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PubMed1991

Effect of vibrator to head coupling force on the auditory brain stem response to bone conducted clicks in newborn infants.

The effect of vibrator to head coupling force on the auditory brain stem response (ABR) to bone conducted clicks in newborn infants was investigated. Twenty full term newborn infants were tested. ABRs to bone conducted clicks were obtained with four different coupling forces (225, 325, 425, and 525 g) at stimulus intensities of 15 and 30 dB nHL. ABRs to air conducted clicks were also obtained at 30 dB nHL. The results of this study indicated that ABR wave V latencies to bone conducted clicks in newborn infants were affected significantly when the vibrator to head coupling force shift exceeded 200 g. It is recommended that the coupling force be controlled and remain consistent when implementing ABR to bone conducted stimuli in newborn infants.

Audiometry, Evoked Response↗
PubMed1990

Effects of contralateral masking on high-frequency bone-conduction thresholds.

The present study reports effects of contralateral masking on high-frequency threshold force levels in 28 normal-hearing subjects. High-frequency air- and bone-conduction thresholds were measured with a high-frequency auditory evaluation system using matched Koss HV/1A earphones and the Pracitronic KH 70/5 bone vibrator. Measurements were made for both unmasked and masked bone-conduction thresholds at the ipsilateral mastoid of the better ear. The contralateral masked condition was performed using 30-dB-SL 400-Hz narrow-band masking noise centered at frequency of test tone. The results demonstrated that masked high-frequency bone-conduction thresholds were 1.5 to 3.4 dB poorer than the unmasked thresholds and that these differences were statistically significant at 0.01 level of confidence except at 12 kHz. ANSI and ISO standards for bone-conduction threshold force levels for frequencies below 8.0 kHz have been established with contralateral masking stimuli. This study supports the need to use effective contralateral masking to eliminate cross hearing in investigations of high-frequency bone-conduction threshold measurements.

Adult↗
PubMedDate not supplied

Clinical implications in calibration requirements in bone conduction standardisation.

Although international agreement has long been reached on a standard threshold for air conduction audiometry, no similar standard exists for bone conduction autiometry. It is argued that the techniques applied to the determination of the air conduction thresholds are not applicable to those for bone conduction which should instead be brought into line with ISO 1964 and not established independently. A pilot study has been carried out which shows that by adopting the new approach now advocated international agreement could be attained with the expenditure of minimal time and effort.

Acoustic Stimulation↗
PubMed1991

The limited accuracy of bone-conduction audiometry: its significance in medicolegal assessments.

Accurate bone-conduction testing with masking is always difficult, but for clinical purposes limited accuracy suffices. However, when assessing claimants for compensation, extreme care is needed since even small apparent air-bone gaps are sometimes translated into financial abatement. This paper sets out the stringent test conditions required to achieve adequate precision. It also indicates the inaccuracies inherent in such tests, and recommends procedures for interpreting the significance of bone-conduction thresholds.

Audiometry↗
PubMedDate not supplied

Occlusion effect: bone conduction speech audiometry using forehead and mastoid placement.

The occlusion effect (OE) was determined for bone conduction speech reception thresholds (SRTs) in 24 normally hearing subjects using forehead and mastoid placement. Results indicated that the OE was about 3 dB greater using forehead as opposed to mastoid placement. The intersubject variability of the OE is similar for the forehead and mastoid positions. The formula for effective masking for bone conduction speech should be equal to the minimum masking level for bone conduction speech plus the air-bone gap of the nontest ear plus 18 dB to account for the OE when using mastoid placement.

Acoustic Stimulation↗
PubMed1992

[Masking in bone-conduction testing--proposal of ABC method].

A new strategic masking technique, namely the ABC method, has been developed. In performing this method of measuring thresholds of bone-conduction, the vibrator is placed at the forehead with both ears occluded by air-conduction earphones. One of the earphones is for masking noise and the other is a dummy which balances out the occlusive effect of the test ear against the nontest ear. The ABC method is based on the ABC rule that, in bone-conduction testing, the effective masking noise level necessary to block out the nontest ear can be calculated by a simple equation: right AC (A) + left AC (B)--unmasked BCu (C) under the assumption that the BCu belongs to the nontest ear. In some cases of hearing loss, the above noise level might produce overmasking, then an additive safety noise level, BCu + Interaural Attenuation, is employed. This method offers testers step by step directions which consist of indications of the noise level and a criterion for determining whether the measured bone-conduction is free from cross hearing and overmasking for the given configuration of air-conduction of both ears, BCu, and the masking noise level. Compared to the well known Plato method, in which measurements of thresholds are repeated at several masking noise levels in order to find a single bone-conduction threshold, the ABC method can essentially find the threshold at only one masking noise level. Therefore the ABC method makes it possible to save a great deal of time in performing bone conduction testing.

Audiometry↗
PubMed1977

[Bone conduction changes in secretory otitis media (author's transl)].

In serous and secretory otitis media a reduction of bone conduction frequently exists besides the loss of air conduction. In 304 audiograms of ears with serous and viscous fluid in the middle ear there was a depression of the bone conduction between 15 and 40 dB in 40%. This bone conduction loss was reversible after the aeration of the tympanic cavity. That means that we deal with a false nerve deafness in many of these cases.

Bone Conduction↗
PubMed1992

High-frequency audiometry. Masking in electric bone-conduction audiometry.

Recently, the 'electric bone-conduction' (EBC) audiometer (Audimax 500) has been used to measure high-frequency (HF) hearing. With this audiometer stimulation is binaural. No commercial masking method was available. In this study, white noise from a Madsen OB822 audiometer and presented via Sony MDR-V4 dynamic earphones, was used for masking. The masking and cross-hearing effect was measured in 8 unilaterally deaf subjects and the masking procedure was tested with 104 young normal-hearing subjects. The results showed that the EBC signals can be masked with air-conduction signals, and thus, the EBC measurements reflect monaural thresholds. The minimum masking level was 50-60 dB SPL in the HF range. There were no cross-hearing problems in the HF range with the earphones used. At the frequencies 0.5-14 kHz, the better ear's masked EBC thresholds were on the average 2.6 dB (range 0-4.5 dB) poorer, compared with the binaural EBC thresholds, indicating a binaural summation effect.

Acoustic Stimulation↗
PubMed1978

Physical and physiological constraints on the use of bone-conduction speech audiometry.

Several authors have recommended the use of bone-conduction speech audiometry, and the literature supports the clinical value of this procedure. It has been claimed that bone-conduction output for speech can be increased to 110-dB HL with the Radioear B-70-A vibrator through supplementary amplification, but this claim is unsubstantiated by objective measurements. Available technical data indicate that the maximum output level attainable with this virbator without incurring serious distortion is 65- to 70-dB HL at midfrequencies and substantially less at lower frequencies. Both behavioral and electromechanical data are presented which show, not only that 70-dB HL is the absolute maximum hearing level for speech attainable through the B-70-A vibrator without serious deterioration of speech-discrimination scores in normal listeners, but also that this appears to be very close to the maximum vibratory level that human observers can comfortably tolerate.

Audiometry↗
PubMedDate not supplied

The middle ear inertial component of bone-conduction hearing in man.

The middle ear inertial component of bone-conduction hearing was studied in 8 normal-hearing young adults. The inertial component was eliminated to varying degrees by introducing various positive and negative air pressures into the ear canal. Sweep-frequency Békésy tracings were obtained from 100 through 5 000 Hz for bone-conducted pure tone stimuli while the air pressure of the test ear was varied and the nontest ear was masked. Air pressures of +/- 100, +/- 300, and +/- 500 mm H2O were utilized. Results revealed maximal shift in the mid frequencies (750 Hz) and an increase in effect with increase in pressure. A second prominent region of threshold shift emerged at 2 000 Hz for the +/- 500 mm H2O air pressure conditions. Considerable variability in the magnitude of threshold shift and in the frequency region of maximum shift was observed.

Acoustic Stimulation↗
PubMed1992

Hearing with the bone-anchored hearing aid (BAHA, HC 200) compared to a conventional bone-conduction hearing aid.

Sixteen patients have been fitted with a standard bone-anchored hearing aid (HC 200), to replace their conventional bone-conduction aid. The average pure tone threshold at 0.5, 1 and 2 kHz varied from 35 to 75 dB HL, with a sensorineural component varying from 0 to 30 dB HL. The patients' performance with the bone-anchored aid was compared to that with the conventional bone-conduction aid in an acoustic-free field. The maximum phoneme score in quiet was 100% in most patients; in 6 patients, the score with the bone-anchored aid was better (range from 5 to 10%). The speech-in-noise ratio was significantly better in 11 patients (range from -1.4 to -8 dB). None of the patients had poorer results on either test with the bone-anchored aid. The improved speech recognition was ascribed to better performance of the hearing aid in the higher frequency range (above 2 kHz) and to relatively less distortion.

Adolescent↗
PubMed1991

Implantable bone-conduction hearing device: practical considerations.

An implantable bone conduction hearing device can be of significant benefit to carefully selected patients with noncorrectable conductive hearing losses. However, for some patients the device has significant limitations. This paper presents several practical issues that need to be considered before a decision is made regarding implant surgery. It is recommended that, whenever possible, air conduction hearing aids remain the first option considered when a patient's conductive hearing loss cannot be resolved through traditional medical management.

Adult↗
PubMed1992

Frequency specificity of the auditory brain stem response to bone-conducted tones in infants and adults.

Auditory brain stem responses were obtained from normal-hearing infants and adults in response to bone-conducted 500 and 2000 Hz tones presented in quiet and high-pass noise masking. The tones were presented at 70 (500 and 2000 Hz) and 46 (2000 Hz) dB peak to peak equivalent (re: 1 dyne RMS). The high-pass noise-masked waveforms were subtracted in succession to obtain derived responses, providing estimates of the cochlear regions contributing to the nonmasked responses. Findings indicate that the auditory brain stem response to bone-conducted 500 Hz tones is frequency specific for both infants and adults. For 2000 Hz tones, the results show maximum amplitudes for cochlear regions representing the nominal frequency of the tone for adults. For infants, maximum response amplitudes for the derived responses to 2000 Hz, 70 dB tones were obtained within 1/2 octave of the nominal frequency (1410-2000 Hz). Wave V latencies of the derived responses are similar for both groups for 2000 Hz tones, but shorter for infants to 500 Hz tones, supporting the hypothesis that low-frequency bone-conducted stimuli are effectively more intense in infants than adults.

Acoustics↗
PubMedDate not supplied

Effects of reflex middle-ear muscle contractions on cochlear responses to bone-conducted sound.

The effects of contralaterally elicited middle-ear muscle (MEM) reflexes on cochlear microphonic responses to air- and bone-conducted tones were examined in decerobrate cats. Stapedius effects on bone condn air conduction were almost identical in configuration and amplitude to those on air conduction at all frequencies. However, tensor tympani effects were more complex, the configuration of the bone-conduction effects varying with the location of the transducer on the skull and with frequency. The relative contributions of the two muscles to the effects of joint contractions varied markedly between animals. It is suggested that non-reflex MEM contractions associated with activity of the facial musculature might provide protection against masking of environmental sounds by the low-frequency bone-conducted sound generated by such activity.

Air↗
PubMedDate not supplied

Bone-conducted stimulation in electrocochleography.

The mechanical vibration patterns close to the cochlea in intact skulls of human cadavers have been studied by means of a miniature accelerometer. A Radioear B70A vibrator and a Brüel & Kjaer Mini Shaker have been used, fed with filtered clicks and with short tone bursts. The tone bursts were found to be superior to the clicks with regard to the vibration spectrum. At 500 Hz a considerable distortion was observed in the accelerometer signal, also when using tone bursts. This distortion was presumably due to resonant vibrations in the skull itself, and may be a source of error not only when using stimuli of short duration as in bone-conduction ECoG but also in conventional bone-conduction audiometry. When the vibrations were applied to the exposed bone surface of the mastoid, vibration levels increased by 10-25 dB compared with when soft tissues covered the point of application. This could be of advantage in bone-conduction ECoG performed at ear surgery.

Acoustic Impedance Tests↗
PubMed1990

The output characteristics of an implanted bone conduction prosthesis.

So far, the published guidelines for patient selection for the Audiant implanted bone conduction device have been derived from clinical trial rather than experimental study. Theoretical considerations suggest that the guidelines should be frequency specific; the need for this was investigated in a laboratory study. Two independent measures of the maximum output of the Audiant device using both the body-worn and ear-level amplifiers have been performed on two subjects. These lead to maximum output figures for the device ranging from 15 dB HL at 250 Hz to 60 dB HL at 6000 Hz for the body-worn amplifier, and from 6 dB HL at 250 Hz to 42 dB HL at 6000 Hz for the ear-level amplifier. These results suggest that the ear-level amplifier is suitable only for candidates with essentially normal bone conduction thresholds at frequencies of 1000 Hz and below.

Adult↗
PubMedDate not supplied

Bone conduction thresholds in patients with otosclerosis.

PURPOSE: Sensorineural hearing loss in patients with otosclerosis is commonly encountered. This study was conducted to determine if surgery on the otosclerotic ear had an effect on the sensorineural hearing. METHODS: A cohort of 262 patients subjected to operation in 311 ears were evaluated. All patients had a minimum of 5 years follow-up and patients over 60 years of age were excluded. Audiograms obtained 1 day before surgery were compared with those obtained 1 year postoperatively and at the last follow-up examination in the study. Results were evaluated using the Student's t test for statistical analysis of hearing results. RESULTS: The mean follow-up was 9.6 years. Deterioration of bone conduction scores occurred in 6.4% of 311 operated ears. Deterioration of bone conduction threshold occurred in the speech frequency in 6 ears (1.9%). CONCLUSIONS: Bone conduction scores of operated ears remained quite stable compared with the otosclerotic ears not subjected to operation. Patients with bilateral otosclerosis may benefit from surgery performed on both ears when indicated.

Adult↗
PubMedDate not supplied

Bone conduction speech audiometry in normal subjects.

The present study was designed to investigate: (1) the relationship among bone conduction (BC) pure tone averages, BC speech reception thresholds (SRTs), and BC speech detection thresholds for normal subjects; (2) short term reliability of BC SRTs; and (3) characteristics of the articulation functions for spondees obtained by bone conduction. Twenty-five normal-hearing young adults participated. The data revealed that BC SRT-pure tone average and SRT-speech detection threshold relationships are essentially the same as for air conduction. A comparison of the articulation functions for air conduction and BC revealed no practical difference between the two modes of stimulus presentation.

Adult↗