A bit over a century ago, compressed air gramophones
[link] were used to play music for large audiences. These
consisted of regular gramophones where the needle,
instead of driving a diaphragm, drove a comb valve that
served
as a pneumatic amplifier, modulating the flow of
compressed air.
This
product is just the pneumatic amplifier packaged as
its own device, with a standard electric audio signal
input
as well as a compressed air input. That audio signal input
drives a voice coil, which drives the comb valve. The
airflow modulated by the comb valve is then put out
through a horn to match the pressure to ambient
pressure, just
the same as in an electric horn speaker. (It occurs to me
just now that this is the same thing a rocket nozzle does.
Impedance matching is everywhere.)
This product enables loud audio playback on remote job
sites where compressed air is available (provided by an
engine-powered compressor) and electricity is not. (This
situation was mentioned to me the other day by someone
I
know, who was suggesting that a pneumatic generator
would be useful, to power electric power tools. You
could use
such a generator to power conventional electric audio
gear, but that seems less efficient and also less rugged.)
N/A [2019-09-28]
PS: Why do we have separate categories "Product: Audio:
Speaker" and "Product: Speaker"?