Transmission of digital audio almost always requires some method of compression to reduce the required bandwidth and to supply larger numbers of services. Many audio compression systems exist, based on very different principles. The tests normally associated with measuring audio performance seldom challenge the best audio compression techniques. In this paper, one audio compression system, SuperSound, is studied. Tests are performed that are intended to evaluate its performance when dealing with complex signals. These tests provide a more realistic measure of actual audio performance than simple test tones. The "compression noise" that is measured quantifies the degree to which the original signal is altered by the compression/decompression process.