the prescribed target formula is often preferred. (Byrne 1986; Fabry and Stypulkowski 1992; Punch et al. 1994; Kuk 1994; van Dijkhuizen et al. 1991).

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2 the prescribed target formula is often preferred. (Byrne 1986; Fabry and Stypulkowski 1992; Punch et al. 1994; Kuk 1994; van Dijkhuizen et al. 1991). The aim of modern amplification technology is the improvement of speech intelligibility and comfort in any acoustic situation. In quiet surroundings most hearing impaired people rate speech intelligibility with hearing instruments positively. In noisy situations, however, speech intelligibility with hearing instruments is rated mostly negatively. The use of directional and multi-microphone technology to enhance signal to noise ratio has proven to be the most successful strategy in background noise. In digital instruments complex noise reduction algorithms can also be employed to improve speech intelligibility in background noise and/or to increase hearing comfort. (Weiss and Neumann 1993; Marzinzik 2000; Dillon and Lovegrove 1993). In many modern hearing instruments different listening programs can be implemented to enable appropriate signal processing for a given situation. However, with conventional multi-program hearing instruments the user must judge the acoustic environment and decide which program is the best for the situation and then select the appropriate program via a switch on the instrument or a remote control. Digital hearing technology enables a running analysis of the input signal and the appropriate adaptation of the processing strategy. The AutoSelect mode of Phonak Claro hearing instruments which is the subject of this study, automatically switches between two programs depending on the acoustic environment. The aim is to achieve the highest possible speech intelligibility in all listening situations. For quiet environments or when there is only background noise the first program is activated by the automatic program selection, and for speech in background noise, the second program. In the second program, the use of adaptive directional microphone technology, noise suppression, and appropriate frequency response and compression parameters aims to improve speech intelligibility in adverse environments. The automatic program selection in the tested hearing instrument is based on an analysis originally suggested by Kates (1995). This comprizes four different specifying dimensions, which contribute to the characterization of the input signal: 1. Overall loudness level 2. Fluctuation of overall loudness 3. Mean frequency of the signal (spectral center of gravity) 4. Fluctuation of mean frequency These four signal characteristics are monitored by the automatic switching mechanism and the instrument switches between the two programs when all four parameters meet the preset criteria. The aim of the implemented sound classification is to identify speech within noise from all other acoustic situations. The noise situations in everyday life as well as the individual hearing needs of the user are diverse and the hearing instrument cannot guess the latter. It is therefore unrealistic to expect AutoSelect to switch correctly in every situation. For this reason it is possible to manually override the automatic switching, with a switch on the instrument or with a remote control. With the help of a questionnaire and subjective reports made by the subjects this study aimed to establish whether the AutoSelect mode switched between programs in the desired way and if it was perceived as being helpful by the hearing impaired subjects. 2

3 Method Twenty-two subjects with moderate hearing impairment (19 men and 3 women) participated in this study. They were fit with Phonak Claro hearing instruments by various Swiss hearingcare professionals. The subjects average age was 63 years. About half of the subjects were retired, the other half working. Seven people were fitted with Claro 211 daz BTEs, 13 people with Claro 21 daz ITEs and two with Claro 22 ITCs. The AutoSelect mode is linked to two of the instrument s three hearing programs. Program 1 is configured for speech intelligibility in quiet. Program 2 activates an adaptive directional microphone, noise suppression, and modified frequency response and compression parameters to achieve improved speech intelligibility in background noise. During the fitting of the instruments each subject was instructed on the differences between the two programs and the function of the AutoSelect mode. At the time of the fitting the hearingcare professionals were not aware that these people were to take part in a study. As a result the participants were not treated or instructed any differently compared to other clients. Questionnaire The questionnaire covered the following topics: Switching mechanism Are you aware of program changes? How do you rate the frequency of switching? Does the instrument switch when expected? Program selection Is the choice of program suitable to the situation? At what times is the program choice not suitable? Usefulness How useful is the automatic program switch? For each question, answers with 5 7 scaled categories were offered, eg. not useful, of little use, a bit useful, quite useful, very useful. For questions on suitability of the selected program, 10 different situations were presented. In addition, the subjects could give individual comments. The subjects had the freedom of choice to use the AutoSelect mode, which automatically chooses between programs, or to manually select the preferred program once they had been fit. The participants tested the hearing instruments over a period of 2 10 weeks in everyday life. Subsequently their experiences with the automatic program selection were recorded with the help of a questionnaire. In the questionnaire the subjects were asked to rate the switching mechanism of the program selection as well as the general usefulness of the automatic program selection. 3

4 Results The evaluation of the questionnaires revealed the following results. Are you aware of program changes? (Fig. 1) Switching between programs is perceived regularly by 67% of the subjects. How often individuals are in speech-in-noise situations will vary from person to person which may explain the variability in awareness of program changes. The results in Fig. 1 are interpreted as indication that most subjects could judge the frequency of switching and the moment of switching. How do you rate the frequency of switching? (Fig. 2) The switching frequency was individually perceived quite differently. For the majority, however, it was considered to be within acceptable limits. Altogether 74% of participants found the frequency exactly right, a bit too often or a bit slow. For the remaining 26% the frequency of switching was too seldom or too often. The possibility of adjusting the frequency of switching would sometimes be useful to satisfy the individual preferences of the wearer. Figure 1 Are you aware of program changes? always 23% most of the time 26% Figure 2 How do you rate the frequency of switching? never too seldom very seldom often 18% seldom 9% now and again 14% Does the instrument change programs when you expect it to? (Fig. 3) More than half of the subjects found that the instruments switched programs always, mostly or often as expected. For the rest the switching seemed more arbitrary. This is related to the delay in the switching mechanism (the classification algorithm has to be met for at least 10 seconds in order to avoid too high a switching rate between programs), as well as to individual user differences in the expectation of program choice for certain acoustic environments (see Fig. 5). a bit too often 21% too often 21% a bit slow 27% exactly right 26% 4

5 Is the program choice suitable to the situation? (Fig. 4) The greater majority of subjects found that the automatically chosen program was suitable often, mostly, or always to the situation. When does the program choice seem to be unsuitable? (Fig. 5) On the whole there are three situations when the automated system did not always comply with the wishes of the subjects: Figure 3 Does the instrument change programs when you expected it to? most of the time 30% always never very occasionally 10% seldom 0% Speech in noise In this situation the program choice is Program 2 with adaptive directional microphone and noise suppression. Some subjects preferred that only the speech of the person they are looking at be amplified. Others found this unsatisfactory at times as they missed what other speakers in a group were saying. In this situation it is impossible even for a perfect algorithm to predict the wishes of the individual user. Traffic noise In background noise without speech the directional microphone and noise suppression is usually not activated. The reason for this is that in a traffic situation important noises such as approaching vehicles usually should be perceived. The disadvantage is that also many unwanted sounds are heard, which some wearers find annoying. Similarly, as with the speech-in-noise situation the needs differ depending on the individual. Figure 4 often 2 Is the program choice suitable to the situation? always never 0% very occasionally 11% now and again 2 seldom now and again Music and singing The signal identification system is currently less robust in these situations. Music is sometimes classified as speech in noise. The activation of the directional microphone and background noise suppression is not suitable when it is music the user wishes to enjoy. A more reliable distinction between speech in noise and music would be desirable. most of the time 42% often 32% 5

6 How useful is the automatic program choice? (Fig. 6) Altogether about 7 of the test subjects found the automatic system quite useful or very useful and only 20% would rather not use it. Therefore the automatic program selection was found to be a valuable and desirable function. This result is consistent with the finding that the automatic program selection is usually suitable to a particular environment (see Fig. 4). Figure 5 When does the program choice seem to be unsuitable? never singing television listening to music traffic noise speech in noise with several speakers speech in noise speech in quiet with several speakers speech in quiet in quiet Number of mentions 10 Figure 6 How useful is the automatic program choice? not useful 10% very useful 33% of little use 10% a bit useful quite useful 42% 6

7 Summary and discussion This study investigated the usefulness and acceptance of an automatic program selection mode in hearing instruments, from the point of view of the wearer. It was shown that the AutoSelect mode in the Phonak Claro instrument was found to be useful by the clear majority of test subjects. The program choice at any given time was found to be appropriate for the majority of situations. With regard to the switching frequency of the automatic program selection, there were clear individual differences. For some subjects the system switched too often, for some not often enough. A fine tuning parameter for the acoustic criteria of the AutoSelect feature would be useful in order to better satisfy the individual preferences of hearing aid wearer. Since completion of this study a new version of the fitting software (PFG 7.2) includes this option. Speech in noise was quite often found to be a situation where the choice of program by the AutoSelect did not concur with the wishes of the test subject. Optimization of the AutoSelect mode could be achieved through further analysis of acoustic parameters in this environment. The description speech in noise, however, can refer to a multitude of different acoustic situations and the transition to other acoustic environments is fluid by nature. Therefore it is difficult to clearly delineate between the two. Still, even a perfect classification of a given acoustic environment does not solve the problem of individual user preferences at any given time. The suitability of a given program depends on whether the wearer is actively listening and needing good speech intelligibility from in front, or whether, for example, the wearer is also wanting good sound clarity from the sides and from behind. For example, one subject, preferred the instrument not to switch to program 2 with noise suppression, when in traffic noise whilst conversing with someone walking next to him. In this case, the reduction of sound from the sides is not suitable. Especially in these sorts of situations the option of a manual program override is a logical solution which is available in these instruments in addition to the automatic program selection. The results of this study are based on the reports of people who were fit with Claro instruments within the normal hearing aid fitting procedure. The investigations were not carried out in special laboratory conditions, nor were the participants trained or instructed in any special way. The results therefore reflect a reasonably accurate account of experiences with AutoSelect in everyday life. Other studies involving the AutoSelect feature have been conducted under controlled clinical circumstances (Gabriel, 2001; Boretzki et al., 2001). The participants were specially fit with Claro instruments for these studies and acclimatized in a training phase for 2 3 weeks in order to distinguish reliably between the two programs. The results of these studies nevertheless showed great concurrence with the results presented here, both with respect to the suitability of the AutoSelect and to the general usefulness of the AutoSelect mode. On average, the subjects reported that they had their instruments in AutoSelect mode 70 7 of the time and preferred the manual choice the rest of the time. While there are some shortcomings in certain acoustic environments (e.g.: music) and sometimes the automatically selected program is inconsistent with the wishes of individual wearers, the AutoSelect feature of Phonak Claro hearing instruments was found to be a very useful and popular feature, which is perceived as beneficial by the majority of wearers. 7

8 Bibliography Boretzki M., Kießling J., Margolf-Hackl S., Kühnel V. and Volpert S. (2001). Adaptive Richtcharakteristik eines Doppelmikrofons und automatische Programmwahl: Nutzen für den schwerhörigen Menschen. Proc. 4. Jahrestagung der Deutschen Gesellschaft für Audiologie, Aachen, Germany (in press). Byrne D. (1986). Effects of frequency response characteristics on speech discrimination and perceived intelligibility and pleasantness of speech for hearingimpaired listeners. J. Acoust. Soc. Am. 80, Dillon H. and Lovegrove R. (1993). Singlemicrophone noise reduction systems for hearing aids: A review and an evaluation. In: Studebake G. A. und Hochberg I. (Hrsg.) Acoustical Factors Affecting Hearing Aid Performance. Allyn and Bacon, Fabry D. A. and Stypulkowski P. (1992). Evaluation of fitting procedures for multiplememory programmable hearing aids. Paper presented at the annual meeting of the American Academy of Audiology, Nashville, TN. Gabriel B. (2001). Nutzen moderner Hörgeräte-Features für Hörgeräte-Träger am Beispiel eines speziellen Hörgeräte-Typs. Zeitschrift für Audiologie, 40 (1), Kates J. M. (1995). Classification of background noises for hearing aid applications. J. Acoust. Soc. Am. 97, Kuk F. K. (1994). A screening procedure for modified simplex in frequency-gain response selection. Ear Hear. 15, Marzinzik M. (2001). Noise Reduction Schemes for Digital Hearing Aids and their Use for the Hearing Impaired. Shaker Verlag, Aachen. Pumford J. M., Scollie S. D. and Jenstad L. M. (2000). Speech recognition with in-the-ear and behind-the-ear dual-microphone hearing instruments. J. Am. Acad. Audiol. 11 (1), Punch J. L., Robb R. and Shovels A. H. (1994). Aided listener preferences in laboratory versus real-world environments. Ear Hear. 15, Ricketts T. (2000). Impact of noise source configuration on directional hearing aid benefit and performance. Ear Hear. 21 (3), Van Dijkhuizen J. N., Festen J. M. and Plomp R. (1991). The effect of frequency selective attenuation on the speech reception threshold of sentences in conditions of low frequency noise. J. Acoust. Soc. Am. 90, Weiss M. and Neumann A. C. (1993). Noise reduction in hearing aids. In: Studebaker G. A. und Hochberg I. (Hrsg.) Acoustical Factors Affecting Hearing Aid Performance. Allyn and Bacon, Killion M. (1997). The SIN report: Circuits haven t solved the hearing-in-noise problem. Hearing Journal 50 (10), Kochkin S. (1996). Customer satisfaction and subjective benefit with high performance hearing aids. Hearing Review 3 (12),

9 Michael Büchler ENT Department, University Hospital Zurich, Switzerland Michael Büchler was born in Zurich in He graduated as an electrical engineer at the Technical University (ETH) Zurich in From he worked as a development engineer and project leader for microcontroller systems for electrical installations technology at a renowned Swiss company. After this he spent one year at Phonak in the research and development unit where he worked on an EU project in the area of algorithms for noise suppression. Since 1998 he has been employed in the laboratory for experimental audiology at the University Hospital Zurich and is writing a dissertation on auditory-based noise classification. 9

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12 News / Ideas / High Technology / Acoustics Usefulness and acceptance of automatic program selection in hearing instruments 27 Focus Michael Büchler ENT Department, University Hospital Zurich, Switzerland Introduction Hearing aid users are exposed to a great variety of listening situations. Quiet environments alternate with noise, making the demands the wearer makes on his hearing instruments equally diverse. Conventional hearing instruments are fit to an individual s hearing loss on the audiometric data such as the audiogram or loudness scaling. The required amplification for each frequency region is evaluated using a formula (DSL [i/o], NAL-RP, etc.). A single setting is supposed to cover all listening situations. Therefore the resulting fitting is most likely a compromise, which is not the optimal setting for all listening environments and signal characteristics. Various studies show that the optimum setting of the frequency response and compression parameters depends on the background noise and characteristics of the signal. In addition an alternate setting to