Record and Playback Speed

[tericb]

I was recording a lecture this morning. I've done this many times before without trouble. About 8 minutes into the lecture, the speed suddenly changed without my doing anything to Audacity. It was running in the background while I showed some PowerPoint slides. The waveform appeared compressed and the total recording time was about 30 muntes rather than the 80 or so that it actually ran. What happened and how do I fix it? Thanks.

[kozikowski]

<<<I've done this many times before without trouble.>>>

Have you filled up your hard drive before? If you're on a PC, when was the last time you defragmented your hard drive?

I personally wouldn't do anything that involves live audio or video on the same machine that I'm doing anything else. Both of those tasks require real time machine performance with no errors. The computer can't go off somewhere to think for a second.

Koz

[tericb]

Thanks for the swift response. I have plenty of drive space but have not defragged for a while. Is there some way I can rescue the recording. I all appears to be there but I sound like a chipmunk.

[steve]

For clarification, were you running Audacity and the Power Point Presentation on the same machine at the same time? If so, then that is probably the cause.

You may be able to salvage the recording using Audacity 1.3.5

Export the track as a wav file first, and make a backup copy as well.

Note that you can open Audacity 1.2.x projects in Audacity 1.3.x, but not the other way round.

Check the exported wav file to make sure that it sounds the same as the Audacity project - if not, stop at this point and let us know what you have.

Open the Audacity project in Audacity 1.3.5
Split the track after the "good" 8 minutes, and Export the good bit (select it, and choose "Export selection")
Now we will work just with the "chipmunk" bit.
Select a small section of the chipmunk part.
From the Effects menu, select "Change Speed"
Move the slider part way to the left and use the "Preview" button to test it.
Keep making adjustments and previewing until it sounds to be at the correct pitch and speed.
When you are satisfied, press "OK"
Compare your "corrected" bit with the undamaged first part of your recording - is the speed and pitch now correct?
Select "Undo" from the Effects menu
Select the entire track (except for the first 8 minutes) and reapply the Change Speed effect.
Export your corrected audio.

Note: there is a bug on some machines that causes Audacity to lock up if you cancel an effect after previewing. If your machine is affected by this bug, do not use "Cancel" (you can still use "Undo" after applying an effect).
Note also that Audacity 1.3.5 is a little different from 1.2.6, but it is well documented in the wiki (see link at the top of the forum page).

[Happy]

I have encountered a similar problem. I record and playback an audio just fine within Audacity, but once I export it as an MP3 and play it back on my car stero, I sound like a chipmunk.

I was hoping to use the recording to review/study lesson material. I repeat the recording 10 times using the effect tool. I was hoping to be able to put my drive time to better use.

Any suggestions - I am a complete newb when it comes to Audacity or recording my own media.

Thanks!

[NyAudio]

Yes I have had the same problem. I record from a microphone and it sounds fine in audacity. But when I export it as mp3 and play it with media player the sound is playing at a far faster rate than I talked creating a chipmunk voice pattern. I have seem the issue of compression and bit rate mentioned but I have no solution as of yet. If I get a solution I will respond.

[kozikowski]

Yo! Listen up!

Everybody go into Audacity Preferences and make sure your bit depth is set to 16-bit and not 32-bit floating. Audacity wakes up from First Birthday in 32-bit floating and that makes unstable MP3 files.

Koz

[NyAudio]

ok I got the message. 16 bit not 32 floating--thanks

[steve]

If you upgrade to Audacity 1.3 Audacity will take care of that particular issue for you and will by default export WAV and MP3 files as 16 bit. You may still need to check the sample rate that you are using - the most compatible sample rate is 44100Hz - to ensure that exported files use 44100Hz, set the project rate (box in lower left corner of the main Audacity window) top 44100 before exporting.