I want to loop play at 8 times normal speed

Special Interest Groups Audio Processing
1

I am using Audacity 2.0.5 and Windows 7, 64 up dated to the latest versions.
I have wave files with a sampling rate of 192 kHz. I want to play back those files at 8 times normal speed with the loop play feature. Is there some way to do that in Audacity or can you recommend a way to do that. I do not want to use any process that decimates the data.
The bandwidth on the data is 12 kHz so running at 8 times playback speed pushes the bandwidth to 96 kHz. That is what I need. This speed and bandwidth are compatible with my DAC.

2

I do not want to use any process that decimates the data.

Reduces by 1/10, or damages?
Koz

3

I may be missing the point, but still.

Define “Decimate”. I thought that meant reducing sample rate.

Do you mean you don’t want to change the pitch, or you do want to ? Effect > Change Tempo or Effect > Sliding Time Scale speed up without changing pitch, but are lossy.

You can’t loop play using Transcription Toolbar (I assume that is the feature request). You can loop play a Time Track ( http://manual.audacityteam.org/o/man/time_tracks.html ) or after using Effect > Change Speed, but they resample, and change the pitch.

Set Rate in the Track Drop-Down Menu does not resample (it just pushes the samples closer together) but it won’t accept a rate of 1536000 Hz. And it also changes the pitch.


Gale

4

By decimate I mean omitting data points such as is done in “change speed.” At constant sampling rate, that decreases the time duration of the file and shifts the frequency upward. The number of sample points in the file is decreased. That is what I meant by decimate.

I don’t want to make any changes to the data in the wave file. I don’t want to use any “effects” that do that. I want to play it back at a speed that is 8 times the normal speed. So it would be like the 3X speed in the transcription option. But I want to do it at 8X. Additionally I want to loop play the wave file at this high play-back rate.

I think I understand the standard options in the effects list. I just thought there might be a trick I am missing.

Thank you for your reply.

Art Thompson

5

You can do that by adding a Time Track Audacity Manual
Set the range to 100% to 800% then move the line to the top of the time track.
To go back to normal speed, delete the Time Track.

6

Thank you, I will give it a try.

Art.

7

If you export or render the speeded up Time Track, surely samples are discarded?

Gale

8

Yes, any exporting or rendering will not retain the speed up and can possibly loose data or distort the data. I am using this method just to run the data into another digital instrument, not an audio application. So I have no need to retain the data that are played back at high speed. A separate piece of digital electronics will do that. It is not easy to explain why I would like this capability. If my computer would handle a file of 30 or 40 Gb I would not need to speed it up and loop play. I would rather not buy such a computer. This is all in a lab setting.

Thanks again.

Art