High-frequency content in MP3s
From Hydrogenaudio Knowledgebase
The amount of high-frequency content in an MP3 cannot be used to reliably predict the quality of the MP3. Therefore, Hydrogenaudio users advise against using frequency graphs
High-frequency content in MP3s
From Hydrogenaudio Knowledgebase
The amount of high-frequency content in an MP3 cannot be used to reliably predict the quality of the MP3. Therefore, Hydrogenaudio users advise against using frequency graphs to assess MP3 quality; "we don't listen with our eyes".
 Why MP3s omit high-frequency content
MP3 encoders typically "lowpass" their input, cutting off the highest frequencies. There are several reasons for this:
- Human hearing tends to drop off sharply somewhere between 16 and 20 KHz, usually toward the low end of that range.
- The input to the encoder is unlikely to have much, if any, audible, musical (non-noise-like) high-frequency content.
- Even if the source does have audible musical content above 16 KHz, preserving it would take away valuable space that could be used by the lower, more important frequency bands.
- The MP3 format has difficulty storing content above 16 KHz without sacrificing quality and increasing the bitrate requirements of the lower frequency bands.
 The limits of human hearing
Human hearing sensitivity peaks at 1 or 2 KHz, and drops from there. Children can't hear above about 20 KHz at all, and this upper limit decreases with age. Many people can't hear anything above ~18 KHz at all, even test tones. This affords an opportunity to limit