What is volume? Part 2
Therefore, a sound with the same absolute volume can be perceived as high or low depending on the surrounding conditions.
Let’s say we adjust the gain level so that the volume of the dialogue in the movie roughly corresponds to reality. So if the movie has the sound of a clock ticking silently, then when we watch a movie in the noise of the city, we will not hear the clock at all, as the sound of the clock is much lower than the surrounding noise, and hearing is adapted to filter out ambient noise. In good listening conditions, when there is no ambient noise, the same watch will be clearly audible.
In many cases, it is convenient to measure the recording volume relative to some reference level. For example, if the recording volume is -20dB, is it high or low? And if we know that the volume of the dialogs in the same recording is -30dB, then we can immediately say that it is loud enough, and if the volume of the dialogs is -10dB, then we can say that it is quite quiet. Dialogue level (average conversation volume) is a very convenient reference level, relative to which you can easily navigate. If the sound volume is 10 dB louder than the dialogue level, then it is loud, and if it is 10 dB lower, then it is quiet. At the same time, the level of the dialogue itself can be arbitrary and depend on the recording: in one recording, the level of the dialogue can be -10dB and in another it can be -30dB. In any case, sounds with a volume below the dialogue level will be perceived as quiet and above the dialogue level as loud, even if the speaker system is incorrectly calibrated and the dialogue will sound at an absolute volume of 40 dB. or 60 dB. Thanks to the adaptive property, the hearing adapts to the current average loudness and makes an appropriate ‘correction’.
Therefore, one more loudness scale can be entered (in addition to the digital signal loudness scale and the absolute loudness scale): the loudness relative to the dialogue level. By comparing different volume levels, we get:
absolute volume of real sounds volume relative to dialogue level recording volume-1 recording volume-2 absolute volume during playback records 1 absolute volume during playback records 2
Silent sounds
low whisper 10dB -40dB -70dB -50dB 10dB 10dB
noise standard in residential premises 20..30dB -20 ..- 30dB -50 ..- 60dB -30 ..- 40dB 20..30dB 20..30dB
quiet conversation 40dB -10dB -40dB -20dB 40dB 40dB
Dialogue level
middle volume talk 50dB 0dB -30dB -10dB 50dB 50dB
Loud sounds
typewriter noise 70dB + 20dB -10dB 0dB (maximum) 70dB 60dB
truck motor 80dB + 30dB 0dB (maximum) 0dB 80dB 60dB
strong signal from the car at a distance of 5-7m 100dB + 50dB 0dB 0dB 80dB 60dB
the noise of a tractor running at a distance of 1 m 120dB + 70dB 0dB 0dB 80dB 60dB
pain threshold 130dB + 80dB 0dB 0dB 80dB 60dB
The table also shows two hypothetical recordings recorded under different conditions: the dialogue level in recording-1 is -30dB, and in recording-2 -10dB. You can see that when played back on a calibrated system, the first recording reproduces loud sounds much better; Sounds can be played with a volume of up to 80 dB, while the second recording plays sounds with a volume of only up to 80 dB. 60 dB.
Also note that the two recordings shown require different speaker calibration. So for acoustics capable of creating 100 dB pressure, the required gain level for the first recording is -20 dB and for the second, 40 dB. So the first recording requires significantly higher gain, and when both recordings are played at the same gain setting, the first recording will sound much quieter. Therefore, the second input is convenient for uncalibrated systems, as it allows large deviations in the gain level.
Therefore, record-1 transmits loud sounds well, but requires a higher level of amplification; with insufficient gain and the presence of external noise, it will be perceived as excessively quiet. Recording-2 does not require much amplification, it is well audible even at low amplification levels and in the presence of noise, but it cannot reproduce loud sounds well.
Now let’s remember that the sound signal is variable:
What to bring to calculate loudness? Obviously, a pressure change over a period of a sound wave does not make sense to change the volume of a sound, since we do not hear individual vibrations. Therefore, loudness is not determined by a point, but by a certain period of time.
