I have recorded a speech using my tablet voice recorder. The output is in m4a. When I open the recording (both in the tablet and in PC), the audio is distorted. Put in layman's terms, it's like he's speaking twice as fast and the pitch is consequently much higher Is there anything I can do to restore the file? This had not happened with previous recordings using the same device.

I'm a total stranger to the area. If you need any information about the file let me know. I used VLC, Media Player, and PotPlayer to open it on PC.

  • I have updated the question with the new info.
    – Rory Alsop
    Feb 17, 2017 at 21:37
  • @RoryAlsop Thanks, could you figure anything out?
    – Goh-shans
    Feb 17, 2017 at 22:22
  • 1
    I'm just pondering as to why this might have happened, and barring some deliberate "squeeky voice" effect during recording. it must be a sample rate problem. The wrong sample rate must be used or reported somewhere.
    – n00dles
    Feb 18, 2017 at 15:26
  • Indeed, this sort of faster playback and pitching of audio is characteristic of playing audio in a higher sample rate than it was recorded. Check the device's recording sample rate and use that to play it.
    – Dalv Olan
    Mar 20, 2017 at 12:42

1 Answer 1


You can use ffmpeg or audacity to do this. Both are free.

In Audacity, use Effect > Change Tempo... or Effect > Sliding Time Scale / Pitch Shift

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  • Much better. Is there anyway to change the tone to normal, human tone? And also, the volume is very low. How to change that?
    – Goh-shans
    Feb 17, 2017 at 23:37
  • To change it to normal pitch just experiment with the settings. Once the speed is right the pitch will be right. For the volume just increase the gain, but that's a separate question.
    – Rory Alsop
    Feb 17, 2017 at 23:39
  • Can you suggest a value to set for pitch change? I've tried 9, 10, and 11 F#/Gb but neither worked fine. Each conversion takes half an hour, so appreciate your help in finding the normal pitch for a masculine voice. Again, I don't even know what these numbers mean.
    – Goh-shans
    Feb 25, 2017 at 21:57
  • 1
    Well, 50% will let everything down an octave and make it last twice as long
    – Rory Alsop
    Feb 25, 2017 at 22:13

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