Mp3 Normalizer – Masking Effects
mp3 encoding: “masking effects” and bitrate
masking effects
The process of information filtering by human consciousness includes a process called “masking”. People who study psychoacoustics are very concerned with the study of this process, which studies the relationship between hearing, consciousness and sound. Mutual relationship. There are two masking effects that affect the Mp3 encoding process: one is acoustic masking and the other is temporal masking.
Sync masking (also called acoustic masking)
To describe the sync masking effect, it’s best to use an analogy. Imagine a bird flying in front of the sun. You see the bird fly from the left between you and the sun, and then the bird disappears because the sun’s rays are too bright. When the bird leaves the area of the sun, you can see it again. Just like in a quiet environment, the sound of a guitarist’s fingers sliding across the strings can be heard, but if the same sound is played in an environment where rock music is being played, the average person cannot hear it.
The Mp3 codec only cares about the interrelationship between frequencies and loudness. Sync masking is described in terms that the mp3 codec can handle as follows: you have a sound signal, it’s a 1000hz sine wave (one), then we have a 1100hz sine wave (two), the wave sine two is weaker, -10db. Most people do not notice the presence of sine wave two in this situation. But sine wave two is not easy to perceive, not only because it is weaker, but also because its frequency is very close to that of sine wave one. To illustrate this phenomenon, we gradually increase the frequency of the second sine wave, but keep its volume constant until we can hear it. Assuming its frequency increases to 4000 Hz, we can hear this sound. When the frequency difference between the two sine waves gradually increases, the second sine wave can be heard gradually, until its frequency increases to a certain point, most people can hear two different tones, one is louder and the other is softer. lower.
This process is what psychoacousticists call the “synchronization masking” phenomenon. Two sounds with similar frequencies but very different volumes are difficult for humans to perceive as two different sounds. Taking this phenomenon into account, mp3 tries to discard those sounds that cannot be perceived during the encoding process, or assign as few bits as possible to these sounds.
Temporary masking Temporary masking Masking effects
synchronous
