Evaluation of a Bone Conducted Vibration Device Designed for Motion Sickness Mitigation
INTRODUCTION: Historical and modern science has produced many remedies for motion sickness; however, few if any of these remedies have demonstrated successful mitigation without producing negative side effects. The purpose of this study was to determine if a newly created commercial bone conducted vibration (BCV) device could reduce motion sickness symptoms in a simulated visual and provocative motion flight environment.
METHODS: Subjects (N = 12) passively experienced two 30-min, auto-pilot simulated flights in a motion-based simulator while wearing a BCV device during experimental or placebo conditions. Trial condition presentations were counterbalanced to control potential order effects with a minimum of 1 d between trials. During each trial, subjects completed a tracking task and verbally reported subjective motion sickness ratings every 2 min. After completion of each trial, a Motion Sickness Assessment Questionnaire (MSAQ) was administered.
RESULTS: No significant differences in overall MSAQ scores were observed between experimental (29.3 ± 19.4) and placebo (31.1 ± 17.4) BCV conditions. Significant differences in motion sickness scores were observed between the first (34.0 ± 17.6) and second (26.3 ± 18.4) trial sessions.
DISCUSSION: The commercial BCV device did not affect the presence or absence of motion sickness during placebo or experimental conditions and had no effect on tracking task performance. During the second trial session, MSAQ scores were lower and time to nausea and failure were longer; however, observed increases in motion tolerance during the second trial sessions likely resulted from sensory adaptation and appeared to be unrelated to the BCV device.
Patterson FR, Kaplan A, Gallimore D, Sherwood S, Horning D, Folga RV. Evaluation of a bone conducted vibration device designed for motion sickness mitigation. Aerosp Med Hum Perform. 2025; 96(11):993–999.
With today’s modern military operations, motion sickness continues to have a negative impact on both training and operational readiness at sea, on land, and in the air; consequently, the Department of Defense has continued to seek easy to use cost-effective remedies that do not have adverse side effects. Among the more recent attempts to develop an effective antimotion sickness remedy is a bone conducted vibration (BCV) device created by Otolith Laboratories.1–3 This device, referred to as the Otoband, has a small, low-voltage bone conduction transducer that uses an elastic band to hold it in place on the skin surface behind the ear, over the mastoid process. By generating low frequency vibrations, this noninvasive device creates vibration stimulation that reportedly transfers sensations of both linear and angular acceleration to the vestibular system.4 Developers of this technology believe creating incongruent randomized vibration signals, within the vestibular system, will cause the brain to disregard sensory signals from the inner ear and thereby reduce motion sickness susceptibility. Unlike similar external vestibular stimulus methods, such as galvanic vestibular stimulation, the Otoband BCV technology has been reported as having no adverse side effects.5 However, since peer-reviewed published data validating the airsickness mitigation benefits of Otolith Laboratories’ Otoband is limited, the purpose of this research was to conduct an independent test and evaluation of the device to determine its effectiveness.
For over two millennia, motion sickness associated with traveling in vehicles has been reported as a common and debilitating occurrence.6 As early as 800 B.C., the Greeks identified wave motion as the cause of seasickness and, by 300 A.D., Chinese medical records documented riding in carts induced an illness known as cart sickness. In addition to inconveniencing vehicular passengers, historical records cited by Huppert indicate motion sickness has also played a critical role in decisive military operations. In 1588, a Spanish Armada intending to invade and conquer England encountered rough weather off the coast of Britain as they came under attack by English ships. Unfortunately for the Spanish, their leader Don Alonzo Perez de Guzman el Bueno was known to be extremely susceptible to seasickness, as were many of his embarked soldiers. Historians have surmised that during the ensuing sea battle, the Armada leader’s illness contributed to his poor tactical decisions that led to the Spanish defeat. Several hundred years later (1798–1799), Napoleon’s army also encountered tactical problems from motion sickness during their invasion of Egypt. After disembarking from their ships, the French ground forces transitioned their primary mode of overland transportation from horse to camel and soon discovered that “… soldiers who were susceptible to motion sickness” could become “seasick” on this “ship of the desert” and “unable to engage in battle.”7
During ancient times, Western medical advice for mitigation of motion sickness included a variety of recommendations such as: “fasting or specific diets, pleasant fragrancies, medicinal plants like white hellebore (containing various alkaloids), or a mixture of wine and wormwood.” Early Eastern medicine gave more earthy suggestions that involved, “…swallowing white sand-syrup, collecting water drops from a bamboo stick, or hiding earth from the kitchen hearth under the [patient’s] hair”.7 Although modern medicine has provided more effective treatments for mitigating motion sickness, such as anticholinergics (scopolamine) or antihistamines (Dramamine), the undesirable side effects of these drugs has led to a reemergence of noninvasive anecdotal remedies. Similar to examples from the past, current unvalidated motion sickness treatments include a variety of approaches ranging from acupressure constricting wrist bands to motion sickness glasses.8,9 Despite the beneficial claims made by manufacturers of these present-day antimotion sickness devices, many of their claims have proven to be highly exaggerated and demonstrably false.10
Although multiple theories exist to explain the underlying causes of motion sickness, the most widely accepted explanation is the sensory conflict theory proposed by Reason and Brand in 1975.11–13 This theory suggests all types of motion sickness can occur when an individual is exposed to a mismatch of spatial sensations (afferent neural transmission) generated from visual, vestibular, or proprioceptor organs. The spatial conflict theory further explains that motion sickness responses are often triggered when the human brain senses conflicting sensory organ information. As an example, if a person in a moving vehicle is looking outside, they would experience optical visual flow of the scenery and at the same time sense vehicle motion from their vestibular and proprioceptor systems. Under these circumstances, they would experience three sources of congruent spatial information telling them they were in motion. In contrast, if a person in a moving vehicle has no outside view (no optical flow), their vestibular and proprioceptive systems would still send signals indicating they were in motion; however, their visual system would send conflicting (incongruent) sensations indicating they were stationary, thereby creating sensory conflict.
Scientists have further theorized that sensory conflict and motion sickness may have an evolutionary link to nausea and vomiting encountered with air, sea, and car travel. When early human ancestors were foraging for food, they may have occasionally consumed readily available plant material containing neurotoxins (i.e., nightshade, hemlock, jimson weed, etc.). If this did occur, consumption of these types of plants would initially create sensory conflict by disrupting the human sensory system, prior to the poison causing fatal circulatory collapse. In the event poisonous plants were ingested by the evolving human species, there would have been considerable natural selection pressure promoting evolution of a rapid vomiting response as a means of removing the substance from the body. Reason suggested that modern humans have retained this sensory conflict/vomiting response, and similarities that exist between ingesting neurotoxins and experiencing incongruent visual-motion sensations is what causes the brain to trigger nauseogenic motion sickness.13
The primary goal of this study was to evaluate the effectiveness of Otolith Laboratories’ BCV device in mitigating motion sickness during provocative motion flight simulations in the Disorientation Research Device (DRD) located at the Naval Medical Research Unit (NAMRU-D), Dayton, OH. The hypothesis for this experiment was: therapeutic BCV exposure (independent variable) will affect onset time, frequency, and magnitude of airsickness symptoms (dependent variables) measured by self-reporting scores of the Motion Sickness Assessment Questionnaire (MSAQ), the Baxter Retching Faces (BARF) scale, time to nausea, and Target Tracking Task performance (TTT).
METHODS
The protocol for this study was approved by the NAMRU-D Institutional Review Board (IRB) in compliance with all applicable federal regulations governing the protection of human participants (IRB approval #NAMRUD.2020.0008).
Subjects
A total of 12 healthy adults (mean age = 28.83 ± 4.01) consisting of 5 men and 7 women participated in this study. All subjects were recruited through flyers, online announcements, or by word of mouth and subjects who completed the study received compensation. Subjects self-reported normal or corrected-to-normal vision and had no history of neurological, vestibular, or other medical diagnoses.
Prior to enrollment, subject candidates confirmed eligibility by completing the Motion Sickness Susceptibility Questionnaire (MSSQ) and verbally answering screening questions over the phone. The MSSQ was used to assess individuals’ experiences with motion sickness (i.e., nausea, vomiting) in nine different types of transport or entertainment (i.e., vehicles, swings, fair rides, etc.) before the age of 12 and within the last 10 yr.14 Subjects rated their frequency of motion sickness for each experience using a 5-point Likert scale from 0 (never) to 4 (always). The MSSQ score is calculated as the total summed symptom rating scaled by the number of transport/entertainment types experienced, and is considered a reliable measure of motion sickness susceptibility during provocative motion stimulation. Only individuals with MSSQ scores greater than or equal to 45.5 were included to ensure enrollment of subjects with moderate to severe motion sickness susceptibility (mean = 144.87 ± 44.56, range 84.15–209.88).
Prior to starting their first trial session, subjects provided written informed consent with a witness present and were instructed to refrain from taking any type of motion sickness medication prior to participating in either the first or second trials. Female subjects were screened for pregnancy using either a validated pregnancy questionnaire or a urine pregnancy test.15 Any female subject candidates with indications of potential pregnancy were excluded from the study as a safety precaution.
Equipment
Subjects were equipped with a comfortable but snug-fitting standard military helmet with the Otolith Laboratories’ BCV device modified to fit inside the right helmet earcup, behind the ear, and over the mastoid bone skin surface. This allowed the device, when activated, to provide localized mastoid vibrations to stimulate the vestibular system.3 Helmet fitting and device placement was done by the same researcher for every subject to ensure reliable placement. The placebo device consisted of an Otolith Laboratories’ BCV power source and bone conduction transducer fixed on top of the helmet in a holding bracket. This provided diffuse vibrations to the entire head and avoided direct stimulation of the vestibular system. The amplitude of the experimental device was 1.47 times greater than the placebo with average amplitudes of 16.9 ft · s−2 (5.15 m · s−2) compared to 11.5 ft · s−2 (3.51 m · s−2), respectively.
This study incorporated motion and visual flight stimuli using the NAMRU-D DRD motion platform. The DRD has six bidirectional axes degrees of freedom: two linear (heave and horizontal) and four rotational (roll, pitch, yaw, and planetary), all on a bidirectional rotating platform (planetary axis) that provides an acceleration field for the occupant capsule.
A standardized DRD motion profile for inducing motion sickness was initially evaluated for inclusion with the study protocol;16 however, after running several test subjects, it was determined the standard profile was not provocative enough for the goals of this study. Subsequently, a rated U.S. Navy test pilot flew and recorded a DRD simulated T-6A Texan aircraft (Laminar X-Plane software) flight profile that consisted of increasing orders of magnitude for pitch, wingover, and near stall maneuvers. This series of aerobatic type maneuvers, coupled with decreasing time between maneuvers, produced a more provocative motion-sickness effect that was considered suitable for evaluating the motion-sickness mitigation capabilities of the BCV device. The revised DRD motion path and synchronized flight simulation consisted of an ellipse pattern, with a maximum achievable distance of ±12.5 ft (3.8 m) in the forward/backward directions and ±7.0 ft (2.1 m) laterally. In this motion space, the maximum achievable acceleration was 1.2 Gz for less than a half second. The DRD angular velocities were created using only the roll and pitch gimbal axes, with the maximum angular positions limited to ±60° for roll and ±45° for pitch. Maximum angular velocity was limited to 30° · s−1. These parameters were combined with motion washout to provide subjects with angular rate cues, as opposed to the sustained angular displacements and rates experienced in real world flight environments.
Procedure
Subjects underwent a simulated flight session during two separate counterbalanced visits: once with a BCV placebo and once with the BCV experimental device. To conceal the identity of the experimental and placebo devices, subjects were deceptively informed that the purpose of this study was to determine whether optimum placement of the BCV device was on top of the helmet or in the right ear cup. Each study session was approximately 90 min with a maximum of 30 min spent on each flight simulation trial and a minimum of 1 d between each trial session. After providing consent, subjects completed health screening and demographics questionnaires and were escorted to the DRD control room for fitting with a helmet equipped with a BCV experimental or placebo device. After donning the BCV equipped helmet, subjects were led to the DRD capsule and briefed on egress and emergency procedures before being strapped into the capsule seat with a five-point harness. They were then given instructions on how to report BARF ratings and how to perform the TTT during their flight session.
The BARF scale is a pictorial scale originally validated for measuring nausea in children.17 Subjects were presented with six faces and asked to rate their nausea on a scale of zero (neutral face) to 10 (vomiting face). BARF scores were averaged to create mean BARF scores for each subject’s session. Cronbach’s alphas for the placebo and experimental conditions were 0.95 and 0.96, respectively. Time to onset of nausea was determined by the time at which subjects reported a BARF rating greater than or equal to one. The session ended when a subject exceeded a BARF score of four or finished the 30-min flight session, whichever came first.
In accordance with the Navy DRD protocol, subjects were informed flight sessions would end if they reached a BARF score of 5 or greater (to avoid potential emesis, per DRD protocol) and were told they could stop the flight simulation session if they felt sick, or for any other reason. A baseline BARF rating was obtained before the start of capsule motion, after which, subjects began their 30-min flight simulation trial. Throughout the flight, subjects verbally reported their BARF ratings every 2 min.
Throughout each flight, subjects used an F-16 type force stick to perform the TTT.18 This task consisted of 4-min epochs of continuously centering an on-screen reticle within a diamond-shaped, moving target. The reticle and diamond shape target were overlaid on the flight simulation background, which consisted of Pensacola, FL, moving scenery as it would be viewed from a cockpit at 5000 ft (1524 m) above mean sea level altitude. TTT data were collected using an in-house developed research operator station. Tracking task performance was quantified in terms of throughput, which was defined as the number of “hits” divided by the time available to complete each TTT session, where a hit was considered to occur whenever the distance between the center of the target diamond and reticle (i.e., TTT distance) was less than 50 pixels.19 When TTT distance was less than 50 pixels, the center of the diamond fell within the inner circle of the reticle. Data at the start of each TTT session was excluded by finding the first point at which the TTT distance value was less than or equal to the session mean following a 10-s buffer. This was done to exclude large spikes that sometimes occurred at session starts due to temporary distraction while reorienting to the TTT. Subjects typically refocused on the TTT quickly following task pauses, resulting in a small difference in discretionary time across BCV conditions (M = 0.58 s, SD = 1.94 s). A custom MATLAB script was written to process the TTT data.
After each 4-min TTT session, there was a 4-min rest interval. During these rest periods subjects were instructed to remain looking forward at the screens; to ensure compliance, a video camera and recorder were used to monitor the subjects’ gaze direction.
After completion of each trial session, subjects were escorted from the capsule and asked to complete the MSAQ.20 The MSAQ assesses four dimensions of motion sickness symptoms: gastrointestinal (e.g., I felt sick to my stomach); central (e.g., I felt faint like); peripheral (e.g., I felt sweaty); and sopite-related (e.g., I felt tired/fatigued). Subjects rated 16 items using a scale from one (not at all) to nine (severely). MSAQ scores were summed for each dimension and were used in a formula for each subscale, where Rating = (Sum of each subclass symptom rating)/[(number of the questions related to the corresponding subclass) × 9]. Overall MSAQ scores were calculated as: score = (sum of all items/[(number of all questions) × 9] × 100. Cronbach’s alphas were 0.94 for both the placebo and experimental conditions.
At the end of the first test session, subjects were reminded not to take any over-the-counter nausea medications prior to the next session. After the study was completed, subjects were debriefed by a researcher on the true purpose of the study, the nature of the deception, and the reasoning and need behind the deception. Subjects were allowed to ask questions and were asked for permission to use their data for the study analysis.
Statistics Analysis
This was a counterbalanced, placebo-controlled study with repeated measures. Based on existing literature and information provided by the BCV device manufacturer, the power analysis for this protocol assumed an effect size of 0.45, which led to an original sample size estimate of 24 subjects. However, after observing no significant changes between the control and experimental conditions during trials for the first 12 subjects, exposing additional subjects to the nauseogenic effects of the protocol was deemed inappropriate under IRB guidelines. Subsequently, only data from the first 12 subjects was used for this study.
RESULTS
On average, 6.58 ± 16.59 d elapsed between subjects’ test sessions, with one outlier having 59 d between sessions. After removing this outlier, the average days between sessions were 1.81 ± 1.78 d and 58.33% (N = 7) of the subjects completed their sessions with a 1-d interval. Per DRD protocol, flight sessions were ended if subjects reached a BARF score of 5 or more. This protocol resulted in five of the first session flights ending before 30 min and one of the second session flights ending before 30 min. On average, elapsed times for the first and second sessions were 24.88 ± 7.57 min and 29.17 ± 2.89 min, respectively.
To examine whether the experience of motion sickness symptoms differed between the placebo and experimental flight sessions, paired-samples t-tests were conducted to compare overall MSAQ scores across BCV conditions. The results indicated there was no significant MSAQ difference between the BCV experimental and placebo conditions (Table I). For this study, order effect was not considered a definitive factor for measuring BCV effectiveness; however, since order effects were mentioned in a previous study that examined Otolith Laboratories’ BCV device with a Head Mounted Display Virtual Reality system, an exploratory analysis was conducted to evaluate possible differences in MSAQ scores across study visits.21 Since onset of nausea caused the first trial sessions of this study to end early for five subjects and only one subject’s trial ended early for the second session, there was a reduction in homogeneity of variance between the first and second trial sessions. Subsequently, a simple t-test analysis was considered a viable exploratory option for evaluating order effects instead of analysis of variance. The paired t-test comparing order effect revealed significant differences in overall and peripheral MSAQ subscales scores between the first and second trials, with lower scores appearing during the second trial session (Table I, Fig. 1).
Citation: Aerospace Medicine and Human Performance 96, 11; 10.3357/AMHP.6694.2025
Using a BARF rating score of 5 for terminating DRD sessions led to a pattern of missing data across time, which contravened the visit order counterbalancing scheme. To compensate for the missing data, BARF sessions were matched within each subject by including only sessions up to the minimum session number across conditions. BARF ratings were then averaged within each condition for each subject. Paired t-tests across BCV conditions and visit number were conducted to compare average BARF ratings and a survival analysis was conducted to compare time to failure. For BARF rating averages across BCV experimental and placebo conditions, paired t-tests revealed no significant difference [t(11) = −0.78, P = 0.22, g = −0.25]. For BARF rating averages across visit numbers, the paired t-test revealed a significant difference [t(11) = −4.24, P < 0.01, g = −0.99], with lower BARF ratings occurring during the second trial sessions (Fig. 2).
Citation: Aerospace Medicine and Human Performance 96, 11; 10.3357/AMHP.6694.2025
For time to nausea across BCV conditions, the paired t-test and Wilcoxon signed-rank test revealed no significant differences [respectively, t(11) = 0.078, P = 0.47, g = 0.016, and Z = 19, P = 0.72]. Comparing time to nausea for trial sessions one and two, paired t-test revealed a significant difference [t(11) = 2.72, P = 0.01, g = 0.46], with longer times during the second trial sessions. The Wilcoxon signed rank test also revealed a significant difference with the increasing time to nausea during the second trial sessions [Z = 44, P = 0.008] (Fig. 3).
Citation: Aerospace Medicine and Human Performance 96, 11; 10.3357/AMHP.6694.2025
The BARF scale failure criterion of 5 resulted in only three subjects reaching failure in both the placebo and experimental conditions (one subject reached failure in both conditions). Consequently, for the purposes of survival analyses, the failure criterion was lowered to a BARF rating of four, which led to 9 out of 12 subjects reaching failure in the placebo condition, and 5 out of 12 subjects reaching failure in the experimental condition. Nonfailure cases were considered right censored. For failure time by BCV condition, the survival analysis revealed a nonsignificant difference between placebo and experimental conditions (Wilcoxon Chi-squared, P = 0.28). For failure time by visit number, the survival analysis indicated a significant difference (Wilcoxon Chi-squared, P = 0.04), with lower probability of failure during the second trial session.
Paired samples t-tests for TTT performance between the placebo and experimental BCV conditions also revealed no significant difference [t(11) = 0.16, P = 0.44, g = 0.01] and, for throughput by visit number, the paired samples t-test indicated no significant difference [t(11) = 1.23, P = 0.12, g = 0.11].
DISCUSSION
The results of this evaluation indicate the tested BCV device did not have a significant impact on motion sickness. These findings are consistent with a similar study that determined BCV intervention did not mitigate head-mounted display virtual reality cybersickness.21 In both studies, the order effect was the only factor that reduced motion sickness, which suggests subjects most likely acclimated and adapted to the nausea-inducing motion stimulus after repeated trials. This study appears to further confirm previous research documenting natural acclimatization to motion environments is the most effective motion-sickness mitigation strategy, regardless of any BCV intervention.13 Although future BCV designs may offer some potential to expand human compatibility with adverse motion environments, more research is needed to quantify and qualify health risks associated with this technology. For several decades the U.S. Army Research Laboratory has been evaluating commercially available BCV devices and reported:
“… state-of-the-art bone conduction systems and bone conduction literature are not easily available due to their commercial limitations, trade restrictions, and military applications. However, there is still a scarcity of information about bone conduction in open literature and in trade magazines. In addition, information available in popular media outlets (e.g., TV, Internet, trade magazines) about the capabilities and physiological basis of bone conduction communication is frequently far from scientific scrutiny and leads to misinformation.”22
Unfortunately, credible health risk assessments for BCV therapeutic uses are limited, even though there is an abundance of research documenting interference with the normal function of the inner ear can have a profound negative impact. Researchers have demonstrated: “… Low Frequency Noise (LFN), defined as broadband noise with dominant content of low frequencies (10–250 Hz) differs in its nature from other environmental noises at comparable levels.”23 Consequently, “… LFN at moderate levels might adversely affect visual functions, concentration, continuous and selective attention, especially in the high-sensitive to LFN subjects.”23 Since the BCV device tested with this study reported using LFN vibrations of 50 Hz with a power level of 98 dB, the existing medical research suggests this range of stimulation could increase health risks.
A more encompassing concern that exists with BCV technology is the “shotgun” approach used to stimulate the inner ear by sending vibrations through the mastoid bone. Vibrations intended for stimulation of vestibular organs (semicircular canals and otoliths) also simultaneously stimulate the cochlea of the inner ear hearing system. An unintended consequence of this collateral stimulation is it bypasses the middle ear acoustic reflex, which is a protective mechanism that reduces transmission of harmful vibrational energy to the cochlea.24 Such transmission also causes a second physiological anomaly to occur when the ear canal is closed or occluded by earplugs or sound attenuation ear cups. In this situation, BCV vibrations sent through the mastoid bone generate airborne sound pressure waves within the external canal and thereby induce oscillation of the tympanic membrane and ossicles. Unfortunately, this indirect BCV stimulation of the external and middle ear has been found to increase transmission of low frequency (LF) mechanical energy to the cochlea by up to 40 dB.25 Since BCV devices intended for reducing motion sickness are designed to produce continuous external LF vibrations between 10–50 Hz with 100–150 dB of acoustic power, adding an additional 40 dB of LF power to the inner ear may significantly increase risk of hearing loss and interference with normal vestibular function.4
Recent auditory research has also discovered that low frequency 30-Hz sound at 120 dB for 90 s “… induces slow oscillations of cochlear compression and gain, subsequently causing several measures of cochlear activity to cycle through phases of increased and decreased sensitivity [aka: bounce pattern].”26 This slow oscillation of the homeostatic control mechanism within the cochlea has been suggested as the source of the bounce pattern during exposure to moderately loud LF vibrations. Based on this observed physiological phenomenon, researchers have suggested if this control mechanism fails to operate correctly, and disturbances of cochlear homeostasis are not rectified, hearing may become impaired and vestibular function could be compromised by formation of endolymphatic hydrops and finally Ménière’s disease.26 Since commercially available BCV devices are known to use LF vibrations that exceed 120 dB for periods extending well beyond 90 s, there exists the possibility that unrestricted use of these devices could incrementally create irreversible cochlear and vestibular damage.
Although this study found the tested commercial BCV device was ineffective for mitigation of motion sickness, applications for commercial use of BCV technology are continuing to expand. Based upon the documented potential risks associated with exposure to low frequency sound vibrations (20–200 Hz) with moderate (80 dB) to high (150 dB) energy levels, further research is needed to make an accurate health risk assessment of BCV stimulation. Establishing safe finite conditions for BCV exposure in civilian and military environments will help mitigate any potential hazards related to hearing loss, induced vertigo, or decreased cognitive function caused by this emerging technology.
Overall MSAQ means by BCV condition and visit number. Heavy lines with dots represent means. Boxes represent within subject standard error. Whiskers represent M ±2·SD. (All mean plots follow the same format.)
BARF rating means by BCV condition and visit number.
Time to nausea means by BCV condition and visit number.
Contributor Notes
