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## Disclaimer
This recommendations about sounds will be thought **for humans!** I suppose that this are the expected listeners of this application, but it is important to claim that this recommendations are **not** for **other animals**.
The standard and recommendations used here will be based on [**EBU R128**](https://tech.ebu.ch/publications/r128/), the standard of European Broadcast Union about audio normalisation and maximum sound levels.
The main unit used will be the LUFS, `Loudness Unit Full Scale`, which is a relative unit to humans hearing. More info [here](https://en.wikipedia.org/wiki/EBU_R_128#Specification).
## Characteristics
Here I'll explain each characteristic that should be taken into account to decide whether a soundclip is ideal for the app.
### LUFS Integrated
The **LUFS Integrated** is an average measure which a sound has through all its length. A soundclip does **not** have the same level at each moment, it changes. With this unit we can measure an average of the clip.
The closer to 0 LUFS, the louder. It is ***inverted***.
### Dynamic Range
A sound has a changing level through its duration. With the **dynamic range** we measure the range between the loudest and
the lowest level registered.
The **higher** the **range** (the difference between the loudest and lowest level), the **more comfortable** the sound will be. Sounds with **poor range exhaust** the listener and, therefore, **annoys**.
This characteristic is almost the most important in ambient sounds, as what we want is to be comfortable, not annoying.
### True Peak (dBTP)
This is the **maximum** level that the sound wave takes through the duration of itself. This is **imperceptible** because this maximum level lasts only **milliseconds**. But having too loud peaks produces annoying clipping (snaps, cracks, pops) and distorted sounds on speakers, so it is better to avoid having them.
### Max LUFS (momentary)
This, unlike True Peak, is a **more perceptible** way to meter **maximum** loudness, as it meters it in a timeframe of 400ms.
### How to measure
To measure the sound levels, all faders (sound-level bars) **must** be to the 100%. The most times this will be the loudest, unless it is indicated with percentage or with a mark of 0 dB.
`0 dB = 100%`
After setting app the faders, the sound source must be connected to an analyzer:
* I use [x42 Meter Collection](http://x42-plugins.com/x42/x42-meters#EBUr128), open source, allongside [Carla](https://kx.studio/Applications:Carla).
* Another good method to measure is using [Ardour](https://ardour.org) and its _Loudness Analysis_.
### How to fit
* **The Range** can **not** be changed upwards. If your clip does not fit in the Technical Criterion, you can send the clip to [porrumentzio@riseup.net](mailto:porrumentzio@riseup.net) explaining the situation, **only** if the range is bigger than 3,5.
* **LUFS Int.** and **Max. LUFS** can be modified changing the clip's **gain** (volume). The change on dBs is approximated to LUFS, so fit and analyze until you have it 😄
* **True Peak** tends to be some very-short-in-time transients, peaks. For fitting those peaks to about at least -6 dBs, use a **limiter** with the _threshold_ a bit more than -6 and short _release times_ (<5 ms).
## Recommendations
* The **longest** the **recording**, possibly the more **comfortable**. Sounds in nature vary a lot, they tend to have large dynamic ranges.
* **Lower** sound levels, specially for those monotonous soundclips.
* Avoid short and [sausage](https://cnet3.cbsistatic.com/img/_EPvPKH6Fg7edW0NeuHUuJ6X0lQ=/2011/07/06/2f50c706-fdc2-11e2-8c7c-d4ae52e62bcc/Arcade_Fire_Ready_to_Start.jpg) clips.
### Criterion that every clip should pass
As the maximum comfortable perceived level is directly correlated to the range, there could be variations, but here is a table:
| Criterion | LUFS (Int.) | Range | True Peak (dBTP) | Max LUFS
| :-: | :-: | :-: | :-: | :-:
| Minimum | -35 | 5-7 | -30 | -30
| Ideal | -27 | 7-🔝 | -7,5 | -25
| Maximum | -23 | 🔝 | -6 | -18
_________
## Made changes
**New sounds:**
| Sound | App version | Author | License | LUFS (Int.) | Range | True Peak (dBTP) | Modifications
| :-: | :-: | :-: | :-: | :-: | :-: | :-: | :-:
| [Waves](https://freesound.org/people/Luftrum/sounds/48412/) | `0.4.0` | Luftrum | CC BY | -23 | 9,8 | -0,4 | -2,5 dB & Lim -6,5 dB : 2,5 ms
| [Birds](https://freesound.org/people/kvgarlic/sounds/156826/) | `0.4.0` | kvgarlic | CC0 | -39,8 | 16,4 | -24,4 | +12 dB
| [Train](https://trains.ambient-mixer.com/rainy-train) | `0.4.0` | vahid | CC Sampling + | -27 | 8,7 | -8,1 | None
| [Stream](https://freesound.org/people/gluckose/sounds/333987/) | `0.4.0` | gluckose | CC0 | -39,2 | 1 | -15,7 | None
| [Boat](https://freesound.org/people/Falcet/sounds/439365/) | `0.4.0` | Falcet | CC0 | -50,5 | 6,6 | -26 | +20 dB
| [City](ttps://freesound.org/people/gezortenplotz/sounds/44796/) | `0.4.0` | gezortenplotz | CC BY | -38,7 | 4 | -18,9 | +11 dB
**Replaced sounds:**
| Sound | App version | Author | License | LUFS (Int.) | Range | True Peak (dBTP) | Modifications
| :-: | :-: | :-: | :-: | :-: | :-: | :-: | :-:
| [Rain](https://freesound.org/people/alex36917/sounds/524605/) | `0.4.0` | alex36917 | CC BY | -29,3 | 4,6 | 0 | +2 dB & Lim -6,1 dB : 3,2 ms
| [Wind](https://freesound.org/people/felix.blume/sounds/217506/)| `0.4.2` | felix.blume | CC0 | -17,9 | 8 | -0,5 | -9 dB (its an extract, not whole clip)
**Modified sounds:**
| Sound | App version | Author | License | LUFS (Int.) | Range | True Peak (dBTP) | Modifications | Needs replacement
| :-: | :-: | :-: | :-: | :-: | :-: | :-: | :-: | :-:
| Storm | `0.4.0` | Digifish music | Unknown | -17,9 | 9,7 | 0 | -7 dB |
| Pink noise | `0.4.0` | Omegatron | Unknown | -11,7 | 4,8 | -0,7 | -10 dB | X [#11](https://github.com/rafaelmardojai/blanket/issues/11)
| Summer night | `0.4.0` | Unknown | Unknown | -14,4 | 2,7 | -3,4 | -12 dB | X
| White noise | `0.4.0` | Jorge Stolfi | Unknown | -1,1 | 1,8 | 4,6 | -25 dB | X [#11](https://github.com/rafaelmardojai/blanket/issues/11)
## Needs replacement
**For `0.4.2`**
* Summer night
* Coffee Shop
* Fireplace
* Pink noise
* White noise
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