One of the most interesting developments in the audio world in recent years is the unprecedented rise in popularity of high-definition (Hi-Res) formats. Among the reasons for the emergence of new formats at one time is dissatisfaction with the sound quality of CDs, because at the dawn of the era of compact discs, all record labels were in a hurry to reissue their analog catalog on a digital medium, caring little about quality: at least plus or minus it is attractive and devoid of all kinds of clicks and other the roughness of the sound seemed like a victory.
Thus, hardware makers and record labels took a long time to fulfill their promises of superior CD sound quality. As a result, the format has suffered irreparable damage in the minds of many audiophiles, and the CD has become a kind of digital villain. Looking ahead, though, it’s worth noting that CDs can sound absolutely great – provided the original recording is of the highest quality, and with due attention to mastering and production. But first things first.
We’ve seen a return to vinyl lately, and we’ve seen an increase in interest in high-definition digital files. But are we not in danger of falling into the trap of the 1970s, when all attention was focused only on technical characteristics? To answer this question, let’s speculate about how and what exactly we hear, as well as about the realities of highrez recording.
To begin with, let’s touch on the technical side of the issue. The CD format with 16-bit quantization and a sampling rate of 44.1 kHz allows you to record audio in the frequency range from 0 Hz to about 22 kHz (that is, slightly beyond the capabilities of human hearing) and a dynamic range of about 95 dB, which is quite enough for the vast majority musical instruments. At the same time, the 24-bit 48 kHz format expands the dynamic range to 150 dB, and the upper frequency to 24 kHz. Moreover, many audiophiles prefer 24-bit 96 kHz, with a high frequency of up to 48 kHz, as well as 24-bit 192 kHz, with an upper limit in the region of 96 kHz. Such high sound frequencies are far beyond the capabilities of human hearing, so a simple and reasonable question arises here: what exactly is all this for?
Some Hi-Res proponents will say that although they don’t hear anything at these frequencies, they can still “feel” the difference, often presenting it as a higher “airiness” of the sound. At the same time, it is curious, what kind of sensory organ do they feel this airiness? In general, we can really “feel” very low frequencies – provided that they act with a high amplitude and from a relatively close distance. Well, as for Hi-Res fans, most likely they perceive the sound as smoother and more consistent due to the high sampling rate. In addition, the ADC and other components used during 192 kHz recording are likely to be of high quality, which in itself will affect the listening experience.
In order to test the advantages of Hi-Res in practice, everyone can conduct an interesting test – to listen in random order to several records with different sampling rates on a good digital audio player. Cover the display of the player with something at hand so that you have no idea what resolution the file is currently playing at. Equip yourself with a pen and notepad (well, or the “notes” application in your smartphone), listen to all the recordings and note what exactly you hear and which track sounds better. If you can pinpoint higher sampling rates accurately, it is safe to say that you have extraordinary hearing.
Most older people are able to hear a tone up to a maximum of 15 kHz. By the age of 60, this frequency can drop to about 12-13 kHz for the average man (and possibly slightly higher for women). Thus, a 96 kHz audio signal means little to sound perception. However, it is likely that many listeners will feel the extra smoothness and fusion in the midrange that Hi-Res boasts. However, many other factors also affect the sound quality of recordings, some of which play a very important role.
For example, you might wonder what equipment is used for recording. After all, ironically, many professional condenser microphones from Sennheiser, Beyerdynamic, AKG, Neumann, Shure, Rode and Audio Technica have frequency responses that drop rapidly just past 20 kHz. Moreover, for some popular microphones, a noticeable decline begins after 18 kHz: thus, they are unlikely to pick up anything at a frequency of 48 or 96 kHz, and in most cases this is just good, because you don’t really want to enter high frequency noise into the mixing chain.
So, in order to record really “high resolution” audio, you first need special microphones that can pick up very high frequencies without introducing too much noise of their own. Next, we need mic preamps and mixers with extended frequency response and ultra-low noise, as well as a high-end analog-to-digital converter. Suppose we have microphones with a flat frequency response from 20 Hz to 96 kHz and ultra-low noise, connected with special audio cables to an ultra-low noise preamplifier. Next, we will send this signal to the mixing section and a high-end A / D converter that feeds the high definition audio signal to a digital recorder or computer with similarly enhanced performance.
And in general, yes, all this is really doable. Moreover, having recorded a violin solo at 24 bit 96 kHz in this way, you will notice that at the highest notes some harmonics reach a frequency of approximately 28 kHz. The soprano flute can also give such harmonics, but whether we are able to hear them is another, no less interesting question. Ultimately, almost all the sound signal that is significant for our hearing in solo violin recordings may well be contained on a 16-bit CD with a sampling rate of 44.1 kHz.
It is doubly surprising that even a full-fledged orchestra, with its widest dynamic range, can be recorded in 16 bits, provided that the levels are initially set correctly (without resorting to compression). Of course, keep in mind that it is quite possible to generate electronic sounds that go beyond the frequency range of human hearing and the dynamic range of 100 dB. But all this remains, as a rule, at the level of theory.
In conclusion, it is worth noting that due to the higher smoothness and fusion of sound in the mid-frequency range, Hi-Res recordings are definitely worthy of listeners’ attention, but only if the audio system allows you to reproduce all these nuances.
Curiously, many audiophiles have favorite recordings of classical music from the late 50s and early 60s. After all, music is not only technical characteristics, but the determining factor is often the performance and professionalism of the sound engineer, which allows you to make a good recording even with a minimal set of microphones. And having listened to some jazz recordings made in the early 60s, it should be noted that they sound very lively and musically: maybe it is not so important that they are not in Hi-Res.