The role of masking in the Franssen effect

Abstract

The sudden onset of a sound which slowly decays at one loudspeaker can occlude the presence and location of the same sound presented simultaneously with a slow rise time at another loudspeaker. This phenomenon, known as the Franssen effect, has been shown in previous research to be specific to low-frequency pure tones in reverberant rooms. To examine the possible mechanisms involved, listeners heard pure-tone transient/steady-state signal pairs at frequencies ranging from 250–4000 Hz from either one loudspeaker or two contralateral loudspeakers in an eight-speaker array. Signals were masked with Gaussian noise. Using a two-interval, forced-choice tracking procedure, thresholds for detecting the steady-state signals were measured. The transient tone was present in both intervals. The results showed increases across frequencies in threshold of approximately 6 dB for two-source (Franssen) conditions compared to single-source conditions. In an auxiliary experiment, signals were masked with tones of differing frequencies. For Franssen conditions, masking was dependent on the interaction of signal and masker frequencies. Both results are discussed in terms of onset dominance, nonecho suppression and free-field masking. [Work supported by NIDCD.]