Presentation on theme: "Testing the perception of speech in noise in children: A test with no verbal response Intelligibility and Quality of Speech in Noise Workshop, UCL 9 th."— Presentation transcript:
Testing the perception of speech in noise in children: A test with no verbal response Intelligibility and Quality of Speech in Noise Workshop, UCL 9 th January 2009 Sam Evans & Stuart Rosen Dept of Speech, Hearing & Phonetic Sciences, UCL
Perception of Speech in Noise in Children Noisy classrooms – academic, literacy and language development. Children with Specific Language Impairment (SLI) and dyslexia have difficulty listening in noise (Ziegler, 2005; Bradlow et al 2003; Ziegler, in press). Speech in noise Language & literacy
Motivation for the Development of a New Test Numerous speech in noise tests. Focus at different levels of morphological and syntactic complexity. Few tests developed specifically for children. Adult tests adapted for children without considering needs.
Motivation for the Development of a New Test We are interested in SLI and dyslexia – perception of single words. Nonsense syllables – poor ecological validity. Sentences – potential syntactic confound. No single word tests that meet our needs.
Specific Challenges for Designing a Test for Children with Language Difficulties Open response problematic – speech production errors. Difficulties often subtle – require minimal speech contrasts. Poor vocabulary - lexical confound. Poor attention – quick to administer.
How we Addressed these Issues: Our Test Non verbal response - choose from a triplet of items: Target + two non word foils: e.g. bite pite dite. Foils differ from target by a single feature of voice, place or manner. Targets chosen from lists of the earliest acquired words. Chance level (33%) – requires less items than 2AFC. Adaptive procedure – negates floor and ceiling effects.
Construction of the Test: Choosing Targets Each triplet met the following criteria: CVCs Acquired by age 3;6, based on estimations from the databases of: Morrison, Chappell & Ellis (1997); Bird, Franklin & Howard (2001); DeCara & Goswami (2002). Could be represented pictorially Altered by a single feature to derive two non-word foils. Difficult to balance the contrasts perfectly: 7 manner-voice, 7 manner-place & 14 place-voice.
Equalising Across Triplets Each target has a different relative level of intelligibility due to phonemic and psycholinguistic factors (Nilsson et al 1994; Papso & Blood, 1989). A relative dB correction calculated for each triplet. Correction factor applied to nominal SNR in the adaptive procedure.
Equalising Across Triplets Correction factor calculated by: Testing each triplet at a range of SNRs – 110 data points. Logistic Regression - 71% correct SRT for each triplet. Mean SRT for all triplets subtracted from the SRT of each individual triplet.
Example Psychometric Functions for triplets containing bite and boot bite dite pite Target Place Voice SRT = (71% correct) boot woot poot Target Manner Voice SRT=-0.7 (71% correct)
Adaptive Procedure 2-down/1-up adaptive procedure tracking 71% correct (Levitt, 1971) Final step size 3dB. Familiarisation & test stages. SRT established by the mean of the reversals in the test phase. Improving Performance
Speech Shaped Noise Masker Speech shaped noise was generated by estimating the long-term average speech spectrum from recent measurements for combined male and female voices (Table II of Byrne et al., 1994).
Result 1: Effects of Age 53 subjects without known hearing or learning impairments, aged from 5 to 25 yrs - speech shaped noise masker. An inverse curve accounted for the most variance using the least number of parameters. In keeping with previous findings showing poorer perception of speech in noise in children (Talarico et al 2007; Fallon, Trehub & Schneider, 2000; Papso & Blood, 1989). SRT (dB) Improving Performance
Result 2: Effects of Vocabulary Development 16 monolingual British English speaking children (mean age=11.12, SD=2.78, range= ). 26 children from a multilingual background (mean =10.32, SD=2.26, range= ). All children were without known hearing or learning impairments. Tested in free-field with a speech shaped noise masker. Vocabulary was assessed with the Renfrew Word Finding Vocabulary Test (raw scores are reported).
Result 2: Effects of Vocabulary Development Vocabulary: Significant effect of age and group. No age*group interaction. SRT: Significant effect of age, no effect of group or age*group interaction. With thanks to Aneeka Degun Improving performance
A Test Robust to Differences in Vocabulary Development Groups differed in vocabulary development but not in SRT, suggesting that we have developed a test which is not sensitive to differences in vocabulary development, at least within the ranges assessed.
Result 3: Effects of Practice 14 children (mean age=8.4,SD=1.82,range= ). 2 subjects excluded – poor performers. All subjects without known hearing or learning impairments. 4 different maskers. Two separate sessions (up to 1 month between) with each masker (randomised in order).
Maskers… Speech shaped Noise One talker – speaker taken from EUROM database, edited to exclude pauses more than 0.1s in duration. Two talkers – the above talker plus an additional talker again taken from the EUROM database. Modulated noise – speech shaped noise multiplied by the envelope of the one talker stimuli.
Practice Effects Control for masker: Each SRT observation was subtracted by the mean SRT of the masker type that it belonged to. Significant effect of age. No significant effect of session, order or interactions. No evidence of practice effects within or between sessions. With thanks to Henri Roe
Looking to the Future Norming with larger samples of children – in process. Analysis of Errors – Ziegler Large SLI study at Guys Hospital – Gillian Baird and colleagues.
Thank yous With thanks to: for the award of a vacation scholarship. And all the students who have worked on/are currently working on the test: Henri Roe, Aneeka Degun & Rebecca Lancaster