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An ear for music

When you listen to music as an MP3, there’s actually a lot of data missing. An MP3 version of a song can be up to 11 times smaller than the CD version. This missing information includes high frequencies above the hearing range of most humans and since dogs are sensitive to much higher frequencies than humans, they’d be able to tell the difference between the two formats.

Psychoacoustic phenomenon

The sounds we hear are composed of many different frequencies of vibration. Humans can hear frequencies from 20-20,000Hz, though this range narrows with age and is most sensitive around 2,000-3,000Hz – the frequency range of speech. This is why most people concentrate on the vocal over anything else in a song; it occurs in the frequency range our ears are most sensitive to.

MP3s take advantage of ‘auditory masking’, a phenomenon you experience on a daily basis. For example, when you’re talking to someone on a train station platform and you notice that it suddenly becomes difficult to hear the other person speaking when a train passes by. The sound of the moving train contains a wide range of frequencies and, because the train is louder, your ears latch onto those frequencies in the range of the human voice, and the speaking gets drowned out or ‘masked’.

Hidden frequencies

Most music is composed of sounds of overlapping frequencies and it is possible to identify which part of a sound is the most dominant and which is being masked. The MP3 format excludes the masked frequencies as you won’t necessarily notice they are missing. This allows the file to be made up of less data and means MP3 players can hold far more songs than previous formats of music.

The debate as to whether people can tell the difference between an MP3 and a CD when compared on a high quality stereo system is still raging, some say they can’t tell the difference – others can. One thing is for sure, MP3s were designed in order to fool the listener into thinking there is no difference in quality, and it definitely succeeds with most of us.

See our top links about the physics of sound

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