sample rate and file size

[khd205]

I recorded some old cassette tapes at 11025 bps in mono. The recorder ran for several minutes after the tapes ended, so I imported the file into WavePad (free version 1.2), deleted the silent ' tail', and saved the file. I was surprised to find that the file had ballooned from about 5MB to over 130MB!

 

Reloading the file showed that it had been converted into 44000 bps stereo. I used the File menu to change the sample rate back to 11025 mono, resaved it and again found it had been converted back to 44000 bps stereo!

 

I found a suggestion on this forum to use Save As... instead of just Save. This worked as it gave a choice of sample rate after renaming the file. On reloading, the file is now 11025 bps mono as desired, but even with the extra minutes deleted, it is still about twice the size (10 MB) as the original.

 

Why does this happen? Is it because I am using the free version? How can I get rid of those extra minutes and make the file smaller?

[nchtj]

no its nothing to do with it being the free version

 

what format are you talking about here anyway? wave files ?

 

you can calculate yourself how big the file should be by multiplying it out:

 

(length of file in seconds) x (sample rate) x (number of channels) x (byte rate - 1 or 2 (8 or 16 bits))

 

now since you verified the sample rate and channels are the same, that must mean the byte rate has increased from 8 bits to 16 bits (which would double the size of the file). so the solution is to load the file in wavepad again, do a "save as..." and select the format "wave" and in the next window that appears, select format "PCM", and attributes "11.025kHz, 8 bit, mono".

[khd205]

Thank you! A good answer, but it creates more questions. I checked the recording length and file sizes. The larger file agrees exactly with the sample rate at one byte per sample and the shorter, original file is about half the calculated size. So that's a puzzle.

 

I also notice that when the cursor hovers over the file names a little box appears that says 88kbps on the larger file and 44kbps on the smaller. I think this is a clue, but both files say 11025 mono when they are loaded into9 WavePad.

 

Oh yes, I am talking about WAV files here. I made them into mp3s but it introduces a periodic artifact into the sound.