Temporal Modulation Frequencies

[FlipFlopRob]

I've been reading up papers about mapping sounds to
their auditory representation, and I'm a bit confused about one bit.

They've given some diagrams of sound waveforms spectral with the y-axis
being spectral frequencies, and the x-axis being temporal modulations

What are temporal modulation frequencies in this case? I've been trying
to find a simple, down to earth explanation on the net, but there seems
to be a few different answers, and I'm not quite sure which one it is,
if any.

Here is an image of what I'm on about.

http://openi.nlm.nih.gov/imgs/rescaled512/2700967_pcbi.1000436.g007.png

 

My guess is its the average frequency of oscillations in a sound? But I'm still really confused!

If someone could give me an answer which an everyman can understand, I would be most grateful!

"Spectral frequencies between 2500 and 5500 Hz, and temporal modulations in the range 1–16 Hz" - if that helps.

Thank you!

[Ringer]

Could you link to the actual paper? At a guess it may be talking about filtering sounds by frequency or pitch (spectral) and filtering by time exposed to sound (temporal).