Exploration of acoustical features reflecting bowel motion using simultaneous measurements of X-ray fluoroscopy and bowel sounds.

In clinical practice, bowel sounds are often used to assess bowel motility. However, the mechanism of bowel-sound occurrence is unknown. Furthermore, there is no objective evidence indicating a relationship between bowel motility and bowel sounds, and diagnoses have been based on empirically established criteria. In this study, simultaneous X-ray fluoroscopy and bowel-sound measurements were used to reveal the mechanism of bowel-sound occurrence. The results indicate that the flow of luminal contents may cause bowel sounds. Additionally, on the basis of the hypothesis that bowel motility recovers with the postoperative course, bowel-sound features that reflect bowel motion were explored, revealing that the current diagnosis indices are appropriate.

Canceling Crosstalk Sound in Bone Conduction Hearing: An Accelerometer-Based Approach.

Bone conduction hearing aids offer a unique solution for people with conductive hearing loss, providing a direct transmission of sound to the cochlea. However, a common issue called "crosstalk" can occur, where sound intended for one ear is received by the opposite ear via bone conduction, affecting the ability to localize sound sources and understand speech in noise. To address this issue, we investigated whether canceling "crosstalk" at an accelerometer located on the mastoid would create a "quiet zone" that reaches the cochlea in the inner ear. Our evaluation with individuals having normal hearing abilities showed that their hearing thresholds were improved with crosstalk cancellation than without. These results indicate that although designed to cancel "crosstalk" at the mastoid, the cancellation still reached the cochlea, making it perceptible and potentially beneficial for those with conductive hearing loss.

Characteristics of Frequency Resolution and Speech Perception Using Bone Conduction on Different Human Facial Parts.

In conventional bone-conduction (BC) devices, a vibrator is typically attached to the mastoid process of the temporal bone or the condyle process of the mandible. However, BC-sound presentations to facial parts such as the nose and cheek have also been investigated recently. As the face is the among the most complex structures of the human body, transmission of sounds using BC on different facial parts are likely to show different perception and propagation characteristics than those presented to conventional parts. However, the characteristics of BC sound presented to different part of the face have not yet been studied in detail. To test the frequency discrimination ability, we measured difference limens for frequency (DLFs). We also conducted monosyllable articulation tests in Japanese to assess the speech-perception characteristics when BC sounds are presented to various facial (nasal, infraorbital region, zygomatic, jaw angle, and chin) and conventional (mastoid and condyle process) parts of a normal-hearing subject. The results suggest that, at least in the parts investigated in the current study, the frequency resolution and intelligibility of the facial parts were about the same as those of the conventional parts. These results indicate that practical frequency information and speech perception are possible with BC devices attached to different facial parts.

Effect of occlusion effect by bone-conducted sound on monosyllable articulation.

Bone conduction (BC) technology allows us to hear sounds without having anything blocking our ears and enables hearing even when wearing earplugs. However, optimizing this technology presents challenges, particularly in relation to the occlusion effect (OE), a phenomenon that takes place when the ear canal is occluded, causing low-frequency sounds to seem louder than their original intensity. While some facial regions exhibit greater OE than conventional areas, the impact of OE on speech perception in different facial regions has not been thoroughly investigated. This study explores the relationship between OE and speech perception in various facial regions to inform the functionality of BC technology. We conducted a quantitative analysis of monosyllable articulation in the mastoid process, condylar process, nasal bone, and infraorbital region using both female and male voices to assess OE's impact on speech perception. Our findings reveal that OE improves articulation, facilitating voice communication; however, the extent of articulation enhancement varies depending on the stimulus location and phoneme. By examining OE's role in speech perception, this research report contributes to the development and use of more effective BC technology applications.

Effects of hardness and dimension of pinna and auricular hematoma on detection threshold of cartilage conduction.

In cartilage conduction (CC), a vibrator is presented onto the cartilage of the ear instead of the bony parts of the head used in ordinary bone conduction (BC). Because the auricle cartilage is softer and lighter than the bone, it doesn't require as much pressure as BC, which may cause discomfort (or pain) in the area where a BC transducer is being pressed. However, CC is a relatively new technology, and whether the less dense characteristics of cartilage, which varies from person to person, result in a better sound perception is still being studied. In this paper, we focused on investigating how the hardness and size of the auricle or pinna affect the effectiveness of CC. We used pure-tone hearing thresholds to evaluate this objectively. We also measured the thresholds of CC in subjects with auricular hematoma or "cauliflower ear" (misshapen ears commonly caused by close contact sports) to see if it affected CC differently. Our results indicate that the hardness and size of the auricle affect CC thresholds and that subjects with auricular hematoma have different perceptual characteristics compared to the normal ear group. These differences are believed to be caused by changes in hardness and mass.

Unilateral crosstalk cancellation via bone conduction: Methods and evaluation.

Bone conduction hearing aids (BCHAs) offer an alternative solution for individuals with outer or middle ear issues who cannot benefit from traditional air conduction hearing aids. However, the phenomenon of "crosstalk," where sound intended for one ear is mistakenly transmitted to the other ear through bone conduction, presents a challenge. This unintended transmission may limit the benefits of binaural hearing that can be achieved using two BCHAs, such as accurately detecting a sound source's direction. In this article, we present a method to suppress "crosstalk" within the human head using an adaptive algorithm to control two audiometric bone transducers. •Our method involves positioning an error sensor at a location considered close to the cochlea, such as the ear canal or the mastoid, and utilizing an adaptive algorithm to estimate the crosstalk compensation filter. This filter generates an anti-signal, which is then transmitted to one of the two transducers, effectively cancelling the crosstalk.•To verify whether the crosstalk cancellation reaches the cochlea in the inner ear, we provide a procedure for measuring hearing thresholds with and without crosstalk cancellation. This acts as a subjective measure of the efficacy of our crosstalk cancellation method. By leveraging an adaptive algorithm, this approach provides personalized cancellation and has the potential to enhance the performance of binaural BCHAs.

Characteristics of speech perception by distantly-presented bone-conducted ultrasound assessed by word intelligibility and monosyllable articulation tests.

High-frequency sounds above 20 kHz presented via bone conduction can be heard clearly and transmit speech information using amplitude modulation. Additionally, bone-conducted ultrasound (BCU) can be perceived even when the vibrator is presented to body parts distant from the head, such as the neck, arm, and trunk. To evaluate this previously presented BCU hearing, word intelligibility and monosyllable articulation tests were conducted in Japanese. The results suggested that a practical speech transmission, comparable to ordinary BCUs presented onto the head, can be obtained by distantly presented BCU.

Perception and Propagation Characteristics of Bone-Conducted Stimuli Presented to the Human Facial Cranium.

Since bone conduction (BC) has the advantage that it does not cover the ear canal and can be easily heard even when earplugs are worn, it has been applied to various communication devices. Conventional BC is mainly applied to the mastoid process of the temporal bone (the osseous bulge behind the ear), however, some of recent BC devices, such as smart glasses, present stimuli to faces. The face has very complex structures in the human body; therefore, it is highly likely that the hearing and propagation characteristics of sound will change depending on the part to which sound is presented. However, the characteristics of BC presented to the face has not yet been studied in detail. In this study, we measured hearing threshold and ear canal sound pressure (ECSP) when BC stimuli were presented to various parts of the facial cranium (nasal, infraorbital region, zygomatic, jaw angle, and chin), and compared them with conventional placements of BC stimulus (the mastoid process, condyle process, and forehead). The facial parts such as the infraorbital region, zygomatic, and jaw angle had similar hearing thresholds and ECSPs to those of the mastoid process. The results suggested that these facial parts can be used as stimulus placements of BC devices.

Gastric Tube Ulcer that Could Be Saved by Early Conservative Treatment.

The patient was an 81-year-old man who had received subtotal esophagectomy for esophageal cancer reconstructed by a gastric tube via a posterior mediastinal route. He presented to our emergency room with a complaint of epigastric pain and a small amount of hematemesis. Thoracoabdominal computed tomography showed that the reconstructed gastric tube was filled fluid and had irregular wall thickening. We suspected upper gastrointestinal bleeding, and we started to treat with administration of proton pump inhibitors (PPIs) since the anemia was mild and his vitals were stable. However, his anemia was rapidly progressed to Hb 6.0 with a large amount of old blood melena. The emergency gastroscopy showed an A2 stage ulcer with active oozing at middle esophagus reconstructed by a gastric tube. Therefore, we applied thrombin spray to treat the bleeding. Fortunately, his recovery was progressing nicely with medical treatments for a week. In this study, we experienced a case in which early administration of PPIs might be a key player to prevent his medical condition worsened further.

Expectations of the timing and intensity of a stimulus propagate to the auditory periphery through the medial olivocochlear reflex.

Expectations concerning the timing of a stimulus enhance attention at the time at which the event occurs, which confers significant sensory and behavioral benefits. Herein, we show that temporal expectations modulate even the sensory transduction in the auditory periphery via the descending pathway. We measured the medial olivocochlear reflex (MOCR), a sound-activated efferent feedback that controls outer hair cell motility and optimizes the dynamic range of the sensory system. MOCR was noninvasively assessed using otoacoustic emissions. We found that the MOCR was enhanced by a visual cue presented at a fixed interval before a sound but was unaffected if the interval was changing between trials. The MOCR was also observed to be stronger when the learned timing expectation matched with the timing of the sound but remained unvaried when these two factors did not match. This implies that the MOCR can be voluntarily controlled in a stimulus- and goal-directed manner. Moreover, we found that the MOCR was enhanced by the expectation of a strong but not a weak, sound intensity. This asymmetrical enhancement could facilitate antimasking and noise protective effects without disrupting the detection of faint signals. Therefore, the descending pathway conveys temporal and intensity expectations to modulate auditory processing.

Generation mechanisms of bowel sounds by simultaneous measurements of X-ray fluoroscopy and bowel sounds.

In clinical practice, bowel sounds are often used to assess bowel motility. However, the diagnosis differs depending on the literature because diagnoses have been based on empirically established criteria. To establish diagnostic criteria, researching the mechanism of bowel-sound occurrence is necessary. In this study, based on simultaneously measured X-ray fluoroscopy and bowel sounds, correlation and Granger causality among bowel movement, luminal content movement, and abdominal sound were estimated. The results supported our hypothesis that the bowel moves luminal contents and luminal contents generate abdominal sounds.

Basic properties of distantly-presented bone-conduction perception.

Since a vibrator needs to be pressed onto the osseous parts of the head, bone-conduction (BC) is often accompanied by pain and esthetic problems. In order to solve these problems, "distant presentation" has been proposed. In the distant presentation, vibrators are presented to the neck, upper limb or trunk. Our previous studies focused on the perception and propagation characteristics of distantly-presented BC sound in the ultrasonic range and an application to a novel audio-interface. On the other hand, a limited number of studies have been conducted on distantly-presented BC in the audible-frequency range. In this study, to examine the basic properties of the distantly-presented BC perception in the audible-frequency range, hearing thresholds, difference limens for frequency (DLFs) and temporal modulation transfer functions (TMTFs) were measured under the condition that AC sounds were insulated sufficiently. The results obtained indicated that BC sounds can be clearly perceived at distal parts of the body even in the audible-frequency range and no significant degradation of frequency and temporal information occurs in the propagation process in the body.

Intelligibility of bone-conducted speech detected on the scalp assessed by mono-syllable articulation and speech transmission index.

Bone-conduction microphones (BCMs) can detect speaker's voices with high signal-to-noise ratio even under extremely noisy environments. However, it is sometimes accompanied by discomfort and esthetic problems because BCMs are ordinarily attached to the front of the neck (larynx). In order to solve such problems, we have been developing a novel BCM systems built in a hard hat [2]. To develop this BCM system, characteristic of bone-conducted speech detected on the scalp need to be clarified. In this study, intelligibilities of bone-conducted speech detected at several locations on the head and neck were assessed by mono-syllable articulation tests and the speech transmission index (STI), objective measure of signal transmission quality. The results obtained indicated that the forehead and the vertex showed better articulation and STI than the mastoid process of the temporal bone, the mandibular condyle and occiput. Additionally, the larynx, commonly used in existing BCM systems, showed lower scores than others. These results suggest that attenuation of high-frequency components are smaller at the forehead and the vertex, and indicate the practicability of these locations as the BCM placement.

Estimation of relationships between transducer placements and peripheral propagation in cartilage conduction.

Bone-conduction (BC) has been applied to hearing aids for the conductive hearing loss, however, also has some disadvantage especially in wearability of a sound transducer. Therefore, as a solution, "cartilage conduction (CC)" has been proposed and applied to devices such as a hearing aid and smartphones. In CC, a sound transducer is placed on the cartilage of the pinna, and the air-conduction (AC) and osseotympanic BC components are dominantly transmitted. However, even in CC, the vibrating surface often contacts not only with the aural cartilage but also with the osseous parts of/around the pinna, and effects of such transducer placement on perception characteristics and propagation mechanisms remain unclear. In this study, we measured hearing thresholds and vibrations of the head when the transducer was placed on (1) the pinna, (2) the mastoid process of the temporal bone, and (3) the ear-front point (middle of between the tragus and the mandibular condyle). The results suggested that the ratios of the inertial and compressional BC components increases when the transducer is placed on the osseous parts, particularly in high frequency range. These findings provide useful information to optimize CC devices and develop a calibration method of CC.

Conversion of amplitude modulation to phase modulation in the human cochlea.

When an amplitude modulated signal with a constant-frequency carrier is fed into a generic nonlinear amplifier, the phase of the carrier of the output signal is also modulated. This phenomenon is referred to as amplitude-modulation-to-phase-modulation (AM-to-PM) conversion and regarded as an unwanted signal distortion in the field of electro-communication engineering. Herein, we offer evidence that AM-to-PM conversion also occurs in the human cochlea and that listeners can use the PM information effectively to process the AM of sounds. We recorded otoacoustic emissions (OAEs) evoked by AM signals. The results showed that the OAE phase was modulated at the same rate as the stimulus modulation. The magnitude of the AM-induced PM of the OAE peaked generally around the stimulus level corresponding to the compression point of individual cochlear input-output functions, as estimated using a psychoacoustic method. A computational cochlear model incorporating a nonlinear active process replicates the abovementioned key features of the AM-induced PM observed in OAEs. These results indicate that AM-induced PM occurring at the cochlear partition can be estimated by measuring OAEs. Psychophysical experiments further revealed that, for individuals with higher sensitivity to PM, the PM magnitude is correlated with AM-detection performance. This result implies that the AM-induced PM information cannot be a dominant cue for AM detection, but listeners with higher sensitivity may partly rely on the AM-induced PM cue.

Assessment of the difference limens for frequency, monosyllable articulation and word intelligibility by distantly-presented bone-conducted ultrasound.

Ultrasound can be clearly perceived by bone-conduction, and this "bone-conducted ultrasound (BCU)" can transmit speech information by using amplitude modulation (AM). Further, BCU can be perceived not only on the head but also on the distal parts of the body like the neck, trunk and arms. This "distantly-presented BCU" can be applied to the novel interface that can transmit sound information selectively to specific users who touches the vibrator. However, the ability to transmit sound information of distantly-presented BCU is unclear. First, to assess frequency discrimination ability, difference limens for frequency (DLFs) of the distantly-presented AM-BCU were measured with/without a low-pass masking noise that masked the self-demodulated components generated by the nonlinearity of biological tissues. DLFs comparable to that of air-conducted sounds were observed, whereas DLFs significantly increased above 1 kHz under the masking condition. These results suggest that practical frequency discrimination ability can be obtained even when BCUs were presented to distal body parts. Additionally, it is indicated that the demodulated components may contribute to transmitting frequency information above 1 kHz. Second, monosyllable articulation and word intelligibility tests were conducted in Japanese. The intelligibility and articulation at the neck were 55% and 38% respectively, whereas they decreased as the stimulus placement gets farther from the head. The results suggest the distantly-presented BCU device can be applied to transmission of speech information.

Effect of interlateral time and intensity differences of distantly-presented bone-conducted ultrasound on lateralization.

Bone-conducted ultrasound (BCU) is perceived even by the profoundly sensorineural deaf and has been applied to the development of a novel hearing aid. In the BCU hearing aid, the vibrator is pressed onto the mastoid process of the temporal bone (the osseous bulge behind the ear). However, BCU can be heard on distal parts of the body; e.g., the muscle of the neck, the clavicle and the upper limbs. Some studies have been carried out to develop other BCU hearing devices using this "distant presentation". However, the possibility of the localization of distantly-presented BCU has not been verified. In this study, we investigated whether listeners could use the interaural time differences (ITDs) and intensity differences (IIDs) as cues for lateralization (left/right discrimination) of distantly-presented BCU. The results showed that lateralization based on ITDs and IIDs is possible to some extent, even for the distant presentation, whereas lateralization become difficult as the stimulus placement gets further from the head. Lateralization based on IIDs was more accurate than that based on ITDs. IIDs seem to give more effective cues than ITDs in the lateralization of BCU.

Relationship between cochlear mechanics and speech-in-noise reception performance.

Some normal-hearing listeners report difficulties in speech perception in noisy environments, and the cause is not well understood. The present study explores the correlation between speech-in-noise reception performance and cochlear mechanical characteristics, which were evaluated using a principal component analysis of the otoacoustic emission (OAE) spectra. A principal component, specifically a characteristic dip at around 2-2.5 kHz in OAE spectra, correlated with speech reception thresholds in noise but not in quiet. The results suggest that subclinical cochlear dysfunction specifically contributes to difficulties in speech perception in noisy environments, which is possibly a new form of "hidden hearing deficits."

Assessments of basic properties of distal-presented bone-conducted ultrasonic hearing.

Bone-conducted ultrasound (BCU) is perceived even by the profoundly sensorineural deaf and a novel hearing aid using the perception of amplitude-modulated BCU (BCU hearing aid) has been developed. In the BCU hearing aid, the vibrator is pressed onto a part of the cranial bone behind the ear (mastoid process). However, BCU can be heard on distal parts of the body; i. e., the muscle of the neck, the clavicle, and the upper limb. In this study, to assess basic properties of such distal-presented BCU hearing, hearing thresholds were measured when 30-kHz tone bursts were presented to the neck and the upper and lower arms in normal hearing participants. Further, to assess the basic capability of transferring information by the distal-presented BCU hearing, temporal modulation transfer functions (TMTFs), that reflect the temporal resolution of the hearing, were estimated for 30-kHz carrier. The results showed that BCUs presented to the distal parts, including the lower arm, can be perceived at least in the normal hearing, whereas threshold increased depending on the distance from the head. Also, the temporal resolutions of the distal-presented BCU hearing at the neck, and the upper and lower arms were comparable to that of the mastoid process of the temporal bone. These results provide useful information not only for the improvement of the existing BCU hearing aid, but also for the development of novel distal-presented BCU devices that can provide sound information selectively to the specific person who touches the device by the arms or so.

Comparison of perceptual properties of auditory streaming between spectral and amplitude modulation domains.

The two-tone sequence (ABA_), which comprises two different sounds (A and B) and a silent gap, has been used to investigate how the auditory system organizes sequential sounds depending on various stimulus conditions or brain states. Auditory streaming can be evoked by differences not only in the tone frequency ("spectral cue": ΔFTONE, TONE condition) but also in the amplitude modulation rate ("AM cue": ΔFAM, AM condition). The aim of the present study was to explore the relationship between the perceptual properties of auditory streaming for the TONE and AM conditions. A sequence with a long duration (400 repetitions of ABA_) was used to examine the property of the bistability of streaming. The ratio of feature differences that evoked an equivalent probability of the segregated percept was close to the ratio of the Q-values of the auditory and modulation filters, consistent with a "channeling theory" of auditory streaming. On the other hand, for values of ΔFAM and ΔFTONE evoking equal probabilities of the segregated percept, the number of perceptual switches was larger for the TONE condition than for the AM condition, indicating that the mechanism(s) that determine the bistability of auditory streaming are different between or sensitive to the two domains. Nevertheless, the number of switches for individual listeners was positively correlated between the spectral and AM domains. The results suggest a possibility that the neural substrates for spectral and AM processes share a common switching mechanism but differ in location and/or in the properties of neural activity or the strength of internal noise at each level.