Myths of Digital Music Part 2
DVD-Audio sounds better than Audio CD (24-bit vs. 16, 96 kHz vs. 44.1, etc.)
Unfortunately, people generally only look at numbers and rarely think about the impact of a particular parameter on objective quality.
Let’s first consider the bit depth. This parameter is only responsible for the dynamic range, that is, the difference between the lowest and highest sounds (in dB). In digital audio, the maximum level is 0 dBFS (FS – full scale), and the minimum is limited by the noise level, that is, in fact, the dynamic range in absolute value is equal to the noise level. For 16-bit audio, the dynamic range is calculated as 20 × log 10 2 16, which is 96.33 wB. The dynamic range of a symphony orchestra is up to 75 dB (mainly around 40-50 dB).
Now let’s imagine the actual conditions. The noise level in the room is about 40 dB (do not forget that dB is a relative value. In this case, the hearing threshold is taken as 0 dB), the maximum volume of music reaches 110 dB (so that no discomfort) – we get a difference of 70 dB. So it turns out that a dynamic range of more than 70 dB in this case is simply useless. That is, at a higher range, loud sounds will reach the pain threshold or soft sounds will be absorbed by the surrounding noise. It is very difficult to achieve an ambient noise level of less than 15 dB (since the volume of human breath and other noises caused by human physiology is at this level), as a result, a range of 95 dB for listening music is completely sufficient.
But there is a “but” here. If you generate a clean tone with a frequency of, for example, 1 kHz and a level of -60 dBFS with a 16-bit quantization depth, and then you listen to it and compare it to the same signal, but generated in 24-bit format , you will hear the differences. The reason lies in the distortion of the waveform and the appearance of parasitic harmonics. But to eliminate this unpleasant effect, fortunately, there are Dithering and Noise Shaping technologies.
Now about the sample rate (sample rate, sample rate). This parameter is responsible for the time sampling rate and directly affects the maximum frequency of the signal that can be described by this audio representation. According to Kotelnikov’s theorem, it is equal to half the sampling frequency. That is, for a typical sampling frequency of 44100 Hz, the maximum frequency of the signal components is 22050 Hz. The maximum frequency. that is perceived by the human ear, just above 20,000 Hz (and even then, at birth; as we age, the threshold drops to 16,000 Hz).
