A general-purpose facility for adaptive testing in psychoacoustics

Abstract

We describe a general-purpose, programmable system that provides high-quality, low-cost devices for experimentation in psychoacoustics and speech perception. The system is controlled by a host computer (e.g., an IBM PC), over a serial line. Through the use of a high-level, general-purpose experiment control program, the designed interconnection of devices can be specified logically, and the settings of the devices modified dynamically, during the experiment.While the stimulus and experimental-control requirements for speech and hearing research are demanding, they are relatively uniform across experiments and laboratories. One must first specify and control the spectra and levels of the presented stimuli, including the contribution of the overall frequency response of the complete electroacoustic environment to the level of the acoustic coupling to the subject's ear. To ensure that testing occurs under standardized conditions, equipment must be calibrated at the beginning of each experimental session. Then, one must be able to present the desired signals in the sequence and at the times specified.A relatively large number of special-purpose and/or expensive components are required for such research: specialized equipment is typically required to filter (antialias) signals for digital-to-analog conversion, to amplify and/or attenuate signals, and to mix signals from different sources. Typically, the preparation for an experiment involves the manual interconnection of the devices used during the experiment, with the associated delays, as well as opportunities for human error. Moreover, the interconnection of equipment with different grounding and cabling systems tends to introduce noise (e.g., 60 Hz) into the circuitry. 1 Also, when two or more experimental conditions requiring different configurations of equipment are used during a given testing session, such concerns are multiplied.In order to improve the efficiency with which experiments can be set up and controlled while reducing the possibilities for noise and error, researchers have adopted several approaches. The first is to use a connector panel,