Can You Really Tell the Difference Between Music at Different Bit Rates?

(Note: this article is written for Mac users. If you have Windows tools to recommend, please mention them in the comments.)

The bit rate debate regarding compressed music is one that will be around for a long time. Some people think that any compression of music files is anathema. Take Neil Young. He complained about the poor quality of digital music files, while greatly misunderstanding much of what is involved in compression. He claimed that only “5 percent of the data present in the original recording” is present in MP3 files, without specifying the bit rate used or the original sources, and without understanding that compression is more than just lopping off bits of the music. (Andy Doe, writing on the Naxos Blog last year, published an article, All About Bitrates, explaining how compression works. You should read this to understand some points that most people overlook.)

When you start ripping music, and decide what bit rate to use, you have several options. You could go for lossless, which compresses music around 40-60%. One advantage to this is that you can then re-convert the lossless files to a lower bit rate if you want, keeping the originals as archival copies. But lossless files take up much more space. While this isn’t an issue on computers – hard drives are huge these days – it is for portable devices like iPods or iPhones.

If you don’t use a lossless format, you have to decide which format to use (AAC or MP3), and what bit rate. For a long time, Apple sold music at 128 kbps at the iTunes Store. It is now 256k, which is roughly what Amazon uses in their MP3 store (their music is in VBR, or variable bit rate, so it is not exactly 256k). This is an excellent compromise between space and quality. But you might want to go even lower. What’s important is to find the point at which you cannot hear the difference between an original file and a compressed file, and stay above that bit rate.

To do this, you need to perform what is called blind ABX testing. You are presented with music and don’t know which bit rate you are hearing, and you must choose whether you think it is compressed or not. While this test takes a bit of time – you need to rip tracks at different bit rates, then test yourself, one pair of tracks at a time – the results can be interesting.

To start with, find several songs or tracks that you know very well. It’s best to use familiar music, because you will be able to hear more of the differences (if any) because of your familiarity with the melodies, arrangements, etc. I’d recommend not ripping full albums for this test, but rather individual songs or tracks from different albums.

Rip these tracks from CD in lossless format. In iTunes, go to Preferences > General, then click on Import Settings. Choose Lossless Encoder from the Import Using menu.



Next, add the tracks you have ripped in lossless format and to a playlist. Select them all and press Command-I, then enter an album name, such as Lossless Tracks. You’ll want this later to be able to find them.

Back in iTunes’ Import Settings preferences, change to the AAC Encoder, and set the bit rate at 64 kbps. Yes, I did say 64 kbps; you want something that is low enough so that you are guaranteed to hear a difference. As above, create a playlist, then tag all these tracks in an album 64 kbps Tracks.

Go to the Mac App Store and download the free ABXTester. This application lets you choose two tracks, then listen five times to a random selection of those tracks, and choose the one you think is better.



Click on Select A. Navigate to your Lossless Tracks album, and select a track. Click on Select B, navigate to your 64 kbps album and select a track. You know that the first track is lossless, and that the second severely compressed.

The next step is to try five tests, listening to tracks selected at random, and choose whether you think each track is A or B; in other words, which is the better sounding track. For example, when you listen to the first track at X1, if you think it’s the lossless track, click on A; if not, click on B. At the end, click on Check answer, and see how well you did.

I suggested starting with 64 kbps tracks so you can hear a difference. The next step is to find at which point you can no longer hear that difference; at which point your results are no better than random (2 or 3 correct, or a score of 40 or 60%). Rip the same tracks at several other bit rates: I suggest you use 128, 256 and 320. If you do too many, the test will take too long. Label each group of tracks. You can now either go to the next level, 128 kbps, for track B, and go through the tests, or you can start from the other end, at 320 kbps, and work your way down. No matter what, I think you will be surprised.

A couple of notes. First, make sure you do this test on the stereo equipment or headphones you use to listen to music. (If you’re curious, these are the headphones I use.) You might find that, if you try this out on a friend’s Really Good Stereo that you might hear a difference. If you don’t plan to buy the same Really Good Stereo, don’t bother testing on it. If not, you won’t hear a difference; I guarantee it.

Of course, this begs the question: if you don’t have good stereo equipment or headphones, is it worth using a higher bit rate? If you’re thinking of upgrading your stereo or headphones, you might want to plan ahead and do this test on better equipment to see if it’s worth ripping your music now at a bit rate higher than where you can currently hear a difference. And if you have plenty of disk space, you might want to rip your music in lossless format for archival purposes, then convert it to a lower bit rate for use with your portable devices. With iTunes, you can rip in Apple Lossless format, then have iTunes convert your music files during the sync process to 128, 192 or 256 kbps.

Also, if you want to compare high-resolution files, make sure you open Audio MIDI Setup (in the /Applications/Utilities folder), and set the sample rate to the highest possible setting. Otherwise, you won’t hear the full resolution of these files.

I’d be interested to hear your results. Feel free to post them in the comments. If you can really hear a difference between a lossless file and a high-bit-rate compressed file, please also post what kind of stereo equipment or headphones you are using.

Share this article:Tweet about this on Twitter0Share on Facebook0Share on Google+1Share on LinkedIn0





46 replies
  1. Dave R says:

    For several years I ripped all my CD’s at 192K AAC. Since external drive prices have dropped over the last few years I switched to ripping everything at 320K MP3. I just ripped 3 of my favorite albums (The Who’s Quadrophenia, The Stone’s Some Girls, and Coltraine’s A Love Supreme) in Apple Lossless… I couldn’t hear a difference between any of them using ABXTester. I’m listening through Grado SR60 headphones plugged into my iMac with no equalization.

    At some point in the next few months I’m going to get a B&W Zeppelin or a similar high-end iPod speaker set-up, so it will be interesting to try the 192K vs Lossless comparison then. Until then, I don’t feel so bad about all those thousands of CD’s ripped at 192K to save space.

    Thanks for pointing out this great free tool.

    Reply
      • Dave R says:

        My wife uses a PC. Once in a while she’ll hear something she likes from my collection and want it on her laptop. It’s easier to drag an MP3 file to a thumb drive and add it to her iTunes that way than to find the original CD and import it. Sonically, I can’t hear a different between 320 AAC and 320 MP3.

        Reply
        • Steven de Mena says:

          iTunes for Windows must support AAC, no? How else could Windows users purchase [AAC encoded] music from the iTunes store?
          My brother used WinAmp and I had to find an AAC codec for him to play AAC and ALAC, so that was a little more work.
          As to the blind tests, it’s been a LOT of work over many years ripping my entire CD collection. I only want to do it once so I do it in Apple Lossless. I probably can’t hear the difference but psychologically I feel better that I’ve done it the best that I can. :)

          Reply
          • kirk says:

            Yes, iTunes for Windows has supported AAC since Apple opened the iTunes Store (which is when they started using AAC). In the early days of iTunes, it didn’t support AAC for either Mac or Windows. I remember ripping my first CDs with iTunes in MP3.

            One reason to rip in Apple Lossless (which I don’t do personally) is to have an archival copy in a lossless format, which you can later convert to whatever format(s) you want.

            Reply
  2. João T. da Costa says:

    Be careful with your advocacy of ABX tests. The Audiophile Inquisition will come to get you.

    Reply
  3. Gene Steinberg says:

    Speaking as someone who used the original A/B/X Comparator years ago, I think Kirk should welcome The Audiophile Inquisition and tell them what they can do with themselves. :)

    Peace,
    Gene

    Reply
  4. Karl says:

    It would be revealing to invite some of the world’s best sound engineers to a studio with top audio equipment for a blind bit rate test of tracks they themselves have recorded and know intimately well. Would they distinguish the lossless format?
    If not, many an audio-phool would be at a loss for words.

    Reply
  5. Tom Negrino says:

    As he was dragged to the bonfire (securely trussed with Shunyata Research’s $495 SideWinder VTX power cord; every facet of the SideWinder VTX power cord has been optimized and measured for ideal peak-current delivery and isolation from high-frequency noise. Despite its reasonable cost, the SideWinder VTX uses the same complex wire-geometry that goes into in Shunyata Research’s more expensive power cord models.), Kirk McElhearn was unrepentant.

    “You can’t hear the difference!” he shouted. “You people are fools!”

    The mob broke into a chant. “Our ears are golden! Our ears are golden!” The greedy flames licked higher.

    Suddenly, a tall figure strode into the firelight, knocking aside maddened audiophiles right, left, center, and to the rear. Freeing McElhearn from his captors, he said, “I’ve got this one, Kirk.” Then he faced the crowd.

    “Disperse!” his voice boomed (though clearly, without sounding boomy at all). “I am Mid-Fi Man, and I have come to cure you from the illness of Audiophile Dementia!”

    “Never!” the mob howled (though, again, with less than .0001% THD, and in a beautifully smooth and transparent fashion).

    “It’s true!” said Mid-Fi Man. “You can get great sound at an affordable price!”

    To be continued…

    Reply
  6. Matt says:

    I read an article this week about the new “iTunes Mastered” audio files available and an engineer slammed them based on this test:

    “a null test. Shepherd explains this procedure as a method of reversing the phase of a song’s waveform so that after a song’s waveforms and volumes are matched in software a mixing engineer can play them back to see if the song’s out of phase waveform cancels or nulls out the normal version of the song.”

    It would be interesting to figure out how to do this in Audacity and really “hear” what you are losing when you compress music.

    Here’s the article: http://www.cepro.com/article/apples_mastered_for_itunes_is_it_legit/

    I signed up for iTunes Match as a easier way of upgrading my old low bitrate albums to 256k AAC rather than re-compressing from the CD. Definitely worth the $25 right there

    Reply
  7. robertjlamb says:

    For all the technical expertise above, looks like mine is the first confession. My ears, after 40 years of going to gigs, playing in bands, and home recording, can’t tell the difference between AAC and 64k mp3, never mind the intermediates. This is true both over headphones and through Tannoy home studio monitors, played through the audio output of an iMac.
    Guess I’d better hand the mixing duties over to younger and fresher ears…

    Reply
  8. robertjlamb says:

    Never mind hearing the difference, I can’t even name them right – I mean “Apple Lossless and 64k”, not AAC…

    Reply
  9. tomcoll says:

    No worries – I usually rip all my music to Apple Lossless and then later create 320 kbps versions to carry around on my iPod and Android smartphone, but then just out of curiosity I tried first 256, then 192 and then 128 rips to see whether or not I actually could hear the difference.

    Well, 256 and 192 are transparent, and with 128, I can hear an eeeeveeeer so slight difference if I listen extremely carefully (with eyes closed and using my high grade Sony headphones), but the difference is really just minuscule. 64 is a fraction worse, but still surprisingly good.

    The funny thing is that the standard iPod earbuds on the other hand have a gross negative impact on the sound quality. Listening to music with those is an almost unbearable experience. I think with those earbuds, I would not need anything higher than 32 kbps rips or maybe even 24 kbps.

    Something that also bothers me, is when people claim that they can hear the difference between lossless and 256 In their cars. IN THE CAR? With all the noise and grumbling from the engine, the wind and the tires against the road surface? Are they kidding????

    Reply
  10. Aescalpius says:

    For most average systems, one will probably not hear much of a difference. However, on a good audio system, the difference between a lossy format and CD or above bit rates the difference is readily apparent, even to someone who listens only casually, like my wife. On a system like this, the lower bit rate music is still enjoyable but it is clearly not as “real” as the full bit rate musc. Having said that, I’ve heard some very well recorded albums at a lower bit rate that were superior to a poorly recorded CD at full definition.
    If your audio system can’t resolve the differences, or you can’t hear them, then don’t bother with higher bit rates. If it can, and you can appreciate the difference then go with higher bit rates. My entire library of ~20,000 songs is ripped at CD quality or above, in the case of HD music files.
    On my iPod or iPhone, I downsample everything to 256K because I can’t really hear the difference on that device, even with good headphones.
    To say that there is no difference is simply not true. To say that most can’t hear the difference on the equipment they have, well I’m sure that’s quite accurate.
    The bottom line, though, is that you enjoy your music, in whatever format you may find it.

    Reply
  11. Aescalpius says:

    Oh, and BTW, Shunyata power cords and power filters make a huge and dramatic difference. But don’t believe me, go listen for yourself.

    Reply
  12. Gene Steinberg says:

    If you believe, anything will sound different, even putting your CD player on special coasters. In the real world, most of it is snake oil. That’s why real audio engineers do blind listening tests to verify audible differences.

    Peace,
    Gene

    Reply
  13. Aescalpius says:

    Gene, Gene, must we get into this? I wasn’t going to take your bait, but here it is but I don’t want to engage in an argument with you. I respect your opinion but here is my empirically based one:

    Everything I have added to my system was done after blind listening with both audiophile and non-audiophile friends. Some things make a difference, some don’t and yes, some are snake oil. Some are merely different, not better. Your ears can tell the difference. In the end, you vote with your dollars. If you can’t hear the difference don’t presume that others can’t. Critical listening, like anything else, is both innate and learned. Enjoyment of music is the ultimate goal and many audiophiles get caught up in listening to their gear and not their music. Most of my casual listening is streamed from Rdio as I work in my office and around the house and I enjoy the variety immensely. I’m listening to an artist I’ve never heard before right now and she’s marvellous. When I find something I like, I go buy the CD or the SACD or the DVD-A or the HD download because it’s better and the experience is more fulfilling to me when I want to sit down and devote my attention to the artist’s expression. There is a reason why LPs and SACDs have not died and why HD downloads are growing in popularity – they sound better than low-def music formats when you have the equipment that can resolve the difference.

    Why do you think top recording studios spend thousands and thousands of dollars on things like power filters and power cords and proper cabling and shielding and the like? Because it makes a difference. There is a big difference in the sound of a recording from a top recording studio and a poor one. That often makes more of a difference than any subsequent format in which the music is later played.

    Oh, and yes, proper mechanical isolation of a CD player on “special coasters” and the like (at least some of them) can make quite a significant positive musical difference.

    Believe it or not, that’s your choice but don’t presume to tell me what I can or cannot hear or imply that it’s merely a matter of belief. I used to scoff at such things as well until I heard what proper mechanical and electrical isolation can do. It won’t make a silk purse out of a sow’s ear. But, when you have decent equipment as a starting point, such tweaks can be quite worthwhile.

    Peace

    Reply
  14. Gene Steinberg says:

    Take a pill, man, you are way off the rails.

    Let’s start with what I wrote about, the special power cards and filters, and add to that your special coasters for CD players.

    Show us the double-blind listening test results that demonstrate repeatable audible differences for properly functioning equipment. If you wish to be scientific about it, tell us the reason why there should be an audible difference with fad products of that sort.

    Don’t presume to insult my intelligence. I’ve been at this game for years and I know the score. You are the one making the claims about audible differences; it has nothing to do with me. Let’s see how you do in the real world.

    Peace,
    Gene

    Reply
  15. Aescalpius says:

    Gene, I don’t want to waste our time on this. We are clearly entrenched in our respective opinions and won’t ever be able to agree on this.

    I’ve been at this game since the mid-eighties and I too, know the score. I am also a scientist and I fully understand what you mean by double blind studies, etc. You know as well as I do that there have been limited scientific efforts made in this regard. There are no absolutes in an endeavour that is, by it’s very nature, subjective. What I hear and what you hear are different by virtue of our physiology and psychoacoustics. It’s a subjective hobby by it’s very nature. What I hear at home in my listening room is the “real world”. You obviously don’t believe in these “snake oil” tweaks and that’s good for you, you’ve just saved yourself some time and money that you can put toward buying more music.

    Let’s just agree to disagree and go our separate ways, shall we?

    Happy listening ;-)

    Reply
  16. Gene Steinberg says:

    You are entitled to your opinions, but not your facts. I regard those things as snake oil for the simple reason that there is no valid evidence (and subjective listening is not valid evidence) that those tweako products make a proven audible difference — or even why.

    Have a nice day.

    Peace,
    Gene

    Reply
  17. Fidelis says:

    While I like using lossless where I can, just for archival reasons, I honestly can’t tell the difference between lossless and a good VBR MP3 from LAME.

    Then again, I don’t have a $10,000 audio system, either. :op

    Reply
  18. Drew says:

    I can. I took Come Undone by Duran Duran at 320 kbs and converted it to mp3 at 64kbs
    for the first few seconds I was like, “I can’t tell the difference.”
    but 10 seconds into the song when more instruments start coming in (particularly drum beats), I can hear a big difference in quality. The lower quality has a more muffled sound to it. Like I’m listening to music on a car stereo while standing outside the car… or something (not sure if that is the analogy I want). The 320 kbs version sounds crisper and cleaner. :) I’ll keep ripping lossless :)

    Reply
    • kirk says:

      Well, you can tell the difference between 320 and 64 kbps; most people can. Now try something in between: 256, 192, 160.

      Reply
      • Drew says:

        I didnt read the entire instructions. I thought the you were suggesting that 64kbs would be difficult, then after I posted, I finished the article to see your conclusion, and found that you wanted me to see higher bitrates. So you see my results now.

        Reply
        • kirk says:

          No, it should be pretty easy to tell that a 64 kbps file is compressed. It starts getting more difficult at 128, then at 256 it is indistinguishable to most.

          Reply
    • Drew says:

      I just did other bit rates
      I went up to the next level and tried 80 kbs, it was bit tougher to distinguish (as one would expect, but I did find the flaw and got 100%) The flaw in the 80 kbs, was the symbol thing in a drum set. In the 80kbs version it wasnt as crisp, had a slight staticness that would tend to trail about it. This one was tougher to spot, I had to listen to both tracks one after the other to spot it.
      At 96 kbs, I got 100%. However, this one I say is where I draw the line for this individual song. I spent too much time trying to find a difference, and in the end relied on instinct. I just felt like the better version punched the notes a little harder. like someone on a keyboard tapping the key vs hitting it. Now granted, this is just a feeling, not sure if it is supported by music theory or anything. But it did get me 100% (though this could just be luck :)
      I got a 60 at a 112 and I basically guessed. But I feel like the bitrate at which I will tell a difference will vary by song, so to be safe (and superstitious) I will continue ripping at lossless. Next I will compare a song I ripped at over a 1000kbps and see. :)

      Reply
      • kirk says:

        There’s no such thing as “over 1000,” unless you listen to a WAV or AIFF file (which is 1411 kpbs). A lossless file will generally be from 400 to 700 kbps, depending on the type of music.

        If you were to try 256 kbps, I guarantee that your results would be no better than random.

        Reply
        • Drew says:

          I ripped a cd into Apple Lossless and got as high as 1047 kbs, I also have tracks i Converted from Flac that go as high as 1411 kbps. Now whether most of that conversion is wasted space idk. but as for the ones i ripped from cd…

          Reply
          • kirk says:

            1411 is the bit rate of a CD, so it’s uncompressed. I’ve never seen lossless files at more than around 800, unless they are high-resolution. What type of music is the file that is 1047?

            Reply
        • Drew says:

          I just want to point out that I am arguing that there is a difference. I’m just as interested as you seem in your article. So please don’t mistake my post as an argument for difference. (and don’t assume that I think I know what I am talking about. I’m just reading what iTunes is telling me the bitrate is :)

          the song that I ripped myself into lossless (I’m not counting ones I converted and are much higher) is “Since I Met You” by DC Talk. I ripped it to Apple Lossless using iTunes. It has a bitrate of 1057 and the file type is .m4a

          Reply
          • kirk says:

            I understand. I’m just curious about a lossless track that compress so little. (Higher bit rate = lower compression.) I don’t think I’ve ever seen any that have an effective (average) bit rate above around 800 or so. The bit rate that iTunes displays is an average for the file.

            Reply
        • Drew says:

          Well don’t you want the Lossless Codec to compress it very little. That Bitrate isnt common for the codec btw. Even on the same CD. half or hovering right above or below ((950>) a thousand and then the rest are between 700 and 850

          Reply
          • kirk says:

            No, you want it to compress as much as possible. Lossless compression is like zip compression for files; none of the original data is lost. But you still want the files as small as possible.

            It’s interesting that you have a CD where the lossless bit rate is that high. I just found that song on YouTube, and it’s somewhat “noisy,” as in there are a lot of complex sounds. The music I’ve found that compresses the least is harpsichord music. Because of the way that instrument sounds, there is a lot of rich harmonic information in the high ends, and longer waves use more data.

            The actual volume may have an effect on compression as well, though I’ve never tested that. This song sounds like it is very loud and there is little dynamic range.

            Reply
        • Drew says:

          Yeah, all of these songs that are in the upper thousands are noisy (by your definition). There are a lot of things going on instrumentally in the background. It’s Killing Me is another one at 131.

          Reply
          • kirk says:

            So the trend toward louder music has an effect on compression. If there is more “data” in the original music, because of its volume, then you technically need a higher bit rate to achieve the same sound quality than you would if the volume on the CD were lower… (I’m going to check with an engineer friend about that, but it does make sense.)

            Reply
          • Drew says:

            oh btw i converted it to 160 kbs to see and I got an 80. But that is the limit for my ears. Of course, I dont really listen to that song a lot, so that might have something to do with it. But even so, side by side analysis proved fruitless for finding a quality difference. So, I am sold on the no difference theory. But being superstitious, I will still rip lossless

            Reply
        • Drew says:

          I think it does. I am only a student of Physics Undergrad right now, but from what I’ve learned of waves, it makes sense. But also thinking of how cheap speakers and sound systems tend to reproduce loud sounds with the same quality as too high and too low (for the system) frequency sounds. It seems like it would make sense.

          Reply
  19. Darren says:

    I’ve done a double blind test with 256AAC vs a lossless file, using headphones and a DAC vastly better than what 95% of people use…. and I had nothing. I didn’t even try to take the test… the files were completely indistinguishable to these 43 year old ears. I’d bet $20 that Neil Young couldn’t tell the difference either.

    I am very, very, very skeptical when anyone claims the difference is “night and day”. The potential for wishful thinking is so high that I simply can’t take you seriously unless you produce some objective evidence.

    There’s no such thing as “the perfect recorded music experience”, because recorded music is inherently a compromise. Enjoy your indistinguishably good compressed audio and spend your money on good speakers and more music!

    Reply
  20. David Toub says:

    I have tried stuff like this in the past with my own collection and can’t tell the difference unless the bitrate is well below 96. I haven’t bought a CD for years but have composer friends who will only buy CDs because they feel “digital” music is inferior, not realizing that CDs are digital. Sigh.

    Reply
  21. Shaun Hutchinson (@shiveringgoat) says:

    Interesting. Sorry but I can tell a difference using lossless files against 256 aac. The lossless files sound crisp and clean and FAT. I am using Klipsch One headphones. I also have a pair of Mackie MR8 speakers I used as a hobby to play techno using my macbook and Traktor. If I buy a new track as a WAV from Beatport and convert to 256 aac there is a big difference in what I can hear. (i Like FAT bass!)
    Storage is cheap now. I have a Drobo with 4x2TB drives in I use this for my iTunes library and all my music is in Apple lossless. I figured that if I was going to make the time to rip my music properly then lossless is a great way to preserve the CD giving me flexibility. I also use iTunes Match for my family’s iOS devices which works great for them.
    I have also DJ’d out in bars and on a few big club systems using Traktor and I am so glad I used lossless files as they sounded fantastic.
    I have the latest Boards of Canada album in 24bit this sounds even better. I hope this is the future.

    Reply
  22. Justin Cohen says:

    Using the stock headphones that came with my HTC One plugged directly into my Macbook Air, I couldn’t tell the difference between Apple Lossless and 128 Kbps using ABXTester.

    I’m looking forward to trying the test with Etymotic ER4Ps, Grado GS1000s, and Mackie HR824 speakers. I’ll post an update after I’ve tried them.

    Thanks for the very helpful post!
    Justin

    Reply

Leave a Reply

Want to join the discussion?
Feel free to contribute!

Leave a Reply