saving a correct sampling rate?

[garip]

I have a WAV file which I export to mp3, then when I play it in audacity I have to change the sampling rate to 11Khz.

I'd like to save 11Khz sampling rate into the file so it knows automatically to play it at that rate

How can I do that?

[steve]

Sorry, I don't understand.
Which are you playing in Audacity, the MP3 or the WAV file?
Why do you have to change the sampling rate to 11Khz?
Where did the original WAV file come from?

[garip]

Sorry, I don't understand.
Which are you playing in Audacity, the MP3 or the WAV file?
Why do you have to change the sampling rate to 11Khz?
Where did the original WAV file come from?

WAV recorded in sndrec32.

Using Audacity to export it to mp3. But it gives it a sampling rate of 22k I want to save a sampling rate of 11k in the mp3.

[Gale Andrews]

WAV recorded in sndrec32.

Using Audacity to export it to mp3. But it gives it a sampling rate of 22k I want to save a sampling rate of 11k in the mp3.

If you import an MP3 having a sample rate of 22050 Hz into an empty Audacity project, the project rate bottom left will change to 22050 Hz if it is not already at that rate.

It you want to halve the potential frequencies in the file by exporting it at 11025 Hz, change the project rate to 11025 Hz before export. Note that "11000 Hz" is not a valid sample rate in the MP3 specification:

MPEG-1 layer III sample frequencies (kHz): 32 48 44.1:
bit rates (kbps): 32 40 48 56 64 80 96 112 128 160 192 224 256 320

MPEG-2 layer III sample frequencies (kHz): 16 24 22.05:
bit rates (kbps): 8 16 24 32 40 48 56 64 80 96 112 128 144 160

MPEG-2.5 layer III sample frequencies (kHz): 8 12 11.025:
bit rates (kbps): 8 16 24 32 40 48 56 64 80 96 112 128 144 160

If you want to avoid having to change the project rate to 11025 Hz every time you import a 22050 Hz file, the only way to do it at present is to save a project containing a track at 11025 Hz and import the 22050 Hz files into that project.

We have a feature request for a preference to always import at the Default Sample Rate - if implemented you could then set the default sample rate (in the Quality Preferences) to 11025 Hz to match the rate you wanted to export at.



Gale

[garip]

ah I see, I didn't realise that project rate there was a drop down menu and could be changed, that worked, I tried opening the high speed mp3 and set the project rate and exported, and got the 11.025 mentioned in mediainfo

Regarding the what the rate to the left of the wave, the drop down menu "set rate" does. I see it affects playback, but does it have any affect on the file that is exported?

[Gale Andrews]

Changing the project rate will not change the playback speed.

Set rate does affect the length (hence tempo and pitch) of the track and will persist in the export. Changing the rate in that menu and changing it back using that menu does not cause any audio losses.

On the other hand, changing tempo and pitch using Effect > Change Speed (which resamples the audio to keep it at the same sample rate) does cause losses if you apply the effect then apply the inverse of it to change the speed back to the original.



Gale