Loudness enhancement and summation in pairs or short sound bursts

When a pair of short, temporally spaced sound bursts is presented and the listeners are requested to match the loudness of a third, comparison burst to the overall loudness of the pair, a fundamentally different result is obtained than when they are instructed to match the loudness of the comparison burst to that of the second burst in the pair. Loudness-level changes occurring in the first situation are designated as loudness summation; those occurring in the second situation, as loudness enhancement. Some parameters of both phenomena are studied. The results lead to the suggestion of a principle of maximum similarity in stimulus matching and to a reinterpretation of some earlier data.