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PubMedDate not supplied

Skull distortion of bone conducted signals.

A previously essentially unknown type of distortion of bone conduction (BC) signal has been studied on the skulls of four human cadavers. The method was based on a miniature accelerometer, rigidly attached to the cranial bone, converting the skull vibration close to the cochlea into an electrical signal which was analysed with regard to harmonic distortion. The BC signals, pure tones, were presented by means of a high-quality vibrator. The distortion was found to be limited to the lower audiometric frequencies, with a maximum around 500 Hz, and of such a degree as to be able to significantly influence the results of BC audiometry. The distortion is probably caused by nonlinear mechanical properties of the human skull.

Audiometry↗
PubMed1991

[A hearing aid anchored in the cranial bone for amplification of bone conduction].

The purpose of this study was to compare hearing and understanding with a bone conduction hearing aid of a new type and with conventional models. The new instrument, BAHA (bone anchored hearing aid) is connected with the skull percutaneously rather than transcutaneously as with the conventional instruments. In the ENT department of Nijmegen University Hospital the understanding of speech with both types of hearing aid was evaluated thoroughly. The patients had a middle-ear loss with in addition an inner-ear loss of 60 dBHL at most. A conventional air conduction hearing aid (behind or inside the ear) was unsuitable for them because of, for instance, chronic runny ears or anomalies of the auditory meatus. A conventional bone conduction hearing aid containing a transducer pressing on the skin was rejected because of poor understanding or serious side effects such as headache and pressure pains. At the first session a titanium screw was implanted in the skull behind the ear. The percutaneous superstructure was put into place a few months later at a second session. In none of the patients were there peroperative problems or postoperative infections of any importance. Understanding of speech in silence and in noise was evaluated with the BAHA and with the conventional aid. Differences in understanding of speech were regarded as significant if they amounted to more than twice the known intra-individual standard deviation. As to understanding of speech in silence, 7 of the 15 patients were found to understand significantly better with the BAHA than with a conventional aid. In the other patients no difference was found.(ABSTRACT TRUNCATED AT 250 WORDS)

Bone Conduction↗
PubMed1989

[Brain stem evoked response audiometry study with a bone conduction receiver in atresia of the auditory canal and microtia].

Conductive hearing loss may be determined from the latency delay of the brainstem auditory evoked response Jewett V, if other reasons that may prolong latency are ruled out. Therefore it is important to determine the bone conduction threshold when examining infants. Two bone vibrators have been chosen, which, with the help of "inverse filtering", provide the possibility of a good sound conduction of the click stimulus and thus a measurement near the hearing threshold. When applying bone vibrators to infants it must be borne in mind, that the sound transfer is reduced because the cranial sutures are not yet closed. The measurement of bone conduction is suitable for securing the result of high-grade combined hearing defects. In two cases of atresia of the external auditory canal and microtia brainstem evoked response audiometry is presented with evaluation of both air and bone conduction.

Adult↗
PubMed1981

Pre-operative bone conduction curves in stapedectomy.

Significant post-stapedectomy cochlear deficit is associated with the following factors in an uncomplicated operation: (1) The age of the patient. (2) A pre-operative bone conduction loss, averaged over 0.25, 0.5, 1.0 and 2.0 KHz, of 20 db or more. (3) A left-to-right sloping bone conduction curve (descending audiometric curve), especially where there is a similar curve in the other ear.

Adult↗
PubMed2001

Bone-conducted sound lateralization of interaural time difference and interaural intensity difference in children and a young adult with bilateral microtia and atresia of the ears.

Bone-conducted sound lateralization tests to determine interaural time difference (ITD) and interaural intensity difference (IID) were conducted by means of a self-recording apparatus in 20 children and a young adult with bilateral microtia and atresia of the ear. This apparatus changes ITD automatically from 0 to 2,000 micros at 50 micros/s and IID from 1 to 40 dB at 1 dB's. When ITD exceeds approximately 200 micros/s and IID exceeds 5 dB in normal subjects the sounds are recognized separately. The test stimulus was a continuous narrow-band noise at 500 Hz and 30 dB SL applied to the right and left mastoids through bone vibrators. In the patients with bilateral atresia of the ears, ITD results revealed approximately normal thresholds of discrimination in half the patients and IID results revealed threshold elevation in only 10%. It is noted that bone-conducted sound lateralization abilities of ITD or IID are maintained in many of these patients.

Adolescent↗
PubMed1986

Reversible and permanent bone conduction threshold shift in cases of chronic suppurative otitis media.

Bone conduction thresholds were measured in sixty-six cases of chronic suppurative otitis media before and after successful oral antimicrobial chemotherapeutic treatment. Comparison of pre- and post-treatment cumulative clinical audiograms of the diseased and the control ears of the same patients disclosed the presence of sensorineural hearing loss with a reversible and a permanent component in the diseased ears. The reversible threshold shift was observed over the higher frequencies, while the permanent threshold shift was equally imposed upon the whole range of the five tested frequencies.

Adolescent↗
PubMed1997

Auditory and tactile bone-conduction thresholds using three different oscillators.

Determination of tactile bone-conduction (BC) thresholds is essential to provide proper diagnosis of individuals with profound hearing loss. In this study, auditory and tactile BC thresholds were compared using three oscillators: the Radioear B-70-A, B-71, and B-72 with mastoid and forehead placement. Subjects included 12 adults with normal hearing (to establish auditory thresholds) and 12 adults with profound sensorineural hearing loss (to establish tactile thresholds). All 24 subjects were tested at octave intervals from 250 through 4000 Hz. As demonstrated in previous studies, tactile thresholds were lower for the low frequencies. Some differences in tactile thresholds were evinced as a function of different oscillators. One fact that emerged from this study is the lower tactile threshold with forehead placement as compared to the mastoid. While ostensibly a disadvantage to forehead BC testing, there are some clinical advantages to be gleaned from this discovery.

Acoustic Stimulation↗
PubMed1995

Auditory brainstem response to bone-conducted clicks in adults and infants with normal hearing and conductive hearing loss.

Knowledge concerning auditory brainstem response (ABR) by bone conduction (BC) is limited, and occasionally controversial. The present study was aimed at further elaboration of this issue. The research population consisted of 107 subjects. Four groups were investigated: group 1, normal-hearing adults aged 20-37 years; group 2, 10 children aged 5.6-8.4 years, with confirmed middle ear effusion (MEE); groups 3 and 4, 22 infants, matched by pairs, aged 5-18 months, 11 with normal otoscopy and 11 with suspected MEE. Comparison between ABR by AC and BC for all four groups is discussed. We observed that the AC-ABR threshold of group 2 was statistically significantly elevated compared to group 1. The same tendency was observed for group 4 compared to group 3. In AC ABR, the mean latency of wave V was significantly prolonged, compared to that of BC ABR in children with confirmed MEE, and infants with suspected MEE. We strongly suggest that by combining AC and BC ABR, more information concerning cochlear reserve status can be obtained in infants and young children who are difficult to test, or wherever a behavioral audiogram cannot be achieved.

Adult↗
PubMed2001

Bone conduction impairment in chronic ear disease.

The preoperative and postoperative bone conduction (BC) thresholds were prospectively investigated in 24 patients with chronic ear disease in the form of cholesteatoma, chronic suppurative otitis media, or adhesive otitis media. All underwent tympanoplasty with mastoidectomy. Ossicular reconstruction was performed in 14, and the remaining 10 were still awaiting second-stage ossicular reconstruction at the time of this investigation. In each group, the postoperative results were compared with the preoperative results by the paired-samples t-test. In the ossicular reconstruction group, the results revealed a significant improvement in the postoperative BC thresholds, as compared with the preoperative BC thresholds, at 250, 1,000, and 2,000 Hz, with the largest mean improvement observed at 2,000 Hz. No significant improvement was observed at any frequency for the group without ossicular reconstruction. Postoperative improvement of at least 10 dB at 2 or more frequencies was observed in 71% of the ossicular reconstruction group, as compared with 0% of the group that did not undergo ossicular reconstruction. The results support the theory that the elevated BC thresholds of patients with chronic ear disease result from the elimination, due to disease, of the middle ear contribution (from the inertial ossicular component and ossicular resonance) to the BC response. The results also suggest that the middle ear contribution to the BC response is restored with ossicular reconstruction.

Adult↗
PubMed1980

[The influence of tympanoplasty on bone conduction (author's transl)].

Seldom tympanoplasty damages the inner ear in a substantial amount: From 1814 operations upon chronic inflamed ears 4 patients (0.22%) became deaf, among the other patients bone conduction (b.c.) in the mean increased at 1000 cps for + 0.8 dB and decreased at 4000 cps for - 2.2 dB. In 9.8% b.c. showed an improvement for 10 dB or more at 1000 and 4000 cps, 9.7% showed an corresponding deterioration. For patients it was confirmed on a statistical base, that the influence on bone conduction demonstrated by animal experiments (Tonndorf), was mainly the result of changing the compliance of oval window and of increasing ossicular inertia. By relieving a mobile stapes of an incus which was fixed in the attic, there results an improvement of mobility of the stapedial footplate with increasing b.c. at 1000 and 4000 cps. By interposition of an incus between tympanic membrane and stapes and by myringoplasty with fascia there results an increasing ossicular inertia with increasing b.c. at 1000 cps and decreasing b.c. at 4000 cps. Noise trauma, mechanical trauma and infection are only of slight importance, only in some single cases they will damage the inner ear in a substantial amount.

Bone Conduction↗
PubMed1997

Normative auditory brainstem response data for bone conduction in the dog.

Auditory brainstem response (ABR) is a valuable tool for the diagnosis of hearing disorders in dogs, but is hampered by the lack of published normative data. The aim of the present study was to obtain normative data for bone conduction, without masking, under clearly defined conditions. Subjects comprised 20 Dalmatians and 20 Jack Russell terriers. Two methods were investigated: holding the bone vibrator against the head by hand or by applying a 500 g weight. The results revealed no difference in hearing threshold between the two breeds or for the two methods of applying the bone vibrator to the head. The mean hearing threshold was close to 0 decibels re normal hearing level (dB nHL), which is the biological norm for humans. Hence, bone conduction thresholds can be used for confirmation of conductive hearing impairment in the dog, in the same way as in humans.

Animals↗
PubMed1976

Input-voltage method of bone-conduction calibration.

Several methods have been proposed for calibrating the bone-conduction section of an audiometer. Because of its low cost and ease of implementation, the input-voltage method is attractive. Only one previous investigation has assessed this calibration method and found it to be lacking. With the availability of updated "required voltages," a reexamination of this calibration method was warranted. Audiometric corrections were determined for 21 combinations of audiometers and bone vibrators at five test frequencies with an artificial-mastoid system. These corrections were compared with those determined with the input-voltage method. The latter yielded corrections that agreed directly with or deviated no more than 5 dB from artificial-mastoid corrections 93.4% of the time and deviated by 10 dB only 6.6% of the time. The use of the input-voltage method for clinical calibration is advocated in the absence of an artificial mastoid.

Audiometry↗
PubMed1990

An electrical network model of inertially induced bone-conducted sound.

A model for the description of inertially induced bone-conducted sound has been developed and a discussion of the appropriate techniques for its representation as an electrical network is described. Predictions are made for the sound pressure produced in the meatus in the cases of normal ears and pathological ears resulting from vibration applied to the skull. Evidence from this modelling suggests that the technique may provide improved discriminability over conventional immitance measurements for some types of pathology.

Acoustics↗
PubMed1982

A standard determination of paired air- and bone-conduction thresholds under different masking noise conditions.

Air-(ac) and bone-conduction (bc) thresholds were determined for 96 subjects in the age range 16-30 years. The bc tests were carried out using a B-71 vibrator applied to left and right mastoid under three conditions at the contralateral ear: unoccluded, masked at 25 dB and at 40 dB sensation level; ac audiometry and masking noise used a TDH-39 earphone. By a systematic process of otological classification of the subjects, the bc threshold for 'normal hearing' could be estimated with an uncertainty of less than 1 dB and interpolated for masking noise levels from zero to 40 dB sensation level. Results are expressed as alternating force levels in an artificial mastoid of current commercial design. Variance of the air-bone difference for individual ears is found to be less than the sum of ac and bc threshold variances calculated separately, implying strong air-bone correlation. Comparison is made with other recent studies using B-71 and KH-70-type vibrators, and average results are presented in the context of a proposed international standard for the normal threshold of hearing by bc.

Adolescent↗
PubMed2002

Factors contributing to bone conduction: the middle ear.

Measurement of the motion of the malleus umbo and stapes footplate during bone conduction (BC) stimulation was conducted in vitro in 26 temporal bones using a laser Doppler vibrometer over the frequency range 0.1 to 10 kHz. For lower frequencies, both ossicular sites followed the motion of the temporal bone. The differential motion between the malleus and the surrounding bone was greater than the differential motion of the stapes footplate; both resonated near 1.5 kHz. Different lesions were shown to affect the response: (1) a mass attached to the umbo lowered the resonance frequency of the ossicular vibration; (2) fixation of either the malleus or stapes increased the stiffness and shifted the resonance frequency upward; and (3) dislocation of the incudo-stapedial joint did not significantly affect the ossicular vibration. The sound radiated from the tympanic membrane was approximately 85 dB SPL at an umbo differential velocity of 1 mm/s for low frequencies in an open ear canal and about 10 dB higher for an occluded one; at higher frequencies (above 2 kHz) resonances of the canal determine the response. It was also found that the motion between the footplate and promontory was within 5 dB when the specimen was stimulated orthogonal to the vibration direction of the ossicles than in line with the same. Measurement of the differential motion of the umbo in one live human skull gave similar response as the average result from the temporal bone specimens.

Bone Conduction↗
PubMed1979

Bone conduction changes following successful tympanoplasty type I.

Pre and one year postoperative bone conduction (b.c.) thresholds were compared for 50 ears of 48 patients, ranging in age from 14 to 42 years, in whom successful tympanic grafts resulted in at least an average improvement of 10 db for 500 to 4000 Hz. While pre and postoperative data are included for all ears and test frequencies, significant BC improvement is seen only at those frequencies, in each case, where the pre-op BC thresholds were worse than 10 db. Normal pre-op BC thresholds cannot show substantial improvement because of audiometric limitations. The amount of BC shift at each frequency for those with pre-op BC thresholds that were subnormal averaged 6 db at 500 Hz, 13.3 db at 1000 Hz, 13.8 db at 2000 Hz and 9 db at 4000 Hz, all highly significant statistically. There were no significant postoperative BC shifts related either to duration of the disease process, length of postoperative period before final test (all were more than one year) or whether the surgical procedure was tympanoplasty type I or myringoplasty.

Adolescent↗
PubMed1989

Clinical experience with the Xomed Audiant osteointegrated bone conducting hearing device: a preliminary report of seven cases.

An osteointegrated bone conducting hearing device has recently become available in North America. As with any new medical treatment, initial enthusiasm is soon tempered by its inherent limitations. Critical and objective analysis of results and candid reporting of clinical experiences will lead to the establishment of realistic indications for any new treatment. We present the current indications for insertion of the Xomed Audiant Bone Conductor, our early clinical experience and our thoughts on its future role in the management of patients with conductive hearing loss.

Adult↗
PubMed2003

Estimating bone conduction transfer functions using otoacoustic emissions.

A technique for estimating the nonparametric bone conduction transfer function using distortion product otoacoustic emissions (DPOAEs) is presented. Individual transfer functions were obtained using DPOAEs recorded from a single ear of five normal-hearing adults. Repeatability of the technique was investigated by performing measurements on at least three dates. Functions were reasonably repeatable, and were unique to each individual as expected from subjective measurements. Input force and DPOAE measurements were made for each individual, and a model of the auditory periphery representative of an average person was employed. The technique is objective and requires only passive cooperation, but robust DPOAEs are needed and the measurement time can be onerous for a wide frequency band or fine frequency resolution. With appropriate adjustments to the model of the auditory periphery, the method could be applied with animal models.

Acoustics↗