It has only been in the past couple years that the audio industry has reached any consensus on what should be considered Hi-Res audio. Essentially it’s been decided that Hi-Res should be defined as audio formats that exceed the level of CD quality, with sampling rates of at least 96 kHz and a bitrate of 24 or greater. So what does that all mean?
Let’s start with some audio format basics. In the age of digital music like mp3 and Spotify most folks have seen audio quality defined in bitrate (128, 192, 320 kbps). Those values tell you how much data compression was applied, with higher numbers meaning less compression and therefore better audio quality. But bitrate values only apply to formats with lossy compression.
Here we’re not talking about bitrate because Hi-Res audio by its definition has to be lossless or uncompressed. Instead we’re defining the audio by its sampling rate and bit depth.
Just like digital video is made up of a series of still images played quickly enough that you see them as continuous, digital audio is comprised of many data points played back at an extremely fast rate. Each one of these audio snapshots is called a sample. Audio sampling rate (in Hertz - Hz) tells you how many samples per second are played, so the higher the number, the greater the resolution. CD-quality audio (typical for most standard music, games, movies) for example uses a sampling rate of 44,100 Hz, or 44,100 samples per second, whereas Hi-Res formats use 96,000 or higher, so more than double!
Well, yes. More samples per second means the audio has a higher resolution. It also means that the audio can contain higher frequencies. Due to something called the Nyquist Theorem (which I will not get into here, go ahead and Google it if you want to nerd out) your highest frequency is always limited to your sampling rate divided by 2. CD quality audio is limited to 22,050 Hz, while Hi-Res audio can produce out to 48,000 Hz or higher.
But can’t human ears only hear up to 20,000 Hz?
Yes, but using a higher sampling rate shifts the Nyquist frequency up, which in turn means that the system’s low pass filter cutoff (the max frequency that can be reproduced) is also higher. Moving the filter cutoff further outside the audible band has a positive impact on sound quality. There is also hot debate whether ultra-sonic frequencies can be “sensed” even if they are not heard. There is a lot of research on the topic that you can dive into if interested.
In my opinion far more important than sampling rate is the audio’s bit depth. (Again, we’re not talking about bitrate here, bit depth is different). The bit depth tells you how many bits are used to define each one of those audio samples. The more bits you have, the greater the detail. It’s like moving from standard def video to HD, having more pixels to define the images makes everything clearer and closer to the original. Same thing with bit depth, more is definitely better.
CD-quality audio is 16 bit, while Hi-Res formats are 24 bit or greater. The extra bits add a lot of depth and detail to the audio. Having a higher bit depth also creates a lower noise floor, meaning less noise in the audio to reduce quality. Ultimately Hi-Res audio formats produce a higher fidelity that has to be experienced to truly appreciate. As a warning, once you head down the path of true high fidelity audio there’s really no going back!
Sounds awesome, so how do I listen to Hi-Res?
There are many albums that have been mastered or remastered in Hi-Res formats. You can find these for purchase on sites like hdtracks.com in FLAC, WAV, and a few other file formats. On the streaming side there are also a few Hi-Res options, but the most popular at the moment is tidal.com. All of their content is lossless, and they feature many tracks and albums that were mastered for and are streamable in Hi-Res.
What about games?
Games have not yet made the leap to Hi-Res and are still using standard audio formats. But with the move towards 4K and HDR content on the graphics side, it’s not a stretch to think that Hi-Res audio could come to gaming in the very near future. But even if games don’t currently support Hi-Res, having a high fidelity audio system that does support it will still provide a significant sound quality benefit, even with standard audio formats.
How do I know if an audio product is Hi-Res capable?
To enjoy Hi-Res audio content, you need hardware that can handle these formats. That’s why the Japanese Audio Society created the Hi-Res Audio certification program, to help consumers understand which products have proven capability to receive and play Hi-Res formats at full quality. This means that a DAC (digital analog converter) must be able to process 96 kHz, 24 bit, and that an amplifier and headphones or speakers must have frequency range out to 40,000 Hz.
SteelSeries is the first gaming brand to introduce a full audio system, DAC and amp plus headset, that is Hi-Res Audio certified: the Arctis Pro + GameDAC.