In this blog post, we’ll explore the principles of digital audio, the characteristics of high-resolution audio, and how it differs from standard audio to understand what high-resolution audio is all about.
High-resolution audio has been steadily gaining attention in the digital music market. While it is often mentioned in the same breath as lossless audio, strictly speaking, the two concepts are distinct. Lossless audio refers to audio files compressed without any loss of the original data, whereas high-resolution audio refers to audio files with a resolution that exceeds standard CD quality (16-bit/44.1 kHz). Recently, various music streaming services have begun offering high-resolution audio, and compatible players, headphones, and earbuds are also being released steadily. So, how does high-resolution audio differ from standard MP3 files, and how significant is that difference in practice? Also, can people actually hear the difference? In this article, we’ll explore these questions by examining the principles of digital audio and the differences between various audio formats.
The biggest difference between analog and digital audio lies in the continuity of sound. Most of the sounds we hear in daily life are analog signals. The chirping of birds, the sound of a car, and human speech—all sounds have a beginning and an end, and they change continuously without interruption. In contrast, digital audio divides these continuous signals into fixed intervals and stores them as numbers. In other words, it records the pitch and volume of sound by dividing them into fixed levels. A music box is a classic example. Of course, the sound actually heard from a music box is an analog sound transmitted through the air, but the way music is recorded on sheet music—using a fixed scale—can be seen as similar to a digital method in a broad sense.
Since digital audio consists of discrete information, how these levels are divided is crucial. For example, suppose there is an audio file “A” that is 3 minutes long. If the specifications for audio file “A” are 16-bit/44.1 kHz, the 16-bit specification means that the volume of the sound is divided into 2¹⁶ levels—that is, 65,536 levels. This is called bit depth, and the higher the bit depth, the more precisely the volume of the sound can be represented.
44.1 kHz means that the original sound was measured and recorded 44,100 times per second. This is called the sampling rate, which indicates how frequently samples are extracted from the original analog signal. The higher the sampling rate, the higher the frequencies that can be reproduced; generally, the higher the bit depth and sampling rate, the greater the amount of information contained in the audio file. Currently, standard audio CDs use the 16-bit/44.1 kHz specification, which has long been established as the standard for digital audio.
In addition to specifications, digital audio files also involve the concept of file formats. A format refers to the method by which audio is stored and compressed. Representative formats include MP3, WAV, and FLAC. The WAV file can be considered the most basic form of digital audio. WAV is a standard format that typically stores raw PCM (Pulse Code Modulation) data without applying any lossy compression. During the recording process, the producer determines the bit depth and sampling rate, generally recording at the highest quality available. While it is possible to convert a high-quality audio file to a lower quality, it is impossible to restore information that has already been lost.
FLAC is a format that reduces file size by losslessly compressing WAV data. Since the original data is preserved, decompressing the file yields the same sound quality as the WAV. In contrast, MP3 uses a lossy compression method that removes audio information that the human ear is relatively less sensitive to. This allows for a significant reduction in file size, and MP3 has long been established as the most widely used audio format.
High-resolution audio generally refers to audio files with specifications exceeding CD quality, typically using 24-bit/96 kHz or 24-bit/192 kHz. These files store more data than CDs, resulting in significantly larger file sizes. For example, even a song lasting about three minutes often ranges from tens of MB to over 100 MB.
To properly play high-resolution audio, a DAC (Digital-to-Analog Converter) that supports it is required. A DAC is a device that converts digital data into analog signals audible to humans, and it is typically built into smartphones and computers. While most recently released smartphones and computers can play audio files at 24-bit or higher, users seeking higher performance and lower noise levels sometimes use a separate external DAC. Prices have dropped significantly compared to the past, making it possible to choose from a wide range of products across various price points.
So, is there actually a noticeable difference between high-resolution audio and standard audio when listened to? This question remains a subject of ongoing debate in the audio field. The most objective method is a blind test, in which standard-resolution and high-resolution audio files are compared without distinguishing between them. Numerous studies conducted to date have consistently reported that most listeners were unable to distinguish between CD-quality audio and high-resolution audio when the same master was used. However, the debate continues, as there are also reports of listeners perceiving differences depending on factors such as the listening environment, equipment, recording quality, and individual hearing ability.
One reason for this debate is the range of human audible frequencies. Generally, humans can hear sounds between approximately 20 Hz and 20 kHz, and the highest frequency they can perceive tends to decrease gradually with age. MP3s are compressed by removing audio information that is relatively difficult for humans to perceive, in order to reduce file size. In contrast, high-resolution audio uses higher sampling rates and bit depths to store more information. However, opinions still vary on the extent to which this additional information actually affects the listening experience.
Nevertheless, the high-resolution audio market is growing steadily. Major music streaming services now offer high-quality and high-resolution audio, and smartphones, DACs, earbuds, and headphones that support these formats are also continuously evolving. Some attribute this trend to improvements in bit depth and more sophisticated recording and playback environments, while others believe the placebo effect—a psychological expectation—plays a role. However, one thing is clear: many people want to listen to music that is closer to the original sound. By understanding the principles and characteristics of these digital audio files and applying that knowledge to your listening experience, you can enjoy a richer and more enjoyable musical experience, whether you’re listening to high-resolution or standard-quality audio.
