MP3 audio distorted

[aneo]

When I listen to imported speak in WAV-format it sounds ok, but once exported to MP3-files the audio is like slightly distorted - as if there's a problem with the low sounds, a sort of slight echo.

How can that be? Some people suggested it's because there's no way to equalize the sound in Audacity and that the bass sounds can soudn distorted.

I have cut off the internal micro, so thats' not it.
I record in a Edirol 09 44Mhz , 16 bite (or maybe 24)

Hope somebody can help... thanx

Aneo

[yeti_07]

At what bitrate did you export the mp3-file?

Yeti

[aneo]

at 32 bit.

[waxcylinder]

at 32 bit.

And that's why it's distorted - you have applied too much compression. MP3 is a lossy format, the more you compress the more audio data is thrown away.

Try upping the exported bitrate till you get quality that is satisfactory for you. 128 is normally regarded as the workable minimum for music and 64 for voice. So give 64 a try.

WC

[aneo]

Are we talking about the same here: you propose 64, but isn't that an FFT size (in Audacity's Spectogram)
Here it's set at 258 default.

My default sample format is set at 32 bit flow (under the Quality menu).

What would be the most apporpriate settings in Preferences?


Aneo

[waxcylinder]

No, I'm talking about the MP3 output bitrate setting.

In 1.2.x go to the File Formats tab fron Edit/Preferences, there you will see in the dialogue box at the bottom a section called "MP3 Export Setup" - there is a drop-down selector in there to enable you to set the deafault bitrate. (Note that in 1.3.x, and presumably in 1.4 when it is releasesd, this is done in a diifferent place - at the time of export.)

The spectogram settings just contol the granularity of the spectogram display - they should have no effect on recording or exporting.

Your sample format for recording at 32 bit is good, as that gives yoy good quality for recording/editing work - but note carefully that if you want to export files for CDS then you need to export WAV at 44.1kHz 16-bit stereo (Red Book standard for CDs).

WC

[aneo]

OK, tried that but same problem.

Found out that the audio sounds ok when played back in the headphones - but not through the loudspeaker sin PC - could be a loudspeaker problem then - but still strange that the WAV-sound is ok when played back on PC....

[steve]

Some people suggested it's because there's no way to equalize the sound in Audacity and that the bass sounds can soudn distorted.

You CAN equalize the sound in Audacity - use "Effects -> Equalisation"
It's correct that excessive bass can sometimes cause distortion on mp3's, and little computer speakers can not handle deep bass (they will rattle, fart, and eventually burn out).

Regarding MP3 bit-rates; as waxcylinder said, 128 kbps is generally regarded as the minimum for music. Higher numbers will give better quality, and lower numbers give worse quality.

If you want to export as mp3, it is generally good to normalise to a little less than 0 dB (say -0.2 ) to avoid clipping, particularly if there is a lot of bass in the music.

[aneo]

not that I will go on and on about this - but there is no music - it's only voice.

And how to chose in Normalize - it's automatically at -0.3

[steve]

In v. 1.3.4, you can select the "normalise to:" value.
In v. 1.2.6, The "Normalise" effect is fixed at -3dB (not -0.3). However, you can use "Amplify" instead of "Normalise". When you select "Amplify", it will automatically set the amplification amount to the maximum amount before clipping (that is, it will normalise to 0 dB), to normalise to, say, -0.2 dB, use "Amplify" and reduce the automatically selected value by 0.2

- but there is no music - it's only voice.

Using a high pass filter, or Equalisation to reduce very low frequencies can be very effective on voice recordings in reducing "pops" caused by your breath on the microphone. It's not as good as avoiding blowing on the mic in the first place, but it is a handy technique nonetheless. Rolling off the bass from around 100Hz is a reasonable approximation, though you may want to raise or lower this.