Acoustic Beats Research Articles

Propagation and interference of thermal waves in turbulent thermal convection

We observe propagation and interference of two coherent thermal waves in the highly turbulent core of convective Rayleigh-B\'enard flow of cryogenic helium gas generated by top and bottom boundaries with harmonically oscillating temperatures. When the same amplitude of modulation is applied to both plates at slightly different frequencies, the resulting temperature interference pattern in the turbulent core shows a periodic increase and decrease in amplitude. If the observed time record of thermal wave interference were converted to corresponding pressure oscillations and shifted to higher frequencies, one would hear the acoustic beats often used, e.g., in tuning stringed musical instruments.

Connectionist Interpretation of Affective Phenomenon Caused by Odd Number of Acoustic Beats

Three-beat sounds are widely used in cheering. Five- or seven-syllable phrases are used in Japanese and Chinese traditional poems. Odd numbers of short sounds seem to relate to an affective phenomenon. Our experiment shows that a three-beat sound is the most exciting beat sound for people. We propose a neural-network model that relates to such a phenomenon. It is realized by the combination of neural networks with reciprocal-inhibition and cascade structures. We additionally take into account the effect of attention fluctuation. We simulate the neural-network operation, indicating that degree of excitement defined for the model takes the highest level for three beats. This result is consistent with our experimental result. When the attention fluctuation is suppressed, the degree of excitement takes higher levels for odd numbers of beats than even numbers of beats. This relates to the ground of five- or seven-syllable phrases used in Japanese and Chinese traditional poems.

Acoustic characterization of magnetic braking with a smartphone

Smartphone sensors have shown to be adequate to perform physics experiments in high school and first-year university physics courses. The published work covers a wide range of topics within general physics such as linear and circular motions, oscillations, beats, acoustics, and optics, among others. The microphone and speakers have been particularly useful for studying sound phenomena, such as the determination of the speed of sound, the study of acoustic beats, or the Doppler effect.

Recording a resonance curve with smartphones and wine glasses

Numerous experiments on acoustics have already been described in this column, e.g., on the different types of sound or on acoustic beats. The topic of cavity resonance and the determination of the speed of sound from the resonance frequencies of various tubes, glasses, and bottles has also been addressed several times. A topic that has not yet been considered is the recording of a resonance curve. We would like to present here an experimental possibility with very simple devices. Apart from two smartphones, all you need is a wine glass.

Neural-Network-Based Account of Affective Phenomenon Caused by Odd Number of Acoustic Beats

Neural-Network-Based Account of Affective Phenomenon Caused by Odd Number of Acoustic Beats

Binaural Acoustic Beats in the Psychological Rehabilitation of Patients with Impaired Motor Functions

The course of diseases associated with movement disorders violates the possibility of independent existence of the individual and is accompanied by the formation of symptoms of increased anxiety, depression and catastrophizing. Over the last years, in addition to psychopharmacological drugs, non-drug methods have been actively included in the complex of treatment and rehabilitation for this patients’ group allowing them to influence the patient’s psyche by neuro-biological activation of sanogenesis links. Aim. To study the possibility of using resonance-acoustic vibration (PRAV) programs in the “relaxation” mode when organizing psychological support for patients with movement disorders in the course of medical rehabilitation. Materials and methods. The study included 93 patients with movement disorders of two nosological groups: movement disorders against the stroke (n=57) and motor disorders against the degenerative-dystrophic diseases of large joints and spine of large joints and spine (n=36), undergoing a standard inpatient course of medical rehabilitation. Results. The dynamics of the emotional state, the intensity of the pain syndrome, characteristics of the cognitive sphere (memory, attention) as a result of psychological correction using PRAV were analyzed. The positive effect of the inclusion of the binaural beats complex in the psychological correction of the patients with impaired motor functions state of health as well as an indifferent response to the attempt to correct memory and attention were determined. Conclusion. It testifies that the application of the method is appropriate in correcting the emotional state, general well-being, overcoming fear of movement and is not effective for pain and recovery of cognitive functions.

Reduced pain and analgesic use after acoustic binaural beats therapy in chronic pain - A double-blind randomized control cross-over trial.

Binaural Beats (BB) consist of two artificial acoustic stimuli with different frequency, presented simultaneously but independently to each ear. The human brain perceives and synchronizes to this frequency difference (entrainment). Aim of this study was to test the hypothesis that brain entrainment to a lower function rhythm, with BB application, can decrease pain perception and analgesic medication use, in chronic pain patients. In a double blind, randomized, cross-over trial, BB at 5Hz (theta rhythm) were applied for 30 minutes, under simultaneous electroencephalogram recordings, followed by liberal, on demand use by chronic pain patients for a week, compared to sham stimulation (SS). Pain as the main outcome (numeric scale, NRS), stress (STAI) and medication usage (defined daily doses, DDD) were assessed at baseline, 30 minutes and week's end. Perceived pain (NRS) was significantly reduced in BB intervention (5.6±2.3 to 3.4±2.6, p<0.001), compared to SS (5.2±2.1 to 4.8±2.3, p=0.78), during the first 30-minute phase, as well as at the week's end (to 3.9±2.5 compared to 5.5±2.6 respectively, p<0.001). The mean EEG theta power at 5Hz was significantly increased only during BB application. Stress was significantly reduced at 30 minutes in both interventions but remained reduced only in the BB group at the week's end. Analgesic medication consumption (DDD, g) during the week was significantly less in the BB intervention (3.9±3.7 vs. 4.6±4.1, p<0.05), while reporting equal to SS mean levels of pain. Acoustic BB reduced pain intensity, stress and analgesic use, compared to SS, in chronic pain patients. This study provides evidence that theta rhythm binaural beats can alleviate pain intensity, both after a brief 30 minute and a longer one week on-demand intervention. The subsequent significant reduction in analgesic medication consumption in chronic pain patients' daily living could offer a valuable tool, augmenting the effect of existing pain therapies.

Possible Effect of Binaural Beat Combined With Autonomous Sensory Meridian Response for Inducing Sleep.

Sleep is important to maintain physical and cognitive functions in everyday life. However, the prevalence of sleep disorders is on the rise. One existing solution to this problem is to induce sleep using an auditory stimulus. When we listen to acoustic beats of two tones in each ear simultaneously, a binaural beat is generated which induces brain signals at a specific desired frequency. However, this auditory stimulus is uncomfortable for users to listen to induce sleep. To overcome this difficulty, we can exploit the feelings of calmness and relaxation that are induced by the perceptual phenomenon of autonomous sensory meridian response (ASMR). In this study, we proposed a novel auditory stimulus for inducing sleep. Specifically, we used a 6 Hz binaural beat corresponding to the center of the theta band (4–8 Hz), which is the frequency at which brain activity is entrained during non-rapid eye movement (NREM) in sleep stage 1. In addition, the “ASMR triggers” that cause ASMR were presented from natural sound as the sensory stimuli. In session 1, we combined two auditory stimuli (the 6 Hz binaural beat and ASMR triggers) at three-decibel ratios to find the optimal combination ratio. As a result, we determined that the combination of a 30:60 dB ratio of binaural beat to ASMR trigger is most effective for inducing theta power and psychological stability. In session 2, the effects of these combined stimuli (CS) were compared with an only binaural beat, only the ASMR trigger, or a sham condition. The combination stimulus retained the advantages of the binaural beat and resolved its shortcomings with the ASMR triggers, including psychological self-reports. Our findings indicate that the proposed auditory stimulus could induce the brain signals required for sleep, while simultaneously keeping the user in a psychologically comfortable state. This technology provides an important opportunity to develop a novel method for increasing the quality of sleep.

ON THE RESULTS OF EXPERIMENTAL STUDIES OF THE PHYSICAL PROCESS OF GENERATING SOUND VIBRATIONS BEATS IN CLOSED AIR CAVITIES OF TECHNICAL ROOMS

This paper gives the results of experimental researches for producing physical processes of acoustic vibration beats, which are spread in a free and in a diffused field of enclosed air volumes in technical rooms of different types. There are defined general regularities and distinct features of forming the physical processes of acoustic vibration beats. A limited frequency range of beats production which includes two different frequency ranges of dynamic frequency interactions with close values of sound frequencies are found out. Sufficiency of frequency detuning of two independent sources of acoustic radiation which exclude physical process creation of sound frequency beats is defined.

Visualizing the acoustic and gestural beats of emphasis in multimodal discourse

AbstractPerceivers’ attention is entrained to the rhythm of a speaker’s gestural and acoustic beats. When different rhythms (polyrhythms) occur across the visual and auditory modalities of speech simultaneously, attention may be heightened, enhancing memorability of the sequence. In this three-stage study, Stage 1 analyzed videorecordings of native English-speaking instructors, focusing on frame-by-frame analysis of time-aligned annotations from Praat and Anvil (video annotation tool) of polyrhythmic sequences. Stage 2 explored the perceivers’ perspective on the sequences’ discourse role. Stage 3 analyzed 10 international teaching assistants’ gestures, and implemented a multistep technology-assisted program to enhance verbal and nonverbal communication skills. Findings demonstrated (a) a dynamic temporal gesture-speech relationship involving perturbations of beat intervals surrounding pitch-accented vowels, (b) the sequences’ important role as highlighters of information, and (c) improvement of ITA confidence, teaching effectiveness, and ability to communicate important points. Findings support the joint production of gesture and prosodically prominent features.

Initial stages of delamination of the aluminum film from silicon wafer

Aluminum films of thickness 0.5 µm were deposited on silicon substrates by pulsed laser physical vapor deposition. The substrate with the film was subjected to laser pulses from the backside of the wafer to initiate delamination of the film. Subsequently, the front side of the film was examined by atomic force, and optical and scanning electron microscopy, and found to contain blisters of different sizes. In addition, larger regions of the film debonded but did not spall. Transient thermo-reflectance was used to study the acoustic oscillations generated in the larger regions of the debonded film using the incidence of a pulsed laser beam with wave length of 532 nm and pulse repetition frequency 10 Hz. The periodicity of the acoustic oscillations was used to determine the size of the film that oscillated. The periods varied from 0.088 to 1.900 µs and the corresponding radii of the oscillating film from 296 to 6384 µm. The work of adhesion was found to reach a maximum value at blister radius close to 25 µm. There were no acoustic oscillations from the delaminated film in the blisters. Acoustic beats were also generated from larger debonded film by superposition of two acoustic oscillations. These results were used to investigate the initial stages of delamination of the films from the substrates.

Binaural Beat: A Failure to Enhance EEG Power and Emotional Arousal.

When two pure tones of slightly different frequencies are delivered simultaneously to the two ears, is generated a beat whose frequency corresponds to the frequency difference between them. That beat is known as acoustic beat. If these two tones are presented one to each ear, they still produce the sensation of the same beat, although no physical combination of the tones occurs outside the auditory system. This phenomenon is called binaural beat. In the present study, we explored the potential contribution of binaural beats to the enhancement of specific electroencephalographic (EEG) bands, as previous studies suggest the potential usefulness of binaural beats as a brainwave entrainment tool. Additionally, we analyzed the effects of binaural-beat stimulation on two psychophysiological measures related to emotional arousal: heart rate and skin conductance. Beats of five different frequencies (4.53 Hz -theta-, 8.97 Hz -alpha-, 17.93 Hz -beta-, 34.49 Hz -gamma- or 57.3 Hz -upper-gamma) were presented binaurally and acoustically for epochs of 3 min (Beat epochs), preceded and followed by pink noise epochs of 90 s (Baseline and Post epochs, respectively). In each of these epochs, we analyzed the EEG spectral power, as well as calculated the heart rate and skin conductance response (SCR). For all the beat frequencies used for stimulation, no significant changes between Baseline and Beat epochs were observed within the corresponding EEG bands, neither with binaural or with acoustic beats. Additional analysis of spectral EEG topographies yielded negative results for the effect of binaural beats in the scalp distribution of EEG spectral power. In the psychophysiological measures, no changes in heart rate and skin conductance were observed for any of the beat frequencies presented. Our results do not support binaural-beat stimulation as a potential tool for the enhancement of EEG oscillatory activity, nor to induce changes in emotional arousal.

Direct Visualization of Mechanical Beats by Means of an Oscillating Smartphone

The resonance phenomenon is widely known in physics courses. Qualitatively speaking, resonance takes place in a driven oscillating system whenever the frequency approaches the natural frequency, resulting in maximal oscillatory amplitude. Very closely related to resonance is the phenomenon of mechanical beating, which occurs when the driving and natural frequencies of the system are slightly different. The frequency of the beat is just the difference of the natural and driving frequencies. Beats are very familiar in acoustic systems. There are several works in this journal on visualizing the beats in acoustic systems. For instance, the microphone and the speaker of two mobile devices were used in previous work to analyze the acoustic beats produced by two signals of close frequencies. The formation of beats can also be visualized in mechanical systems, such as a mass-spring system or a double-driven string. Here, the mechanical beats in a smartphone-spring system are directly visualized in a simple way. The frequency of the beats is measured by means of the acceleration sensor of a smartphone, which hangs from a spring attached to a mechanical driver. This laboratory experiment is suitable for both high school and first-year university physics courses.

The Simplest Demonstration on Acoustic Beats

The classical demonstration experiment on acoustic beats using two signal generators and a dual trace oscilloscope is an important ingredient in teaching the subject.1 This short laboratory note aims to point out what may be the simplest demonstrative experiment on acoustic beats to carry out in a classroom without employing any lab apparatus.

Analyzing the acoustic beat with mobile devices

In this column, we have previously presented various examples of how physical relationships can be examined by analyzing acoustic signals using smartphones or tablet PCs.1–3 In this example, we will be exploring the acoustic phenomenon of small beats, which is produced by the overlapping of two tones with a low difference in frequency Δf. The resulting auditory sensation is a tone with a volume that varies periodically. Acoustic beats can be perceived repeatedly in day-to-day life and have some interesting applications. For example, string instruments are still tuned with the help of an acoustic beat, even with modern technology. If a reference tone (e.g., 440 Hz) and, for example, a slightly out-of-tune violin string produce a tone simultaneously, a beat can be perceived. The more similar the frequencies, the longer the duration of the beat. In the extreme case, when the frequencies are identical, a beat no longer arises. The string is therefore correctly tuned. Using the Oscilloscope app,4 it is possible to capture and save acoustic signals of this kind and determine the beat frequency fS of the signal, which represents the difference in frequency Δf of the two overlapping tones (for Android smartphones, the app OsciPrime Oscilloscope can be used).

A comparison of auditory evoked potentials to acoustic beats and to binaural beats

The purpose of this study was to compare cortical brain responses evoked by amplitude modulated acoustic beats of 3 and 6 Hz in tones of 250 and 1000 Hz with those evoked by their binaural beats counterparts in unmodulated tones to indicate whether the cortical processes involved differ. Event-related potentials (ERPs) were recorded to 3- and 6-Hz acoustic and binaural beats in 2000 ms duration 250 and 1000 Hz tones presented with approximately 1 s intervals. Latency, amplitude and source current density estimates of ERP components to beats-evoked oscillations were determined and compared across beat types, beat frequencies and base (carrier) frequencies. All stimuli evoked tone-onset components followed by oscillations corresponding to the beat frequency, and a subsequent tone-offset complex. Beats-evoked oscillations were higher in amplitude in response to acoustic than to binaural beats, to 250 than to 1000 Hz base frequency and to 3 Hz than to 6 Hz beat frequency. Sources of the beats-evoked oscillations across all stimulus conditions located mostly to left temporal lobe areas. Differences between estimated sources of potentials to acoustic and binaural beats were not significant. The perceptions of binaural beats involve cortical activity that is not different than acoustic beats in distribution and in the effects of beat- and base frequency, indicating similar cortical processing.

Stimulated Brillouin scattering of the beat wave of two lasers in a plasma

Stimulated Brillouin scattering of two collinear lasers in a plasma is investigated. Lasers exert a longitudinal ponderomotive force on electrons, imparting them oscillatory axial velocity at the beat frequency. This velocity acts as a driver for parametric excitation of an ion acoustic wave (ω,k⃗) and a noncollinear sideband electromagnetic wave (ω′,k⃗′). The driver velocity v⃗0− couples to the sideband wave to exert a ponderomotive force at (ω,k⃗) on the electrons, driving the ion acoustic wave. The density perturbation of ion acoustic wave beats with v⃗0− to produce a nonlinear current at (ω′,k⃗′), driving the sideband. In the case of finite spot size Gaussian laser beams, the beat wave has a Gaussian profile and excites an ion acoustic wave (ω,k⃗) and a backscattered TM mode (ω′,k⃗z′). The growth rate scales as the product of amplitudes of the lasers and maximizes at optimum values of scattering angles. The parametric instability of difference frequency driver is stronger than the sum frequency driver.

Novel vocal repertoire and paired swimbladders of the three-spined toadfish,Batrachomoeus trispinosus: insights into the diversity of the Batrachoididae

Toadfishes (Teleostei: Batrachoididae) are one of the best-studied groups for understanding vocal communication in fishes. However, sounds have only been recorded from a low proportion of taxa within the family. Here, we used quantitative bioacoustic, morphological and phylogenetic methods to characterize vocal behavior and mechanisms in the three-spined toadfish, Batrachomoeus trispinosus. B. trispinosus produced two types of sound: long-duration 'hoots' and short-duration 'grunts' that were multiharmonic, amplitude and frequency modulated, with a dominant frequency below 1 kHz. Grunts and hoots formed four major classes of calls. Hoots were typically produced in succession as trains, while grunts occurred either singly or as grunt trains. Aside from hoot trains, grunts and grunt trains, a fourth class of calls consisted of single grunts with acoustic beats, apparently not previously reported for individuals from any teleost taxon. Beats typically had a predominant frequency around 2 kHz with a beat frequency around 300 Hz. Vocalizations also exhibited diel and lunar periodicities. Spectrographic cross-correlation and principal coordinates analysis of hoots from five other toadfish species revealed that B. trispinosus hoots were distinct. Unlike any other reported fish, B. trispinosus had a bilaterally divided swimbladder, forming two separate swimbladders. Phylogenetic analysis suggested B. trispinosus was a relatively basal batrachoidid, and the swimbladder and acoustic beats were independently derived. The swimbladder in B. trispinosus demonstrates that toadfishes have undergone a diversification of peripheral sonic mechanisms, which may be responsible for the concomitant innovations in vocal communication, namely the individual production of acoustic beats as reported in some tetrapods.

Evolution and diversity of batrachoidid vocalizations.

Despite the fact that toadfishes are one of the best‐studied taxa for understanding fish vocal communication, vocalizations have only been recorded from a low proportion of taxa within the family. Here, we describe the diverse vocal repertoire and novel swimbladder morphology of a tropical Pacific euryhaline toadfish, Batrachomoeus trispinosus. B. trispinosus produces four classes of vocalizations: long duration hoots, grunts, grunt trains, and grunts exhibiting acoustic beats; the majority exhibiting prominent harmonic features. Calls with acoustic beats, previously unreported for any individual actinopterygian taxon and convergent with songbirds, typically had a predominant frequency around 2 kHz with a beat frequency around 300 Hz. B. trispinosus possesses a bilaterally divided swimbladder, forming two completely separate bladders. Grunts exhibiting beats may be produced by bilateral control of the bladders. Phylogenetic analysis based on available molecular data show that B. trispinosus and Halobatrachus didactylus represent basal lineages in the Batrachoididae, and the separated swimbladders are an independently derived feature of B. trispinosus. Thus, the toadfishes may possess higher levels of vocal, motor, and morphological diversity than previously appreciated, and now provide a framework for understanding integrated mechanisms underlying the evolution of acoustic novelty in fishes.

Subjectively divided tone components in the gap transfer illusion

When a long glide with a short temporal gap in its middle crosses with a continuous short glide at the temporal midpoint of both glides, the gap is perceived in the short glide instead of in the long glide. In the present article, we tested possible explanations for this "gap transfer illusion" by obtaining points of subjective equality of the pitches and durations of the two short tones that are subjectively divided by the gap. The results of two experiments showed that neither an explanation in terms ofenvelope patterns nor explanations in terms of combinationtones or acoustic beats could account for the perception of the short tones in the gap transfer illusion. Rather, the results were compatible with the idea that the illusory tones were formed by the perceptual integration of onsets and offsets of acoustically different sounds. Implications for the perceptual construction of auditory events are discussed.