Technology Of Audio: Music is now one of the most familiar things in our lives. Music streaming services and video sharing sites make it easy to listen to your favorite music anytime, anywhere.
In particular, due to recent technological advances, high-quality music can be played even on small and portable devices such as smartphones. In the future, with the spread of 5G, restrictions such as communication speed and capacity will be removed even more than at present (* at the time of writing the article, 2020). Including video expression during performances such as VR, everyday life where you can enjoy more realistic and powerful music than ever before at home or on the move will soon come.
Therefore, this time, we will focus on how sound is reproduced in the first place, and approach the technology hidden in the music that we enjoy every day.
Three elements that make up audio
In everyday life, the word “audio” is used casually to refer to speakers. However, audio is roughly divided into three mechanisms (devices).
First of all, I will briefly explain each of the three mechanisms, “player”, “amplifier”, and “speaker”.
Player that reads the sound source in the recording media
Music playback begins with reading the digitized sound source. The player plays that role.
This player reads the recorded music information (sound source) and converts it into an electrical signal. How to read information differs depending on the recording medium, such as a needle for records and a laser for CDs. In the digital sound sources stored in CDs and memories that are currently mainstream, semiconductors designed exclusively for audio (such as servo ICs that read sound sources recorded on CDs and audio SoCs that read sound sources in memory) are used for music information. It plays the role of taking out. These ICs are provided by semiconductor manufacturers such as ROHM to audio manufacturers.
The digital sound source read from the recording medium is either as a digital signal or converted to an analog signal by a device called a DAC (digital/analog converter), and then passed to the amplifier described later. Especially when using a DAC, it is very important how to make an analog signal without degrading the sound quality, which is also the reason why the DAC is said to be the component that most affects the sound quality.
Amplifier that amplifies the signal read by the player
The “amplifier” performs “amplification” so that the signal read by the player can be reproduced as audio. By the way, the amplifier is an abbreviation for an amplifier.
In order to drive the speaker, the signal read by the player must have a large amount of energy. Therefore, the amplifier plays the role of driving the speaker by amplifying (largening) the waveform of the signal without changing it as much as possible. If you compare it to sports, the best thing about the amplifier is how good an “assist pass” can be for the speaker.
As with human telephone games, the more processes that intervene, the more likely it is that the original sound source will deteriorate (change), so it can be said that the sound quality changes greatly depending on the performance of the amplifier.
Speaker that turns the data-converted sound source into actual voice
Perhaps the most commonly known audio is this “speaker”. Speakers have the role of delivering sound to the human ear by shaking the air using electrical signals converted and amplified by players and amplifiers as energy.
The same applies to players and amplifiers, but speakers, in particular, have a wide variety of shapes, sizes, structures, and materials. Therefore, here we will explain the general mechanism.
The electrical signal transmitted from the amplifier vibrates the unit inside the speaker. Simply put, this unit uses the mechanism of a magnet to move the parts inside the unit according to the electrical signal, causing the air to quiver. There are several types of mechanisms that make the air tremble, that is, make the sound resonate, and the mainstream types are the cone type and the horn type. In addition, there are speakers that produce bass, midrange, and treble sounds by dividing the unit into multiple units.
Also, like a guitar, piano, flute, or drum, the sound reverberates in a cavity (the housing that makes up the instrument). How to make this cavity also differs depending on the speaker.
Components, smartphones, and personal computers have three elements.
It turns out that music is played by combining the players, amplifiers, and speakers introduced so far. A single audio system is made up of all of these.
But how does the smartphone, computer, or stereo component that we usually enjoy music work with? In fact, these devices come with a set of several functions from the beginning.
Smartphones and PCs
You can play all the roles of a player, an amplifier, and a speaker in one unit. You can also connect headphones and take out only the speaker functions outside your smartphone or computer.
It is a set of players, amplifier,s and speakers. By the way, components are derived from components.
2. Everyone is aware of it, but it’s actually ambiguous … What is “sound quality”?
Perhaps the most familiar audio for many people today is the combination of smartphones and headphones (earphones). If you look at home electronics mass retailers and mail-order sites, you can find a variety of products with various prices and brands, ranging from thousands of yen to hundreds of thousands of yen. Isn’t “sound quality” always included in the points that you are aware of when purchasing?
On the other hand, I think it’s true that not everyone can answer when asked “What is the sound quality?” (And the answer varies from person to person). Also, as introduced in the previous chapter, many mechanisms and devices are used before music is played. Therefore, the sound quality depends not only on the performance of the headphones but also on the entire audio system, including the quality of the sound source in the first place.
Next, let’s think about this sound quality. Here, we will look at two aspects: “absolute definition” and “relative definition”.
When asked about sound quality, the element that everyone commonly mentions is the “absolute element.” Therefore, “the ability to faithfully reproduce the sound source” is always mentioned. Specifically, the sound is not distorted, the entire range can be sounded properly, and no jarring noise is generated.
Here, I would like to consider the case where the sound source itself is not faithful. For example, if you import a CD with a computer and convert it to another format such as MP3 irreversibly, the sound source will be compressed (of course, it also has the advantage of reducing the file size). This is easy to understand if you imagine compressing high-quality photo data taken with a camera for attaching to an email or posting on social media.
The interesting aspect of sound quality is that, unlike the “absolute definition” that everyone commonly imagines, the definition differs depending on individual tastes, ideals, and music that is often listened to. This is briefly described as a “relative definition”.
For example, if you look at the headphone package or introductory text, you will find words such as “clear sound” and “powerful deep bass.” However, when you think about it, is it better to have a clear sound, or is it better to have a deep bass sound? ——This is the part where the evaluation changes depending on the individual.
When listening to recent pop, R & B, hip hop, or dance music, the deep bass will create a groove and create a feeling of comfort. However, when listening to orchestral symphonies, it will be necessary to be able to clearly reproduce sounds of various ranges and timbres, and to enjoy the realism of having a performer in front of you and the complex interaction of sounds. ..
In other words, it can be said that sound quality is defined based on “how you want to hear” that changes depending on the music you play, in addition to being able to play the sound source properly.
Sound quality depends on electronic components that are only 1 cm square
To reiterate at the beginning, the recorded sound source is converted into data and played back by the audio system. Therefore, the sound quality, players, and amplifiers have a great influence on the quality of sound quality.
ROHM is not a manufacturer of audio equipment itself, but it makes many electronic components for audio equipment used in players and amplifiers, and it is also widely used in high-end audio equipment, car audio, and car navigation systems that are particular about sound. I am. In particular, volume control ICs and DACs are products that achieve the world’s highest class in low noise and low distortion, which are the most important characteristics for improving the sound quality of audio equipment.
Finally, I would like to touch on the driving force behind the creation of these products by ROHM, an electronic component manufacturer. Underlying is the idea of quality first. The corporate purpose is “We always put quality first.” With this in mind, we are working to thoroughly improve the quality of every detail of our products. Also, I think there are many engineers who have an inquisitive mind to improve the sound quality of audio equipment.
For products for audio equipment, we are still refining our sound quality design technology, including identifying 28 parameters that affect sound quality. Product development that enhances sound quality such as resolution, presence, and power as intended by controlling not only circuit/mask design but also manufacturing sound quality parameters related to wafers and packages, and by repeatedly playing and checking music at the prototype stage. I am doing.
Please see here for the thoughts and commitments that can be put into such ROHM products for audio equipment.