I presume the tinnitus alternates in pitch and volume and therefore sounds
like a "busy" signal.  I get a similar effect first thing in the morning, on
awakening, and I find it unpleasant in the extreme. (No, it's not my alarm
clock going off!)   It tends to wear off during the day and the normal
one-pitch tinnitus gradually takes over.

I can get rid of the busy tone sometimes by "listening" to white noise
whilst asleep for a week or so.  This is probably more than residual
inhibition as the effect can then last for weeks.  The normal tinnitus is
always there though.

John