The evolution of sound from 1877 to 2022 - Myths about Hi-Fi sound

8695

What is Hi-Fi sound - myths and reality . This article provides a brief historical background of audio technologies, as well as myths popular among music lovers. To understand what Hi-Fi sound is, it is advisable to at least briefly know about the evolution of sound, where it all began and at what stage of development we are now.

• Myth No. 1. Modern vinyl heads have a hi-fi sound;
• Myth No. 2. Recording on vinyl is fundamentally different from recording on tape;
• Myth No. 3. Analog tape recorders have purely analog sound;
• Myth No. 4. Warm tube sound and “cold” transistor sound;
• Myth No. 5. CD quality is HI-FI quality;

⭐ Best Wireless Headphones 2022:

Invention of sound recording, analogue era, mechanical period

It all started with the invention of sound recording . A sound recording of a folk song was made by the French inventor Edouard Leon Scott de Martinville in 1860, using a device called a phonautograph. It is 10 seconds long and is an excerpt from a French folk song. The phonautograph scratched sound tracks on a sheet of paper blackened by smoke from an oil lamp. Naturally, there was no talk about sound quality then. The main thing was that the sound was able to be recorded and reproduced at all.

In 1877, the French scientist Charles Cros was the first to scientifically substantiate the principles of recording sound on a drum (or disk) and its subsequent playback. In the same year, namely in the middle of 1877, the young American inventor Thomas Edison invented and patented a phonograph device in which sound is recorded on a cylindrical roller wrapped in tin foil (or paper tape coated with a layer of wax) using a needle (cutter) , associated with the membrane; the needle draws a helical groove of variable depth on the surface of the foil. His wax roller phonograph was not widely used due to the difficulty of copying the recording, the rapid wear of the rollers, and poor playback quality.

Lifting cables from the floor

We don't mean that cables need to be suspended from the ceiling so that you can pass through without touching them. But if you remember that wires can transmit vibrations to system components, it becomes clear that they should be kept away from their sources - especially from the floor in the case of speaker cables. That's why you see fittings at hi-fi shows such as the Bristol Show.

If you don't agree with this, remember that companies like Naim use loose power cord connectors in all their hi-fi components - for this very reason. They are designed to dampen unwanted vibrations before they are transmitted to the body and cause disgrace. The next time you come to a hardware store and see a loose connector when connecting some expensive component, you will know that the problem is not lazy assemblers.

Besides the fact that cables should not be scattered on the floor, try to avoid twisting them and forming knots; This will help improve the sound quality of the hi-fi system a little more.

Gramophone and gramophone record

In 1887, an American engineer of Jewish origin, Emil Berliner, proposed using a disk-shaped medium for recording. While working on his idea, Berliner first built and tested Charles Cros' device, proposed 20 years earlier, using a zinc plate instead of a chrome plate. Emil Berliner replaced the rollers with disks - metal matrices from which copies could be made. With their help, gramophone records were pressed. One matrix made it possible to print an entire circulation - at least 500 records, which significantly reduced production costs and, accordingly, the cost of production. This was the main advantage of Emil Berliner's gramophone records, which were difficult to replicate compared to Edison's wax rollers.

• Unlike Edison's phonograph, Berliner developed a special apparatus for recording sound - a recorder;

• And to reproduce sound he created another - a gramophone , for which a patent was received on September 26, 1887;

Instead of Edison's depth recording, Berliner used transverse recording, in which the needle left a sinuous trace of constant depth. In the 20th century, the membrane was replaced by microphones that convert sound vibrations into electrical vibrations, and by electronic amplifiers.

For the gramophone (not yet electric, but mechanical) its own medium and format appeared, in one person - the gramophone record.

In 1892, a method was developed for galvanic replication of a zinc disk from a positive, as well as a technology for pressing ebonite records using a steel printing matrix. But ebonite was quite expensive and was soon replaced by a composite mass based on shellac, a wax-like substance produced by tropical insects from the family of lac bugs that live in southeast Asia. The plates became of better quality and cheaper, and therefore more accessible, but their main drawback was their low mechanical strength - they resembled glass in their fragility. Shellac records were produced until the middle of the 20th century, until they were replaced by cheaper and unbreakable ones - made from vinylite (a copolymer of vinyl chloride and vinyl acetate), the so-called. vinyl records. One of the first vinyl records was released in 1897 by Victor in the USA.

The first mass-produced records had a diameter of 6.89 inches (175 mm) and were called 7-inch records. This oldest standard dates back to the early 1890s. Such gramophone records are designated as “7″”, where “″” is the inch sign. At the beginning of their evolution, gramophone records had a high rotation speed and a large track width, which significantly reduced the duration of the sound - only 2 minutes on one side.

Double-sided records became available in 1903, thanks to developments. In the same year, the first 12-inch (12″) gramophone records with an actual diameter of 11.89″ (300 mm) appeared. Until the early 1910s, they released mainly excerpts from the works of musical classics, since they contained a total of up to five minutes of sound.

The third and most popular size was 10 inches (10″), or 250 mm. These records held one and a half times more material than a standard 7-inch record.

The three main record sizes – 12″, 10″ and 7″ – are traditionally called “giant”, “grand” and “minion”, respectively.
⭐ Best wireless TWS headphones 2022:

Electric Sound - The Beginning

Recorder for recording onto a copper master disc (Germany, early 1930s). On the right is a support with a cutter, on the left is a microscope for visual inspection of the recorded audio track.

At the end of the 1920s, the first revolution took place in the world of recording, when instead of the method of recording through a horn, they began to use the electroacoustic method - recording through a microphone . The revolution did not happen by chance - electromechanics, electronics and mechanics have come to the point that this would become possible. The ancestors of electric sound were first the telephone and then the radio. By reducing distortion, the frequency range has expanded from 150–4000 to 50–10000 Hz. This can be considered the first step into the world of Hi-Fi. Naturally, on expensive devices the sound was better and already had a rather natural sound.

In the 1930s, records were released with one track on one side, and often a single concert by one artist was sold as a set of multiple records, usually in cardboard or, less commonly, leather boxes. Due to the external similarity of such boxes with photo albums, they began to be called record albums (“albums with records”).

Squash balls under components

You've probably heard about them (or at least read about them on hi-fi forums) - and this is the honest truth. However, a bicycle tube will work even better than whole balls or halves. However, let's not get ahead of ourselves.

To ensure that as little vibration as possible is transmitted to the system, all components must have a reliable base. Ideally, this should be a rack for equipment. The best is completely horizontal, low-resonance and located as far as possible from vibration sources.

There is one more factor to consider. Although vibrations do not affect CD players as much as they do on vinyl turntables, things as simple as heavy footsteps on the floor, cars passing by a house, flying airplanes, and even the sound from speakers, especially at high volumes, cause the reader to the mechanism exerts more effort, which can affect the sound of the entire system.

A low-cost experiment can be carried out to absorb such vibrations. Place a slightly inflated bicycle tube under the player and amplifier and listen to see if the sound changes. The goal is to make the camera as soft as possible, but at the same time high enough so that the legs of the device do not touch the surface of the stand.

It may be difficult to level the cabinet horizontally, but the improvement in sound will be worth the effort; and if you don’t notice it, then at least have a lot of fun (of course, if no one is watching).

First Hi-Fi, vinyls

In 1948, the largest at that time and one of the oldest US record companies, Columbia, for the first time released the so-called long-playing record , or Long Play (LP), designed for a rotation speed of 33⅓ rpm. Methods of increasing the duration of sound have been produced before - for example, during World War II, “B” discs were produced in the United States. The release of long-playing records was dictated mainly by competition with magnetic audio media.

In order to compete on price with tapes or not lose sound quality, a new material was invented - vinylate . This innovation made it possible to significantly expand the range of recorded frequencies to 50–16,000 Hz, completely preserve the timbre of the sound, and also increase the dynamic range of recording to 50–57 dB, reduce the noise level and greatly extend high-quality sound. In 1958, stereo players and stereo records appeared. This can already be called Hi-Fi characteristics =) of that time.

Myth No. 1. Modern vinyl heads have hi-fi sound

Of course, a frequency range of 50-16,000 Hz and a dynamic range of 50-57 dB (assuming you have an expensive high-end turntable) gives quite realistic sound, especially for an inexperienced listener =). But any listener with experience will be able to distinguish a modern high-quality recording, in one of the new lossless digital formats, from the sound of a grammatical recording.

Modern grammatical recording has not advanced very far. Playing vinyl is first and foremost a tribute to history. The process itself is important, the ritual, sound quality fades into the background. Of course, a considerable percentage of people will disagree with me. Moreover, on the Internet, on well-known torrents, there are blatantly wild cases when it is offered to download huge files with digitization of vinyls in 24-bit 192 KHz quality =))). But let's leave this to people with “tender” ears.

Almost all music lovers are unfamiliar with radio engineering and vaguely imagine the process of producing vinyl and tape recordings. Many of them believe that the sound in tape recorders and vinyl players (unless stated otherwise) is analog. Much to the dismay of lovers of true analog sound, I will dispel these myths.

Myth No. 2. Recording on vinyl is fundamentally different from recording on tape.

Let's start with the most “holy” thing - vinyl. Alas, recordings for vinyl in recording studios are prepared in advance, using a tape recorder (or a modern version of a computer).

More precisely, the first grammatical recordings until the early 30s of the last century were actually made without tape recorders. But almost immediately with the advent of the first tape recorders (at first very expensive, bulky and inaccessible for mass production), studio recordings began to be made on a tape recorder and only then, after mixing and mastering, this recording was copied onto a matrix for producing records.

As a result, we do not have vinyl sound as an independent phenomenon, but a tape recording prepared for vinyl. Thus, all vinyl lovers actually listen to tape sound, but in a reduced “vinyl” range.

Music

Until 2003, the HI-FI group released many songs that became hits (“The Princess’s Song”, “Brother”, “He”, “I Love”, “Black Raven”, “The Seventh Petal”). The clips have repeatedly become chart winners on Russian music channels. In 2002, a video for the song “The Seventh Petal” was released. In its original version, the song existed in English. The chorus for the Russian version was written by Zemfira.

The first composition of the group "Hi-Fi"

Already in 1999, HI-FI received the first Golden Gramophone award for the composition “Black Raven”. The following songs won the same award: “Follow me” in 2010, “And we loved” in 2002 and “The Seventh Petal” in 2004.

In 2003, Oksana Oleshko announced her decision to leave the stage. This concerned not only the HI-FI group, but also show business in general. The ex-vocalist of the pop group preferred family life. Oleshko married the lead singer of the Na-Na group, Vladimir Levkin, but the marriage broke up. Oksana's second husband was businessman Anton Petrov. The singer gave birth to two daughters, but this time there was a divorce. The father of the third child, Oksana's son, is businessman Sergei Tsvitnenko.

Song “And we loved” by the group “Hi-Fi”

Also in 2003, the producers found a replacement for Oleshko. For two years, Tatyana Tereshina became the new soloist of HI-FI. But later she left the group, pursuing a solo career. After Tereshina left, the group members changed periodically. Among them: Katya Li, Olesya Lipchanskaya, Marina Drozhdina.

2005 was marked for the group by winning the “Muz-TV Award” in the “Most Fashionable Group” nomination. This is the largest award in the history of the team.

Song "Besprizornik" by the group "Hi-Fi"

In 2009, Mitya Fomin left the HI-FI group. Now he has a solo career. The producers decided to replace the lead singer with Kirill Kolgushkin. The new soloist was never able to become the leader of the group; this privilege went to Timofey Pronkin.

During his solo career, Mitya Fomin achieved no less success than the legendary pop group. A year after working outside the team, the video “Everything will be fine” was shot. The audience appreciated Fomin's work, and soon the song was playing at the top of the radio charts.

Song "Stupid People" by the group "Hi-Fi"

In addition, the singer worked thoroughly on the hit “Everything will be fine”: he was the director. The song brought Mitya an award from the Golden Gramophone. In 2010, the first album “So It Will Be” was released. Mitya Fomin also began working as a TV presenter at Muz-TV.

In 2012, Vyacheslav Samarin replaced Kolgushkin. Although he left the team that same year, he managed to make an unsustainable contribution. He wrote several songs for the group. A video was shot for the track “Don’t Leave”. From 2016 to 2022, HI-FI existed as a duo of Timofey Pronkin and Marina Drozhdina.

Song “Take Off” by the group “Hi-Fi”

The girl was previously familiar with the group’s work, but does not call herself a fan: she admired the quality of the vocals and the choreography. When she joined the group, she didn’t have to get used to the stage and learn the words of the songs: Marina knew each of them by heart, so much so did the group become a cult group at that time.

Tape recorders

The principle of magnetic recording on steel wire was first developed by Oberlin Smith in 1888, influenced by his visit to Edison's laboratory in 1878. However, the first working device was made by the Danish engineer Waldemar Poulsen only in 1895. The inventor called the device itself a “telegraph” . Wiki source about the tape recorder.

From wire to tape:

5.1 From wire to tape

In 1925, Curt Stille introduced an electromagnetic device that recorded speech on a magnetic wire . Subsequently, devices of his design, using a thin steel tape as a carrier, were produced under the Marconi-Stille brand, and were used at the BBC from 1935 to 1950. In 1925, the USSR patented “a flexible celluloid tape coated with steel filings (for example, using wood glue),” but the invention was not developed. In 1927, Dr. Fritz Pfleumer patented magnetic tape (first on paper, then on polymer). This principle itself began to be developed in parallel with Smith, in the BASF laboratory.

5.2 Birth of the first tape recorder =):

5.2 Birth of the first tape recorder =):

In 1934-1935, BASF began serial production of magnetic tape based on carbonyl iron or diacetate-based magnetite . In 1935, AEG released the first commercial tape recorder called Magnetophon K1. The word Magnetophon itself has long been a trademark of AEG-Telefunken, but later it became the name of this class of devices for playing tape recordings.

5.3 First qualitative step::

5.3 First qualitative step:

The principle of high-frequency magnetization (mixing a high-frequency component into the recorded signal) was proposed in the early 30s. Braunmuhl and Weber , improved in the late 30s.
Nagai, Carpenter, etc. Before the invention of high-frequency magnetization, tape recordings were of terrible quality. The fact is that the magnetization of magnetic film never occurs according to a linear law, which is necessary for high-quality recording and playback of sound. This invention solved the problem. 5.4 Reel-to-reel (or reel-to-reel) tape recorders:

5.4 Reel-to-reel (or reel-to-reel) tape recorders

The media used is magnetic tape wound on plastic or metal reels (in everyday life the name “reel” was also used). Before the advent of cassette tape recorders, reels were called cassettes.

5.5 HI-FI tape recorders:

What is Hi-End?

It is generally accepted that Hi-End meets the highest quality standards. No formal criteria have been developed for this. Typically, manufacturers themselves assign this level to their products.

The difference is that the highest quality components are usually used to get the job done. Moreover, such equipment is very expensive. Companies that produce Hi-End products guarantee the highest quality of their products. Often equipment of this quality is produced in small batches or in single copies. The player or phone cannot provide this level of sound.

top class amplifier Brig 001

The developments use innovative technology and use all available methods to obtain the best sound quality. Sometimes tube devices are used instead of electronic devices, and non-standard technological methods may be used.

To justify the quality level of reproduction, not objective indicators are used, but the opinion of those who tested the sound quality “by ear”. Reviews may use subjective terms: lampiness, softness, sandiness, sound quality, holographic accuracy and others. Often a formal study of characteristics cannot be as accurate as a subjective one.

Users of Hi-End equipment are people for whom quality is more important than cost. Some of them are able to sense the resulting gain in quality. For these users, the ability to experience sound excellence is worth the money spent. Therefore, the demand for Hi-End equipment is constantly growing.

Digital era, electromechanical period - analogue media, digital format

A natural development of magnetic tape recording technology was the use of the digital recording method . Tape recorders that work with digital recordings are designated by the abbreviation DAT (Digital Audio Tape) or DASH (Digital Audio Stationary Head). At the stage of laboratory prototypes, there were two types of DAT tape recorders:

1. S-DAT – with parallel multi-track recording (fixed head);
2. R-DAT - has a recording system similar to that used in video technology - recording by a block of heads placed on a rotating drum (RDD).

Due to the obvious advantages in access speed, capacity and throughput, R-DAT technology has become the main one.

DAT tape recorders record a digitized audio signal on tape (the standard provides for recording two audio channels) with different sampling rates (currently the standard is the presence of frequencies of 32, 44.1 and 48 kHz). At a sampling frequency of 44.1 kHz with a bit depth of 16 bits, studio master recordings are made to prepare an Audio CD.

The legendary Audio CD - the first digital media

One of the significant drawbacks of all tape recorders, including digital ones, was sequential access, where it was necessary to rewind the tape to move between recordings . The previous generation of media - gramophone records or vinyl - was free of this drawback. The advantage of vinyl has been realized in digital quality.

In 1980, Philips and Sony released the Red Book standard, which later became the CD standard. Subsequently, the companies worked separately on CD playback devices.

In April 1982, Philips introduced its first CD player with amazing performance - a frequency range of 20-20,000 Hz , a dynamic range of 96 dB. Digital stream - 705,600 bps per channel. Playing time up to 80 minutes. Until now, the quality standard proposed for the CD is the main and most popular among all digital audio formats. In the modern world, these characteristics can be considered the entry level of HI-FI sound.

In April 1982, Philips introduced its first CD player

In 2000, global CD album sales peaked at 2.455 billion.

Notes

1. ↑ 12
   [hifigroup.ru/history/ Official Hi-Fi website]
2. [tophit.ru/cgi-bin/trackinfo.cgi?id=1082 Information about the rotation of the track “Ticket”] on Tophit.ru.
3. [tophit.ru/cgi-bin/trackinfo.cgi?id=6969 Information about the rotation of the track “In the Footsteps”] on Tophit.ru.
4. Winners of the Muz-TV 2005 Award
5. ↑ 12
   [www.afisha.ru/article/russian-pop/page48/ History of pop music from Vetlitskaya to Yolka 1991-2011]
6. Latypov B.
   [volna.afisha.ru/sounds/30-luchshih-russkih-popalbomov/ “30 best Russian pop albums”] // Poster: Magazine. — M.: Afisha Company LLC, March 5, 2014.
7. Section “News” on [www.hifigroup.ru/ official website]
8. [www.hifigroup.ru/ Official website of the group. Section “News” dated 05/18/2011]
9. [hifigroup.ru/history/complete/ History (continued)]
10. [novaya.com.ua/?/articles/2009/01/05/102033-12 Alena Vinnitskaya: “I really want a child - and there will definitely be one”]

Digital era, digital media, digital formats...

Before the advent of digital media, digital tape recorders were the only way to work with digital audio. But the development of digital, primarily computer systems, and the emergence first of compact high-capacity hard drives and then of high-capacity flash drives at the beginning of the 21st century put an end to analog media. The purely digital era has begun .

In 2006, sales of CDs dropped by almost half. This was caused by the spread of purely digital formats that used flash drives and the Internet for storage. It is from this moment that we can move on to considering formats, since the media are losing their relevance.

Composition of the group

Internet, mp3 and sound degradation

It all started with the Internet. With the advent of the Internet, there was a need to download music files and stream broadcasts . Conventional audio formats were completely unsuitable for this. There was simply not enough speed of information transfer on the network. In the 90s of the last century, the development of audio encoding formats with quality losses was actively carried out, because Lossless data compression did not have much effect. The maximum lossless audio compression ratio is 4:1 or even just 2:1.

In 1993, great success was achieved with the development of a new lossy audio compression format, Mpeg 1 Layer 3, or more simply "Empe Three".

MP3 uses spectral clippings, according to the psychoacoustic model . The sound signal is divided into segments of equal duration, each of which, after processing, is packed into its own frame (frame). Decomposition into a spectrum requires continuity of the input signal, and therefore the previous and next frames are also used for calculations. The sound signal contains harmonics with a lower amplitude and harmonics that lie close to more intense ones - such harmonics are cut off, since the average human ear will not always be able to determine the presence or absence of such harmonics. This feature of hearing is called the masking effect.

The amount of compression and quality depend on the so-called bitrate, i.e. the number of bits per second of sound - the higher the bitrate, the higher the quality and the lower the compression ratio. For MP3, the standard bitrates are from 8 to 320 kbps. Starting from a bitrate of 128 Kbps, the sound quality of stereo tracks can be considered acceptable for listening on cheap equipment.

In the past, it was widely believed that 128 kbps recording was suitable for music intended to be listened to by most people, providing Audio-CD quality sound. In reality this is not the case. With good equipment and using a high-quality acoustic system (speakers or headphones), a music lover can hear the difference in sound between mp3 with bitrates of 128kbps and 320kbps , as well as between tracks with a bitrate of 320 (the highest quality mp3) and the sound of an uncompressed or lossless compressed format. When compressed into mp3, both the frequency range and, partly (due to losses in frequency and coarse quantization) the dynamic range suffer. The detail of the sound also disappears throughout the entire range.

For a music lover, as a last resort, an mp3 format with a quality of at least 320 kbps is acceptable, but lossless formats are preferable. Of course, everything is individual here =)

9.1 Other lossy formats

There are many alternative formats. AAC, WMA, Ogg and others . All of them (the latest versions) are superior in sound quality to the mp3 format at the same bitrate, but I consider mp3 more preferable since it has become a de facto standard.

9.2 True HI-FI or lossless formats

The most common lossless (and uncompressed) format is CD with 44100 Hz 16 bit performance..

• For lossless compression formats, the undisputed leader is the free and free FLAC format.
• Well, for audiophiles, the best formats are DSD (used in SuperAudioCD) and DXD (used for professional recording and SACD production).

The evolution of audio electronics

At first everything was simple - no electronics =). Then, at the beginning of the 20th century, vacuum tubes appeared. They had many shortcomings. To produce high-quality lamps, high mechanical precision of the equipment was required, but even with this, the characteristics of the produced electronic lamps had a wide spread. The second drawback of the lamps is that they required a powerful source of energy and overheated, and also required pre-heating for their operation. The third disadvantage is compactness. The compactness of transistors that appeared later, and then microcircuits, was an order of magnitude higher. This and other shortcomings led to the gradual replacement of vacuum tubes with transistors and microcircuits.

Myth No. 4 - warm tube sound and “cold” transistor sound

A little theory. What is a warm sound? Which one we feel is warm? It's a matter of acoustics, or more precisely psychoacoustics.

The fact is that we associate warm sounds with major chords in music, and cold sounds with minor chords and dissonance. Now a little mathematics and physics. In a major harmonic chord, harmonic resonances predominate over dissonances. In minor it's the other way around. And accordingly, in dissonance, the harmonics are in a noise-like relationship. What do tubes and transistors have to do with it? The fact is that when the first transistors and compact transistor receivers and players appeared, electronic circuits were often more primitive than tube ones. Add there the not the best quality characteristics of the first transistors and the answer is on the surface. Low-quality transistor electronic circuits have a high percentage of nonlinear amplifier distortions. And nonlinearity is the essence of the deviation of the transfer function from the linear harmonic law.

All these non-harmonic distortions are a large set of harmonics-dissonances, which ultimately gives a cold sound. In fact, the cold transistor sound is a thing of the past. But among some music lovers there is a myth about warm tube sound. It is from the same opera as “HI-FI vinyls”.

Myth No. 5. CD quality is HI-FI quality

Is everything really that bad and is there another catch waiting for us? Yes and no =) The CD's dynamic range of 96dB is truly hi-fi worthy . It's a matter of frequency range.

Let me remind you that in music the accepted range is from 20 to 20,000 kHz. A person hears sounds much lower, approximately starting from 14-16 Hz and higher up to 17000-2... here it is individual.

Often the limiter of the sound range is the acoustic path and the speaker system (headphones) . For example, in my Sony MDR-XB950AP headphones, when playing test tracks on a computer with a built-in 2015 audio codec, a range from 15 Hz to 15500 Hz is heard. In the cheaper Sony MDR-570LP, a range from 22 to 16500 Hz is audible. Of course, with better sound-reproducing equipment (for example, a HI-FI player), the range will be wider.

Let's go back to the CD. What's the catch? The reason is high frequencies .

According to the Kotelnikov-Shannon theorem, the frequency of discrediting a digital signal should be at least 2 times higher than the maximum recorded frequency.

This is where the answer is - the minimum. In a CD we have a quantization frequency of 44100 Hz, which is equal to twice the frequency of 22050 Hz. It would seem that there is even a small reserve here. But in reality everything is worse. The fact is that one period of the highest frequency (about 20,000 Hz) is recorded in just two digits, which means that the frequency will be recorded with maximum amplitude and without distortion only if the phases of the recorded frequency and the quantization frequency are perfectly aligned. In practice, only about 20% of all high frequencies fall into these conditions - the rest are distorted and recorded at very low volume levels. For a frequency of about 16000 Hz, the situation is better - there are already 3 quantization digits per recording of one period, which allows you to record up to 65% of frequencies.

The highest frequencies from 10,000 to approximately 14,000 Hz are best recorded. This is the real upper frequency range of CD