Effects of very high-frequency sound and ultrasound on humans. Part II: A double-blind randomized provocation study of inaudible 20-kHz ultrasound

Air-conducted ultrasound below the hearing threshold elicits functional changes in the cognitive control network

Air-conducted ultrasound (> 17.8 kHz; US) is produced by an increasing number of technical devices in our daily environment. While several studies indicate that exposure to US in public spaces can lead to subjective symptoms such as 'annoyance' or 'difficulties in concentration', the effects of US on brain activity are poorly understood. In the present study, individual hearing thresholds (HT) for sounds in the US frequency spectrum were assessed in 21 normal-hearing participants. The effects of US were then investigated by means of functional magnetic resonance imaging (fMRI). 15 of these participants underwent three resting-state acquisitions, two with a 21.5 kHz tone presented monaurally at 5 dB above (ATC) and 10 dB below (BTC) the HT and one without auditory stimulation (NTC), as well as three runs of an n-back working memory task involving similar stimulus conditions (n-ATC, n-BTC, n-NTC). Comparing data gathered during n-NTC vs. fixation, we found that task performance was associated with the recruitment of regions within the cognitive control network, including prefrontal and parietal areas as well as the cerebellum. Direct contrasts of the two stimulus conditions (n-ATC & n-BTC) vs. n-NTC showed no significant differences in brain activity, irrespective of whether a whole-brain or a region of interest approach with primary auditory cortex as the seed was used. Likewise, no differences were found when the resting-state runs were compared. However, contrast analysis (n-BTC vs. n-ATC) revealed a strong activation in bilateral inferior frontal gyrus (IFG, triangular part) only when US was presented below the HT (p < 0.001, cluster > 30). In addition, IFG activation was also associated with faster reaction times during n-BTC (p = 0.033) as well as with verbal reports obtained after resting-state, i.e., the more unpleasant sound was perceived during BTC vs. ATC, the higher activation in bilateral IFG was and vice versa (p = 0.003). While this study provides no evidence for activation of primary auditory cortex in response to audible US (even though participants heard the sounds), it indicates that US can lead to changes in the cognitive control network and affect cognitive performance only when presented below the HT. Activation of bilateral IFG could reflect an increase in cognitive demand when focusing on task performance in the presence of slightly unpleasant and/or distracting US that may not be fully controllable by attentional mechanisms.

The influence of nocebo information on fatigue and urge to stop: An experimental investigation

BACKGROUND AND OBJECTIVES

Fatigue is an adaptive state after prolonged effort and often goes hand in hand with changes in behavior and motivation, such as the urge to stop exerting further effort. However, fatigue may become chronic in nature, as seen in multiple psychiatric disorders and chronic diseases, thereby losing its adaptive function. The etiology of fatigue symptoms remains poorly understood. We aimed to investigate whether nocebo information about the fatigue inducing nature of a cognitive task may contribute to the experience of fatigue and the motivational urge to stop.

METHODS

Participants (N = 46) repeatedly rated currently experienced fatigue while engaging in cognitive effort (working memory task). Crucially, half of participants received nocebo instructions prior to this task, whereas the other half only received neutral information.

RESULTS

Over the entire sample, results showed an increase in fatigue and urge to stop as the task progressed. Crucially, participants in the nocebo condition reported a higher urge to stop throughout the task relative to participants in the neutral condition. No significant effects were found for fatigue. Interestingly however, after controlling for baseline differences between conditions in negative affect, there was a significant Condition*Task block interaction effect on fatigue.

LIMITATIONS

Limitations include the relatively short experimental protocol and the underrepresentation of male relative to female participants.

CONCLUSIONS

These findings suggest that heightened awareness among clinicians and therapists about potential nocebo effects in their communication is warranted.

Mobile surveys and machine learning can improve urban noise mapping: Beyond A-weighted measurements of exposure

Urban noise pollution is a major environmental issue, second only to fine particulate matter in its impacts on physical and mental health. To identify who is affected and where to prioritise actions, noise maps derived from traffic flows and propagation algorithms are widely used. These may not reflect true levels of exposure because they fail to consider noise from all sources and may leave gaps where roads or traffic data are absent. We present an improved approach to overcome these limitations. Using walking surveys, we recorded 52,366 audio clips of 10 s each along 733 km of routes throughout the port city of Southampton. We extracted power levels in low (11 to 177 Hz), mid (177 Hz to 5.68 kHz), high (5.68 to 22.72 kHz) and A-weighted frequencies and then built machine-learning (ML) models to predict noise levels at 30 m resolution across the entire city, driven by urban form. Model performance (r²) ranged from 0.41 (low frequencies) to 0.61 (mid frequencies) with mean absolute errors of 4.05 to 4.75 dB. The main predictors of noise were related to modes of transport (road, air, rail and water) but for low frequencies, port activities were also important. When mapped to the city scale, A-weighted frequencies produced a similar spatial pattern to mid-frequencies, but did not capture the major sources of low frequency noise from the port or scattered hotspots of high frequencies. We question whether A-weighted noise mapping is adequate for health and wellbeing impact assessments. We conclude that mobile surveys combined with ML offer an alternative way to map noise from all sources and at fine resolution across entire cities that may more accurately reflect true exposures. Our approach is suitable for noise data gathered by citizen scientists, or from a network of sensors, as well as from structured surveys.

A longitudinal, randomized experimental pilot study to investigate the effects of airborne ultrasound on human mental health, cognition, and brain structure

Ultrasound-(US) emitting sources are highly present in modern human environments (e.g., movement sensors, electric transformers). US affecting humans or even posing a health hazard remains understudied. Hence, ultrasonic (22.4 kHz) vs. sham devices were installed in participants' bedrooms, and active for 28 nights. Somatic and psychiatric symptoms, sound-sensitivity, sleep quality, executive function, and structural MRI were assessed pre-post. Somatization (possible nocebo) and phasic alertness increased significantly in sham, accuracy in a flexibility task decreased significantly in the verum condition (indicating hastier responses). Effects were not sustained after p-level adjustment. Exploratory voxel-based morphometry (VBM) revealed regional grey matter (rGMV) but no regional white matter volume changes in verum (relative to placebo). rGMV increased in bilateral cerebellum VIIb/Crus II and anterior cingulate (BA24). There were rGMV decreases in two bilateral frontal clusters: in the middle frontal gyri/opercular part of inferior frontal gyrus (BA46, 44), and the superior frontal gyri (BA4 ,6, 8). No brain-behavior-links were identified. Given the overall pattern of results, it is suggested that ultrasound may particularly induce regional gray matter decline in frontal areas, however with yet unclear behavioral consequences. Given the localization of clusters, candidate behavioral variables for follow-up investigation are complex motor control/coordination, stress regulation, speech processing, and inhibition tasks.Trial registration: The trial was registered at NIH www.clinicaltrials.gov , trial identifier: NCT03459183, trial name: SonicBrain01, full trial protocol available here: https://clinicaltrials.gov/ct2/show/NCT03459183 .

Deductive development and validation of a questionnaire to assess sensitivity to very low and very high frequency sounds: SISUS-Q (Sensitivity to Infra-Sound and Ultra-Sound Questionnaire)

Objective:

Auditory research and complaints about environmental noise indicate that there exists a significant, small subgroup within the population which is sensitive towards infra- and low-frequency or ultra- and high-frequency sounds (ILF/UHF). This paper reports on the development, factorization and validation of measures of sensitivity towards frequencies outside the common hearing range.

Design:

A multinational, cross-sectional survey study was run. Principal component analyses and exploratory factor analyses were conducted in a sample of 267 Europeans (from the UK, Slovenia, and Germany).

Results:

The factor analyses suggested that ILF versus UHF sensitivity constitute different factors, each characterized by sensory perception, stress-responsivity, and behavioral avoidance. A third factor comprising beliefs of dangerousness of ILF and UHF emerged. The factors explained 72% of the variance. The factor-solution was replicated separately for the English (n = 98) and German (n = 169) versions of the questionnaire (Slovenians and UK residents filled out the English version). Acceptable to excellent reliability was found. ILF and UHF sensitivity were moderately related to noise sensitivity in the normal hearing range, suggesting the new measures are not redundant. Correlations with psychiatric and somatic symptoms were small to moderate. ILF sensitivity correlated with neuroticism (small effect) and daytime sleepiness (moderate effect). ILF and UHF sensitivity were related to agreeableness (small effects). Overall, the novel ILF and UHF sensitivity scales seems to provide a solid tool for conducting further research on the role of sensitivity concerning adverse effects of ILF and UHF sound (e.g. health outcomes, annoyance ratings). The questionnaire consortium recommends using the new scales in combination with established measures of normal hearing range sensitivity.

Exposure to High-Frequency Sound and Ultrasound in Public Places: Examples from Zurich, Switzerland

The public is unknowingly exposed to very high-frequency sound (VHFS; 11.2–17.8 kHz) and ultrasound (US; >17.8 kHz) signals in air in public places, as evidenced by previously published reports. The present report provides evidence for the presence of VHFS/US signals in the air at public places in Zurich, Switzerland. The analysis of the signals measured revealed that they: (i) contain one, two or multiple frequencies; (ii) comprise frequencies ranged from 15.5 kHz to 36.0 kHz; (iii) were either quasi constant in their amplitude or exhibit a clear amplitude modulation; and (iv) were in their characteristics (frequencies, modulation, intensity) specific for each place. Based on the signal characteristic it is likely that the signals are generated by public-address voice-alarm (PAVA) systems. The work presented: (i) documents the presence of VHFS/US signals at public places in Zurich, possibly caused by PAVA systems; and should (ii) show that is easily possibly to measure the signals with an affordable measurement equipment as a “citizen scientist”, and stimulate others also to measure and analyse VHFS/US signals with this citizen scientist approach in other cities worldwide. Due to the possible negative health-related effects of a human exposure to VHFS/US signals, further research is needed to document VHFS/US signals at public places and to evaluate biological effects of this exposure with laboratory studies.

Placebo and Nocebo Effects Across Symptoms: From Pain to Fatigue, Dyspnea, Nausea, and Itch

Placebo and nocebo effects are, respectively, the helpful and harmful treatment effects that do not arise from active treatment components. These effects have thus far been researched most often in pain. It is not yet clear to what extent these findings from pain can be generalized to other somatic symptoms. This review investigates placebo and nocebo effects in four other highly prevalent symptoms: dyspnea, fatigue, nausea, and itch. The role of learning mechanisms (verbal suggestions, conditioning) in placebo and nocebo effects on various outcomes (self-reported, behavioral, and physiological) of these different somatic symptoms is explored. A search of experimental studies indicated that, as in pain, the combination of verbal suggestion and conditioning is generally more effective than suggestion alone for evoking placebo and nocebo effects. However, conditioning appears more and verbal suggestions less relevant in symptoms other than pain, with the exception of placebo effects on fatigue and nocebo effects on itch. Physiological measures, such as heart rate, lung function, or gastric activity, are rarely affected even when self-reported symptoms are. Neurobiological correlates are rarely investigated, and few commonalities appear across symptoms. Expectations generally predict placebo and nocebo effects for dyspnea and itch but seem less involved in fatigue and nausea. Individual characteristics do not consistently predict placebo or nocebo effects across symptoms or studies. In sum, many conclusions deriving from placebo and nocebo pain studies do appear to apply to other somatic symptoms, but a number of important differences exist. Understanding what type of learning mechanisms for which symptom are most likely to trigger placebo and nocebo effects is crucial for generalizing knowledge for research and therapies across symptoms and can help clinicians to optimize placebo effects in practice.

Measurements of ultrasonic deterrents and an acoustically branded hairdryer: Ambiguities in guideline compliance

Acoustic radiation from three commercial pest deterrents and two hair dryers were measured in an anechoic chamber. The deterrents were chosen because the frequency range at which they emit the most energy is either in the very high-frequency sound band (11.2-17.8 kHz) or the ultrasound band (greater than 17.8 kHz). These are sources that may be heard by a subset of the general population, with the young typically having better high frequency sensitivity. A hairdryer reported to increase the frequency of the motor noise above the audible hearing range was compared with a standard hairdryer. The outputs of the deterrents are compared against six international regulations and guidelines for audible and ultrasound exposure. Multiple ambiguities in the application of these guidelines are discussed. These ambiguities could lead to a device being considered as in compliance despite unconventionally high levels. Even if a device measured here meets a guideline, actual exposures can exceed those taken here and may therefore breach guidelines if the listener is closer to the device or reflections increase the exposure level.

Ultrasound in air-Guidelines, applications, public exposures, and claims of attacks in Cuba and China

This editorial introduces a Special Issue of the Journal of the Acoustical Society of America, on "Ultrasound in Air." In this Special Issue, one paper covers ways of categorizing the ultrasonic regimes, and three papers cover human effects. One of those three, plus five others, constitute the six papers that report on the measured outputs of commercial devices. Two cover calibration, and the final three papers cover novel applications. This editorial outlines the context in which these papers provide individual studies, including the development of technology and guidelines for safe exposure, and ending with an analysis of what is currently known about claims of sonic attacks on embassy staff in Cuba and China.