Loudness of sounds

[Fatima Husain <fhusain@xxxxxxxxxx>]

We keep running into this problem in my lab and I am wondering if you could
help. We often have stimuli sets that includes both speech and non-speech
stimuli. How do we equalize their loudness? The first step is to see
that they all have the same RMS power. But, the different stimuli being
broadband and narrowband,the stimuli may still seem to have differing loudness.

Is this enough?
If not, what do we do as the next step? Do we measure output at the end of
the headphones and equalize then? This is not always possible, esp. for
headphones which are already part of the fMRI scanner...or we are piping
sounds through a convoluted system. I am asking primarily with reference
to fMRI studies.

Any info if appreciated. Thanks! I will post a summary of responses on
the list.

--fatima

fhusain@cns.bu.edu
fthusain@helix.nih.gov