Comparison of MP3 Bitrates

Here is shown the difference between a WAVE file and derived MP3 files of different bitrates.

  • Music: “Sea of Sorrow” by Get Your Gun recorded at a sampling rate of 48 kHz.

  • The WAVE is converted to MP3 using lame: lame -b XYZ song.wav song.mp3 where XYZ is 64, 128, 256, and 320, respectively.

  • Analysis was performed by Sonic Visualiser.

The following figures show a spectrograms for WAVE, 64 kbps, 128 kbps, 256 kbps, and 320 kbps, respectively. The y-axis is frequency [Hz] and the x-axis is time.

 

WAVE format. The highest represented frequency is 24 kHz (i.e. half the sampling rate). The spectrum is very tight-looking.

 

320 kbps MP3. It is seen that a low-pass filter is applied to remove everything above 20 kHz. At high frequencies a bit of “holes” appear.

 

256 kbps MP3. The audio is still cut at around 20 kHz, but more “holes” now appear at high frequencies.

 

128 kbps MP3. The high-cut now occurs already at around 16 kHz. High frequency content is definitely lost.

 

64 kbps MP3. Note the change of scaling on the y-axis. The filter cuts at around 11 kHz and the spectrum is very “holey”.

As a result of this, I have chosen to use 320 kbps MP3s for my collection. Make sure to give the song a listen :-)