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I'm trying to make a video tutorial, so i decided to record the speeches using a TTS online service.

I use Audacity to capture the sound, and the sound was clear !

After dinning, i wanted to finish the last speeches, but the sound wasn't the same anymore, there is a background noise(parasite) which is disturbing, i removed it with Audacity, but despite this, the voice isn't the same ...

You can see here the difference between the soundtrack of the same speech before and after the occurrence of the problem. enter image description here

The codec used by the stereo mix peripheral is "IDT High Definition Codec".

Thank you.

YOo Slim
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  • Question of understanding: "The speech after the occurence of the problem" is another take you recorded, speaking exactly the same text as in the "speech before", right? – Simon Repp Jul 28 '13 at 08:43
  • @SimonRepp Yes, the same text with the same voice ! – YOo Slim Jul 28 '13 at 19:00

1 Answers1

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Perhaps some cable or plug got loose? Do check for this!

If you are using really cheap gear (built-in soundcard and the likes) it might very well also be a problem of electrical interference, anything from ...

  • Switching on some device emitting a electro magnetic field (e.g. another monitor close by)
  • Repositioning electrical devices on your desk
  • Changes in CPU load on your computer (yes i'm serious!)

... could very well cause some kinds of noises with low-fi sound hardware.

Generally, if you need help on audio sounding wrong make sure that you provide a way to LISTEN to the files, not just a visual representation.

Also in your posted waveform graphics i can see that the latter signal is more compressed, which may point to some kind of automated levelling going on somewhere in the audio chain.

Simon Repp
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    Here is a before/after simple, it's in french, i hope it doesn't matter ! https://soundcloud.com/yooslim/original-clean https://soundcloud.com/yooslim/after I disabled all the peripheral that can be disabled, there is no electrical device close to me, and i didn't make any changes before the problem's occurrence, i just reopened the computer, and directly started recording a new speech ! I tried to record the speeches on another computer, the sound was clean !!! – YOo Slim Jul 28 '13 at 19:23
  • Thanks, i think I understand now what you are doing: It sounds as though you are recording the output from the TTS by playing it back over your speakers and recording it back into Audacity via your microphone - Right? What then happens is that you seem to re-record that same piece you have already recorded in Audacity by taking it along the same route again: Out through the speakers, in through the microphone. This adds more noise to the signal and makes the audio sound more like your room (which it passed through twice at that point) and less like the original voice. – Simon Repp Jul 29 '13 at 11:23
  • You should be able to fix this by getting your affected track out of any recording mode after first having recorded it. It's been a while since I used Audacity, but something like deactivating a record-toggle, explicitly de-selecting the track, unsetting the input dropdown to no input at all should do the trick! In any case it should also be well documented on the internet how to get tracks into and out of recording mode in Audacity. – Simon Repp Jul 29 '13 at 11:29
  • One more thing: The audio output from other programs can also be (and that's actually the preferable way to do it) re-routed internally, via software, going directly to your recording software. (no speakers or microphones involved!) How this is done depends on your operating system and/or audio hardware, in fact there are many ways to do it, so if you're interested in doing it this way (which gives you the purest signal btw.) do some research on google for this :) – Simon Repp Jul 29 '13 at 11:39
  • Thank's for the answers ... I actually don't record the sound from the microphone, it would make so much noises, i record the computer sound (Stereo Mix), which records all the sounds made by the speakers. when i try to record a new track, i always mute the last ones that i just recorded, so that it doesn't mix up everything in one soundtrack. Until i took a break, i've made 50 clean soundtracks, so what did change, i don't know ! – YOo Slim Jul 29 '13 at 14:31
  • Hhm ok ... Regarding "but the sound wasn't the same anymore, there is a background noise(parasite) which is disturbing" ... Can you post the audio you describe here without the noise removed? (I didn't hear any disturbing noise in the "after" version you posted, so I assume you removed it there already?) – Simon Repp Jul 29 '13 at 16:53
  • Another thing: If you just listen to the audio directly from the TTS online service over your speakers (on the computer where you are having the problems) - does that sound wrong too? Or is it only after you record it in Audacity that it sounds noisy and wrong? Maybe your TTS provider is intentionally garbling up the output after X times of usage in order to prevent exactly the thing you are trying to do (using it as a source for a audio production)? – Simon Repp Jul 29 '13 at 16:58
  • No, i left the noise on purpose in the "After" version, you can hear it in the end of the speech, and you can also notice that the voice changed. For the question, it's only after i record that the problem appears (in Audacity), [Here is the TTS website](http://www.oddcast.com/home/demos/tts/tts_example.php) ... even if the problem comes from the TTS Service provider, why did it work perfectly the first time i used it ? – YOo Slim Jul 29 '13 at 19:06
  • Regarding the noise: From a technical viewpoint the "disturbing noise" at the end of your "After" version is negligible, any sound that is not purely synthesized on the computer will feature some kind of background noise, and yours (wherever it comes from) is well below any level where it should concern you. I don't know how loud you are monitoring, but I need to crank up my speakers quite a bit to make the noise obviously audible, at which point the voice however, is insanely loud, at a level you would never want to listen to it ... which is why the noise is negligible, again. :) – Simon Repp Jul 29 '13 at 20:45
  • Regarding "... even if the problem comes from the TTS Service provider, why did it work perfectly the first time i used it ?": As you can see they are also SELLING their service as an API. Now if you come along and heavily use their free service over a considerable timespan, they might get the impression that you are using their free web version as an API for some program of yours, unpaid. Which might be a reason for them to intentionally degrade the audio they send you, don't you think? It's still a wild theory (and as you now affirmed also incorrect), but it's not unreasonable i think. – Simon Repp Jul 29 '13 at 20:50
  • I'm sorta stuck now, if you find out something else, do add it to your question, but for the time being i feel like i am not knowledgeable or not informed enough to continue helping you remotely :) Good luck! – Simon Repp Jul 29 '13 at 20:55