Abstract: A portable test hammer apparatus that produces repeatable and adjustable impacts to make traditional "tap testing" more reliable and quantified. The apparatus includes an impactor head device having a housing sized to be held in a human hand and engageable with the structural member, a plurality of adaptor bases, each readily mounted on the housing, an impactor head disposed within the housing for reciprocating movement therein, and a fluid piston assembly for moving the impactor head from a retracted position within the housing to a projected position in which the impactor head impacts the structural member. Impactor devices can be rapidly slid across test surfaces on non-marring feet, vacuum adhered to the test surface, or both. The apparatus further includes a rugged acoustic transducer for generating and transmitting an electrical signal based on the acoustic signature of the strike of the impactor head against the structural member.