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Conclusion Cochlea can be directly excited by fluid (soft-tissue) stimulation. Objective To determine whether there is no difference in auditory-nerve-brainstem evoked response (ABR) thresholds to fluid stimulation between normal and animal models of post radical-mastoidectomy, as seen in a previous human study. Background It has been shown in humans that hearing can be elicited with stimulation to fluid in the external auditory meatus (EAM), and radical-mastoidectomy cavity. These groups differed in age, initial hearing, and drilling exposure. To overcome this difference, experiments were conducted in sand-rats, first intact, and after inducing a radical-mastoidectomy. Methods The EAM of five sand-rats was filled with 0.3 ml saline. ABR thresholds were determined in response to vibratory stimulation by a clinical bone-vibrator with a plastic rod, applied to the saline in the EAM. Then the tympanic membrane was removed, and malleus dislocated (radical-mastoidectomy model). The cavity was filled with 0.45 ml saline and the ABR threshold was determined in response to vibratory stimulation to the cavity fluid. Results There was no difference in ABR fluid thresholds to EAM and mastoidectomy cavity stimulation. Air-conduction stimulation from the bone-vibrator was not involved (conductive loss due to fluid). Bone-conduction stimulation was not involved (large difference in acoustic impedance between fluid and bone).

The mechanism of human hearing under water is debated. Some suggest it is by air conduction (AC), others by bone conduction (BC), and others by a combination of AC and BC. A clinical bone vibrator applied to soft tissue sites on the head, neck, and thorax also elicits hearing by a mechanism called soft tissue conduction (STC) or nonosseous BC. The present study was designed to test whether underwater hearing at low intensities is by AC or by osseous BC based on bone vibrations or by nonosseous BC (STC). Thresholds of normal hearing participants to bone vibrator stimulation with their forehead in air were recorded and again when forehead and bone vibrator were under water. A vibrometer detected vibrations of a dry human skull in all similar conditions (in air and under water) but not when water was the intermediary between the sound source and the skull forehead. Therefore, the intensities required to induce vibrations of the dry skull in water were significantly higher than the underwater hearing thresholds of the participants, under conditions when hearing by AC and osseous BC is not likely. The results support the hypothesis that hearing under water at low sound intensities may be attributed to nonosseous BC (STC).

Hearing is elicited by applying the clinical bone vibrator to soft tissue sites on the head, neck, and thorax. Two mapping experiments were conducted in normal hearing subjects differing in body build: determination of the lowest soft tissue stimulation site at which a 60 dB SL tone at 2.0 kHz was effective in eliciting auditory sensation and assessment of actual thresholds along the midline of the head, neck, and back. In males, a lower site for hearing on the back was strongly correlated with a leaner body build. A correlation was not found in females. In both groups, thresholds on the head were lower, and they were higher on the back, with a transition along the neck. This relation between the soft tissue stimulation site and hearing sensation is likely due to the different distribution of soft tissues in various parts of the body.

Background: Active middle ear implants such as the vibrant sound bridge (VSB) have been placed on the round window (RW) in patients with conductive or mixed hearing loss, with satisfactory hearing results. Several observations show that the mechanism of RW stimulation is not completely understood. The purpose of the present study was to compare different coupling procedures between the transducer and the RW in order to contribute to an understanding of the mechanism of RW stimulation., Methods: Five fat sand rats underwent ablation of the left ear and opening of the right bulla, followed by baseline measurements of thresholds of auditory nerve brainstem evoked responses (ABR) to air and bone conduction click stimuli. Subsequently the malleus and incus were removed from the right middle ear, modeling a conductive hearing loss in which the VSB on the RW is indicated. In the next stage of the experiment, a rod attached to the bone vibrator was placed gently on the RW membrane and then on saline fluid applied to the RW niche. ABR thresholds were recorded following both placements., Results: Mean baseline ABR threshold in response to air conduction stimuli was 48 ± 4 dB; mean ABR threshold when the rod was placed on the dry RW membrane was 99 ± 12 dB; mean ABR threshold when the rod was in the saline on RW niche was 79 ± 7 dB., Conclusions: ABR thresholds were better (lower) with stimulation of fluid on the RW membrane compared to direct stimulation of the RW, providing further evidence of a direct fluid pathway.

Background: The aim of this study was to describe the results of the Auditory Behavior in Everyday Life (ABEL) questionnaire adapted to Hebrew and to Arabic and its association to clinical test results in children with cochlear implants. As assessment of hearing by audiometry does not always adequately reflect performance in daily life, questionnaires have been developed to assess functioning in natural surroundings and to track progress. In order to evaluate cochlear-implanted children's verbal and communicative abilities, the parental ABEL questionnaire was developed in 2002. The advantages of the ABEL questionnaire are that it is intended for a wide age range, is quick to administer, and is filled out by parents themselves., Methods: The ABEL questionnaire was translated into Hebrew and into Arabic and routinely used in the clinic. A total of 61 questionnaires were thus filled out by parents of children with cochlear implants (ages 3.9-14.3 years) when they came for routine mapping. Retrospectively, data were analyzed and questionnaire results were compared with performance with the implant on several clinical tests: audiometric thresholds, discrimination (percentage) of vowel-consonant-vowel nonsense syllables, and results of speech perception tests with monosyllabic and bisyllabic words and with sentences in quiet and in noise., Results: A correlation was found between the different sections of the questionnaire, and age at implantation had a significant effect on questionnaire scores. However, correlations between questionnaire score and clinical tests were found only for speech perception tests in noise and not in quiet or to audiogram and speech reception threshold., Conclusions: As has been reported previously, self-evaluation or parental evaluation does not always correlate with all measured results of hearing performance. However, the subjective information collected through questionnaires can be valuable for evaluation of progress, for counseling and rehabilitation training, as well as for mapping.

Soft tissue conduction (STC) is a recently expounded mode of auditory stimulation in which the clinical bone vibrator delivers auditory frequency vibratory stimuli to skin sites on the head, neck, and thorax. Investigation of the mechanism of STC stimulation has served as a platform for the elucidation of the mechanics of cochlear activation, in general, and to a better understanding of several perplexing auditory phenomena. This review demonstrates that it is likely that the cochlear hair cells can be directly activated at low sound intensities by the fluid pressures initiated in the cochlea; that the fetus in utero, completely enveloped in amniotic fluid, hears by STC; that a speaker hears his/her own voice by air conduction and by STC; and that pulsatile tinnitus is likely due to pulsatile turbulent blood flow producing fluid pressures that reach the cochlea through the soft tissues.

This study was designed to compare the thresholds to a standard clinical bone vibrator applied to sites on the head over skull bone (bone conduction, BC) and to soft tissue sites on the head and neck (soft tissue conduction, STC) with static application forces of 100 and 500 g in order to assess the possibility that STC is actually a form of BC, since both are elicited by stimulation with the same bone vibrator. Thresholds to 2.0-kHz tones were assessed in dB hearing level settings of the audiometer in the BC stimulation mode. There was no difference in threshold between forces of 100 and 500 g when applied to the skull bone sites (e.g. mastoid, forehead). However, at soft tissue sites (e.g. below the ear lobe, under the chin, on the sterno-cleido-mastoid muscle), thresholds to 100 g were significantly higher (poorer) than those to 500 g. With the 500 g static force (and also with the 100 g force), the thresholds at the STC sites were higher (poorer) than those at the skull bone sites. These findings have implications for understanding BC and STC modes of auditory activation., (Copyright © 2012 S. Karger AG, Basel.)

Background: Soft tissue conduction (STC), a recently described mode of auditory stimulation elicited when the clinical bone vibrator is applied to skin sites over the head, neck, and thorax, complements air conduction (AC) and bone conduction (BC), elicited by the same vibrator. The study assessed skull bone vibrations induced during STC and BC stimulation., Methods: The experiments were conducted on fat sand rats. Thresholds of auditory nerve brainstem evoked responses (ABRs) were recorded and compared to the lowest-intensity sound stimuli that elicited vibrations at the bony vestibule of the inner ear detected by a laser Doppler vibrometer., Results: Vibrations were detected during BC but not during STC stimulation. ABR was recorded to both STC and to BC stimulation., Conclusions: Low-intensity STC stimulation does not induce vibrations of the inner ear, showing that STC apparently does not involve mechanisms based on vibrations of bone.

Background: Soft tissue conduction (STC) is a recently described mode of auditory stimulation in which vibrations induced by a clinical bone vibrator applied to soft tissue sites on the head, neck, and thorax of human subjects reach the cochlea and elicit auditory sensation. In humans, STC stimulation interacts with air conduction stimulation and with bone conduction (BC) stimulation in several ways, e.g., mutual masking., Methods: This study investigated whether mutual masking between STC and BC stimulation can be demonstrated in an experimental animal. In fat sand rats, auditory nerve and brainstem evoked response to BC stimulation was recorded in the presence of noise masking presented by STC and vice versa., Results: STC successfully masked BC, and BC also masked STC responses., Conclusions: Mutual masking, now demonstrated in animals, paves the way for animal experiments to clarify the pathway between the STC stimulation sites and the cochlea.

Objectives: Auditory sensation can be elicited by air conduction (AC) and by bone conduction (BC). It is also possible to elicit such responses by applying the standard clinical bone vibrator to the skin over soft tissue sites on the head, neck, or thorax of humans and animals. This mode of auditory stimulation has been called soft tissue conduction (STC). This study was designed to investigate the pathway between soft tissue sites and the ear., Methods: The air in the middle ear was replaced with saline solution in an animal with unique anatomy--the fat sand rat, in which about 70% of a thin-walled inner ear bulges into the middle ear bulla cavity--while we recorded the auditory brain stem responses (ABRs) to AC, BC, and STC stimulation., Results: This replacement of air with saline solution led to a significant improvement in STC threshold. With AC stimulation, the ABR threshold was elevated and the latency of the first ABR wave was prolonged. Consistent changes were not seen with BC stimulation., Conclusions: When the air (which has a very low acoustic impedance) that normally surrounds most of the inner ear is replaced with saline solution (which has an acoustic impedance similar to that of soft tissues), the STC threshold is improved. This improvement may be due to improved transmission of acoustic energy from the soft tissues to the inner ear.

Since air-conducted (AC) and clinical (mastoid) bone-conducted (BC) sounds interact in the cochlea (e.g. pitch, cancellation, masking, beats), it has been thought that both AC and BC stimulations lead to a mechanical wave in the cochlea. However, there are also "non-osseous" forms of BC, i.e. auditory sensation produced when the clinical bone vibrator is applied to "non-osseous" soft tissue sites. In the present study, such "non-osseous" sites were identified (e.g. eye, cheek, neck) and they interacted with AC and osseous BC (pitch matching, beats, masking), indicating that all of these forms of auditory stimulation converge in the cochlea, producing the same pattern of mechanical activity, leading to their interactions.

Background: A new mode of auditory stimulation has been demonstrated which is through soft tissue conduction (STC). It involves evoking auditory sensations by applying the clinical bone vibrator to the skin over soft tissue (not over bone) sites on the head and neck., Methods: This study was designed to show that stimulation by STC excites the cochlea in a way similar to that of air conduction (AC) and bone conduction (BC)., Results: It is shown here that auditory nerve brainstem evoked response (ABR) thresholds in mice and in the fat sand rat to AC, to BC and to STC stimulation are all elevated following administration of drugs (salicylic acid and furosemide) which depress the cochlear amplifier. In addition, the present study brings evidence that STC stimulation is not a variant of BC since the sound pressures recorded in the occluded external auditory canal (the occlusion effect) in response to STC are significantly smaller than that to BC stimulation, though both are of equal loudness., Conclusions: This new mode, STC, therefore appears to bypass the middle ear mechanisms and consequently may contribute to auditory diagnosis.