  A resonant photoacoustic cell capable of detecting the traces of gases at an
amplitude-modulation regime is represented. The cell is designed so as to
minimize the window background for the cell operation at a selected acoustic
resonance. A compact prototype cell (the volume of acoustic cavity of ~ 0.2
cm^3, total cell weight of 3.5 g) adapted to the narrow diffraction-limited
beam of near-infrared laser is produced and examined experimentally. The
noise-associated measurement error and laser-initiated signals are studied as
functions of modulation frequency. The background signal and useful response to
light absorption by the gas are analyzed in measurements of absorption for
ammonia traces in nitrogen flow with the help of a pigtailed DFB laser diode
operated near a wavelength of 1.53 um. The performance of absorption detection
and gas-leak sensing for the prototype operated at the second longitudinal
acoustic resonance (the resonance frequency of ~ 4.38 kHz, Q-factor of ~ 13.9)
is estimated. The noise-equivalent absorption normalized to laser-beam power
and detection bandwidth is ~ 1.44x10^{-9} cm^{-1} W Hz^{-1/2}. The amplitude of
the window-background signal is equivalent to an absorption coefficient of ~
2.82x10^{-7} cm^{-1}.
