High-resolution audio — or hi-res audio, for short — is a term you come across a lot when comparing different speakers or audio formats. As you’ve likely guessed, it indicates a high level of audio quality. But high relative to what? The answer is not simply in the eye (or ear) of the beholder.

Let’s start with some points of comparison. High-resolution audio sounds better than MP3-quality audio. It even sounds better than standard CD quality audio, which was once considered sufficient to capture every aspect of sound perceivable to the human ear. We now know that many people can perceive differences in quality beyond what a CD is capable of reproducing, which brings us to a working definition of high-resolution audio.

Put simply, if a digital audio track manages to surpass the quality of a standard CD track, it qualifies as hi-res audio. ‘Quality’ may seem like a subjective term, but we can evaluate the quality of an audio track using two objective measurements — bit depth (expressed in ‘bits’) and sample rate (expressed in kilohertz, or ‘kHz’).

What is high-resolution audio?

High-resolution audio is generally defined as audio that captures more of the original track’s subtle nuances and details than is possible with standard CD quality. In practical terms, this means a more immersive listening experience, with greater detail and clarity. In technical terms, it means bit depths of at least 24 bits and sampling rates of at least 48 kHz — higher than a standard CD’s quality of 16 bits and 44.1 kHz.

Those may just sound like numbers to you. But it’s important to understand bit depth and sample rate if you’re interested in enjoying the best possible listening experience.

Bit depth and sample rate: The key components of audio quality

When we talk about audio quality, we’re really talking about how fully and accurately an audio track captures the live sound of a recording. The better the quality, the more you feel like you’re actually in the room listening to a song performed live.

When recording live sounds onto digital audio formats, sound engineers generally want to capture as much dynamic range and frequency response as possible. Dynamic range is the difference between the quietest and loudest sound a recording can produce. Frequency response measures how well an audio track can produce frequencies from the lowest bass to the highest treble.

Each of these qualities corresponds to a specific measurement: bit depth and sample rate, respectively.

• Bit depth describes how many tiny pieces of information (i.e. ‘bits’) make up a single snapshot of a soundwave. The higher the bit depth, the more dynamic range the sound has — in other words, the more you can hear the loudest and quietest sounds.
• Sample rate describes how many snapshots (i.e. ‘samples’) are taken from the original soundwave. The higher the sample rate, the more the track captures the details of the original recording. Higher sample rates also capture and reproduce higher frequencies of sound.

As noted above, hi-res audio files typically feature a 24-bit bit depth and a sample rate of 48 kHz or higher. Both measurements are significantly higher than standard CD quality, which features a 16-bit bit depth and a sample rate of 44.1 kHz.

The below graphic visualises how a 24-bit recording actually captures a wider dynamic range of sounds. You might compare it to using a bigger net when fishing to catch more fish. We’ll get to that in a moment.

What audio file types support hi-res audio?

You might be wondering, If hi-res audio is so great, why haven’t we been listening to it forever? The answer comes down to technology. More specifically, it comes down to what different audio file types can support — and how big they must be to fit all that audio data.

One of the major differences between audio file types relates to a process called compression. This process takes the original audio waveform of a recording and shrinks it down to a smaller size that’s easier to transfer and store.

Compression can be split into two general types:

• Lossy compression loses some of the data contained in the original audio recording, which may result in a perceivable loss of audio quality.
• Lossless compression retains all of the audio information from the original recording, while still managing to shrink the file size. This is the type of compression associated with hi-res audio.

Some audio file types are uncompressed, and these also retain every aspect of the original recording. The downside is that these file sizes can be huge! So, historically, there’s been a real trade-off between audio quality and storage/convenience. This is beginning to change with the evolution of new file formats that support lossless compression.

To better visualise this, let’s trace the path of how a song recorded in hi-res (24-bit, 48 kHz) makes its way to the listener in the form of an audio file:

As you can see, the original recording is typically split into two versions for distribution: an uncompressed raw audio format, and a standard CD format. Data from the uncompressed format can then be used to create lossless file formats like FLAC and ALAC, as well as lossy formats like MP3 and AAC.

Hi-res vs. lossless audio

Another thing you may have noticed from the above diagram is that both hi-res and CD quality are labelled ‘lossless’. Audio encoded in the CD format is indeed considered lossless because it represents a precise and accurate snapshot of the analogue waveform. Though it may not have the same dynamic range or frequency response of a live performance, a CD doesn’t compress the data in a way that distorts or loses information from the original recording.

When comparing hi-res audio to lossless audio, the salient point is that hi-res audio isn’t simply about whether data is lost in compression. It refers specifically to audio that offers higher bitrates and sampling rates than what standard CD quality can achieve. So, a lossless audio track can be hi-res, but it isn’t necessarily hi-res.

Does high-res audio sound better?

The short answer is yes. But not everyone can really tell the difference.

Remember, standard CD quality (16-bit, 44.1 kHz) was once thought to include the full range of frequencies humans can hear. It’s since been shown that some people can actually hear frequencies beyond what CD quality is capable of reproducing. For these people, hi-res audio will almost certainly sound better. But for people whose hearing is damaged or not as good as it once was, it may sound no different from a CD or even an MP3.

If you’re wondering whether you can hear the difference, this audio test from NPR is a good starting place. For the most accurate results, be sure to listen to it through a pair of quality headphones like Sonos Ace, or through a system that’s capable of high-fidelity audio playback.

How to listen to hi-res audio

More streaming services are beginning to offer lossless or hi-res audio options. Amazon Music, for example, now has many songs available in Ultra High Definition, which they define as “better than CD quality audio (up to 24 bits, 192 kHz).” Apple Music’s ALAC file format is also capable of delivering up to 24-bit/192 kHz hi-res audio, though you’ll have to switch it on in your settings.

A true hi-res audio experience requires not just a particular streaming service or file type, but also equipment that’s capable of accurately reproducing the depth and detail of original recordings.

You can actually stream lossless audio over Bluetooth with Sonos Ace headphones — and it’s sure to sound incredible. But for the most accurate hi-res playback experience, you’ll need to connect to a WiFi-enabled speaker, or use Sonos Ace’s included 3.5 mm cable to plug your headphones into an audio source.

It’s not just music that benefits from hi-res audio. A Sonos home theatre system brings hi-res sound quality to your favourite films and TV shows. A premium soundbar such as Arc Ultra not only supports hi-res audio, but beams sound around the entire room for a more immersive experience.

Experience hi-res audio with Sonos

As the capabilities of streaming and file types continue to expand, Sonos is keeping pace with products capable of doing justice to hi-res audio. You can see which streaming services support hi-res playback (such as Apple Music and Amazon Music) in our support article here. Our lineup of wireless speakers feature several premium options capable of hi-res playback, including Era 300 and Five.

But it doesn’t stop there. Our soundbars offer a first-class high-res audio experience, thanks in part to Dolby Atmos technology and their ability to create an immersive, multi-dimensional soundstages that redefine the possibilities of spatial audio. And our premium over-ear Sonos Ace headphones plug in with a 3.5 mm for a hi-res experience that’s all your own. (Sonos Ace can also achieve lossless quality via Bluetooth or a USB-C connection.)

If you’re interested in upgrading your home audio setup to hi-res, get in touch with a Sonos expert by phone or chat.

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