Effect of Cochlear Window Fixation on Air- and Bone-Conduction Thresholds

Two experiments were conducted to determine the effects of central masking on both air and bone-conduction thresholds. In the first investigation, 10 normal listeners were tested by air conduction and by bone conduction via the mastoid process and the frontal bone as various levels of narrow-band noise were presented to the contralateral ear. Generally, as the noise level increased, there was a small but gradual increase in the threshold on the test ear. However, the threshold shift for frontal bone measurements was always greater than comparable air-conduction or bone-conduction thresholds from the mastoid process. The additional shift in threshold for frontal bone measurements may have been the result of changing from binaural stimulation in quiet to monaural stimulation during the masking conditions. This proposition was investigated in Experiment II. The test ears of 6 subjects were occluded with plugs which induced an appreciable increase in bone-conduction sensitivity. Thus, the frontal bone threshold as well as the mastoid threshold was monaural, even in the quiet condition. If the above proposition were correct, it was predicted that identical shifts in threshold due to central masking would be found for frontal bone measurements as for mastoid measurements. The threshold shifts for air conduction and bone conduction via mastoid or frontal bone vibrator placements were found to be similar.

Background: Two different pathways of sound transmission to the inner ear are differentiated; air conduction (AC) and bone conduction (BC). The transmission pathway of AC, which is physiological for human hearing, implies the transmission of sound to the cochlea via the ear canal, eardrum, and middle-ear ossicles, while BC bypasses the Pinna, the external auditory canal and the middle ear. The transmission pathway by BC has not been fully understood and many aspects still remain questionable. The aim of this study is to characterize two ways of direct transmission of vibrations to the inner ear by measuring hearing thresholds and vibrations of the skull. The bone-vibrator, which is usually used to measure the BC hearing thresholds in contact with the mastoid, can also be used to simulate other contents of skull, such as the eye. Methods: Ten adults (age range of 25-40) with normal hearing and five patients (age range of 21-31) with single sided profound deafness (SSD) were included in this study. The AC audiometry by pure tones was measured using insert earphones and the BC audiometry was measured by stimulating four different locations of the skull; the forehead, the temporal region, the mastoid, and the ipsilateral eyeball with two different contact pressure magnitudes of 2N and of 5N. The vibrations of the skull bones induced by air and bone conduction stimuli were measured by an accelerometer positioned between an upper and lower front incisor tooth. Results: The BC hearing thresholds by stimulating the temporal region and the mastoid were the lowest in both of normal hearing and SSD subjects and the values by both stimulations were similar. Thresholds were significantly higher for stimulations on the forehead and the eye (p<0.05). The difference between the thresholds by stimulation at the mastoid or temporal region and at the eye was more pronounced in SSD subjects (p<0.01). The averaged BC thresholds of normal subjects by stimulation on the contralateral temporal region were significantly lower than the averaged BC thresholds of SSD subjects only at the frequency of 0.25 kHz (p<0.01). The BC thresholds by stimulation on the contralateral mastoid of the normal hearing subjects were significantly lower in 5 N headband than in 2 N headband at the whole frequency range (p<0.05). The BC thresholds by stimulation on the ipsilateral mastoid of the normal hearing subjects showed significant differences between the contact pressure forces of 5 N and 2 N at the frequencies of 1, 2, and 3 kHz (p<0.5). The stimulation on the contralateral mastoid with the 5 N headband resulted in a significantly lower BC threshold than the stimulation with 5 the 2 N headband at the entire frequency range (p<0.05). In SSD subjects, the stimulation on the ipsilateral mastoid side with the 5 N headband had a significantly lower BC thresholds than stimulation with the 2 N headband at all frequencies except for 0.5 and 4 kHz (p<0.05). The BC thresholds in normal hearing subjects were significantly lower with the ipsilateral temporal stimulation than with a corresponding contralateral stimulation for the all frequencies except for 0.5 and 1 kHz (p<0.01). For the SSD subjects, the BC thresholds with the ipsilateral temporal stimulation were significantly lower at 2, 3 and 4 kHz than those with the corresponding contralateral stimulation. Skull vibrations in the normal hearing subjects showed similar behaviors at low frequencies up to 2 kHz for all stimulations except for stimulation on the eye, where vibrations were smaller. In contrast, skull vibrations measured from stimulation at the eye were increasing with higher frequencies. Under 2 kHz skull vibrations at eye were significantly smaller than those from stimulation of the mastoid, but above 2 kHz, they were significantly bigger (p<0.05). Skull vibrations between stimulation at the ipsilateral mastoid and forehead were significantly different at 0.25, 3 and 4 kHz (p<0.05). The subjects with SSD showed similar patterns. Conclusion: The patterns of BC hearing thresholds were similar in normal subjects and subjects with SSD. Hearing thresholds in all subjects were significantly better for mastoid and temple stimulation compared to eye stimulation. One reason for that may be the different pressures applied. Skull vibrations as measured at teeth did not match the same pattern as the hearing thresholds. Eye stimulation induced low vibrations below 2 kHz, but high vibrations above 2 kHz. This finding demonstrates special acoustic properties of the living organism, the distance from stimulation might also contribute. Skull-bone vibrations decreased with increasing frequency for mastoid and temple stimulation. Stimulation of soft tissue, presumably including skull contents, seems to induce high frequency skull vibrations. That might be involved with the distance form the front teeth. The transcranial attenuation of vibration should be considered especially in high frequencies.

In order to differentiate between a conductive hearing loss (CHL) and a sensorineural hearing loss (SNHL) in the hearing-impaired individual, we compared thresholds to air conduction (AC) and bone conduction (BC) auditory stimulation. The presence of a gap between these thresholds (an air-bone gap) is taken as a sign of a CHL, whereas similar threshold elevations reflect an SNHL. This is based on the assumption that BC stimulation directly excites the inner ear, bypassing the middle ear. However, several of the classic mechanisms of BC stimulation such as ossicular chain inertia and the occlusion effect involve middle ear structures. An additional mode of auditory stimulation, called soft tissue conduction (STC; also called nonosseous BC) has been demonstrated, in which the clinical bone vibrator elicits hearing when it is applied to soft tissue sites on the head, neck, and thorax. The purpose of this study was to assess the relative contributions of threshold determinations to stimulation by STC, in addition to AC and osseous BC, to the differential diagnosis between a CHL and an SNHL. Baseline auditory thresholds were determined in normal participants to AC (supra-aural earphones), BC (B71 bone vibrator at the mastoid, with 5 N application force), and STC (B71 bone vibrator) to the submental area and to the submandibular triangle with 5 N application force) stimulation in response to 0.5, 1.0, 2.0, and 4.0 kHz tones. A CHL was then simulated in the participants by means of an ear plug. Separately, an SNHL was simulated in these participants with 30 dB effective masking. STUDY SAMPLE consisted of 10 normal-hearing participants (4 males; 6 females, aged 20-30 yr). AC, BC, and STC thresholds were determined in the initial normal state and in the presence of each of the simulations. The earplug-induced CHL simulation led to a mean AC threshold elevation of 21-37 dB (depending on frequency), but not of BC and STC thresholds. The masking-induced SNHL led to a mean elevation of AC, BC, and STC thresholds (23-36 dB, depending on frequency). In each type of simulation, the BC threshold shift was similar to that of the STC threshold shift. These results, which show a similar threshold shift for STC and for BC as a result of these simulations, together with additional clinical and laboratory findings, provide evidence that BC thresholds likely represent the threshold of the nonosseous BC (STC) component of multicomponent BC at the BC stimulation site, and thereby succeed in clinical practice to contribute to the differential diagnosis. This also provides evidence that STC (nonosseous BC) stimulation at low intensities probably does not involve components of the middle ear, represents true cochlear function, and therefore can also contribute to a differential diagnosis (e.g., in situations where the clinical bone vibrator cannot be applied to the mastoid or forehead with a 5 N force, such as in severe skull fracture).

Besides the normal hearing pathway known as air conduction (AC), sound can also transmit to the cochlea through the skull, known as bone conduction (BC). During BC stimulation, the cochlear walls demonstrate rigid body motion (RBM) and compressional motion (CPM), both inducing the basilar membrane traveling wave (TW). Despite numerous measuring and modeling efforts for the TW phenomenon, the mechanism remains unclear, especially in the case of BC. This paper proposes a 3D finite element cochlea model mimicking the TW under BC. The model uses a traditional "box model" form, but in a spiral shape, with two fluid chambers separated by the long and flexible BM. The cochlear fluid was enclosed by bony walls, the oval and round window membranes. Contingent boundary conditions and stimulations are introduced according to the physical basis of AC and BC. Particularly for BC, both RBM and CPM of the cochlea walls are simulated. Harmonic numerical solutions are obtained at multiple frequencies among the hearing range. The BM vibration amplitude ([Formula: see text]) and its relation with volume displacement difference between the oval and round windows [Formula: see text], as well as the pressure difference at the base of the cochlea ([Formula: see text]), are analyzed. The simulated BM response at 12mm from the base is peaked at about 3kHz, which is consistent with published experimental data. The TW properties under AC and BC are the same and have a common mechanism. (1) [Formula: see text] is proportional to [Formula: see text] at low frequencies. (2) [Formula: see text] is also proportional to [Formula: see text], within 5dB error at high frequencies such as 16kHz. This study partly reveals the common quantitative relations between the TW and related factors under AC and BC hearing.

The auditory impact of a cochlear third window differs by its location in the scala vestibuli or scala tympani. Pathologic third window has been investigated primarily in the vestibular apparatus of animals and humans. Dehiscence of the superior semicircular canal is the clinical model. Fat sand rats (n = 11) have a unique inner-ear anatomy that allows easy surgical access. A window was drilled in the bony labyrinth over the scala vestibuli in 1 group (12 ears) and over the scala tympani in another (7 ears) while preserving the membranous labyrinth. Auditory brain stem responses to high- and low-frequency stimuli delivered by air and bone conduction were recorded before and after the procedure. Scala vestibuli group: preoperative air-conduction thresholds to clicks and tone-bursts averaged 8.3 and 9.6 dB, respectively, and bone-conduction thresholds, 4.6 and 3.3 dB, respectively; after fenestration, air-conduction thresholds averaged 40.4 and 41.8 dB, respectively, and bone-conduction thresholds, -1 and 5.6 dB, respectively. Scala tympani group: preoperative air-conduction thresholds to clicks and tone-bursts averaged 8.6 dB each, and bone-conduction thresholds, 7.9 dB and 7.1 dB, respectively; after fenestration, air-conduction thresholds averaged 11.4 and 9.3 dB, respectively, and bone-conduction thresholds, 9.3 and 4.2 dB, respectively. The changes in air- (p = 0.0001) and bone-conduction (p = 0.04) thresholds were statistically significant only in the scala vestibuli group. The presence of a cochlear third window over the scala vestibuli, but not over the scala tympani, causes a significant increase in air-conduction auditory thresholds. These results agree with the theoretic model and clinical findings and contribute to our understanding of vestibular dehiscence.

Background: Simple or non-syndromic types of oval window (OW) or round window (RW) atresia are relatively rare in clinical. Few studies have assessed bone conduction (BC) hearing in OW or RW atresia patients, with some reporting that BC hearing lies within the normal range, whereas others observing impaired BC hearing.Aims/Objectives: This study explored the effect of blocking the OW and RW during BC in cat models.Material and Methods: Twenty-four cats were randomly divided into three immobilization groups (OW blockage, RW blockage, and OW + RW blockage) and control group. Each immobilization group also had the initial control state before blockage. Medical adhesive and ear mould glue were used to immobilise the stapes footplate and RW, respectively. Comparisons were made of the auditory brainstem response (ABR) thresholds before and after immobilization for the three immobilization groups during three different stimuli [air conduction (AC) click, BC click, and BC pure tones].Results: The AC click thresholds increased after immobilisation in three experimental groups compared to the control group (p < .05). The AC click thresholds increased compared to their initial control state after all three immobilization groups (p < .05). With an increase in frequency from 2 to 8 kHz, there was a general decrease in the difference between pre- and post-immobilization BC hearing thresholds in all three immobilization groups. The BC click threshold and BC tone thresholds at 2–4 kHz in both OW blockage and OW + RW blockage groups exceeded those in RW blockage group (p < .05).Conclusions and Significance: The use of medical adhesive and ear mould glue for the blockages of OW and RW, respectively in cats was feasible. The effect of blocking the OW and RW in BC hearing was larger at low frequencies than high frequencies between 2 and 8 kHz. OW blockage had a greater effect than RW blockage on BC hearing at 2–4 kHz range.

To measure the outcomes of laser treatment of cholesteatoma covering cochlear and vestibular fistulas. Cholesteatoma matrix over the fistula was denatured; the power density was sufficient only to gradually heat, but not vaporise, the keratin-forming matrix. The denaturing speed was controlled so that the integrity of the fistula cover was maintained. The change in bone conduction threshold and the residual rate of cholesteatoma at the fistula were measured. Thirty-six fistulas were assessed. There were seven cochlear fistulas. All were 5 mm or less in maximum length. For the entire group, the average change in bone conduction threshold was -0.3 dB. For cochlear fistulas, the average change in bone conduction was + 0.2 dB. The distribution of hearing results for the entire group was Gaussian; the apparent changes in hearing could be attributed to errors associated with testing. All patients underwent second-stage surgery. In all cases, the cholesteatoma was completely cleared from the fistula site. There were no facial palsies. Laser denaturing of cholesteatoma matrix over fistulas measuring 5 mm or less of vestibular apparatus and the cochlea is effective at eliminating cholesteatoma, and is not associated with cochlear hearing loss or facial palsy.

The objective was to assess audiological results after total ossicular reconstruction for stapes fixation. The study is a retrospective evaluation conducted in a tertiary referral centre. The patients were 16 adults with conductive or mixed hearing loss and stapes fixation due to tympanosclerosis or otosclerosis. A total or partial stapedectomy with perichondrium interposition on the oval window and ossicular reconstruction with titanium total prosthesis were done. To assess pre- and post-operative (1 and 4 years) air and bone-conduction thresholds (frequencies 0.5, 1, 2, 3 kHz), pure-tone average air and bone conduction, and air-bone gaps were measured and the number of decibels of closure of the air-bone gap at 1 year and at 4 years were compared. One year after surgery, air conduction thresholds and pure-tone average air conduction were improved for all frequencies, and there were no significant differences in bone conduction thresholds or in pure-tone average bone conduction. There were no differences in air and bone conduction thresholds, pure-tone average air or bone conduction between 1 and 4 years. The air-bone gap was significantly reduced 1 year after surgery and remained so at 4 years. (Preoperative air-bone gap, 34.04 dB; at 1 year, 16.40 dB; at 4 years, 17.3 dB. Decibels of closure of the air-bone gap at 1 year, 17.64 dB; at 4 years, 16.74 dB.) No differences were found between otosclerosis subjects and all other cases combined. Total ossicular reconstruction in stapes fixation due to tympanosclerosis or otosclerosis produces satisfactory short- and long-term auditory results.

Patients with elevated bone conduction (BC) thresholds are not considered a good candidate for otosclerosis surgery. Sometimes, it might be difficult to decide to operate these patients considering relatively poor cochlear function. However, viewpoints may vary among otologists. This study was undertaken to compare hearing outcome following otosclerosis surgery in patients who had bone conduction (BC) thresholds >or= 30 dB, and to investigate whether BC thresholds >30 dB has a negative impact on hearing outcome. Medical records of 111 patients who had undergone otosclerosis surgery were reviewed. Of 111 patients, 83 had undergone stapedotomy, and 28 stapedectomy. The patients were grouped based on preoperative four-tone BC threshold. Eighty-seven patients had average BC threshold <or= 30 dB, and were assigned to good-cochlear reserve group. The remaining 24 patients had average BC > 30 dB, and constituted poor-cochlear reserve group. Pre- and postoperative air conduction (AC) and BC thresholds, air-bone (AB) gap, vocal audiometry results and amount of deterioration in BC were determined. Mean postoperative AB gap was almost the same in both groups (14 and 15 dB) (P > 0.05). Percentage of AB gap = 10 dB favored good-cochlear reserve group (41 vs 29%)(P > 0.05). Analysis of mean hearing gain was slightly in favor of good-cochlear reserve group (19 vs 15 dB) (P > 0.05). Better BC thresholds were obtained postoperatively in good-cochlear reserve group (P < 0.001). Deterioration > 10 dB in BC was observed in 5.7 and 12.5% of the patients with good- and poor-cochlear reserve, respectively (P > 0.05). Based on the results of this small sample-size study, even though BC threshold of 30 dB was not considered a negative factor for hearing gain, otosclerosis surgery might have detrimental effects on postoperative BC thresholds in patients who had BC thresholds >30 dB.

This study aimed to investigate the factors affecting permanent sensorineural hearing loss (SNHL) and causing changes in bone conduction (BC) thresholds over time in patients after receiving radiotherapy (RT) or chemoradiotherapy (CRT) to the head and neck region. A total of 63 patients with irradiated HNC that were admitted to the Radiation Oncology Department between 2011 and 2018 were included in the study. All patients were assessed with pure tone audiometry at eight different time points (first before RT and last five years after completion of RT). A chi-square test was used to analyze the variables that affected permanent SNHL occurrence. Repeated measure analysis of variance was conducted to investigate the factors affecting change in the BC threshold at pure-tone average (0.5-2 kHz) and the air conduction (AC) threshold at 4 and 6 kHz frequencies over time. Median follow-up was 52 months (range, 12-110 months). SNHL was found in 18 (14%) of the 126 ears. According to the receiver operating characteristic analysis, the cut-off values of cochlear Dmean and Dmax radiation doses were 40 Gy [p=0.017, area under the curve (AUC): 0.676] and 45 Gy (p=0.008, AUC: 0.695). Dmean (≤40 Gy vs. >40 Gy) and Dmax (≤45 Gy vs. >45 Gy) cochlear doses and age (≤40 vs. >40 years) were determined as factors affecting SNHL in the chi-square test. Repeated measures showed that BC thresholds between 0.5-2 kHz and AC thresholds at 4 and 6 kHz increased over time. Age (≤40 vs. >40 years), treatment of head and neck cancer (RT vs. CRT), cisplatin use, and Dmean (≤40 Gy vs. >40 Gy) and Dmax cochlear dose (≤45 Gy vs. >45 Gy) were important factors affecting the course of BC threshold over time. Dmean and Dmax cochlear doses and age were found to be associated with permanent SNHL. Conduction thresholds worsened over time at all frequencies, and this trend was affected by cochlear doses, age, CRT, and cisplatin use.

The aim of this study was to investigate the following: (1) the vibration pattern of the round window (RW) membrane in human cadavers during air (AC) and bone conduction (BC) stimulation at different excitation sites; (2) the effect of the stimulation on the fluid volume displacement (VD) at the RW and compare the VD between BC and AC stimulation procedures; (3) the effectiveness of cochlear stimulation by the bone implant at different excitation sites. The RW membrane vibrations were measured by using a commercial scanning laser Doppler vibrometer. The RW vibration amplitude was recorded at 69 measurement points evenly distributed in the measurement field covering the entire surface of the RW membrane and a part of the surrounding bony surface. RW vibration was induced first with AC and then with BC stimulation through an implant positioned at two sites. The first site was on the skull surface at the squamous part of the temporal bone (implant no. 1), a place typical for bone-anchored hearing aids. The second site was close to the cochlea at the bone forming the ampulla of the lateral semicircular canal (implant no. 2). The displacement amplitude (dP) of the point P on the promontory was determined and used to calculate the relative displacement (drRW) of points on the RW membrane, drRW = dRW - dP. VD parameter was used to analyze the effectiveness of cochlear stimulation by the bone implant screwed at different excitation sites. RW membrane displacement amplitude of the central part of the RW was similar for AC and BC implant no. 1 stimulation, and for BC implant no. 2 much larger for frequency range >1 kHz. BC implant no. 2 causes a larger displacement amplitude of peripheral parts of the RW and the promontory than AC and BC implant no. 1, and BC implant no. 1 causes larger than AC stimulation. The effect of BC stimulation exceeds that of AC with identical intensity, and that the closer BC stimulation to the otic capsule, the more effective this stimulation is. A significant decrease in the value of VD at the RW is observed for frequencies >2 kHz for both AC and BC stimulation with BC at both locations of the titanium implant placement. For frequencies >1 kHz, BC implant no. 2 leads to a significantly larger VD at the RW compared to BC implant no. 1. Thus, the closer to the otic capsule the BC stimulation is located, the more effective it is. Experimental conditions allow for an effective acoustic stimulation of the inner ear by an implant screwed to the osseous otic capsule. The mechanical effect of BC stimulation with a titanium implant placed in the bone of the ampulla of the lateral semicircular canal significantly exceeds the effect of an identical stimulation with an implant placed in the temporal squama at a conventional site for an implant anchored in the bone. The developed research method requires the implementation on a larger number of temporal bones in order to obtain data concerning interindividual variability of the observed mechanical phenomena.

To improve understanding of normal responses in infants by comparing air conduction (AC) and bone conduction (BC) auditory thresholds using both the auditory steady state response (ASSR) and behavioral testing methods in normal-hearing infants (6 to 18 months of age) and adults. At present, there are no correction factors available for estimating BC behavioral thresholds from BC ASSR thresholds, which is a barrier to clinical implementation of the ASSR. In addition, previous studies have reported infant-adult differences in AC and BC sensitivity, which suggest a "maturational" air-bone gap (ABG) that is not attributable to a conductive pathology; no study has yet compared AC and BC thresholds for either ASSR or behavioral methods in the same individuals. The objectives of the present study are: (1) to compare BC thresholds between methods and provide the initial step toward positing correction factors to predict BC behavioral thresholds, (2) to directly compare AC and BC thresholds to provide an accurate estimate of the maturational ABG, (3) to determine preliminary normal levels for BC and AC ASSRs to exponentially amplitude modulated stimuli, and (4) to investigate infant-adult differences in AC and BC thresholds using ASSRs and behavioral assessment tools. Participants were 23 infants (6.5 to 19.0 months of age) and 12 adults (17 to 50 years of age) with normal hearing. Thresholds were estimated at 500, 1000, 2000, and 4000 Hz using air- and bone-conducted stimuli for ASSRs and behavioral testing. The ASSR stimuli were exponential envelope modulated (amplitude modulation [AM]) at modulation frequencies of 78, 85, 93, and 101 Hz for 500, 1000, 2000, and 4000 Hz, respectively, presented simultaneously. Frequency-modulated (warble tone) stimuli were used for behavioral testing for both infants and adults, respectively. All stimuli were calibrated in dB HL. Thresholds were compared across frequency and between stimulus presentation modes, between age groups and assessment method. Normal levels for AC and BC ASSRs to AM stimuli were also calculated. The findings indicated that BC thresholds were, on average, 7 to 16 dB poorer for ASSR compared with visual reinforcement audiometry (VRA), but varied widely across infants. For infants, mean ABGs of 14 to 17 dB were found for low-frequency ASSR thresholds but mean ABGs for VRA thresholds were less than 10 dB. The preliminary normal levels for ASSR AM stimuli at 500, 1000, 2000, and 4000 Hz, respectively, were: (i) AC: 30, 30, 20, and 20 dB HL, and (ii) BC: 20, 20, 30, and 30 dB HL. There was a tendency for infant and adult ASSR thresholds to differ for BC, but not for AC. Behavioral thresholds for AC and BC were similar between infants and adults and across frequency. Infant-adult and AC-BC threshold differences are greater for ASSRs compared with behavioral measures. The results support the presence of a clinically significant maturational ABG in the low frequencies for infant ASSRs but not for VRA. The findings also show a significant offset between BC ASSR and BC VRA thresholds and large intersubject variability.

Distinct audiometric patterns in congenital round window atresia: A comparative study with common congenital middle ear anomalies

To study normative thresholds and latencies for click and tone-burst auditory brainstem response (TB-ABR) for air and bone conduction in normal infants and those discharged from neonatal intensive care units, who passed newborn hearing screening and follow-up distortion product otoacoustic emission. An evoked potential system (Vivosonic Integrity) that incorporates Bluetooth electrical isolation and Kalman-weighted adaptive processing to improve signal to noise ratios was employed for this study. Results were compared with other published data. One hundred forty-five infants who passed two-stage hearing screening with transient-evoked otoacoustic emission or automated auditory brainstem response were assessed with clicks at 70 dB nHL and threshold TB-ABR. Tone bursts at frequencies between 500 and 4000 Hz were used for air and bone conduction auditory brainstem response testing using a specified staircase threshold search to establish threshold levels and wave V peak latencies. Median air conduction hearing thresholds using TB-ABR ranged from 0 to 20 dB nHL, depending on stimulus frequency. Median bone conduction thresholds were 10 dB nHL across all frequencies, and median air-bone gaps were 0 dB across all frequencies. There was no significant threshold difference between left and right ears and no significant relationship between thresholds and hearing loss risk factors, ethnicity, or gender. Older age was related to decreased latency for air conduction. Compared with previous studies, mean air conduction thresholds were found at slightly lower (better) levels, while bone conduction levels were better at 2000 Hz and higher at 500 Hz. Latency values were longer at 500 Hz than previous studies using other instrumentation. Sleep state did not affect air or bone conduction thresholds. This study demonstrated slightly better wave V thresholds for air conduction than previous infant studies. The differences found in the present study, while statistically significant, were within the test step size of 10 dB. This suggests that threshold responses obtained using the Kalman weighting software were within the range of other published studies using traditional signal averaging, given step-size limitations. Thresholds were not adversely affected by variable sleep states.

Round window membrane motion with air conduction and bone conduction stimulation