Digital sound: DSD vs PCM
Digital sound. How many myths revolve around this phrase. How many disputes have arisen between lovers of comfort and digital quality and supporters of “live airy” vinyl sound multiplied by “warm tube” sound. In addition, there is a lot of controversy among lovers of “numbers”: is 16×44.1 enough or is 24×192 necessary? Which is better: multibit or delta sigma? CDDA or SACD? PCM or DSD? In this article, I will try to explain the basics of digital sound in simple language and will also expand in more detail on comparing two types of encoding of an analog to digital signal: DSD and PCM.
First, let’s answer the question, what is digital sound? How is it different from analog? In short, in mathematical terms, an analog audio signal is a continuous function, a digital audio signal is a discrete function. What does that mean?
Analog signal
If you draw in your imagination a graph of a sinusoid (this is how a sound wave is most often represented): then no matter how we magnify it, trying to see all the details, we will always see a smooth, smooth line – this is an analog audio signal (Fig. 1).
analog Analog (recording) sound has many parameters that can be used to evaluate its quality. Consider the three most important: frequency range, dynamic range, distortion.
frequency range – a set of frequencies contained in sound. It is generally accepted that the frequency range of human hearing is 20 … 20,000 Hz (sometimes 16 to 22,000 Hz is indicated). The frequency range of the music itself is of no interest in terms of quality assessment (for example, the frequency range of the same plane taking off will be very wide and the tenor’s vocal part will be much narrower). A qualitative parameter, say, of an earphone is the potential frequency range, and it is estimated using the amplitude frequency characteristic (AFC). The ideal frequency response, a straight line across the entire range of hearing frequencies, means that the sound source does not amplify or attenuate any individual frequencies, meaning that the extracted sound matches the original.
Dynamic Range (DD) is the difference between the lowest and highest sound. Loudness is measured in decibels (dB). It is generally accepted that the maximum volume that does not cause injury to a person is 130 dB, the sound of an airplane taking off, and the minimum audible volume, 5 … 10 dB, is at the level of the rustling of the leaves in low wind conditions. Naturally, it will be impossible to distinguish the rustle of leaves against the background of a plane taking off, and listening to music at a level of 130 dB is extremely unpleasant. Therefore, it is generally accepted that a comfortable DD for listening to music is 80 … 100 dB.
The distortion is nothing more than a deviation of the signal from the original.
