Scratch

Hi, Murkle.

I'm sorry you're having problems.

I'd be happy to investigate this issue if you can upload a project that has one of these imported sounds that does not play well. When you upload it, be sure to uncheck the box that says "compress sounds and images". Then post the URL for the project here.

For the volume issue, you can try using the new "set volume to" block to turn down the sound level in Scratch.

  -- John

Hi, Murkle.

The peaks of that sound do get close to the limit, but don't go over it. So if you adjust your computer volume or use the Scratch volume block to reduce the level, it should not distort (a.k.a. "clip"). I'm not sure why the other sound editors are not playing the sound as loudly, but perhaps they have their own volume levels and they are not set to maximum. By default, the Scratch volume level is set to 100% (maximum).

You can use the right-shift menu on the sound to export it, then play the exported sound in one of your wave editors. Let me know if the exported sound seems louder than the original sound in your wave editor.

But I also notice that the sampling rate is 11025. That low sampling rate also contributes to a rough sound. Was the original sound sampled at that rate? Versions of Scratch before 1.2 had a "compress sounds" option that just reduced the sampling rate. It could be that you had applied that to an earlier version of this project. If you still have the original sound file, you might try re-importing it into Scratch 1.2.1. The new sound compression does not work by reducing the sampling rate, although Scratch does reduce sampling rates over 30k by half to save space. So if you sound is sampled at 44k (CD rate) then Scratch will reduce it to 22050, which still sounds very good.

I hope this helps.

  -- John

Hi, Murkle.

What I think is happening is that your system volume is high enough that it is actually adding some gain to the sound. So, even though Scratch is playing the sound at 100%, the system is boosting that by another few percent--enough to create that harsh sound that you report. (The harsh sound arises when the sound peaks try to go beyond the maximum sound level that can be represented with a 16-bit number, which is 32,767. But the system limits the digital sound signal to the value 32,767. The result, if you looked at it as a graph, would show that the highest peaks of your smooth sound wave had been leveled off, giving them flat tops. That effect is called clipping. All sound systems clip when they are over-driven, but with digital sound the clipping is very abrubt, which creates that extremely unpleasant distortion.)

I think that perhaps your wave editor programs may be bypassing the system sound setting, thus avoiding this problem. Or, as you say, SoundForge may be doing some intelligent volume adjustment to save your speakers.

As you discovered, turning down the sound level outside of Scratch makes the problem go away. Using the Scratch "set volume to" command should have the same effect: try "set volume to 50%" and then go up or down from there.

I am using a Mac and I don't get clipping when I play the sound in Scratch at the system volume level that I usually use. Also, I searched for the maximum sample value and it was below 32,767. If Scratch has introduced clipping when it imported the sound then the sound would contain many samples with the value 32,767.

This particular sound seems unusually "hot" (recorded at a high level). You observed that it has peaks of -0.1 db, which is consistent with the peak sample values I observed. Since you have SoundForge available, you could try reducing the level in SoundForge, exporting the quieter version, and importing that into Scratch. A quieter version of the sound might balance better with other sounds you are using.

It doesn't appear that there is a bug in Scratch related to the sound level.

What about the stuttering problem you mentioned? Could you upload or point me to a project that illustrates that problem?

  -- John

Re-starting Scratch may fix this problem. It fixes the problem when I get it!