Audacity Forum

Whenever I export an Audacity project I have into mp3, there's always this strange, annoying static-like sound during some parts of it that ruins the sound. How do I stop it from exporting with this strange static?

rpvee wrote:Whenever I export an Audacity project I have into mp3, there's always this strange, annoying static-like sound during some parts of it that ruins the sound. How do I stop it from exporting with this strange static?

We wouldn't know, because we don't have an example to listen to. Please upload an example MP3 about 30 seconds long by using "Upload attachment" underneath the "Preview/Post Message" buttons. That will let us know if the problem is playback crackle in your computer. Where are you playing the MP3? Do you hear this crackle in Audacity before you export the MP3?

You would expect loss of quality (loss of high frequencies, distortion artifacts) with MP3 because it is a lossy format. You can reduce the quality loss (at the expense of increasing the file size) by increasing the MP3 export bit rate (Edit > Preferences: File Formats tab).



Gale

Gale Andrews wrote:

rpvee wrote:Whenever I export an Audacity project I have into mp3, there's always this strange, annoying static-like sound during some parts of it that ruins the sound. How do I stop it from exporting with this strange static?

We wouldn't know, because we don't have an example to listen to. Please upload an example MP3 about 30 seconds long by using "Upload attachment" underneath the "Preview/Post Message" buttons. That will let us know if the problem is playback crackle in your computer. Where are you playing the MP3? Do you hear this crackle in Audacity before you export the MP3?

You would expect loss of quality (loss of high frequencies, distortion artifacts) with MP3 because it is a lossy format. You can reduce the quality loss (at the expense of increasing the file size) by increasing the MP3 export bit rate (Edit > Preferences: File Formats tab).



Gale

You can hear it in this Youtube video of the mp3 itself, from about 4:00 - 4:50:

http://www.youtube.com/watch?v=dpiLNewcwBk

It's a bit quiet, but if you listen closely, you'll hear this deep warping sound in the background. It was not there when listening to the project in Audacity.

rpvee wrote:You can hear it in this Youtube video of the mp3 itself, from about 4:00 - 4:50:

http://www.youtube.com/watch?v=dpiLNewcwBk

It's a bit quiet, but if you listen closely, you'll hear this deep warping sound in the background. It was not there when listening to the project in Audacity.

Up the MP3 bit rate, and don't use LAME v3.97 because that does warble unless you use at least 192 kbps. You can get LAME 3.98.2 from the LAME FAQ.



Gale

I was searching for an answer to this same problem awhile back, and can't find the original thread this was in - but I did copy out the relevant info and saved it for reference:

"[...] One thing I was frustrated with though is some of my audio clips were sounding all warbly and degraded after I exported my project as an MP3. I finally figured out what was happening. Most of my clips were recorded in mono. A couple of clips I imported were stereo. After I split those stereo tracks and deleted a channel, then the warbling disappeared. Another thing I was playing around with was the bit-rate and sample rate. That can also make a difference, but definitely split your stereo tracks into mono if you’re doing multi-track editing. [...]"

Dunno if that's going to be of help to you, but this is what solved my problem with warbling exports.

rinscewind wrote:After I split those stereo tracks and deleted a channel, then the warbling disappeared.

The reason that works is because then the MP3 file can use all of the bits per second for just that one channel rather than having to produce 2 channels with the same number of bits. In effect it is doubling the MP3 rate. A stereo MP3 set at 128 kbps will use approximately 64 kbits for each second of audio in the left channel, and 64 kbits for each second of audio in the right channel, whereas a mono MP3 set at 128 kbps will use 128 kbits for the one channel.
If stereo tracks are required, then for reasonable quality the MP3 bit rate should be at least 128 kbps - preferably higher.
For mono tracks the bit rate should be at least 64 kbps - preferably higher.
256 kbps will give very good sound quality for mono or stereo tracks.

I have been trying to solve this issue for the last couple of days. Created a DVD slideshow, with various mp3 (all @ 128kbps) files sprinkled throughout. Though the mp3 play fine on a computer, once burned to a DVD and played in a player, static (echo), crackling, and underwater-sounding voices/music (warbly?) could be heard. It would be easy to say these 'imperfections' were born during the DVD burning process. I am going to try splitting the tracks from stereo to mono, and do some tweaking with the bit rate and see what kind of results I get. I am also open to any further suggestions.

Scenario... (1)jpegs/mp3s are the files used, (2) Photo Story 3 is used to create the dvd slideshow (wmv format), (3) Sothink Movie DVD Maker is used to convert/burn the wmv to DVD. I guess the question is where does the echo/crackling/warble begin? Is it; (1) before the jpegs/mp3s are put together, (2) after Photo Story 3 creates the wmv, or after Movie DVD Maker creates the DVD.

The loss of sound quality begins as soon as the audio is converted into a "lossy" compressed format.
Then the sound quality deteriorates a little bit more each time the audio is re-compressed.

Original recording -> lossy compression -> 128kbps MP3 -> lossy compression -> wmv -> lossy compression -> DVD format (AC-3)

The better way is:
Original recording -> lossy compression -> DVD format (AC-3)
or
Original recording -> uncompressed (WAV) -> uncompressed (WAV) -> uncompressed (WAV) -> ...... -> lossy compression -> DVD format (AC-3)

cptroc wrote:Created a DVD slideshow, with various mp3 (all @ 128kbps) files sprinkled throughout. Though the mp3 play fine on a computer, once burned to a DVD and played in a player, static (echo), crackling, and underwater-sounding voices/music (warbly?) could be heard...

Scenario... (1)jpegs/mp3s are the files used, (2) Photo Story 3 is used to create the dvd slideshow (wmv format), (3) Sothink Movie DVD Maker is used to convert/burn the wmv to DVD. I guess the question is where does the echo/crackling/warble begin? Is it; (1) before the jpegs/mp3s are put together, (2) after Photo Story 3 creates the wmv, or after Movie DVD Maker creates the DVD.

Steve just pipped me to the post, but maybe this is a bit less technical, so posted as is anyway.

Is PhotoStory re-encoding the MP3s? I would assume it is encoding them to small-sized WMA lossy format, hence subjecting them to a second loss of quality. PhotoStory may have a WMA lossless option but it will take circa 4 MB of space per minute in addition to the video space. You can check the contents of the WMV in MediaInfo.

So if you want to use a lossy format in the WMV, export as WAV files from Audacity, then you will only have one generation of quality loss.


Gale

@ Steve - Thanks for responding
@ G.Andrews - Thanks for responding (incl the MediaInfo link)

I was writing my reply to Steve when G.Andrews' post popped up. I was going to ask if there would be ANY benefit to converting the MP3s to WAVs (using Audacity) prior to merging them with the JPEGs. If so, then I could go with Steve's second 'The Better Way is:' suggestion.