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The new Hi-Fi debate and the science of sound

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Music today is listened to almost exclusively through digital compression. The most common digital compression format is called MP3 (MPEG-2 Audio Layer III.) A competing digital compression format is FLAC (Free Lossless Audio Codec.)

Many audio enthusiasts believe that FLAC provides significantly more accurate sound reproduction, which can be heard by listeners. Most audio enthusiasts, however, hold that more is not always better, and that the FLAC format does not produce any audible benefits for listeners. PONO is a highly publicized FLAC-based digital music player, a high-tech MP3 player of sorts, that promises significantly better music reproduction.

Both FLAC proponents and skeptics use math and physics based arguments to explain their position. Here’s a brief overview, with links to articles that have more detail.

Our physics article on sound :
Sources of sound
The physics of sound.

Hi Fi classic ad

On Cnet, Stephen Shankland writes about the science of sound, in the latest generation of audio devices:

Pono Music’s roaring success on Kickstarter, raising $4.3 million so far, shows that thousands of people believe better audio quality is worth paying for. The company — backed by star musician Neil Young and selling a $400 digital audio player along with accompanying music — promises people will hear a difference between Pono Music and ordinary music that’s “surprising and dramatic.” The company’s promise is based in part on music files that can contain more data than not only conventional MP3 files, but also compact discs.

… Just as some skeptics think 4K TVs is wasted on human eyes, which mostly can’t perceive an image quality improvement over mainstream HD 1080p under normal viewing conditions, others think CD audio technology that’s now more than three decades old is actually very well matched to human hearing abilities. For playback, they’re fine with two key aspects of CD audio encoding: its 16-bit dynamic range, which means audio is measured with a precision of 65,536 levels, and its 44.1kHz “sampling” frequency that means those levels are measured 44,100 times each second.

“From a scientific point of view, there’s no need to go beyond,” said Bernhard Grill, leader of Fraunhofer Institute’s audio and multimedia division and one of the creators of the MP3 and AAC audio compression formats. “It’s always nice to have higher numbers on the box, and 24 bits sounds better than 16 bits. But practically, I think people should much more worry about speakers and room acoustics.”

Pono’s recordings will range from CD-quality 16-bit/44.1kHz to 24-bit/192kHz “ultra-high resolution.” To house the data, Pono follows in the footsteps of the digital audiophile industry by sticking with a file format called FLAC (Free Lossless Audio Codec) that compresses files for smaller sizes but not to the degree of alternatives including MP3 and AAC that throw away some of the original data. The company also is betting its success on a player with better electronics and a catalog of HD music designed to let listeners hear music true to its original sound in the recording studio.

…The idea is that more data allows a higher dynamic range — the span between the loudest and quietest passages of music — and comes closer to the detail of live, original sound….

A prominent part of the case against high-resolution audio is a 2007 study by E. Brad Meyer and David Moran of the Boston Audio Society – that concluded listeners couldn’t tell the difference between SACD and DVD-A music on the one hand and CD-quality versions of the same recordings on the other.

Results of a blind audio test. By E. Brad Meyer and David R. Moran

In that experiment’s 554 tests, listeners correctly identified when a SACD or DVD-A recording compared to a CD only 49.8 percent of the time — in other words, they didn’t do better than randomly guessing.

Another high-profile non-believer is Christopher “Monty” Montgomery, an engineer who writes codec software for the Xiph.Org Foundation and who works for Firefox developer Mozilla. The most prominent part of his effort is a video arguing that CD quality sound is good enough. Montgomery’s video, illustrated with lucid demonstrations and backed by a blog post, persuasively debunks misconceptions such as the idea that encoding music digitally reduces it to a series of jagged stairsteps instead of the original smooth curves.

24/192 Music Downloads …and why they make no sense:

Video on 24/192 music downloads: D/A and A/D | Digital Show and Tell (Monty Montgomery @ xiph.org)

Video on 24/192 (second copy)

Montgomery and his allies have yet to persuade everyone on two points, including the idea that 16-bit resolution and 44.1kHz is sufficient.

“Monty is wrong. Twenty-four bits does matter — but for a very small sliver of the music business,” said Mark Waldrep, an audio engineer who’s founder and chief executive of AIX Records and iTrax.com and who focuses on high-resolution audio — including efforts of his own to debunk some claims. And of the sampling frequency he said, “I’d rather err on having those frequencies in the signal rather than assuming we don’t need them.”

But Grill thinks any purported benefit would be lost in the real world. “The limiting factor is the loudspeaker, the room acoustics, and the human ear,” he said.

From “The Digital Myth: Why Digital Audio Sounds Better Than You Think”
By Gordon Reid

Now, perhaps the greatest myth in digital audio relates to the misconception that digital signals are shaped like staircases, and that much of their ‘brittleness’ is a consequence of the steps. This is nonsense. Digital signals are not shaped like anything — they are sequences of numbers. Unfortunately, the type of representation in diagram 8 has led many people to confuse graphics with reality.

Let’s be clear. When the samples in a digital signal are converted back into an analogue signal, they pass through a device called a reconstruction filter. This is the process that makes the Sampling Theorem work in the real world. If there are enough samples and they are of sufficient resolution, the signal that emerges is not only smooth but virtually identical to the analogue signal from which the samples were originally derived. Of course, it’s possible to design a poor reconstruction filter that introduces unwanted changes and artifacts but, again, this is an engineering consideration, not a deficiency in the concept itself.


Source: Sound bite: Despite Pono’s promise, experts pan HD audio

Another great article on this topic

What is FLAC? The high-def MP3 explained. C|Net

Here is a detailed physics experiment showing an analysis of FLAC and MP3 audio files. The result is that there is no audible difference between any of these formats! Each is equally good. There are, however, significant problems in how iTunes engineers (and probably engineers from other companies) are choosing to compress original recordings. many times they make choices which negatively affect the music. However, those errors are independent of whether one ends up using MP3, FLAC or other formats.

FLAC vs WAV vs MP3 vs M4A Experiment : http://www.computeraudiophile.com/blogs/mitchco/flac-vs-wav-vs-mp3-vs-m4a-experiment-94/

Also see “There are no “stair steps” in digital audio ! What The Matrix can teach us about “resolution””

There are no “stair steps” in digital audio ! What The Matrix can teach us about “resolution”

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