Export of 8-bit PCM 4000 Hz samples fail

Audacity Help Forum Windows
1

Hi,

I use Windows 10 and Audacity 2.1.2.

I found information on this forum and elsewhere on the net about how to export 8-bit samples (and change sample rate). Here is what I did:

Starting point:

  • I have one track, it is 44 kHz, 16-bit PCM and mono.
    Activities:
  1. Change sample rate to 4000 Hz using “track → change sampling frequency” manually writing 4000 there.
  2. Export track using “File → export audio” and choosing “other uncompressed formats” (or similar, I have swedish language) and choose format as
  • WAV (Microsoft)
  • Unsigned 8-bit PCM


    My audio file is less than 2 seconds long. Without (the small header) it should be less than 2x4000 Bytes, ie. less than 8 kB.

However, it turns out as around 76 kB.

I check the header of the outputted WAV using a binary tool (FRHED). Based on specs found online, everything looks good:
Num of channels = 1
Bits per sample = 8
… and more … until:
Sample rate = $AC44 = 44100
Byte rate = $AC44 = 44100

Even the data chunk size is correct, listed at 77 704 Bytes which makes sense with my filesize of 76kB.

So why is the sample rate not maintained in the export?
It is clear the actual sample rate change down to 4000 Hz does take place, because sound quality is reduce substantially.

Please help!

Regards,
Peter

2

Try changing the sample rate with the little window at Audacity lower left.

What is the application? 2KHz sound is not enough for clear voice.

Koz

3

Thanks, that works! Not so obvious, maybe a candidate for future improvement/change?

The application is old-computers … Very tight on memory, quality have to suffer. I will test different options to see what yields the best result. Basically I can do max 8-bit/8kHz.

4

We do have a Manual that might have told you http://manual.audacityteam.org/.

To search it you can bookmark this https://www.google.co.uk/search?&q=toolbars+site%3Ahttp%3A%2F%2Fmanual.audacityteam.org - just change “toolbars” in the search box to what you are looking for.

Do you want to “vote” for choice of sample rate when you export?


Gale

5

I definatelly vote for a choice of sample rate during export. Default may still be project setting, but I would prefer default to be that of a single track (when only a single track is exported and its samplefreq differ from project).

Thanks
Peter

6

Thanks. I added your vote: http://wiki.audacityteam.org/wiki/Feature_Requests#Other_Import.2FExports.


Gale