"New Year’s Day… now is the accepted time to make your regular annual good resolutions. Next week you can begin paving hell with them as usual.”
Mark Twain

Have you made your resolutions yet? Why bother, no one keeps them anyway. So let's talk about resolution instead. In particular how low-resolution MP3s can affect your emotional reaction to music. In a study out of the Hong Kong University of Science and Technology (HKUST), researchers found that the fidelity of an MP3 recording of musical instruments can affect their emotional characteristics. Most of you who know me understand both my delight and disdain for MP3s. When compressed correctly, they can decrease file space/download time with very little degradation to fidelity. However, in practice they are usually over-compressed for squeezing into an email or onto a smart phone. This results in a swirling, watery, and dull facsimile of the the original song. A lot of people are able to dismiss this as a trade off between quality and convenience, much like how the cassette tape was accepted.

How does an MP3 work? Let's pretend we're kids again and imagine standing before the great Rocky Mountains. Now imagine you must make a resemblance of the mountain landscape from a set of 1,000 Legos. With enough Legos you can create a jagged, but very close likeness. Step back a little and it looks pretty realistic (except for the red and yellow Legos). This is roughly equivalent to CD quality audio.

Now suppose you have to create the same scene with only 250 Legos. You can still make it look fairly real, especially if you keep the smaller Legos to create the sharp mountain tops. This is similar to compressing that song from a CD to the best quality MP3.

Ready for an even tougher challenge? You now only have 50 Legos to work with. In order to make your work of art look even remotely real, you must use mostly large and medium Legos. You have to step really far away and squint to be able to see the Rockies in your creation. This is just like a highly compressed MP3. The question you are probably asking is, "Why do you keep taking my Legos away?"

Mo, Choi, Lee, and Horner at HKUST asked a different question: "Does MP3 compression affect emotional response to music?" A musical instrument can be played at different pitches, speeds, or volumes. Play high, fast, or loud, and it will usually be perceived as heroic, joyful, or angry. Add audio processing such as reverb, and it can sound more mysterious or romantic. But other audio processing unrelated to musical intention, such as MP3 compression, can change the timbre and emotional characteristics. Increased MP3 compression adds jitter and reduces the clarity, affecting some instruments such as the saxophone and trumpet more than others.

So, Mo, et al. asked another question, "Just how do these MP3 artifacts change the emotional characteristics of the sound?" They selected eight classical instruments with similar fundamental tones. Then they chose ten emotional categories, much like all the characters in "One Flew Over the Cuckoo's Nest." The non-professional, non-musically-trained test subjects listened to these instruments with low, medium, and high compression rates. Listeners heard a pair of sounds from the same instrument with different compressions and were asked to select which one sounded more like a given emotion.

When researchers used more MP3 compression, neutral and negative emotions (mysterious, shy, scary and sad) increased, while positive emotions (happy, heroic, romantic, comic, and calm) decreased. They surmised this was caused by the background "growl" artifacts. Curiously, the angry emotion was nearly unaffected by any MP3 compression.

Since this is the first study of its kind, this group at HKUST wants to do further testing with actual musical passages to see if MP3 compression affects their intended emotions. I hope they made this one of their 2017 resolutions because what they found is fascinating. I guess my 2017 resolution will have to be "Don't get angry when I hear a badly compressed MP3." But I guess I'm off the hook because angry isn't affected by MP3 compression.




Explore More
Read the white paper HERE in the Journal of the Audio Engineering Society
Read more about MP3 compression in my 2015 article.
Read "It's Not What You Play, It's How You Play It" in the Quarterly Journal of Experimental Psychology
Read "When Room Size Matters: Acoustic Influences on Emotional Responses to Sounds" from the American Psychological Association
The genius of Warner Bros. composer Carl Stalling in "Music and Humor: The Cartoon Music Aesthetic of Car Stalling."