September 28, 2011 at 3:26 PM
"You may be surprised at what you are not hearing online"
First, I must apologize for the delay to those who have anticipated my posts. Life sometimes gets in the way of the most well-meant intentions. This month, I will discuss the degradation of audio quality in the name of convenience.
When was the last time you sat down in front of a quality home stereo system for the express purpose of listening to a new recording or one of your favorite selections from a music collection? Like me, it was probably a while back--much more so than it would have been 10 to 20 years ago. Some of this could be attributable to the quickening and demanding pace of your life, though I would surmise an additional reason would be the declining quality of music reproduction that is foisted upon the general listening populace.
Audiophiles still purchase vinyl LPs to hear through vintage tube amplifiers in a tuned environment. There is also an increasing availability of quality digital recordings with studio-quality resolution as high as 192 KHz 24 bit. But this is certainly the exception in the day of MP3 players, earbuds and hearing loss among young adults.
Let’s take a quick look at some of the digital formats in use today. In contrast to the aforementioned high-end recording studio resolution, a compact disc recording that is considered “master quality” is less than one quarter the sample rate at 44.1 KHz and two thirds of the bit rate at 16. This has been deemed by the industry to be the standard, as it provides for the reproduction of a range of primary frequencies that exceed the ability of humans to hear. This does not take into account harmonic frequencies beyond the 20 Hz to 20 KHz range that an audiophile will contend are part of the listening experience. Calling this CD resolution the uncompressed audio standard, let us examine the most commonly used lossy
compression algorithm that we know as MP3.
This compression format complies with the 44.1 KHz 16 bit standard, but in order to make the file size smaller and more convenient to distribute and store, discards bits of information deemed to be “un-essential” to the interpretation of the resultant audio. A comparative figure to uncompressed audio is usually considered to be a sample rate of more than 300 kb/s. This can be compared to sample rates of audio that is streamed or downloaded at 96 to 128 kb/s. You see that this audio is compressed down to be about one third of the size of uncompressed audio. This means that the other two thirds of
the audio information has been discarded in order to make the file more convenient to handle. By all measurements, this is well below the quality of the all but extinct analog cassette or 8-track cartridge, albeit without the tape hiss, wow, flutter and other measurable distortions. In fact, it is comparableto AM radio, which these days has been relegated primarily to talk radio that is acceptable for a low frequency response reproduction.
It is easy to find the bit rate of a downloaded audio file by simply examining the properties of the file on your computer. Music providers from artist to record label have realized that they can give away a taste of their music for free and still sell quality reproductions to customers who are really interested in hearing all of the music. Music purchased online is normally at or above 256 kb/s. So when you actually pay to download a track, you are getting at least twice the audio information as you get when you get a free download offer or torrent dump. You might be able to understand the lyrics and hear the rhythm of a low bit rate download, but would you really want to play that quality for party guests in your home?
Most high-quality audio heard nowadays accompanies video in home theater systems. As an experiment to demonstrate the degradation of reproduced audio, try listening to a song from a DVD soundtrack or a CD and compare it to the same song on a YouTube video. You may be surprised at what you are not hearing online.