Scandinavian Audiology
ISSN: 0105-0397 (Print) (Online) Journal homepage: http://www.tandfonline.com/loi/iaud20
The Super-Bass Bone-Anchored Hearing AID Compared to Conventional Hearing AIDS. Audiological Results and the Patients' Opinions A. F. M. Snik, F. F. Jorritsma, C. W. R. J. Cremers, A. J. Beynon & N. W. van den Berge To cite this article: A. F. M. Snik, F. F. Jorritsma, C. W. R. J. Cremers, A. J. Beynon & N. W. van den Berge (1992) The Super-Bass Bone-Anchored Hearing AID Compared to Conventional Hearing AIDS. Audiological Results and the Patients' Opinions, Scandinavian Audiology, 21:3, 157-161, DOI: 10.3109/01050399209045997 To link to this article: http://dx.doi.org/10.3109/01050399209045997
Published online: 12 Oct 2009.
Submit your article to this journal
Article views: 20
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Citing articles: 2 View citing articles
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Date: 29 March 2016, At: 23:34
Scand Audiol 1992; 21: 157-161
THE SUPER-BASS BONE-ANCHORED HEARING AID COMPARED TO CONVENTIONAL HEARING AIDS. AUDIOLOGICAL RESULTS A N D THE PATIENTS' OPINIONS A. F. M. Snik,' F. F. Jorritsma,2 C. W. R. J. Cremers,' A. J. Beynon' and N. W. van den Berge3
'
From the ENT Department. University Hospital. Nijmegen, the 2Audiologic Center and 3Diaconessenhuis,Eindhoven, The Netherlands
Downloaded by [University of Newcastle] at 23:34 29 March 2016
ABSTRACT The super-bass bone-anchored hearing aid compared to conventional hearing aids. Audiological results and the patients' opinions. Snik. A.F.M., Jorritsma, F.F., Cremers, C.W.R.J., Beynon, A.J. and van den Berge, N.W. (The ENT Department, University Hospital, Nijmegen, the Audiologic Center, and Diaconessenhuis, Eindhoven, The Netherlands). ScandAudiol 1992; 21: 157-161. Twelve patients with severe mixed hearing loss (PTA ranging from 70 to 108 dB HL) were provided with the percutaneous 'super-bass H C 220' bone-anchored hearing aid (BAHA) to replace their former hearing aid. Five had previously worn an air-conduction hearing aid (behind-the-ear type, BTE) which could no longer be used because of recurrent otorrhoea; the others had previously worn a conventional (transcutaneous) bone-conduction hearing aid (CBHA) which had caused seriouscomplaints, such as headaches or skin irritation. Freefield speech audiometry in the subgroup of patients who used to wear a CBHA revealed that the maximum intelligibility score with the BAHA was euual to or better than that obtained with the CBHA (range'from 0 to f27'X). In three of the five patients who used to wear a BTE, the speech scores were poorer with the BAHA than with the BTE (range from - I 3 to -40%)). For the remaining two patients, the difference in scores was 0 and 10%. In conclusion, speech recognition with the BAHA HC220 in the patients with severe mixed hearing loss was comparable to, or better than, that with a CBHA. Comoared to an air-conduction hearine . aid, the results may be considerably poorer. The results of the questionnaire were in good agreement with the measurements and support the conclusions.
+
Key words: bone-anchored hearing system, hearing aid, skin penetration, titanium implant.
INTRODUCTION During the 1980s, an alternative to the bone-conduction hearing aid was introduced by a Swedish group (Tjellstrom et a]., 1983; HBkansson et al., 1985; Carlsson, 1990). In this new aid (the bone-anchored hearing aid @AHA)), the acoustical signal, generated by a transducer, is led directly to the sku11by means of a percutaneous coupling.
The standard BAHA, the H C 200 (Carlsson, 1990), can be applied in patients with conductive or mixed hearing loss, as long as the average bone conduction threshold at 500, 1000, 2000 and 3000 Hz does not exceed 45 d B HL. For patients with a sensorineural component which exceeds 45 d B HL, a more powerful BAHA was introduced, called the super-bass H C 220. In this hearing aid a transducer is combined with a conventional body-level hearing aid (Carlsson, 1990). An advantage of this set-up is the increased distance between the oscilator and the microphone, which reduces the acoustical feed-back problems. Furthermore, the output of the H C 220 is higher than that of the standard type, so it is suggested that the H C 220 will be of benefit to patients with sensorineural components of up to 60 dB H L (Carlsson, 1990). This is a bromising option because many of the patients with sensorineural hearing components Of between 45 and 60 d B HL, for whom a conventional air-conduction hearing aid cannot be used, benefit poorly from a conventional bone-conduction hearing aid. The present paper deals with an audiological comparison between the BAHA H C 220 and the patients' previous conventional hearing aid as well as the patients' opinions on the two hearing aids, as derived from a questionnaire. ~~
METHODS Subjects Twelve patients were provided with a BAHA H C 220, six in Eindhoven (numbers I to 6) and six in Nijmegen (numbers 7 to 12). All patients were suffering from recurrent otorrhoea and therefore occluding ear moulds could not be applied. Some characteristics ofthe patients are given in Table I. All the patients had a mixed hearing 10% They had all worn a hearing aid for an average of 23 years (range 7 to 40 years). Five patients used to wear a behind-the-ear (BTE) hearing aid, which could not be used any longer because of recurrent Srund Audiol 21
158
A . F. M . Snik et al.
Table I. Individualpatient data concerning hearing thresholds ofthe ear at the implanted side, previous hearing aid and speech recognition scores obtained with the B A H A and with the previous hearing aid
Downloaded by [University of Newcastle] at 23:34 29 March 2016
~
Patient no.
PTAbc (dB HL)
PTAac (dB HL)
CHA
Age (years)
1 2 3 4 5 6 7 8 9 10 I1 12
28 52 > 62 40 42 57 57 47 62 > 55 47 47
70 I07 I08 82 85 75 I00 72 97 93 95 78
BC BC BC BTE BC BTE BTE BTE BC BC BTE BC
69 73 62 46 84 63 73 50 36 34 78 66
MPS CHA
MPS BAHA
(YO)
(O/O
30 40 0 85 53 70 88 75 85 5 90 40
30 60 0 45 53 43 75 85 I00 33 90 65
1
SRT CHA (dB(A))
SRT BAHA (dB(A))
-
-
-
35
-
-
20 45 40 45 45 35
-
~
45 ~
45 ~
50 45 25 -
40 50
PTA =pure-tone average for air-conduction (PTAac) or bone-conduction (PTAbc) MPS =maximum phoneme score SRT =speech recognition threshold CHA =conventional (previous) hearing aid BTE = behind-the-ear hearing aid (air conduction) BC =conventional bone-conduction hearing aid
otorrhoea. The other seven patients had worn a conventional bone-conduction hearing aid (CBHA). The implanted screw was placed a t the ‘best’ side, near the ear with the best bone-conduction thresholds. Surgery was uneventful1 in all patients and no serious postoperative complications occurred. Most of the patients were first fitted with the standard H C 200. This was subsequently rejected owing to insufficient gain. As the H C 220 is only a transducer, it had to be connected to a conventional (body-level) hearing aid. After a trial period of a t least three weeks, five of the patients chose the Philips SI594 and six patients the Danavox 107-2 as amplifier. One patient (number 4) did not want a body-worn hearing aid: in this case, the H C 200 was connected to a superpower BTE CROS hearing aid (Oticon E 39PL).
Measurements Pure-tone audiometry was performed using an Interacoustics AC-5 audiometer with TDH-39P headphones. The technical performance of the BAHAs was measured using the skull simulator (Hikansson & Carlsson, 1989), connected to a B & K measuring system. Input-output curves were obtained at a fixed frequency of I000 Hz. The sound input level was varied from 60 to 90 dB SPL. For comparison, the patients participatcd in audiological tests with the BAHA and, separately, with their former conventional hearing aid (CHA). Another possibility would have been to compare the results obtained with the BAHA and a standard CHA. The latter set-up was not chosen becausc the aim was to compare individually adapted hearing aids. Both the CHA and BAHA were individually adaptcd. All the CHAs were checked for normal functioning. The audiometric tests to compare the two hearing aids, which were performed after a t least a four-week period of daily use, comprised free-field tone and speech audiometry. During all tests, the BAHA or the CHA was worn separately at the normal (daily) volume. Scand Audio/ 21
All tests were performed in special, sound-proof rooms. The warble tones used to obtain free-field thresholds were generated by the standard audiometer (Interacoustics AC-5, calibrated according to I S 0 389), with a frequency modulation of 5%. The tones were presented by means of a loudspeaker, placed 1 m in front of the patient. The free-field set-up was calibrated according to Morgan el al. (1979). Thresholds werc determined a t frequencies of 250,500, I 000, 2000, 4000 and 8000 Hz. The free-field speech audiogram was obtained using the same set-up and standard Dutch P.B. word lists consisting of 10 monosyllables. The level of the words was calibrated using a B & K 2205 sound-level meter, placed I m in front of the loudspeaker. The level of the (fluctuating) signal was read a t the slow speed, using the ‘A’ filter. The readings for 40 words were averaged: as a result, the free-Geld spccch levels are presented in dB(A). For all the patients, phoneme scores as a function of the presentation level were recorded separately for the BAHA and the CHA. From these measurements, the maximum phoneme score (MPS) and the speech recognition threshold (SRT) wcre determined, the latter being the presentation level in dB(A) at which 50%) of the presented phonemes were repeated properly by the patient. Q ueslionrroire Data on the patients’ opinions about their former hearing aid and the new BAHA were gathered by means of a questionnaire. With regard to the BAHA, the questionnairc was presented to the patient after at lcast a four-month period of daily use. The questions asked concerned the number of hours of daily use, skin irritations, the recognition of speech in a quiet condition (How well can you understand in a quiet room: a manja women/a childlthe radio and television), the recognition of speech in noisy situations (How well can you understand another person: in the car/bus or train/during partieshn shopsion streets/while the radio, television is on) and the comfort (the adjustment, ease of handling, irritating
The super-bass bone-anchored hearing aid
sounds, feed-back problems). The patient was asked to rate his/her answer on a scale from I to 10. Afterwards, three scores were calculated: the speech recognition-in-quiet (SQ) score, the speech recognition-in-noise (SN) score and the comfort (COM) score. These scores were the average of the rated scores of the questions involved per topic.
RESULTS A N D DISCUSSION
Downloaded by [University of Newcastle] at 23:34 29 March 2016
Considering the MPS in Table I, remarkable differences were seen between the subgroup of patients who used to wear a BTE ( n = 5 ) and the subgroup who used to wear a CBHA ( n = 7). Therefore, the results of both subgroups are presented separately. In several patients, the SRT could not be determined because the maximum score with the CHA or the BAHA was less than 50%. The SRT values of both hearing aids could only be compared in five patients. Comparison between the BAHA and the CBHA results In Fig. 1 the average difference between the free-field warble thresholds, obtained by subtracting the thresholds obtained with the BAHA from those obtained with the CBHA, is presented as a function of frequency. At the higher frequencies, the average difference was negative, indicating that the hearing in this region was, on average, better with the BAHA than
(dB)
30r---
~- --~
t
159
with the CBHA. This is in agreement with the literature (Carlsson, 1990; Cremers et al., 1991). In Table I it can be seen that the MPS with the BAHA is cqual to that with the CBHA in three patients and better in four patients (range of improvement from 15 to 28%). The SRT values can only be compared in two patients (numbers 5 and 9, see Table I): in one patient the SRT obtained with the BAHA was 10 dB better than that obtained with the CBHA; for the other patient, both values were equal. The MPS values of patient number 1 were disappointing (30%) while the PTAbc value was relatively good. The low MPS values were most probably caused by the abrupt high frequency sensorineural loss as seen in this patient: the sensorineural threshold increased from 20 dB H L at 1000 Hz to more than 50 dB H L at 2 000 Hz. The results of the questionnaire are presented in Table 11. The BAHA minus CBHA scores (the socalled ASQ, ASN and ACOM) are presented: a positive A score means that the patient was more satisfied with the BAHA than with the CBHA. In agreement with the results of the speech recognition tests, the ASQ and ASN scores were near zero or positive for all except one patient (number I). On the other hand, patient
Table 11. Individual results from the questionnaire. The results of patients who used a conuentionul boneconduction hearing aid and those who used an air7conduction hearing aidprior to ihe BAHA are grouped. f = a better score with the BAHA, - = a poorer score ASQ
Patient no.
ASN
ACOM
-3.0
+2.1
-0.1
0 +1.0 1.0
BAHA versus CBHA
-20
I
-301250
I
J
L
L - - i
-~,--_L _ L
500
1000
2000
1 2 3 5 9 10 12
4000
+
0 0 +2.8 +2.8 +0.6
+
+ 1.8 +0.4 0
BAHA versus BTE
8000
Frequency (Hz) Fig. 1. Average frce-field thresholds obtained with the bone-
anchored hearing aid (BAHA) minus those obtained with the conventional hearing aid versus frequency. The crosses refer to the BAHA minus the conventional bone-conduction hearing aid (CBHA) thresholds (seven patients), the squares to the BAHA minus the behind-thc-ear air-conduction hearing aid (BTE) thresholds (five patients). The SD are indicated.
-1.2 -0.1 -0.9 -0.6 f2.2 t4.4 1.4
~~~~~
4
-5.6
6
- 5.8
I
+ 3.4
8 11
-0.4 +3.5 ~
-4.2 -2.0
+0.8 - 3.2 5.4 - 1.4 1.2
+3.7
+
0 +2.9
+
~
=BAHA minus CHA (CBHA or BTE) scores as obtained from the questionnaire SQ =speech recognition in quiet SN =speech recognition in noisy situations COM = comfort A
160 A . F. M . Snik et al.
Downloaded by [University of Newcastle] at 23:34 29 March 2016
number 1 had the highest ACOM score, which means that, in his opinion, the BAHA was much more convenient. All the patients wore the BAHA all day. Most patients complained about skin irritation caused by the pressure needed to apply the transducer of a CBHA. With the BAHA, no lasting skin irritations were reported by either patient. With respect to skin irritations, all seven patients preferred the BAHA. Comparison belween the B A H A and the BTE results The average difference between the free-field warble thresholds, obtained by subtracting the thresholds obtained with the BAHA from those obtained with the BTE, is also presented in Fig. 1 . At the higher frequencies, the average difference was positive, indicating that the hearing in this region was, on average, better with the BTE than with the BAHA. The SRT values could be compared in three patients in this subgroup (numbers 7, 8 and 11. see Table I): the SRT values obtained with the BAHA and the BTE were equal within 5 dB. The MPS scores with the BAHA compared to the BTE were better in one patient (+ loo/,), equal in one patient, but worse in the other three patients (see Table I, range of worsening: - I 3 to -40%). To discuss this in more detail, a typical freefield speech Sudiogram of one of the latter four patients is shown in Fig. 2. As can be seen, the phoneme score with the BAHA levels-off at 70 dB(A) while that of the BTE does not. Obviously, the output of the BAHA at the volume chosen by the patient (volume 6) was saturated at these input levels. This
dB ref 0 U
t P U
t F 0
r
60
70
~~
__~___ 80
1 90
Input dB (SPL)
Fig. 3 . Input-output curves at 1000 Hz of the HC 220 combined with a Philips S1594 hearing aid as obtained with the skull simulator. The numbers in the figure refer to the volume setting (maximum volume: 9).
was verified on the skull simulator, as can be seen in the input-output measurement presented in Fig. 3. Similar level-off effects were seen in the speech audiograms of the other three patients who had lower MPS scores with the BAHA than with the BTE. The results for patient number 4 were especially disappointing: it should be remembered that this patient did not want to use a body-level hearing aid so a BTE combined with the H C 220 was used instead. The input-output curve of this combination at the volume chosen by the patient (volume 3) was inferior to that given in Fig. 3: this may explain the poor results. % 100 Concerning the questionnaire results, the scores BTE in this subgroup varied greatly (see Table 11). Two 80 1 patients (numbers 4 and 6) experienced worse speech recognition both in quiet and in noise when wearing BAHA 60 the BAHA (negative ASN and ASQ values). On the other hand, two patients (numbers 7 and 11) experi40 enced better speech recognition with the BAHA (positive ASN and ASQ values). The reason for those 20 ' differences in not clear. However, it should be noted , a ; /_I 0 " ' that the air-conduction thresholds ofpatients numbcrs 0 10 20 30 40 50 60 70 80 90 7 and 1 1 were poor compared to those of patients dB(A) numbers 4 and 6 (see PTAac values, Table I). ThereFig. 2. A typical example of a free-field speech audiogram of one of the patients as obtained with the BAHA (HC 220 fore, it may be argued that patients 4 and 6 received combined with the Philips S1594) and with the previous airgreater benefit from their air-conduction hearing aid conduction hearing aid (BTE, Philips A D 446). Both hearing leading to poor ASN and ASQ scores. aids were adjusted to the volume normally chosen by the For one patient (number 8) both the ASN and ASQ patient.
,---
~
~
SrartJ Audio1 21
1
The super-bass bone-anchored hearing aid 16 1
Downloaded by [University of Newcastle] at 23:34 29 March 2016
values were near zero. The latter three patients wore the BAHA all day while the former two used it only for a limited number of hours a day, in addition to their BTE. Correlations were calculated which assumcd linear relations between the subjective ASQ, ASN and ACOM scores on the one hand, and the objective AMPS score on the other, i.e. the MPS with the BAHA minus that with the CHA, The AMPS and ASQ values were positively and significantly correlated ( p =0.71, p
ISSN: 0105-0397 (Print) (Online) Journal homepage: http://www.tandfonline.com/loi/iaud20
The Super-Bass Bone-Anchored Hearing AID Compared to Conventional Hearing AIDS. Audiological Results and the Patients' Opinions A. F. M. Snik, F. F. Jorritsma, C. W. R. J. Cremers, A. J. Beynon & N. W. van den Berge To cite this article: A. F. M. Snik, F. F. Jorritsma, C. W. R. J. Cremers, A. J. Beynon & N. W. van den Berge (1992) The Super-Bass Bone-Anchored Hearing AID Compared to Conventional Hearing AIDS. Audiological Results and the Patients' Opinions, Scandinavian Audiology, 21:3, 157-161, DOI: 10.3109/01050399209045997 To link to this article: http://dx.doi.org/10.3109/01050399209045997
Published online: 12 Oct 2009.
Submit your article to this journal
Article views: 20
View related articles
Citing articles: 2 View citing articles
Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=iaud20 Download by: [University of Newcastle]
Date: 29 March 2016, At: 23:34
Scand Audiol 1992; 21: 157-161
THE SUPER-BASS BONE-ANCHORED HEARING AID COMPARED TO CONVENTIONAL HEARING AIDS. AUDIOLOGICAL RESULTS A N D THE PATIENTS' OPINIONS A. F. M. Snik,' F. F. Jorritsma,2 C. W. R. J. Cremers,' A. J. Beynon' and N. W. van den Berge3
'
From the ENT Department. University Hospital. Nijmegen, the 2Audiologic Center and 3Diaconessenhuis,Eindhoven, The Netherlands
Downloaded by [University of Newcastle] at 23:34 29 March 2016
ABSTRACT The super-bass bone-anchored hearing aid compared to conventional hearing aids. Audiological results and the patients' opinions. Snik. A.F.M., Jorritsma, F.F., Cremers, C.W.R.J., Beynon, A.J. and van den Berge, N.W. (The ENT Department, University Hospital, Nijmegen, the Audiologic Center, and Diaconessenhuis, Eindhoven, The Netherlands). ScandAudiol 1992; 21: 157-161. Twelve patients with severe mixed hearing loss (PTA ranging from 70 to 108 dB HL) were provided with the percutaneous 'super-bass H C 220' bone-anchored hearing aid (BAHA) to replace their former hearing aid. Five had previously worn an air-conduction hearing aid (behind-the-ear type, BTE) which could no longer be used because of recurrent otorrhoea; the others had previously worn a conventional (transcutaneous) bone-conduction hearing aid (CBHA) which had caused seriouscomplaints, such as headaches or skin irritation. Freefield speech audiometry in the subgroup of patients who used to wear a CBHA revealed that the maximum intelligibility score with the BAHA was euual to or better than that obtained with the CBHA (range'from 0 to f27'X). In three of the five patients who used to wear a BTE, the speech scores were poorer with the BAHA than with the BTE (range from - I 3 to -40%)). For the remaining two patients, the difference in scores was 0 and 10%. In conclusion, speech recognition with the BAHA HC220 in the patients with severe mixed hearing loss was comparable to, or better than, that with a CBHA. Comoared to an air-conduction hearine . aid, the results may be considerably poorer. The results of the questionnaire were in good agreement with the measurements and support the conclusions.
+
Key words: bone-anchored hearing system, hearing aid, skin penetration, titanium implant.
INTRODUCTION During the 1980s, an alternative to the bone-conduction hearing aid was introduced by a Swedish group (Tjellstrom et a]., 1983; HBkansson et al., 1985; Carlsson, 1990). In this new aid (the bone-anchored hearing aid @AHA)), the acoustical signal, generated by a transducer, is led directly to the sku11by means of a percutaneous coupling.
The standard BAHA, the H C 200 (Carlsson, 1990), can be applied in patients with conductive or mixed hearing loss, as long as the average bone conduction threshold at 500, 1000, 2000 and 3000 Hz does not exceed 45 d B HL. For patients with a sensorineural component which exceeds 45 d B HL, a more powerful BAHA was introduced, called the super-bass H C 220. In this hearing aid a transducer is combined with a conventional body-level hearing aid (Carlsson, 1990). An advantage of this set-up is the increased distance between the oscilator and the microphone, which reduces the acoustical feed-back problems. Furthermore, the output of the H C 220 is higher than that of the standard type, so it is suggested that the H C 220 will be of benefit to patients with sensorineural components of up to 60 dB H L (Carlsson, 1990). This is a bromising option because many of the patients with sensorineural hearing components Of between 45 and 60 d B HL, for whom a conventional air-conduction hearing aid cannot be used, benefit poorly from a conventional bone-conduction hearing aid. The present paper deals with an audiological comparison between the BAHA H C 220 and the patients' previous conventional hearing aid as well as the patients' opinions on the two hearing aids, as derived from a questionnaire. ~~
METHODS Subjects Twelve patients were provided with a BAHA H C 220, six in Eindhoven (numbers I to 6) and six in Nijmegen (numbers 7 to 12). All patients were suffering from recurrent otorrhoea and therefore occluding ear moulds could not be applied. Some characteristics ofthe patients are given in Table I. All the patients had a mixed hearing 10% They had all worn a hearing aid for an average of 23 years (range 7 to 40 years). Five patients used to wear a behind-the-ear (BTE) hearing aid, which could not be used any longer because of recurrent Srund Audiol 21
158
A . F. M . Snik et al.
Table I. Individualpatient data concerning hearing thresholds ofthe ear at the implanted side, previous hearing aid and speech recognition scores obtained with the B A H A and with the previous hearing aid
Downloaded by [University of Newcastle] at 23:34 29 March 2016
~
Patient no.
PTAbc (dB HL)
PTAac (dB HL)
CHA
Age (years)
1 2 3 4 5 6 7 8 9 10 I1 12
28 52 > 62 40 42 57 57 47 62 > 55 47 47
70 I07 I08 82 85 75 I00 72 97 93 95 78
BC BC BC BTE BC BTE BTE BTE BC BC BTE BC
69 73 62 46 84 63 73 50 36 34 78 66
MPS CHA
MPS BAHA
(YO)
(O/O
30 40 0 85 53 70 88 75 85 5 90 40
30 60 0 45 53 43 75 85 I00 33 90 65
1
SRT CHA (dB(A))
SRT BAHA (dB(A))
-
-
-
35
-
-
20 45 40 45 45 35
-
~
45 ~
45 ~
50 45 25 -
40 50
PTA =pure-tone average for air-conduction (PTAac) or bone-conduction (PTAbc) MPS =maximum phoneme score SRT =speech recognition threshold CHA =conventional (previous) hearing aid BTE = behind-the-ear hearing aid (air conduction) BC =conventional bone-conduction hearing aid
otorrhoea. The other seven patients had worn a conventional bone-conduction hearing aid (CBHA). The implanted screw was placed a t the ‘best’ side, near the ear with the best bone-conduction thresholds. Surgery was uneventful1 in all patients and no serious postoperative complications occurred. Most of the patients were first fitted with the standard H C 200. This was subsequently rejected owing to insufficient gain. As the H C 220 is only a transducer, it had to be connected to a conventional (body-level) hearing aid. After a trial period of a t least three weeks, five of the patients chose the Philips SI594 and six patients the Danavox 107-2 as amplifier. One patient (number 4) did not want a body-worn hearing aid: in this case, the H C 200 was connected to a superpower BTE CROS hearing aid (Oticon E 39PL).
Measurements Pure-tone audiometry was performed using an Interacoustics AC-5 audiometer with TDH-39P headphones. The technical performance of the BAHAs was measured using the skull simulator (Hikansson & Carlsson, 1989), connected to a B & K measuring system. Input-output curves were obtained at a fixed frequency of I000 Hz. The sound input level was varied from 60 to 90 dB SPL. For comparison, the patients participatcd in audiological tests with the BAHA and, separately, with their former conventional hearing aid (CHA). Another possibility would have been to compare the results obtained with the BAHA and a standard CHA. The latter set-up was not chosen becausc the aim was to compare individually adapted hearing aids. Both the CHA and BAHA were individually adaptcd. All the CHAs were checked for normal functioning. The audiometric tests to compare the two hearing aids, which were performed after a t least a four-week period of daily use, comprised free-field tone and speech audiometry. During all tests, the BAHA or the CHA was worn separately at the normal (daily) volume. Scand Audio/ 21
All tests were performed in special, sound-proof rooms. The warble tones used to obtain free-field thresholds were generated by the standard audiometer (Interacoustics AC-5, calibrated according to I S 0 389), with a frequency modulation of 5%. The tones were presented by means of a loudspeaker, placed 1 m in front of the patient. The free-field set-up was calibrated according to Morgan el al. (1979). Thresholds werc determined a t frequencies of 250,500, I 000, 2000, 4000 and 8000 Hz. The free-field speech audiogram was obtained using the same set-up and standard Dutch P.B. word lists consisting of 10 monosyllables. The level of the words was calibrated using a B & K 2205 sound-level meter, placed I m in front of the loudspeaker. The level of the (fluctuating) signal was read a t the slow speed, using the ‘A’ filter. The readings for 40 words were averaged: as a result, the free-Geld spccch levels are presented in dB(A). For all the patients, phoneme scores as a function of the presentation level were recorded separately for the BAHA and the CHA. From these measurements, the maximum phoneme score (MPS) and the speech recognition threshold (SRT) wcre determined, the latter being the presentation level in dB(A) at which 50%) of the presented phonemes were repeated properly by the patient. Q ueslionrroire Data on the patients’ opinions about their former hearing aid and the new BAHA were gathered by means of a questionnaire. With regard to the BAHA, the questionnairc was presented to the patient after at lcast a four-month period of daily use. The questions asked concerned the number of hours of daily use, skin irritations, the recognition of speech in a quiet condition (How well can you understand in a quiet room: a manja women/a childlthe radio and television), the recognition of speech in noisy situations (How well can you understand another person: in the car/bus or train/during partieshn shopsion streets/while the radio, television is on) and the comfort (the adjustment, ease of handling, irritating
The super-bass bone-anchored hearing aid
sounds, feed-back problems). The patient was asked to rate his/her answer on a scale from I to 10. Afterwards, three scores were calculated: the speech recognition-in-quiet (SQ) score, the speech recognition-in-noise (SN) score and the comfort (COM) score. These scores were the average of the rated scores of the questions involved per topic.
RESULTS A N D DISCUSSION
Downloaded by [University of Newcastle] at 23:34 29 March 2016
Considering the MPS in Table I, remarkable differences were seen between the subgroup of patients who used to wear a BTE ( n = 5 ) and the subgroup who used to wear a CBHA ( n = 7). Therefore, the results of both subgroups are presented separately. In several patients, the SRT could not be determined because the maximum score with the CHA or the BAHA was less than 50%. The SRT values of both hearing aids could only be compared in five patients. Comparison between the BAHA and the CBHA results In Fig. 1 the average difference between the free-field warble thresholds, obtained by subtracting the thresholds obtained with the BAHA from those obtained with the CBHA, is presented as a function of frequency. At the higher frequencies, the average difference was negative, indicating that the hearing in this region was, on average, better with the BAHA than
(dB)
30r---
~- --~
t
159
with the CBHA. This is in agreement with the literature (Carlsson, 1990; Cremers et al., 1991). In Table I it can be seen that the MPS with the BAHA is cqual to that with the CBHA in three patients and better in four patients (range of improvement from 15 to 28%). The SRT values can only be compared in two patients (numbers 5 and 9, see Table I): in one patient the SRT obtained with the BAHA was 10 dB better than that obtained with the CBHA; for the other patient, both values were equal. The MPS values of patient number 1 were disappointing (30%) while the PTAbc value was relatively good. The low MPS values were most probably caused by the abrupt high frequency sensorineural loss as seen in this patient: the sensorineural threshold increased from 20 dB H L at 1000 Hz to more than 50 dB H L at 2 000 Hz. The results of the questionnaire are presented in Table 11. The BAHA minus CBHA scores (the socalled ASQ, ASN and ACOM) are presented: a positive A score means that the patient was more satisfied with the BAHA than with the CBHA. In agreement with the results of the speech recognition tests, the ASQ and ASN scores were near zero or positive for all except one patient (number I). On the other hand, patient
Table 11. Individual results from the questionnaire. The results of patients who used a conuentionul boneconduction hearing aid and those who used an air7conduction hearing aidprior to ihe BAHA are grouped. f = a better score with the BAHA, - = a poorer score ASQ
Patient no.
ASN
ACOM
-3.0
+2.1
-0.1
0 +1.0 1.0
BAHA versus CBHA
-20
I
-301250
I
J
L
L - - i
-~,--_L _ L
500
1000
2000
1 2 3 5 9 10 12
4000
+
0 0 +2.8 +2.8 +0.6
+
+ 1.8 +0.4 0
BAHA versus BTE
8000
Frequency (Hz) Fig. 1. Average frce-field thresholds obtained with the bone-
anchored hearing aid (BAHA) minus those obtained with the conventional hearing aid versus frequency. The crosses refer to the BAHA minus the conventional bone-conduction hearing aid (CBHA) thresholds (seven patients), the squares to the BAHA minus the behind-thc-ear air-conduction hearing aid (BTE) thresholds (five patients). The SD are indicated.
-1.2 -0.1 -0.9 -0.6 f2.2 t4.4 1.4
~~~~~
4
-5.6
6
- 5.8
I
+ 3.4
8 11
-0.4 +3.5 ~
-4.2 -2.0
+0.8 - 3.2 5.4 - 1.4 1.2
+3.7
+
0 +2.9
+
~
=BAHA minus CHA (CBHA or BTE) scores as obtained from the questionnaire SQ =speech recognition in quiet SN =speech recognition in noisy situations COM = comfort A
160 A . F. M . Snik et al.
Downloaded by [University of Newcastle] at 23:34 29 March 2016
number 1 had the highest ACOM score, which means that, in his opinion, the BAHA was much more convenient. All the patients wore the BAHA all day. Most patients complained about skin irritation caused by the pressure needed to apply the transducer of a CBHA. With the BAHA, no lasting skin irritations were reported by either patient. With respect to skin irritations, all seven patients preferred the BAHA. Comparison belween the B A H A and the BTE results The average difference between the free-field warble thresholds, obtained by subtracting the thresholds obtained with the BAHA from those obtained with the BTE, is also presented in Fig. 1 . At the higher frequencies, the average difference was positive, indicating that the hearing in this region was, on average, better with the BTE than with the BAHA. The SRT values could be compared in three patients in this subgroup (numbers 7, 8 and 11. see Table I): the SRT values obtained with the BAHA and the BTE were equal within 5 dB. The MPS scores with the BAHA compared to the BTE were better in one patient (+ loo/,), equal in one patient, but worse in the other three patients (see Table I, range of worsening: - I 3 to -40%). To discuss this in more detail, a typical freefield speech Sudiogram of one of the latter four patients is shown in Fig. 2. As can be seen, the phoneme score with the BAHA levels-off at 70 dB(A) while that of the BTE does not. Obviously, the output of the BAHA at the volume chosen by the patient (volume 6) was saturated at these input levels. This
dB ref 0 U
t P U
t F 0
r
60
70
~~
__~___ 80
1 90
Input dB (SPL)
Fig. 3 . Input-output curves at 1000 Hz of the HC 220 combined with a Philips S1594 hearing aid as obtained with the skull simulator. The numbers in the figure refer to the volume setting (maximum volume: 9).
was verified on the skull simulator, as can be seen in the input-output measurement presented in Fig. 3. Similar level-off effects were seen in the speech audiograms of the other three patients who had lower MPS scores with the BAHA than with the BTE. The results for patient number 4 were especially disappointing: it should be remembered that this patient did not want to use a body-level hearing aid so a BTE combined with the H C 220 was used instead. The input-output curve of this combination at the volume chosen by the patient (volume 3) was inferior to that given in Fig. 3: this may explain the poor results. % 100 Concerning the questionnaire results, the scores BTE in this subgroup varied greatly (see Table 11). Two 80 1 patients (numbers 4 and 6) experienced worse speech recognition both in quiet and in noise when wearing BAHA 60 the BAHA (negative ASN and ASQ values). On the other hand, two patients (numbers 7 and 11) experi40 enced better speech recognition with the BAHA (positive ASN and ASQ values). The reason for those 20 ' differences in not clear. However, it should be noted , a ; /_I 0 " ' that the air-conduction thresholds ofpatients numbcrs 0 10 20 30 40 50 60 70 80 90 7 and 1 1 were poor compared to those of patients dB(A) numbers 4 and 6 (see PTAac values, Table I). ThereFig. 2. A typical example of a free-field speech audiogram of one of the patients as obtained with the BAHA (HC 220 fore, it may be argued that patients 4 and 6 received combined with the Philips S1594) and with the previous airgreater benefit from their air-conduction hearing aid conduction hearing aid (BTE, Philips A D 446). Both hearing leading to poor ASN and ASQ scores. aids were adjusted to the volume normally chosen by the For one patient (number 8) both the ASN and ASQ patient.
,---
~
~
SrartJ Audio1 21
1
The super-bass bone-anchored hearing aid 16 1
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values were near zero. The latter three patients wore the BAHA all day while the former two used it only for a limited number of hours a day, in addition to their BTE. Correlations were calculated which assumcd linear relations between the subjective ASQ, ASN and ACOM scores on the one hand, and the objective AMPS score on the other, i.e. the MPS with the BAHA minus that with the CHA, The AMPS and ASQ values were positively and significantly correlated ( p =0.71, p
