A lightweight impedance tube has been developed primarily as an instrument for practical research. It can be used also for precision measurements of acoustical-impedance and sound-absorption coefficients in both laboratory and field installations, over the frequency range 400 to 900 cps. It is useful for the development and manufacturing control of acoustical materials, acceptance testing of acoustical installations in the field, and determination of aging, staining, and redecoration effects on the absorptivity of acoustical materials. Experimental results are presented.