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kschuler / words-in-noise-EEG

An EEG task for Kelly Michaelis and Peter Turkeltaub. Learners try to determine words presented in a noise mask with either just auditory information or both auditory and visual information.
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Figure out what staircase max and min should be based on SOX volume manipulation #9

Open kschuler opened 7 years ago

kschuler commented 7 years ago

@kcm1231

This is something you and Peter will have to do. It depends on what you decide about how exactly you want to manipulate your sounds.

kcm1231 commented 7 years ago

Hey Katie,

I talked to Peter, and we're gonna go with the volume manipulation rather than gain. I think that's what you already had it set up to do, correct? That way we can calculate the SNR using the ratio of the noise and stimulus files.

kschuler commented 7 years ago

Hi there,

Yes I do manipulate volume. You may want to look into the limits that sox has. At the moment I assume limits of 0 and 1 (min and max). So the noise is set to 1 and the stimulus is set to a value between 0 and 1 depending on the what the staircase says.

But when I read about sox volume, it says this:

Intended for use when combining multiple input files, this option adjusts the volume of the file that follows it on the command line by a factor of FACTOR. This allows it to be ‘balanced’ w.r.t. the other input files. This is a linear (amplitude) adjustment, so a number less than 1 decreases the volume and a number greater than 1 increases it. If a negative number is given then in addition to the volume adjustment, the audio signal will be inverted. See also the norm, vol, and gain effects, and see Input File Balancing above.

Which means something different than what I've assumed. The staircase is choosing the FACTOR that the volume of the file will be adjusted by. So if you want the volume to go down, you choose a number less than 1 and if you want the volume to go up, you choose a value greater than 1.

I'm not sure what the limits are on volume adjustments in this way. You and Peter will have to figure that out and set the parameters of the study accordingly.