Optimal Filter Perception of Speech Sounds: Implications to Hearing Aid Fitting through Verbotonal Rehabilitation

Transcription

1 Optimal Filter Perception of Speech Sounds: Implications to Hearing Aid Fitting through Verbotonal Rehabilitation Kazunari J. Koike, Ph.D., CCC-A Professor & Director of Audiology Department of Otolaryngology Head & Neck Surgery What is Verbotonal? It s an auditory-based strategy that maximizes the listening skills of children and adults with hearing impairment and other communications disorders, while simultaneously developing intelligible spoken language through binaural listening. 1

2 What is Verbotonal? In 1939, Petar Guberina completed his dissertation at the Sorbonne University, Paris, which established how vocal pitch change (intonation) affected the meaning of a phrase, and discussed how spoken language affected the learning of written language. His study became the theoretical foundation of a practical strategy for teaching normal hearing people to speak before reading a foreign language (Renard and Van Vlasselaer, 1976). More popularly used in Europe, the methodology was later expanded to teach people with hearing impairment how to speak their native language by learning to listen first. This methodology has been coined The Verbotonal Method. Basic Principles of Verbotonal Neuroplasticity of the human brain Vibrotactile phase of listening Listening through rhythm and intonation Error analysis and correction Listening through spoken language 2

3 What is Optimal Filter Perception? Optimal Best possible combination of variables at a particular time for a particular person To filter is to. Primary focus: Perception of speech sounds Analogous to: Balance; Ideal Listening Lab I American English has 25 consonants, and 15 vowels and diphthongs. Guberina (1972) proposed to use octave-band filters to determine what would be the most important frequency region for the perception of a particular phoneme (vowel or consonant). [cf. Articulation Score: Bell Lab] In his experiment, when he set the octave-band filter s center frequency at 200 Hz, the listener heard the recorded vowel /i/ as the vowel /u/. When the center frequency was changed to 1000 Hz, the vowel /i/ was heard as the vowel /a/, and so forth. Therefore, he concluded that, All phonemes are contained in one phoneme because the perception of different phonemes (e.g., the vowels /i, e, a, o, u/) was possible from the same phoneme (e.g., the vowel /i/) depending on which filter frequency in which the phoneme was passed. Guberina further defined each of these various filter settings as an optimal octave for each vowel or consonant. 3

4 Optimal Octave Matrix Clinical Tool 1 Optimal octaves for vowels Optimal octaves for consonants Optimal octaves for a certain sound are different across different languages Speech perception: Structured or imprinted in brain based on a mother tongue 4

5 Practical Application: Error Analysis of Speech Perception In practice, this principle is a helpful tool in analyzing errors, i.e., why a certain error occurs with an individual with a certain audiometric pattern. For example, it would explain why a child with only low frequency hearing below 300 Hz, will say the vowel /u/ when the vowel /i/ is presented as a stimulus. The vowel /i/ is filtered through the child s hearing loss that is equivalent to a low pass filter, optimal for perceiving the vowel /u/. 5

6 Acoustic Spectrum of Vowels Analysis of Speech Production Phonemic Boundaries of Different English Vowels 6

7 Utah Vowel Imitation Test (U-VIT) Normal hearing children Utah Vowel Imitation Test (U-VIT) Hearing impaired children 7

8 Tonality Syllables for Detection Clinical Tool 2 Tonality Model: Application to Error Analysis Asp, Berry & Bessel (19878) Clinical Tool 3 8

9 List of Tonality Words (5 Categories) 9

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11 PI TTT Normal Hearing Subjects Endo (1987) PI TTT Hearing Impaired Subjects Endo (1987) 11

12 My Clinic Work Sheet (Front) 12

13 My Clinic Work Sheet (Back) Phonemic Audiogram Northern and Downs (1974) Sound Placement Based on Analysis of Speech Production/Acoustics 13

14 Pitch Ranking of Prevocalic Consonants Peterson & Asp (1972) Pure tone audiogram vs Tonality 14

15 Pure tone audiogram vs Tonality Pure tone audiogram vs Tonality 15

16 Open Ear Fitting Will it improve tonality word score? 16

17 Pure tone audiogram vs Tonality Pure tone audiogram vs Tonality 17

18 Pure tone audiogram vs Tonality Pure tone audiogram vs Tonality 18

19 Pure tone audiogram vs Tonality How about children? 19

20 Low tonality words tend to develop earlier than high tonality words Tonality Sentences for Children 20

21 Sound Awareness through Speech Vibrator A sound is a vibration: Clinical Tool 4 Adjustment of Hearing Aid Frequency Response: Based on Analysis of Speech Perception Errors Input: Speech (Tonality Words) Hearing Loss: Peripheral Filter Selective Amplification/Processing Based on prescription formulas Manufacture s software Analysis of speech perception errors Central Auditory Processing Central Filter Neuroplasticity of Brain 21

22 Listening Lab II Listen and Repeat Principle of Standard Speech Discrimination Test But, we only score the responses as correct or incorrect Analysis of speech perception errors Tonality test can be used as a tool You say Cease, patient says Tooth Optimal filter may be higher = more high Use Optimal Octave Matrix as a guide 22

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24 Optimal Frequency Response A Holy grail of various hearing aid prescription formulas (NAL, DSL, Killion, Half Gain, CID, Memphis, Sensogram, Audiogram-Direct, etc.) Verbotonal: Utilization of optimal octaves to fine tune filter settings (center frequency, cut-off frequency, bandwidth, slope, etc.) and gain Optimal Frequency Response Ching et al. (2001) NAL NL1 less gain is provided at frequencies where the hearing is most impaired to allow more gain at frequencies where audibility is most useful If the truly optimal frequency response is obtained, less gain may be required. Adding more gain in the higher frequency region may not necessarily be the solution. Goal: The patient s brain is trained under the optimal setting. 24

25 Pure tone audiogram vs Tonality Transition to Hearing Aid 25

26 Diagnostic Therapy Guberina In order to diagnose a problem with a man, you need to work with the man Small children often shy away from the audiologist that they meet in clinic and cling to their mother; Scared of the strange environment (audio booth) that they may not perform the desired task for diagnosis of hearing loss Often required multiple visits to play with children Be friended with the audiologist Adults with a difficult fitting may require multiple visits/adjustments including some auditory rehabilitation Diagnostic Therapy Go Outside the Booth Unaided stimulation Unaided vs aided Distance Training Doubling of the distance =? db decrease Incidental learning (Beck & Flexer, 2011) Speech Tracking (DeFilippo & Scott, 1978) Speech vibrator: Sound awareness (on-off awareness) to towards Conditioning Multisensory vs Auditiory alone Vibrotactile, visual, proprioception, auditory Check auditory perception: Cover your mouth 26

27 Incidental Learning Beck & Flexer. Listening is where hearing meets brain in children and adults. Hear Rev 2011;Feb: Children listen to conversations not directed to them, yet they learn from it maintaining their distance hearing ability is ciritical in such learning situations Remember, the brain is what matters!!! (Neuroplasticity) 27

28 There is a Hope: Even for Homer Simpson Can a hearing aid solve every problem? 28

29 Are we doing enough? Admittedly, we as hearing professionals often do not think beyond the peripheral hearing loss to what is happening at the level of the auditory cortex. We fit the patient with a hearing aid, the patient hears sounds louder, and that is it. The question is, Are we doing enough? 29

30 Are we doing enough? Pallarito K: Retraining the brain when hearing aids aren t enough. Hear J 2011;64(8): Martin R: Wear your hearing aids or your brain will rust. Hear J 2004;57 (1):46 Are we doing enough? Asp CW, Koike KJ, Kline M: Breaking News: Verbotonal rehabilitation: Are we doing enough? Hear J 2012:65(1);28,30,32,34. 30

31 HABRAT: Hearing Aid Brain Rewiring Accommodation Time (Gatehouse & Killion, 1993) the brain s habit of rewiring itself takes time, an important concern in good fittings. Back to Verbotonal Guberina emphasized those principles are to provide the opportunity of studying a man very deeply and to allow us to discover in his body and brain a dynamic creativity that outmatches itself every moment. 31

32 Clinical Tools Optimal Octaves Tonality Syllables for Detection Tonality Words & Sentences Speech Vibrator Diagnostic Therapy Don t forget the brain Welcome to West Virginia to the place I belong 32