International Collegium of Rehabilitative Audiology (ICRA) recommendations for the construction of multilingual speech tests

Abstract

(Short communication)An important goal in audiology is to establish internationally standardized diagnostic tests that can be applied and interpreted in the same way everywhere -an endeavor with severe limitations as soon as speaker and language-specific considerations come into play. Speech intelligibility tests with a closed-set design (i.e., a limited amount of response alternatives the test subject may choose from in order to identify which speech item she or he has heard) have the advantage that they can be performed in the native language of the respective test subject (if available) even if the test conductor does not understand this language. Such a format therefore supports speech audiometric testing in several languages which makes it attractive for a multilingual society. A prerequisite for a multilingual application, however, is that the construction and the respective results of these closedset speech tests are as comparable across languages as possible. This calls for ICRA as an international body of leading experts in this field to produce guidelines concerned with the development of any new test of this kind in any new language. The current guidelines were therefore agreed on by an ICRA working group on multilingual speech tests constituted by the authors of this paper. The guidelines primarily concern the digit triplets test (as prototype for a screening test, see below) and the matrix test (as prototype for an audiologic diagnostic test for professional use, see below) but may also be used for other test designs. They complement the ISO 8253-3:2012 standard "Acoustics-Audiometric test methods -Part 3: Speech audiometry" by considering in more detail the steps necessary for developing a specific test in any new language.The digit triplet test originally proposed by Smits and colleagues in Dutch (Smits et al.,2004) has meanwhile been produced in about 15 languages, such as, e.g., British English, American English, German, Spanish, Italian, Mandarin, Polish, Russian, and Spanish (see Zokoll et al 2012Zokoll et al , 2013 for a comprehensive review). It has primarily been designed for use as a screening test using a telephone: A string of three digits is presented together with a background noise to the listener who has to press the appropriate digits on the telephone keypad as a response. An adaptive tracking algorithm allows altering the speech-to-noise ratio (SNR) according to the listener´s responses in such a way that the individual speech recognition threshold (SRT, i.e. SNR corresponding to 50 (or 80) percent speech intelligibility) is determined within a few trials. The matrix test -originally proposed by Hagerman (1982) in Swedish and in a modified version by Wagener et al (1999a,b,c) in German -is intended as an audiological diagnostic sentence recognition test consisting of syntactically fixed, but semantically unpredictable sentences like "Thomas buys eight red cars". For each of the five word positions (i.e., name, verb, numeral, adjective, and object), ten alternatives are available t...

The development and evaluation of the Finnish digit triplet test

“…In accordance with the current recommendations [7,8], the masking noise for the Finnish DTT is quasi-stationary masking noise that has a long-term spectrum corresponding to the long-term spectrum of the triplets without fluctuations in level. It was generated by superposing all individual digit files 30-fold using variable and random delays before the start of the sound files and between the sound files.…”

“…Recently, the International Collegium of Rehabilitative Audiology (ICRA) also published their recommendations for constructing multilingual speech tests [8]. In both of these recommendations the digit triplet test (DTT) was the choice for an internationally comparable screening test for hearing impairment.…”

“…The success of the early versions of the DTT has led to the development of similar tests in different languages [7,8]. It has been shown that these tests can accurately discriminate between normal-hearing and hearing-impaired individuals, and their results correlate well with other speech tests in noise that utilize more complex speech material [9,10].…”

The development and validation of the Closed-set Mandarin Sentence (CMS) test

“…The main goal for developing the CMS were to create a large stimulus set of sentences that could be used to reliably and repeatedly used to measure Mandarin speech understanding in noise using a closed-set paradigm, and that performance would be comparable to existing Mandarin sentence recognition tests. The CMS test materials were developed similarly to previous matrix tests (Akeroyd et al, 2015; Kollmeier et al 2015), but with some notable differences. Similar to previous matrix tests, a fixed structure was used to generate sentences (Name, Verb, Number, Adjective, Object).…”

“…However, the CMS test differs from previous matrix tests in several ways. For example, Akeroyd et al (2015) recommends that matrix test stimuli should allow for generation of semantically nonsensical sentences. In the CMS, words were selected to produce similar semantic sense, as the possibility of nonsensical sentences could affect intelligibility during testing.…”