Actually we will refer to an audio normalization in general, regardless of the format.
-First attempts to normalize the audio
As soon as the digital format emerged and people were able to store audio files on their computers, it was necessary to encode them to save space, without losing quality.
This is how formats such as mp3 emerged, because they managed to make the same song occupy 10 times less space than a wav format, and if it was well coded and / or with a quality encoder, it sounded practically the same. It was gained in space and the loss of quality was practically zero.
For this it was necessary to maintain a samplerate of at least 44,100 kHz and a bitrate of at least 128.
Initially the most accessible format was the mp3 and although later other formats have emerged (even looseless like FLAC), the mp3 continues to take the place of favorite.
But when a person listens one song after another, he will soon perceive differences in the sonority of these songs. It seems that the volume level is not even, and that is when it becomes necessary to normalize, to avoid having to manually correct the audio volume level of each song by turning the volume knob.
Even Spotify has had to incorporate some normalize option to avoid these annoying volume gain level changes between songs.
The difference is that Spotify only normalizes the volume while playing the songs, so if we stored them on our hard drive, the volumes would remain uneven.
-The solution of volume peaks
The first attempts to normalize the audio of an mp3 were inefficient, they only looked for the peak of a song and amplified it all to the point where those peaks did not distort.
But this did not eliminate the perception that one song would sound louder than others.
Over time the volume level normalization algorithms have been refined and have become more subtle and complex. They have been achieving similar results to those obtained by the great sound consoles in musical concerts, where the music is highly processed to – among other things – make the volume levels are even and unchanged, and also achieve a sussuro of The singer’s voice is audivble even if the battery gives tremendous blows in a roll.
Mp4Gain has come to obtain these results, without the need for you to invest thousands of dollars in hardware like these musical groups or large radio stations do.
Today, audio normalization really is a combination of compression, limiters and normalization, which achieves an amazing result. Far from those first attempts to level the volume gain of each song to avoid big differences.
