Hi,
my colleague Rod Elliot has designed a neat, tone burst gate that you can
build yourself quite cheaply.
It can produce bursts of 1 to 32 "on" cycles followed by 4 to 64 "off"
cycles at any audio frequency.
Perfect for amp testing, comp/limiter testing, VU meter testing and speaker
performance testing.
http://sound.westhost.com/project143.htm
For speaker testing, you will need an suitable omni electret or omni
condenser mic and preamp.
The Behringer ECM8000 is a possible candidate.
.... Phil