Pulse extender - ish

[tim_d]

Hi all,

I'm looking for a form of pulse extender, but not exactly what a monostable 555 provides.  Basically, I'm looking at an audio signal, and want a trigger when the signal peaks outside an envelope, and hold the signal high for a period after the signal finishes exceeding this envelope.  My current plan is to use a pair of comparators to detect the audio signal crossing the positive and negative ends of the envelope.  Each of these will be generating a series of short pulses - I'd like to feed each into some form of extender functional block to hold high for the duration of the timeout after the last falling edge it saw, and then drop low again.  These two will then feed an and gate and that signal is the output.  The timeout would ideally be provided by a (presumably dual) potentiometer.

Any advice on where to go with this?  Even the name of the functional block I'm actually looking for would be helpful.  I should note that I've picked up electronics by doing, so I've got enormous gaps in my knowledge, 555s being one of them!

Thanks.
Tim