Audibility Extender Feature from Widex
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A presentation on the Audibility Extender feature from Widex..
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Audibility Extender Feature from Widex
- 7. Dead regions in the cochlea Kuk et al, 2009
- 8. Good hearing, good resolution Low to high frequencies Poorer hearing, poorer resolution Why use transposition? Good resolution Moderate resolution Poor resolution Dead region
Editor's Notes
- Welcome to this presentation on the Audibility Extender from Widex. The Audibility Extender program uses linear frequency transposition to lower inaudible high frequency sounds to frequency regions where audibility can be obtained.
- Using frequency lowering techniques in the form of either frequency transposition or frequency compression to make high frequency sounds audible has been a subject of research for several decades. Targeting sloping high frequency hearing losses, as well as more severe and profound hearing losses [click] , several researchers have over the years gathered evidence supporting the use of such frequency lowering techniques.
- Frequency lowering is a term applied to a wide range of schemes. Overall, we can distinguish between linear frequency transposition , where a part of the signal is moved to a lower frequency area [click], and frequency compression , where all or some of the frequency range is compressed [click]. Widex hearing aids make use of linear frequency transposition in the Audibility Extender program.
- In this presentation you will learn more about the Audibility Extender from Widex. First, an explanation of how the Audibility Extender improves audibility will be given You will learn how linear frequency transposition, the algorithm behind the Audibility Extender, functions Furthermore we would like to share the evidence on the efficacy of the Audibility Extender and the many success stories gathered over several years of research with you And offer some recommendations for the use of the Audibility Extender in the clinical setting Now let’s take a closer look at the benefits of using the Audibility Extender with a hearing impaired client.
- For clients with a steeply sloping or severe-to-profound hearing loss, high frequency sounds are often not aidable with traditional amplification due to the issue of dead regions in the cochlea. For these kinds of hearing losses, the Audibility Extender makes otherwise inaudible sounds audible by transposing (or moving) the information in the high frequency regions to the aidable lower frequencies. This will help the hearing impaired client detect sounds in the environment such as birdsong or high frequency components of music. Above all it will aid the important identification of high frequency speech sounds.
- In this example the sounds above 2500 Hz are inaudible to our client. The Audibility Extender analyses the spectrum of sounds [click] and identifies the sound in the inaudible region where transposition is needed [click] . In this example, the peak of the sound lies at 4000 Hz. After the selection is made, the Audibility Extender sets the target [click] and moves the sound down by one octave [click] . So if the peak intensity is 4000 Hz, one octave down will be 2000 Hz. Then the sounds around the peak frequency of the transposed sound are filtered off in order to minimise any masking effect of the transposed sounds [click]. The transposed sound will be amplified so it is above the threshold of the area it was transposed to. The transposed sound, in this case 4000 Hz, then overlaps the original sound of 2000 Hz. Besides improving audibility for high frequency consonants, this way of lowering frequencies has the benefit that it preserves the temporal structure of sounds which is especially important for the identification of the primarily low frequency vowel sounds.
- But why do we want to use an alternative solution to high frequency amplification? The Audibility Extender program is intended for use primarily with children and adults with a steeply sloping or a severe to profound hearing loss where traditional amplification is not sufficient. These are some examples of typical audiograms. With these types of hearing losses so called dead regions may be present. Dead regions are found in parts of the cochlea with no or very few functioning inner hair cells - typically where hearing thresholds have dropped below 70 db HL [click] (Moore 2004, Hogan and Turner, 1998) . With a basal cochlear dead region many high frequency sounds will not be audible which could lead to confusion between words and meanings (Robinson et al, 2007). Several researchers have pointed out that simply amplifying high frequencies under these conditions may lead to deteriorated speech discrimination ( Hogan and Turner, 1998, Vickers et al, 2001, Baer et al, 2002 ). So with the presence of dead regions important acoustic information is either lost or one could try to make the information available by moving the information to parts of the cochlea where audibility can be established. Baer, T., Moore, B.C.J. & Kluk, K. 2002. Effects of low-pass filtering on the intelligibility of speech in noise for people with and without dead regions at high frequencies. J Acoust Soc Am, 112, 1133-1144. Hogan, C.A., and Turner, C.W. (1998). "High-frequency audibility: Benefits for hearing-impaired listeners,'' J. Acoust. Soc. Am. 104 (1) 432-441 Moore B. (2004) Dead regions in the cochlea: conceptual foundations, diagnosis, and clinical applications. Ear Hear 25(2):98-116 Robinson J, Baer T, Moore B. (2007) Using transposition to improve consonant discrimination and detection for listeners with severe high-frequency hearing loss. Int J Audiol. 46(6): 293-308 Vickers, D.A., Moore, B.C.J. & Baer, T. 2001. Effects of lowpass filtering on the intelligibility of speech in quiet for people with and without dead regions at high frequencies. J Acoust Soc Am, 110, 1164-1175
- A way to illustrate the concept of frequency transposition is by using a visual analogy. To a certain extent, good resolution means sharpness or clarity. So in this picture, which illustrates good resolution across frequencies - from low to high or from left to right - we see a clear and sharp picture with high contrasts – we can see the details. Please notice the face of the little girl to the far right. [click] As the degree of hearing loss increases, resolution decreases. We cannot tell the difference between two frequencies as easily – they sound the same. The picture becomes more fuzzy. In this case, with a steeply sloping loss, the sharpness or resolution may be good in the low and mid frequencies, but poor in the high frequency regions. And in cases where there may be a dead region, you simply see a “blur” and you cannot tell what it is. Simply amplifying the “blur” tells you there is a “blur”, but does not make identification easier. In this case, we can say that there is a dead region – the information in the high frequencies is missing. [click] The purpose of frequency transposition is to move the important information in the high frequency regions to a lower frequency where it can be identified. In frequency transposition, the information in the high frequencies is moved down to a frequency region where the resolution is still acceptable so the auditory system can utilise the information. Note that the high frequency, when transposed to a mid frequency region, would need good resolution in order for it to be identifiable. The beauty of transposition is that it preserves the lower and mid frequencies – especially the temporal structures – but as you can see, there is a “crowding” of information in the mid frequencies – and thus initial confusion may happen in some cases, making adjustment, training and counselling particularly necessary.
- Hearing aids features and fitting options should whenever possible be based on proven technology, client choice and individual clinical judgment. This is the idea behind evidence based practice. Since the introduction of the Audibility Extender in Widex hearing aids the efficacy and effectiveness of the frequency transposition algorithm has been investigated thoroughly through extensive clinical trials as well as case studies. Many aspects have been researched and we would like to share the knowledge we have obtained from these studies. References will be given at the end of the presentation.
- Studies with children as well as adults have investigated the initial preference for the Audibility Extender program compared to the standard program setting. The stimuli used for the subjective ratings were birdsong, music and speech. They differ in the complexity in harmonic structures with birdsong being the most simple and speech the most complex. The studies show that the initial preference is highest when simple stimuli such as birdsong and music are used. For complex stimuli such as speech, the rating is initially lower for the Audibility Extender compared to the standard program of the hearing aid. Results from the studies, however, also show that after only a few weeks of acclimatisation, preference for the Audibility Extender increases dramatically for speech stimuli and only very little for birdsong and music. This important information illustrates the difficulty of introducing new acoustic cues for speech and the importance of allowing time for acclimatisation. The main conclusion is that even complex stimuli such as speech end up being preferred using the Audibility Extender. In this way the results are promising since audibility for speech is the primary concern when providing amplification. Auriemmo J, Kuk F, Lau C, Marshall S, Thiele N, Pikora M, Quick D, Stenger P (2009). Effect of Linear Frequency Transposition on Speech Recognition and Production of School-Aged Children. Journal of the American Academy of Audiology, 20(5) Kuk F, Korhonen P, Peeters H, Keenan D, Jessen A, Andersen H. (2006). Linear Frequency Transposition: Extending the Audibility of High-Frequency Information, Hear Rev, 13(11), 42, 44-46, 48 Kuk F, Peeters H, Keenan D, Lau C (2007c), Use of Frequency Transposition in a Tin-Tube Open-Ear Fitting, Hearing Journal, 60(4), 59-63
- Over the past years, data has been collected from studies with both children and adults, all documenting that the use of the Audibility Extender does over time improve the perception and production of speech – especially for high frequency consonants. Being able to discriminate sounds in spoken language depends to a great extent on the degree to which you have access to high frequency sounds. Whereas vowels are predominantly low frequency sounds, most consonant sounds consist of energy in the higher frequency area. High frequency phonemes are thus difficult to discriminate with a high frequency hearing loss.
- In the English language, especially the high frequency /s/ sound carries a lot of important information such as tense, possessiveness and plurals. The graph illustrates the spectral distribution of an /s/ spoken by male, female and child talkers and clearly shows that the energy predominantly lies in the high frequencies. When this information cannot be heard, it may cause errors that can significantly impact communication with others. Pittman, A. L., Stelmachowicz, P. G., Lewis, D. E., & Hoover, B. M. (2003). Spectral characteristics of speech at the ear: implications for amplification in children. Journal of Speech, Language, and Hearing Research, 46(3), 649-657 JSHR 2003
- So access to high frequency speech sounds is essential and research has shown that using the Audibility Extender provides a viable solution. Improvement of both perception and production of speech has been documented in a wide range of studies. Most recently by Kuk et al in 2009. The table shows consonant perception scores grouped according to phoneme class. These were measured with the standard program, with the Audibility Extender program at initial visit, with the Audibility Extender program after one months’ use, and again after 2 months’ use. The results from the study show that the consonants receiving the most positive impact are the ones with most high frequency energy – the fricatives and the affricatives. Notice the initial confusion with the introduction of the new language cues for the stops, approximants and nasals. These quickly improve over time. Auriemmo J, Kuk F, Stenger P (2008). Criteria for Evaluating Performance of Linear Frequency Transposition in Children, Hearing Journal, 61(4), 50-54 Auriemmo J, Kuk F, Lau C, Marshall S, Thiele N, Pikora M, Quick D, Stenger P (2009). Effect of Linear Frequency Transposition on Speech Recognition and Production of School-Aged Children. Journal of the American Academy of Audiology, 20(5) Kuk F, Keenan D, Peeters H, Korhonen P, Hau O, Andersen H.(2007a). Critical Factors in Ensuring Efficacy of Frequency Transposition. Part 1: Individualizing the Start Frequency, Hear Rev 14(3): 60, 62-64, 66 Kuk F, Keenan D, Peeters H, Lau C, Crose, B.(2007b), Critical Factors in Ensuring Efficacy of Frequency Transposition. Part 2: Facilitating initial adjustment, Hearing Review, 14(4), 90, 92,95-96 Kuk F, Peeters H, Keenan D, Lau C (2007c), Use of Frequency Transposition in a Tin-Tube Open-Ear Fitting, Hearing Journal, 60(4), 59-63 Korhonen P, Kuk F (2008), Use of Linear Frequency Transposition in Simulated Hearing Loss. J Am Acad Audiol, 19(10) Kuk F, Keenan D, Korhonen P, Lau C (2009). Efficacy of Linear, Efficacy of Linear Frequency Transposition on Consonant Identification in Quiet and Noise, J Am Acad Audiol , 20(8) Smith J, Dann M, Brown M (2009), An Evaluation of Frequency Transposition for Hearing-Impaired School-Age Children. Deafness & Education International, 11 (2), 62-82
- Language development is of special importance in paediatric audiology. The Audibility Extender has shown good language development results in studies with school age children. This example, from a study by Auriemmo et al in 2009, shows the production of the fricatives /s/ and /z/ in reading and conversation for a group of school aged children. The figure shows the accuracy of the /s/ and /z/ production measured on a reading task (yellow bar) and a conversational task (red bar) with the children’s own hearing aids, the study hearing aid in the standard program after training, and the study hearing aid in the Audibility Extender program after 3 and 6 weeks of training. Analyses of the results show significant improvement in the accuracy and consistency of /s/ and /z/ articulation during both the reading and the conversational task. Further benefits have been recorded in the classroom setting. Here teachers involved in studies with the Audibility Extender have reported improved auditory function as well as increases in confidence and self-esteem for the children after they were fitted with the Audibility Extender (Smith, 2009) Auriemmo J, Kuk F, Stenger P (2008). Criteria for Evaluating Performance of Linear Frequency Transposition in Children, Hearing Journal, 61(4), 50-54 Auriemmo J, Kuk F, Lau C, Marshall S, Thiele N, Pikora M, Quick D, Stenger P (2009). Effect of Linear Frequency Transposition on Speech Recognition and Production of School-Aged Children. Journal of the American Academy of Audiology, 20(5) Smith J, Dann M, Brown M (2009), An Evaluation of Frequency Transposition for Hearing-Impaired School-Age Children. Deafness & Education International, 11 (2), 62-82
- These two video clips are from the before mentioned study. They show the development in the speech production of a school aged boy after being fitted with the Audibility Extender program. Listen to the /s/-sounds highlighted in the text. The videos were recorded at the initial fitting of the Audibility Extender program and again after 6 weeks Auriemmo J, Kuk F, Stenger P (2008). Criteria for Evaluating Performance of Linear Frequency Transposition in Children, Hearing Journal, 61(4), 50-54 Auriemmo J, Kuk F, Lau C, Marshall S, Thiele N, Pikora M, Quick D, Stenger P (2009). Effect of Linear Frequency Transposition on Speech Recognition and Production of School-Aged Children. Journal of the American Academy of Audiology, 20(5) Smith J, Dann M, Brown M (2009), An Evaluation of Frequency Transposition for Hearing-Impaired School-Age Children. Deafness & Education International, 11 (2), 62-82
- As will be apparent from the language studies with both adults and children, there is a clear effect of training and acclimatisation related to the use of the Audibility Extender. Several studies have documented the effect of these parameters showing that training improves the utilisation of the new acoustic cues and that training as well as acclimatisation is essential in order to fully realise the potential of the Audibility Extender. I would especially like to highlight results from a study by Korhonen et al (2008), which are illustrated in the graphs. They show identification scores for phonemes without (to the left) and with (to the right) frequency transposition at different time intervals. Results determine that the identification score for phonemes improved significantly for the transposed stimuli (the Audibility Extender) over the non-transposed stimuli (the standard program) after only 30 minutes of training. This indicates that the improvement is not only an effect of training; it is an effect of training combined with the effect of the transposed stimuli. Korhonen P, Kuk F (2008), Use of Linear Frequency Transposition in Simulated Hearing Loss. J Am Acad Audiol, 19(10) Kuk F, Keenan D, Korhonen P, Lau C (2009). Efficacy of Linear, Efficacy of Linear Frequency Transposition on Consonant Identification in Quiet and Noise, J Am Acad Audiol , 20(8)
- Along with training, counselling on expectations when using the Audibility Extender has been shown to facilitate acceptance (Kuk et al, 2007b) Kuk F, Keenan D, Peeters H, Lau C, Crose, B.(2007b), Critical Factors in Ensuring Efficacy of Frequency Transposition. Part 2: Facilitating initial adjustment, Hearing Review, 14(4), 90, 92,95-96
- Compass, the Widex fitting software, selects a default start frequency for the Audibility Extender programme depending on the hearing loss of the client. Although the the default start frequency is appropriate for the majority of clients case studies have shown that individualised fine tuning of the start frequency further improves scores on language tests for some clients. Therefore the individualised procedure for selecting the start frequency can also be said to contribute to the ultimate success. The recommended procedure for further individualisation is described by Kuk et al. 2007 in the Hearing Review Kuk F, Keenan D, Peeters H, Korhonen P, Hau O, Andersen H.(2007a). Critical Factors in Ensuring Efficacy of Frequency Transposition. Part 1: Individualizing the Start Frequency, Hear Rev 14(3): 60, 62-64, 66
- So here is a short summary of what we have learned through extensive studies testing the Audibility Extender for adult and child users. They document the benefits and optimal use of the Audibility Extender and provide the foundation for an evidence based practice. [1] The Audibility Extender improves speech perception and production for children and adults with a severe-to-profound high frequency hearing loss [2] Initial low preference for speech sounds [3] Counselling is necessary to facilitate acceptance [4] Acclimatisation and training are essential for improvements in speech perception/production [5] Progress in language scores and acceptance occur fast after targeted use of the Audibility Extender [6] Individualising the start frequency further improves performance on language tests [7] Further substantive benefits have been recorded in the classroom. Teachers have reported improved auditory function with concomitant increases in confidence and self-esteem in school-aged children
- Derived from study results we have some clinical recommendations on using the Audibility Extender. This graph shows the recommended audiogram range for the Audibility Extender. It should be used for clients, children as well as adults, who may have dead regions in the higher frequencies or whose hearing loss is too severe for traditional amplification. The mid-frequency region must have reasonable resolution. Do not use the Audibility Extender if traditional amplification will do the job. For mild to moderate losses where dead regions are not present, or the client performs well with a standard listening program, selecting a hearing aid with good high frequency gain, a wide frequency bandwidth and an efficient feedback cancellation system will provide the necessary audibility for the high frequency sounds.
- The Audibility Extender program should first and foremost be used to improve audibility. The main concern is to support speech perception and production especially for children where language development is dependent on the audibility for all speech sounds. To fulfil this purpose the Audibility Extender is optimally set as the default program in the hearing aid and used 24/7. But in real-life clinical practice the use of the Audibility Extender may not be completely straight forward. As mentioned earlier, the initial preference for Audibility Extender may be low for speech, and acclimatisation is necessary. For clients with acceptability issues it may help to make the acclimatisation softer. We ask clients to consistently use the Audibility Extender program to facilitate speech improvement, but it may also be necessary to accept occasional use. Because acceptance has to do with the start frequency, setting a higher start frequency than the default may be an option. This means that the client could have reduced audibility – but some audibility will nonetheless be added - just not the maximum potential. Start frequencies above 4000 Hz rarely lead to acceptance problems. The start frequency can then be gradually adjusted over time. Be aware that training and further counselling may be required after the initial fitting of the Audibility Extender to ensure successful use.
- This is the reference list for the studies that have been conducted with the Audibility Extender and which have been referred to in this ppt. Auriemmo J, Kuk F, Stenger P (2008). Criteria for Evaluating Performance of Linear Frequency Transposition in Children, Hearing Journal, 61(4), 50-54 Auriemmo J, Kuk F, Lau C, Marshall S, Thiele N, Pikora M, Quick D, Stenger P (2009). Effect of Linear Frequency Transposition on Speech Recognition and Production of School-Aged Children. Journal of the American Academy of Audiology, 20(5) Kuk F, Korhonen P, Peeters H, Keenan D, Jessen A, Andersen H. (2006). Linear Frequency Transposition: Extending the Audibility of High-Frequency Information, Hear Rev, 13(11), 42, 44-46, 48 Kuk F, Keenan D, Peeters H, Korhonen P, Hau O, Andersen H.(2007a). Critical Factors in Ensuring Efficacy of Frequency Transposition. Part 1: Individualizing the Start Frequency, Hear Rev 14(3): 60, 62-64, 66 Kuk F, Keenan D, Peeters H, Lau C, Crose, B.(2007b), Critical Factors in Ensuring Efficacy of Frequency Transposition. Part 2: Facilitating initial adjustment, Hearing Review, 14(4), 90, 92,95-96 Kuk F, Peeters H, Keenan D, Lau C (2007c), Use of Frequency Transposition in a Tin-Tube Open-Ear Fitting, Hearing Journal, 60(4), 59-63 Korhonen P, Kuk F (2008), Use of Linear Frequency Transposition in Simulated Hearing Loss. J Am Acad Audiol, 19(10) Kuk F, Keenan D, Korhonen P, Lau C (2009). Efficacy of Linear, Efficacy of Linear Frequency Transposition on Consonant Identification in Quiet and Noise, J Am Acad Audiol , 20(8) Smith J, Dann M, Brown M (2009), An Evaluation of Frequency Transposition for Hearing-Impaired School-Age Children. Deafness & Education International, 11 (2), 62-82
- At the Widex website www.widex.pro you will find additional information on the Audibility Extender. The studies referred to in this presentation are available as pdf files for download. You will also find fitting guidelines for how to fit and fine tune the Audibility Extender as well as inspiration for training materials. If you have further questions regarding the use of the Audibility Extender please find your country specific contact information on widex.pro