>We are looking for a transducer that emits acoustic waves
>(preferably using air as a medium) with relatively flat, or at
>least well known, response in the low kHz (approx 10kHz)
>to high kHz or low MHz (1.1-1.2MHz max) range.
>
>Does anyone know of such a device(s). It may be necessary to
>use several devices, each covering a portion of the spectrum,
>to get a reasonable transducer response.

I think one of the professors in my building makes ultrasonic transducers
in this range.  They are electrostatic nitride membranes.  Try talking to
Dr. Khuri-Yakub at Stanford University.
                                                                        J.

Justin Mansell  |       "Only a risk tests the reality of a belief"
Ginzton Laboratory      |                       - C. S. Lewis
445 Via Palou St.       |
Stanford, CA 94305      |