Strong Tone Research Articles

Phasic heart rate change and the U-shaped relationship between choice reaction time and auditory signal intensity.

ABSTRACTThe effect of auditory intensity on choice reaction time (RT) and heart rate (HR) was studied in two experiments using a 2.5‐sec fixed foreperiod paradigm and a mixed block intensity presentation mode. Experiment I showed a U‐shaped RT/intensity function and a triphasic HR response. However, the usually obtained anticipatory HR deceleration did not appear. There was only a slight deceleration after the onset of the imperative signal. Both strong tones and faster responding were associated with a more rapid shift from less deceleration to more acceleratory recovery. A second experiment produced similar findings. In addition, differential warning with respect to signal intensity reduced its effect on RT and accelerated the HR response to the imperative signal. The triphasic HR response disappeared in reaction to a “No‐Go” warning signal instructing the subject to withhold his motor response to the imperative signal. It was argued that, apart from being an input variable, auditory intensity has an additional effect upon the motor system. It was concluded that this immediate arousal effect of loud auditory signals (Sanders, 1977) could be related to Graham's (1980) notion of defense as primarily a motor facilitating system.Finally, the finding of a consistent relationship between fast reactions and less deceleration together with the absence of the anticipatory deceleration clearly does not fit either the Obrist model or the Lacey model.

Modulation of the acoustic startle reflex in humans in the absence of anticipatory changes in the middle ear reflex.

If a weak tone precedes an intense tone, then the acoustic startle eyeblink reflex elicited by the stronger stimulus is inhibited. It has been suggested that the leading stimulus gives rise to a protective middle ear reflex that attenuates the effective intensity of the second. This hypothesis was tested and disproved. In seven subjects intense tone bursts sufficient to elicit both intratympanic and eyeblink responses were presented sometimes alone and sometimes preceded at various lead times (25 to 400 msec) by a weak tone. The weak tone inhibited the amplitude of the eye blink to the strong tone, maximally at intervals of 100 to 200 msec, but was never seen to produce any of the anticipatory impedance changes that would be characteristic of middle ear reflex activity during the interval between the two stimuli.

Self-induced sound generation by flow over perforated duct liners

An adverse “singing” phenomenon due to flow over perforated liners in a duct was studied experimentally. The liners consisted of honeycomb structures bonded to and sandwiched between two flat aluminum skins. The inner skin in contact with the flow had holes (perforations) with pitch distances either equal to or different from those of the honeycomb structures, forming, respectively, narrow-band or broadband liners. The shedding of vortices in the flow over these holes induced excitation of acoustic modes within the duct, and under the condition whereby the cut-on frequency of an excited mode coincided with, or was very near to, the shedding frequency a very strong tone corresponding to that particular modal cut-on frequency resulted. For narrow-band liners, the “singing” phenomenon could also be induced by cavity resonance. The shedding frequency increased with increase in flow velocities and thus higher order acoustic modes were excited consecutively in a similar manner. The Strouhal number calculated from the observed shedding frequency and the flow velocity was found to vary directly with the hole diameter of the perforate. The high signal to noise ratio during the peak of self-excitation presents a new method in the determination of the wall admittance under the flow conditions.

Cylindrical Spoiler Effects on the Sound Power of Subsonic Jets

The degree of coupling between sources of unsteadiness inside a duct and the flow through the duct is studied with regard to the external noise contribution from such internal sources. Flow over cylindrical spoilers inside the duct exhibits several regimes of varying acoustic behavior. Below the (1,0) mode cutoff frequency, the additional noise is due only to fluctuations in the drag component of the strut on the flow, while above the cutoff the lift component of fluctuation, which is in the lateral direction, propagates through the duct, resulting in a strong lateral dipole in the farfield sound. Theoretical predictions of the acoustic power output due to the spoiler were made, accounting for the source convection, the span-wise correlation of the vortex shedding, and the variation in lift coefficient with Reynolds number. These predictions are compared with experimental results. It was found that a spoiler immersed in the duct upstream of the exit generated strong tones, while the same strut placed in the core flow immediately downstream of the nozzle generated broad-band noise of a much lower intensity. In each case, the spoiler markedly increased the noise. [Supported by ONR Contract N00014-67-A-0151-0029].

Shock Wave Behavior in Transonic Compressor Noise Generation

Compressor noise at transonic tip speeds contains strong tones at multiples of shaft rotation frequency as well as harmonics of blade passage frequency. These multiple pure tones or combination tones are caused by rotor blade nonuniformities which result in pronounced irregularities in the shock pattern attached to the rotor. Nonlinear first-order theory, similar to that used in analysis of sonic boom strength, is utilized to determine shock wave decay with upstream distance. In the extreme near field of the rotor, shock strength varies inversely as the square root of upstream distance from the blade leading edge, as with an isolated airfoil. Somewhat further upstream, the expansion region from the neighboring blade in the cascade interacts with the shock so that shock strength varies as the inverse first power of distance. These aerodynamic results are used to infer some characteristics of transonic compressor noise which in turn are compared with experimental results.

Electromyographic Study of Click Evoked Middle Ear Muscle Activity in Cats

ELECTROMYOGRAPHIC STUDY OF CLICK EVOKED MIDDLE EAR MUSCLE ACTIVITY IN CATS * G. Salomon and A. Starr In waking cats middle ear muscles responded to clicks with activity, which on emg. consisted of an initial burst of activity (latency 4.5 - 10 msec.), a pause, and a later sustained period of activity (latency 34 - 56 msec., duration 1 sec.). The latency of the first response decreased with increasing sound in- tensity, whereas the latency of the second response varied independently of intensity. These two responses behaved differently during repetitive stimulat- ion with clicks; the first response remained constant while the second de- creased in amplitude and disappeared. The second response would reappear promptly, however, by adding extra sounds, by decreasing or increasing the click intensity, by cutaneous stimulation, or by the animal's own movements. Sound transmission through the middle ear did not change during the first response (measuring cochlea output elicited by tone of constant intensity) but an attenuation of sound transmission occurred during the second res- ponse. The lack of attenuation during the first response was due to the brief duration of this response. Sudden strong tones evoked activity in middle ear muscles after a latency of 5 - 10 msec. This activity consisted of a 20 - 30 msec. discharge, a silent period, and a sustained activity. The silent period was most pronounced in muscle tensor tympani. After termination of a tone activity persisted in both muscles and returned only gradually to spontaneous activity levels. lntercollicular decerebration modified middle ear muscle responses to click and continuous sounds: the second long latency response to clicks was abo- lished and the after discharge to tone bursts no longer occurred. These results demonstrate that descending influences from dienchephalic centers modify brainstem mechanisms regulating reflex middle ear muscle activity. These higher controls most likely account for the variability of middle ear muscle responses described in humans and in waking animals. UNE ETUDE ELECTRO-MYOGRAPHIQUE DE L'ACTIVITE MUSCULAIRE DE L'OREILLE MOYENNE ENGENDREE PAR VOIE DE CLICK CHEZ LES CHATS Des clicks ont engendre, chez des chats eveilles, une activite des deux muscles de l'oreille moyenne qui, d'apres l'electro-myogramme, consistait en une premiere reponse de courte duree (periode latente de 4, 5 a 10 msec), * This work was supported in part by the Secretariat of Science of the Copenhagen Municipal Hospitals.

The Nature of Vowel Sounds

THE first essential point of the interesting communication of Mr. Preston Edwards lies in the question of the weakness of the fundamental in the tone of a vowel. This tone is that of the larynx, or the voice tone. To the ear this is always the predominating tone. We may not be able to distinguish what vowel a singer is producing, but if we can hear him at all we hear the tone he is singing—that is, the tone from his larynx. When a larynx from a freshly killed animal is subjected to a blast of air and the vocal chords are brought together, a strong tone is produced.

Letters to Editor

THE above letter very properly directs attention to the excellent work of Prof. Miller. It is worth while to study Fig. 130 of his book, reproduced below. For the tuning-fork there is only one tone, namely, the fundamental. For the other instruments the fundamental appears clearly, but for the voice the fundamental is lacking. Thus the strongest tone in a vowel, the voice tone, does not appear in the plot. This is in agreement with the work of Hermann and myself. As explained in NATURE of January 13 and 20, this arises from the fact that the voice tone consists of a series of puffs.

A Long-lived Solar Halo

THERE has been visible here to-day a solar halo remarkable both for its vivid intensity and for its protracted duration. It was first noticed by me at 12.35 p.m. It then formed an unbroken ring, of which the most intensely luminous portion was to the south of the sun, and the least luminous portion to the west-north-west. Half an hour later the southern and northern quadrants of the circle were equally bright, but the northern appeared the more compact and definite; meanwhile, the eastern and western portions continued comparatively feeble, more especially the latter. These conditions remained unchanged for fully 11/2 hours! After 2.15 p.m. the northern segment of the halo was alone conspicuous, and after 3.30 p.m. the ring was never again complete, though two mock suns (to the southward and eastward respectively) still testified to the original configuration. By 4.50 p.m. nothing remained but a diffused, pale rainbow-coloured mock-sun to the north of the sun; but after 5.15 p.m. this became less indefinite, and by 6 p.m. fully a semicircle of a halo was again traceable above the sun, but this faded gradually, nothing surviving after about 6.20 p.m. The unusually strong tone of rusty orange colouring, and the conspicuous darkness of the region enclosed, made the halo an unusually striking object when at its best (12.30 to 2 p.m.).

Note on a Sensitive Flame

Dr M'Kendrick showed an extremely sensitive flame made by Dr R. Koenig. It is constructed on the type of the sensitive flame apparatus devised by Barrett and improved by Govi. A Lecomte burner directs the gas towards a fine wire gauze screen, and when the gas is lit above the screen the flame is very sensitive at ordinary pressures. The special part of the apparatus now shown consisted of a funnel or resonator placed at right angles to the Lecomte gas-jet and opening into the space below the gauze screen. To ensure success a fine stop-cock or clip must be used for the regulation of the quantity of gas. Dr M‘Kendrick showed also that by placing a glass tube 460 mm. in length by 40 mm. in diameter over the flame, and about 4 mm. above the level of the gauze, as first suggested by Geyer, a musical note was heard which was disturbed by vibrations acting on the flame. The apparatus not only showed the ticking of a watch, placed in the resonator, by the movements of the flame, but with each “tic” the tube sounded slightly. The slightest movement in the vicinity of the apparatus agitated the flame; and as the latter was arranged so as to be near the point when it evoked the tone of the tube, now and again the tube gave forth a strong tone as a vibration acted on the mass of gas below the gauze.