Development of the Connected Speech Test (CST)

TLDR

The Connected Speech Test (CST) is an everyday‑speech intelligibility measure developed mainly as a criterion tool for evaluating hearing‑aid benefit. This paper reports the first phase of developing the CST. The CST comprises 48 conversational passages, each with 25 key words, all equally intelligible to normal listeners, and scores are obtained by averaging results from several passages. Scores based on four passages have a 95 % critical difference of about 14 rationalized arcsine units, and the CST’s performance‑intensity function slopes 12 rau per dB signal‑to‑babble ratio.

Abstract

This paper describes the first phase in the development of the Connected Speech Test (CST). This test of intelligibility of everyday speech has been developed primarily for use as a criterion measure in investigations of hearing aid benefit. The test consists of 48 passages of conversationally produced connected speech. Each passage contains 25 key words for scoring. All passages are of equal intelligibility for the average normal hearer. Key words vary in intelligibility within a passage but span the same intelligibility range in all passages. Several passages are administered, and the results averaged, to yield a single intelligibility score. For pairs of scores, each based on mean performance across 4 randomly-chosen passages, the 95% critical difference is estimated to be about 14 rationalized arcsine units (rau). The performance-intensity function for the CST has a slope of 12 rau/dB signal-to-babble ratio. Investigations of the test are continuing with hearing-impaired listeners.