Resampling audio using audacity

Resampling to decrease audio file size

To deposit audio files in PARADISEC, we request that you record your audio at the highest sampling rate and bitrate possible (see: Recording standards and best practices guide for more information). These files can be large and difficult to work with. An easy solution is to create a smaller, working-version of the file, remembering to retain your high quality file for archiving.

Load your audio file in Audacity. Note the areas where you can see sampling rate information. The rate of your file is located in the grey area to the left of the waveform.  The project sampling rate is located in the lower left-hand corner (Project Rate (Hz)).  To change the rate of your file, you need to select the Tracks menu and scroll down to Resample… (If you were to change the rate by altering the project sampling rate below, it would merely change the rate Audacity plays the file, not the file’s actual sample rate).

Load your audio file in Audacity

Once you select Resample… you get to choose the new rate. I would suggest 44100, as most players have no difficulty playing this rate. Then click OK.

Once you select RESAMPLE

Once your file has been down-sampled, you need to change the project’s sampling rate, otherwise you get an error message that the two rates do not match.  Just use the drop –down menu under the Project Rate and select 44100.

Once your file has been down-sampled

Now that you have changed the sampling rate, the next step is to change the 24 bit rate to a lower rate. To do this, you go to the drop down menu within the track window, go to Set Sample Format and select 16-bit float.

Once both sampling and bit rates have been altered to match, play your audio. If you are satisfied, then you can save the new file.  Under the File menu, select Export audio… and rename your file so that you can easily keep track of the new, down-sampled version.  These new sampling and bit rates are essentially CD quality settings.

Under the FILE menu, select EXPORT AUDIO

Once you export your new file, you can see that it is less than half the size of the original.

save your new file

Resampling to increase your lower-sampled files to the archival formats of 96 kHz, 24 bit or 48 kHz, 24 bit

If you have recordings that you collected at a lower sample-rate, you can re-sample those to create the formats that we can archive with PARADISEC. This process does not change the quality of the file. However, we request this be done to help futureproof PARADISEC. It will be necessary at some point in the future to migrate all files archived in PARADISEC to new technologies. If all files have the same rates, this process can be easily managed in batch processes. Consistency and standardization will be key in moving the archive toward new technologies as needed.

Simply follow the same steps for down-sampling, selecting the higher sampling rate of 96kHz or 48 kHz and bit-rate of 24.

After reading through this guide, if you still have questions, or you wish to request a service, feel free to email me (julia.miller@anu.edu.au), or better, visit the CoEDL Service Request Form. CoEDL members use the Member login at the bottom of the CoEDL webpage. Then click the General Members tab, the link to the request form is in the left-hand panel.

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