Pitch Of Sound Research Articles

Pitch Variations Arising from Certain Types of Frequency Modulation

This report deals with an investigation of the pitch of sounds characterized by frequency modulation. It has to do mainly with the perceived extent of pitch glides. By means of a specially-designed variable condenser the frequency of an oscillator could be modulated, intensity of output remaining essentially constant. Either sinusoidal or linear modulation could be obtained, and the amount and rate of modulation were both subject to control. It was possible to secure, among others, the following types of variation: (a) isolated frequency sweeps, either upward or downward in direction; (b) upward-downward or downward-upward sweeps; (c) sweeps, either upward or downward, at the beginning or end of a steady-state sound; (d) periodic modulation, that is, frequency vibrato. Sounds with vibrato were studied only casually. The experimental data, which reveal the relationship between perceived extent of glide and both the amount and the rate of frequency modulation, are interpreted to indicate their bearing on problems of pitch perception in speech and music. The results are further shown to have a significant bearing on auditory theory in that they reveal the great rapidity with which the ear responds to sounds of continuously varying frequency.

Demonstration of Dorsey Fathometer

This instrument was recently developed at the U. S. Coast and Geodetic Survey Hydrosonic Laboratory as a precision instrument for visually measuring ocean depths by echoes. It has been regularly used on the surveying ships in place of the lead and line and gives 20 echoes per second, or a measurement about every foot. No moving contacts are used, the signals being sent by light reflected to a photoelectric tube. The speed is accurately controlled by operating the indicator with a synchronous motor, driven from a tuning fork. Results are so accurate that phenomena of surveying are discovered which were never revealed by the hand lead methods. The demonstration will show echoes in air at distances of a few feet by high pitched sounds, results considered impossible with sounds of ordinary frequencies.

Transmission of Sonic and Ultrasonic Waves through Partitions

IN other places I have pointed out that recently devised methods of experiment with ultrasonic waves offer possibilities for a more complete experimental solution of certain acoustic problems than can conveniently be carried out with low or ordinary pitched sounds. A case in point is the reflection from and transmission through material partitions of acoustic waves.

A NEW COMBINED STETHOSCOPE CHEST PIECE

Because of the variable qualities of different cardiac murmurs, it has been evident for a considerable time that no single stethoscope chest piece is satisfactory in transmitting all the sounds produced in the heart. Ideally, a stethoscope that could be made to vary its optimal resonating qualities between wide limits in order to respond correctly to both high and low pitched sounds would be the most sensitive instrument to use. Practically, such instruments are cumbersome and complicated. For clinical uses two forms of stethoscope chest piece have been found adequate in transmitting heart sounds and murmurs, except in the rare instances in which the naked ear is more satisfactory in responding to high pitched, blowing murmurs, such as those of aortic regurgitation. These two chest pieces are the bell type, which is most useful for low pitched murmurs, and the Bowles type, which registers high pitched murmurs more accurately. The

Anomalous Action of the Rayleigh Disk

Torque on Rayleigh disk in a resonating tube, for high pitch sounds.---In the case of a disk 15 cm in diam. in a tube 16 cm in diam., a study of the deflection as a function of wave-length, 4 to 28 cm, showed that for a wave-length of 28 cm the disk tended to set itself parallel to the axis of the resonator, and hence was deflected in a direction opposite to the usual one. Other negative maxima were observed for waves of about 14 and 7 cm. Experiments with smaller disks showed that beyond a certain tube length the maximum critical wave-length for a negative maximum is independent of tube length and depends more on tube diameter than on disk diameter, approaching twice the tube diameter as the size of the disk is increased nearly to that of the tube.

Photographs of Seven Vocal Notes

DR. A. O. RANKINE, by means of the invention described by him in NATURE of February 5, has placed me under a great obligation in furnishing ocular confirmation, desirable for those whose hearing is undisciplined or poor, of observations made by the unassisted ear on the inherent pitches of vowel sounds. No one who can hear harmonics of a sustained note from the larynx reinforced successively by a continuous change in the pitch of the mouth-cavity acting as a resonator should remain in doubt as to their place in the tablature, for, the pitch of the voice being known, if a harmonic sequence is heard, such as 4:5:6:7, the vibration number of any one of these overtones is the product of a simple multiplication. The well-known spherical resonators, applied in turn to the ear, cannot be changed instantaneously, destroy the all-important contrast, and have failed. The late Lord Rayleigh's compound resonator (Phil. Mag., 1907, p. 321) would do better service, but I do not know that anyone has used it for this purpose. The table in text-books of physics, physiology, etc., shows an extreme error of two octaves. The inherent pitches of the vowels of ordinary speech from oo to ee range from about fii to div. Taking two octaves as the extreme compass of the mouth shaped for vowels, this supplies such “real characters” for vowel sounds as Bishop Wilkins and his friends looked for in vain, and the use of an alphabet thus rectified will make it unnecessary for English-speaking children to learn to spell, while the re-formed print writing will obviate spelling reform. I have explained this seeming paradox in a book now in the press.

Obituary notices of fellows deceased

Sydney Ringer, who died at Lastingham, in Yorkshire, on October 14, 1910, was the son of John and Harriet Ringer, of Norwich, where he was born in 1835. He was educated at private schools, and at the age of 19 entered, as a medical student, University College, London, with which institution he was to remain connected during the remainder of his active life. At the hospital connected with that school he was successively House Physician, Resident Medical Officer (1861), Assistant Physician (1863), full Physician (1866), and Consulting Physician (on his retirement in 1900); and in the Faculty of Medicine of University College he held successively the chairs of Materia Medica and Therapeutics, of Medicine and of Clinical Medicine. The School of Medicine with which Ringer was associated has produced many distinguished clinicists, but it may be safely affirmed that it has produced no better clinical teacher than the subject of this memoir. It was not, however, on the ground of his clinical reputation that Ringer was elected a Fellow of the Royal Society, and it is not in the notices of this Society that his eminence as a clinicist need be accentuated. For Ringer was more than a great physician, much as that may mean: he was a scientific enquirer. His bent in that direction showed itself early, for even while still a student of medicine he presented a paper to the Royal Society, “On the Alteration of the Pitch of Sound by Conduction through different Media,” and others to the Royal Medical and Chirurgical Society on Metabolism in Disease. These were followed by an investigation (conducted jointly with A. P. Stuart) into the diurnal variations of temperature in the human body, which was, however, not published in full until 1878. The subject of this enquiry, from its bearing on the variations of temperature in fever, never lost interest for him. But his appointment to the chair of Materia Medica and Therapeutics directed his attention towards the action of medicinal substances and agencies. His experiences of their action on the human body he embodied in his well-known ‘Handbook of Therapeutics,' of which a very large number of editions have appeared; no more thoroughly practical handbook of treatment has probably ever been written. Ringer, however, recognised that it is necessary for the understanding of the action of remedies in disease for their action in health first to be determined, and that, to comprehend their effects upon the body generally, their influence upon the individual organs and tissues must be understood. There was then no laboratory of pharmacology in London, but he found the opportunity for carrying out researches of this nature in the Physiological Laboratory of University College, where a place was always at his disposal. Here, in the intervals of a busy consulting practice, he carried out the remarkable series of researches on the action of various salts upon the tissues, and especially upon the muscular tissue of the heart, which resulted in the recognition of the influence exerted by simple inorganic constituents of the blood in maintaining the activity of the living tissues—an influence which had remained obscure, in spite of the elaborate series of researches of the same nature which were conducted in the famous Physiological Laboratory of Leipzig and elsewhere.

Change of Pitch of Sound with Distance

I HAVE read with considerable interest the letter by Mr. Paul R. Heyl on this subject in your issue for January 23. Speaking off-hand, I should have agreed with Mr. West, that pitch rises with distance; but, in view of the experience of your later correspondent's grandfather, I am inclined to adopt the contrary view. Many years ago I was sitting with an organist friend listening to a fugue on an organ—I think the player was the late Mr. Thomas Adams, and the fugue one of the immortal “Forty-eight” of Bach. At any rate, it was in a minor key; but I noticed that the last chord was major. “Why,” I asked my friend, “does he end with a major chord?” “Because,” was the reply, “sound has a tendency to rise in a long building like a church, and therefore the writer anticipated this by writing his final chord with a major third.” But was this the reason? If the late Mr. Knauff was right, it was probably to allow for the third dropping, and the chord reaching the listeners as a minor chord, in keeping with the rest of the piece.

Change of Pitch of Sound with Distance

IN Mr. West's letter in NATURE of December 12, 1901, he suggests that a lowering of pitch with distance may have been noticed, although his experience has been the reverse. My grandfather, the late Mr. Henry Knaŭff, who, during his lifetime, was an organist and organ builder in Philadelphia, mentioned having noticed this lowering of pitch on several occasions. In long churches, with the organ over the front doorway, he claimed that the voice of the celebrant at the altar sounded distinctly flat to a listener at the organ, but on advancing to the altar this flatness disappeared. I have never noticed this myself, but I have not his ear for small differences of pitch.

Change of Pitch in certain Sounds with Distance

SEVERAL years ago the late Prebendary Simpson, of Fittleworth, Sussex, told me of an interesting observation he had made, which some of your readers may be able to explain. While walking up and down the platform of a railway station, he noticed a peculiarity in the sound of a steam jet from an engine standing on the lines. The pitch of the sound appeared to rise as he retreated from the engine and to fall as he drew near to it. Some time after, Mr. Simpson observed the same thing again, but in this instance the noise was made by a gas flare in the open air, about which some men were at work. Since then I have found that this alteration of pitch with distance occurs with any fizzing noise of the kind, such as that of air jets, burning logs, frying fat, pouring rice or coffee beans, waterfalls, or even the rustling leaves of a single tree; with all those noises, in fact, whose sources are sufficiently localised to admit of observations of the kind being made. I found, also, on withdrawing from such a source that a point is reached after which the pitch ceases to rise, and remains practically stationary as far onward as the sound continues audible. This point is sometimes pretty definitely marked, and varies in distance from the source with different sounds, and the pitch of the stationary portion also varies in the same way. I do not think, however, that the pitch of the whole volume of sound changes, though it often appears to do so, for a similar impression is created by moving a fizzing air jet to and fro close to a wall. As it nears the wall, the whole sound seems gradually to rise in pitch and to sink again as the jet is withdrawn. But here the effect is clearly due to successive reinforcement of one part of the noise after another in the order of their wave-lengths. It is only a shifting of the point of greatest intensity, and not an actual change of pitch at all. Assuming, then, that the effect noticed by Mr. Simpson is of the same nature, that is to say, caused by a readjustment of the relative intensity of the parts, how is it to be accounted for? Is it simply a process of sifting by distance, the weaker groups of small noises, of which the fizzing sound is composed, dropping out of earshot in succession, as the observer retires from the source, till only the largest and loudest group is left, which last continues to be heard for the remainder of the distance without sensible change of pitch? If that is so, then the deeper tones of such noises would seem to have a proportionally shorter range of audibility than the higher ones; for, so far as I have observed, the pitch always sinks on approach to the source and rises on withdrawal from it, never the reverse way, as might be expected in the case of very bass roaring sounds. Perhaps, however, others may have noticed instances of the latter sort. The behaviour of the airjet fizz at the wall illustrates a kind of reciprocal action, which no doubt plays an important part in the adjustment of the pitch. The tone which is loudest for the moment appears to dominate and obscure the rest, so that, near the source, where the deeper tones are most powerful, these latter, to some extent, subdue and lower the principal one, while further off, where they become enfeebled by distance, they are in their turn still more diminished by the presence of the principal far-reaching tone.

Change of Pitch of Certain Sounds with Distance

IN NATURE of December 12 (p. 129), Mr. F. M. West describes an observation made while walking up and down the platform of a railway station. The pitch of the sound caused by the steam escaping from an engine rose as he retreated from it and fell as he drew near to it.