What is volume? Part 3
A completely different volume distribution immediately catches your eye.
All sounds are heavily shifted to the ‘loud’ part of the dynamic range. The difference in the average volume of movies and music reaches 40 dB. In addition, movies are characterized by a smooth drop in the histogram in the noisy area. For music, the maximum of the histogram is usually at the maximum level (0 dB). There are few such charts, but this situation is very common.
The concept of dialogue level is often inapplicable to music, so it is very difficult to separate high and low sounds. Therefore, it is also difficult to determine the subjective volume of the composition. Therefore, a subjectively noisy composition can be objectively quieter than a subjectively noisy one. Here positive or negative drops in volume, which are not visible in these histograms, are of great importance.
The lack of a single reference point leads to chaos – the sound from different sources has different loudness – the difference in the maximums of the composition histograms reaches 20 dB. And, in general, the concept of ‘volume of a composition’ is very difficult to formalize in any way. Many people are likely familiar with the situation when there is a lot of different music from different sources and when they play it back-to-back (for example, if you record an audio CD), the volume constantly changes when you switch from song to song, which is unpleasant (and the aforementioned effect of a discrepancy between actual and subjective volume can be an even more confusing perception). The graphs given illustrate this situation very well.
The dynamic range of musical compositions (the difference between the loudest and quietest sound) is 20 to 40 dB, which is significantly less than the dynamic range of movies (70 dB).
3. DVD volume problem
On average, the volume level of music recordings (as well as Windows system sounds) is significantly louder than that of DVD movies. Therefore, with the same system volume settings, the absolute volume of the movies will be much lower and in the presence of external noise it may be insufficient, it will be difficult to hear (sic!) And it will seem that the sound is of poor quality . Increasing the gain in the system settings and in the amplifier even to the maximum may not solve the problem: the difference in the average volume reaches 40 dB, which is a lot. However, even if the power of the amplifier turns out to be sufficient and the DVD is played with enough absolute volume, it is not always convenient, since the sounds of the operating system
This problem is typical mainly of computer playback, since in hardware players, the gain level is controlled by the decoder itself. Some software DVD players can control the volume of the system, but this is also not always convenient, as the volume of all system sounds changes (you can accidentally stun the neighbors) and the program still cannot control the volume in a external amplifier. So this is only a partial solution to the problem.
The trade-off is to process the sound just before playing it. Such processing can greatly improve the playback quality of a specific recording and under specific conditions. Many may argue that this is a loss of ‘quality’, however, as already mentioned, there is no absolute quality, we did not set ourselves the goal of editing the sound, our goal is to achieve listening in our conditions, yours was pleasant . If the speaker system does not have enough power, or if we have nervous neighbors, watching a movie at a reduced volume, when half the words cannot be distinguished and half the silent sounds cannot be heard, it will be just unpleasant. Even self-hypnosis about the maximum “quality” achieved will not be able to soften this impression. I’ll repeat the main idea one more time: quality is what we hear. Sound goes through many stages of processing before reaching the listener, and the variety of acoustics and their properties is so great that the last stage of processing just before playback is practically a necessity.
4. Level change. Overflow, circumcision and limitation.
A level change is simply a multiplication of the amplitude of a signal by a certain value, as a result of which the volume of the entire signal changes (increases or decreases).
