Why MP3s (& MP4s) suck
In 2005 I bought Laura, my wife, an iPod for Christmas. She loaded up a bunch of tunes, put it on shuffle play, and fell in love. Shuffle play would be very nice to have on our main sound system and Apple said you can have “CD quality sound” if you connect your iPod up to your main sound system using their dock. Sounded good to me. I hooked Laura’s iPod up to our sound system according to the Apple instructions to give it a test run. I was fully prepared for the sound quality from the iPod to be less than the CD no matter what Apple said about “CD quality sound” but I thought we’d be using the iPod for shuffle play when we were busy doing things around the house and sound quality wouldn’t be so important. When we wanted to listen, we’d use the CD player. We picked a song that she had ripped to the iPod at random, cued up the CD the song had been ripped from in the CD player, and got ready to compare the two. First I played about 30 seconds of the CD to have a reference, stopped it, and then played the same song on the iPod. It literally hadn’t played 10 seconds before we both knew we wouldn’t pay 20 cents for sound that bad let alone the $200 or whatever it was that iPod’s cost at the time. “CD quality sound”? Not even remotely close. I like music. A lot. I’d go out of my way to avoid having to listen to music that sounded this bad.
I hadn’t payed much attention to MP3 technology because I hadn’t had any interest in downloading music from the net. I thought the awful sound might be due to something we were doing wrong based on not knowing about the tech so I started to learn about it. Took about 5 minutes to see what the problem is. With MP3 and MP4 compression you’re throwing away most of the information present on the CD; it’s not surprising that what you have left sounds terrible.
Music is sound and sound propagates as a wave that is continuous in time. Digital recording technology is not continuous in time, it records information in discreet bits. When music is digitally recorded the continuous sound wave is sampled many times each second. In other words, very brief snapshots of the sound wave are taken very quickly and then these short sound samples are strung together at playback so that it sounds to the listener like you have one continuous sound. Because the bits of sound that fall in between each of the samples is lost, the digital recording has less information in it than the original sound wave. This is why a digital recording never sounds just like a live instrument or voice. The more samples you take each second, the more of the original sound wave you capture and the better the music sounds (assuming each of the samples is the same size). The number of samples taken per second is called the bitrate and it is usually measured in kilobits per second abbreviated as kb/s.
MP3 and MP4 are compression formats that are designed to shrink the size of digitized files so that they take up less space when stored and less bandwidth when moved. They are called “lossy” compression formats because information that was present in the orignal file is thrown away or lost when the file is compressed. The designers of lossy compression formats for music claim that some of the info that is thrown away is “inaudible, or less audible to human hearing”. Maybe it is, maybe it isn’t. And what, exactly, does “less audible” mean? Lots of room for marketing bullshit like “CD quality sound” there.
The question you want to ask is, how much info are they throwing away? The bitrate for standard recording on a CD is 1411.2 kb/s. MP3 and MP4 allow for variable bitrates with the trade off being smaller files but lower quality with lower bitrates and higher sound quality but larger files with higher bitrates. The minimum “it’s good enough” bitrate (in other words, the crappiest sound quality they think people will pay money to hear) that has become something like an online standard is 128 kb/s. This is the bitrate iTunes uses, for example. Now compare the amount of info on the CD and the amount of info on the MP3 or 4 file ripped from the CD; 1411.2 kb/s of info on the CD and 128 kb/s left in the MP file. An MP3 or 4 file has only kept a wee bit over 9% of the info that is on the CD. In other words, a wee bit less than 91% of the musical info on the CD is thrown away when it is compressed into MP3 or MP4 format.
91% of the info is lost!? Are you kidding? Nope. If you threw away 91% of a two hour movie, you’d be left with an 11 minute film. How good would your favorite movie be if all of it except for 11 minutes was cut? For a lot of films you’d still be watching the opening credits when the movie ended. If you threw away 91% of an hour long TV show, all you’d have left would be commercials – and you wouldn’t even have half of those. How happy would you be if 9 out of every 10 songs on your iPod were deleted? How well would your head do if your body was cut off and thrown away? The question shouldn’t be why does it sound so bad, it should be why does it sound like anything at all.
The problem here is related to bandwidth, in both senses of the term. “Bandwith” traditionally refers to a range of frequencies such as the range of audio frequencies, or the bandwidth, that humans can hear. When MP3s and 4s eliminate info from the original CD source they probably shrink this bandwidth by cutting off the top and bottom ends of the human auditory bandwidth – they cut off the high treble and the low bass. In order to achive a 91% reduction they must also eliminate a lot of info from within the bandwidth they keep. By cutting way back on the richness of the info present in the bandwidth they retain, all of which is info people make use of when listening to music, MP3s and 4s are severely compromising the quality of the music as originally recorded.
This drastic reduction of info within the bandwidth of human hearing that results in such a marked decrease in sound quality is carried out in order to save “bandwidth” in the “data transfer rate” sense of the term. Internet connections, fast as some of them currently are, cannot move the enormous amount of data recorded at a 1411.2 kb/s bitrate at speeds that will make consumers happy and encourage them to download music from the net. They also take up a lot more storage space on the hardrives of playback devices like iPods. Would you have been willing to pay whatever you did for your iPod if it only held one tenth as many songs?
The multinational companies marketing the hardware you buy to listen to music in MP3 and 4 formats tell you that the sound they produce is indistinguishable from the sound present on a CD of the same music. “CD quality sound!” They tell you panels of experts say so. If you believe this, I have a beautiful parcel of land in sunny Florida you’d surely been interested in buying. Another approach they take is to tell you that, yes, CDs will sound better than MP3s and 4s but only if you have a really expensive “audiophile” sound system that is well beyond the means of most people. The people who make cheap, crappy electronic equipment that can be mass-produced in low-wage factories outside the US and sold for enormous profits at Best Buy would love it if you believe this. You’re going to have to have better sound reproduction equipment than an iPod or a $250 stereo-in-a-box to hear the difference between a CD and an MP3, but not that much better. Another way to look at it is this: The difference between an MP3 or 4 and the same music on a CD is huge. If your sound reproduction gear doesn’t let you hear it, you’ve got shitty gear. Most CDs sound infinitely better on a decent entry level sound system. Just because you can’t hear that it’s there doesn’t mean you’re not missing it.
Discussion of other issues with limitations in sound quality of music heard in compressed formats can be found in the post The (Deteriorating) Sound of Music.
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