# Why would a higher bitrate MP3 include more high frequency noise?

**URL:** <https://boards.straightdope.com/t/why-would-a-higher-bitrate-mp3-include-more-high-frequency-noise/828750>\
**Category:** Factual Questions\
**Created:** [January 31, 2019, 8:38pm UTC](https://boards.straightdope.com/t/why-would-a-higher-bitrate-mp3-include-more-high-frequency-noise/828750 "2019-01-31T20:38:39Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![KneadToKnow](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kneadtoknow/32/3999_2.png) [@KneadToKnow](https://boards.straightdope.com/u/KneadToKnow)\
**Post date:** [January 31, 2019, 8:38pm UTC](https://boards.straightdope.com/t/why-would-a-higher-bitrate-mp3-include-more-high-frequency-noise/828750/1 "2019-01-31T20:38:39Z")

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(I know just enough about this topic to accomplish what I need to, so please forgive layman’s terms.)

I use a PC to time-shift some radio shows I like. Most of the shows are very talk-heavy; I record those at 96 Kbps because trial and error showed me that was good enough. But one show is very music-heavy, so I record it at 128 Kbps, because that’s sufficient for my needs but gives me better sound for the music.

Here’s the thing: on that music-heavy show, there is _noticeably_ more high-end noise (you can actually hear the hiss kick in a second or two after the recording starts as the recording software’s volume-leveling setting finds its happy spot).

What’s up with that?

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**Author:** ![Folly](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/folly/32/3219_2.png) [@Folly](https://boards.straightdope.com/u/Folly)\
**Post date:** [January 31, 2019, 8:52pm UTC](https://boards.straightdope.com/t/why-would-a-higher-bitrate-mp3-include-more-high-frequency-noise/828750/2 "2019-01-31T20:52:42Z")

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The way you get more compression is to get rid of frequencies that are less likely to be important. Mp3 is a ‘lossy’ format. High end frequencies are the first to get booted.

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**Author:** ![Richard\_Pearse](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/richard_pearse/32/13144_2.png) [@Richard\_Pearse](https://boards.straightdope.com/u/Richard_Pearse)\
**Post date:** [January 31, 2019, 8:52pm UTC](https://boards.straightdope.com/t/why-would-a-higher-bitrate-mp3-include-more-high-frequency-noise/828750/3 "2019-01-31T20:52:57Z")

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WAG: The noise is in the source material and the higher bit rate is faithfully recording it.

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**Author:** ![DPRK](https://avatars.discourse-cdn.com/v4/letter/d/4491bb/32.png) [@DPRK](https://boards.straightdope.com/u/DPRK)\
**Post date:** [January 31, 2019, 9:39pm UTC](https://boards.straightdope.com/t/why-would-a-higher-bitrate-mp3-include-more-high-frequency-noise/828750/4 "2019-01-31T21:39:13Z")

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For comparison, MP3 encoding at 128 kb/s using LAME (-V 6) employs a low-pass filter at 16538 Hz – 17071 Hz, and furthermore encodes frequencies above 16 kHz less accurately in case a more accurate encoding would cause an increase in bitrate.

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**Author:** ![KneadToKnow](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kneadtoknow/32/3999_2.png) [@KneadToKnow](https://boards.straightdope.com/u/KneadToKnow)\
**Post date:** [January 31, 2019, 9:43pm UTC](https://boards.straightdope.com/t/why-would-a-higher-bitrate-mp3-include-more-high-frequency-noise/828750/5 "2019-01-31T21:43:38Z")

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I think you’re all essentially saying the same thing, and it makes enough sense to me to qualify as a logical explanation. 🙂