I loaded a .wav file that was 3 megabytes into Audacity and exported
it back out as a .mp3 file. When I checked the results, I discovered
that the .mp3 file was four and a half megabytes in size!

As far as I know, .wav files are uncompressed whereas .mp3 files are
compressed. Therefore, if you convert a .wav file into an .mp3 file,
the result should be smaller (or at most, the same size) than the
original .wav file.

So why was this .mp3 file bigger? Was this just a fluke?

Wylbur,

> I loaded a .wav file that was 3 megabytes <

How many seconds long was it? A stereo Wave file occupies about 10 MB per
running minute at 44.1 KHz and 16 bits, so a three minute song uses about 30
MB.

A lot of people don't know that you can rename an MP3 file to have a .wav
extension and, amazingly, it will still play in many programs such as
Windows Media Player. So if your original Wave file was a full song in only
3 MB, that's why it was so small.

As for why compressing again made it bigger, that would depend on the
compression settings you used.

--Ethan

wylbur37 wrote:
> I loaded a .wav file that was 3 megabytes into Audacity and exported
> it back out as a .mp3 file. When I checked the results, I discovered
> that the .mp3 file was four and a half megabytes in size!
>
> As far as I know, .wav files are uncompressed whereas .mp3 files are
> compressed. Therefore, if you convert a .wav file into an .mp3 file,
> the result should be smaller (or at most, the same size) than the
> original .wav file.
>
> So why was this .mp3 file bigger? Was this just a fluke?


Compression or lack of doesn't enter into it here. The size of a wave file
of a particular duration is determined by the sampling rate. If originally
sampled at the normal rate of 44,100Hz, it is about 10.3 megs per minute.

If - as is probable - your original wave file was sampled at a lower rate
and you then saved/exported it without changing Audacity's default sample
rate of 44,100 Hz (lower left corner) then it was resampled and that
resulted in an MP3 (and underlying wave) that was bigger than the original.

IOW, it wasn't a fluke, you just need to learn more about what is happening.

--
dadiOH
_____________________________

dadiOH's dandies v3.0...
....a help file of info about MP3s, recording from
LP/cassette and tips & tricks on this and that.
Get it at http://mysite.verizon.net/xico
____________________________

On 21 Aug 2004 04:16:35 -0700, (E-Mail Removed) (wylbur37)
wrote:

>I loaded a .wav file that was 3 megabytes into Audacity and exported
>it back out as a .mp3 file. When I checked the results, I discovered
>that the .mp3 file was four and a half megabytes in size!
>
>As far as I know, .wav files are uncompressed whereas .mp3 files are
>compressed. Therefore, if you convert a .wav file into an .mp3 file,
>the result should be smaller (or at most, the same size) than the
>original .wav file.
>
>So why was this .mp3 file bigger? Was this just a fluke?

It's not uncommon for a MP3 to be saved with the WAV extension.

Maybe it WAS a WAV, but at a low sample rate.? Maybe it was mono, but
you encoded it as stereo?

(E-Mail Removed) (wylbur37) wrote in message news:<(E-Mail Removed)>...
> I loaded a .wav file that was 3 megabytes into Audacity and exported
> it back out as a .mp3 file. When I checked the results, I discovered
> that the .mp3 file was four and a half megabytes in size!
>
> As far as I know, .wav files are uncompressed whereas .mp3 files are
> compressed. Therefore, if you convert a .wav file into an .mp3 file,
> the result should be smaller (or at most, the same size) than the
> original .wav file.
>
> So why was this .mp3 file bigger? Was this just a fluke?

When I display my files in "My Computer" and hover the mouse over the
icon for the original WAV file, it says "Bit Rate 88kbps", whereas
when the mouse is over the MP3 file (that got created from the WAV by
Audacity), it says "Bit Rate 128kbps".
That probably already answers the question of why the MP3 file was
bigger than the WAV file.

However, when I went into Audacity and changed the default "Project
Rate" from the current value of "44100 Hz" to "11025 Hz", then loaded
the original WAV file and exported it out under a different filename
than the first time, the resultant file was the exact same size as the
first result! When I did a file-compare, they were exactly the same in
contents!

I then looked in the Preferences and changed the MP3 Export Bit Rate
from 128 to 80. When I exported the WAV file again, this time it was
down to about 2.8 megs, so I'm apparently on the right track. I guess
the lesson here is to make sure the output bit rate is not higher than
the input bit rate.

Thanks very much for your help.

"Ethan Winer" <ethanw at ethanwiner dot com> wrote in message news:<7pudnc9B3f4l3brcRVn-(E-Mail Removed)>...
>
> > I loaded a .wav file that was 3 megabytes <
>
> How many seconds long was it? A stereo Wave file occupies about 10 MB per
> running minute at 44.1 KHz and 16 bits, so a three minute song uses about 30
> MB.
>
> A lot of people don't know that you can rename an MP3 file to have a .wav
> extension and, amazingly, it will still play in many programs such as
> Windows Media Player. So if your original Wave file was a full song in only
> 3 MB, that's why it was so small.

The original WAV file was almost five minutes long, so maybe you're right
(that it might have actually been an MP3 file that was named as a WAV).
Is there some kind of test to determine for sure?