Suitable Recording Sound Levels

Sound Accessibility 

Signal

Audio signal is a representation of sound. Usually it in an electrical voltage. Audio signals have frequencies in the audio frequency of around 20 to 20,000Hz. 20,000Hz is the limit of the human hearing.

(Source: en.wikipedia.org/wiki/Audio_signal)

Noise

This can be a range of things. Commonly it sounds like a buzz/fuzz in the background. It can be caused by things such as a fan, traffic or even an air conditioning unit. Some microphones can pickup very little sounds that sometimes can't even be noticed by people because their brain naturally filters it out.

Interference

Unwanted noise. Noise that comes in every now and then, not consistent.

Potential locations that can lead to audio problems

Top of a mountain/hill due to high winds. A waterfall/weir.

Built up areas such as a city, Roads, Inside a busy room/building.

Next to tree's on a windy day due to rustling leaves.
Next to a Racetrack.

Accessibility

Many, many places in most parts of the world have accessibility features to cover a wide a range of people as possible. Such as people with hearing difficulties. Places like cinemas or concerts etc.. have setups such as subtitles or hearing loops (which is a magnetic signal that can be detected by a hearing aid) to people can hear the audio still.

Standards

Digital audio reference level is -18dBFS.

Stereo programme audio levels are currently measured by Peak Programme Meters (PPM).

PPM    dB

0         -10

1         -12

2         -14

3         -16

4         -18

5         -20

6         -22

PPM  = -2(dB-5)