags default = 7**

> Bit flags that modify the behavior of properties
>
> * 1 - Automatic setting of 'Direct' due to distance from listener
> * 2 - Automatic setting of 'Room' due to distance from listener
> * 4 - Automatic setting of 'RoomHF' due to distance from listener

### See also
- [vars (sound)](https://ref.dm-lang.org/sound/var/index.md)
- [x, y, z vars (sound)](https://ref.dm-lang.org/sound/var/xyz.md)
- [atom var (sound)](https://ref.dm-lang.org/sound/var/atom.md)
- [environment var (sound)](https://ref.dm-lang.org/sound/var/environment.md)