High-resolution audio explained

AP News
Posted: Jun 26, 2015 12:59 PM

LOS ANGELES (AP) — In recent times, musicians like Neil Young and James Taylor have come out to tell you that the quality of music you've been listening to for the last 20 years is dreck.

The cutoff they usually point to is around the turn of the millennium, when the iPod and ubiquitous MP3 standard took off, followed by Apple's AAC. These file formats, while conveniently small, trimmed sound for space, which critics say gutted the soul out of the art.

The digital alternative being offered is what's broadly known as "high-resolution" audio.

Here's a primer on various hi-res providers:


The Young-backed PonoMusic store and sites like HDtracks use files sampled at as high as 192 kHz, or 192,000 times per second. That's good to capture sound waves up to half that frequency, or 96 kHz.

But human hearing drops off around 20 kHz, contained amply by the good old CD with its 44.1 kHz sample rate. And resolution doesn't improve for sounds in the frequencies that you can hear.

Most headphones and speakers have frequency responses that top out around human hearing, too. One benefit of the higher sampling rate, however, is it allows engineers to place necessary filters further outside the range of hearing to reduce some distortion that we can hear.

PonoMusic and HDtracks also tout using 24 bits per sample, up from 16 in CDs. This merely extends the dynamic range, or the difference between the loudest and softest sounds. That's also more than necessary, unless you want a range from the tiniest whisper to a jet engine blasting. One benefit of using more bits is that it helps capture reverberation and room echo more precisely for relatively quiet sounds.


Both Tidal and Deezer Elite offer CD-quality streaming for a premium price, $20 per month versus $10 a month for standard on-demand listening. The format is known as "lossless" because no sounds are lost to data compression.

Tidal even offers a video that demonstrates the sounds you are missing when you use a compressed audio format like an MP3.

But we don't actually hear a lot of sounds that have been removed. There are two kinds of "masking" that occur with all sounds, "spectral masking" in which a louder sound can cover up a quieter sound that is nearby in frequency, or pitch; and "temporal masking," which means big sounds muffle sounds that come before and after it. In other words, if a bird tweets right before or after a cannon blast, you're probably not going to hear the bird. Removing it doesn't affect our perception of it.

And 24 writers and editors of The Associated Press across a range of listening equipment couldn't tell the difference between CD-quality files and compressed files on the Tidal website.

The journalists picked the high-fidelity choice a measly 2.2 out of 5 times on average. Two people got zero correct, and no one got them all.