Sound change

“ We recognize at once a difference between the sound of a vowel, say ah, sung by different persons to the same note of the piano and with the same loudness. There is a personal element, an individuality, about voices which at once arrests our attention, apart altogether from the tone or loudness. This sound-quality is determined by the form of the wave-motion, that is, by the nature of the movement of the air-particle during its little excursion to and fro in which it takes part in producing a zone of compression or rarefaction in the air and so forms a sound wave. ”

“ After listening for a few moments, a distant, unearthly noise becomes faintly audible—a long, low, mysterious moaning, which never changes, which is felt on the ear as well as heard by it—a sound that might proceed from some incalculable distance, from some far invisible height—a sound so unlike anything that is heard on the upper ground, in the free air of heaven ”

“ The sensation of sound is produced by rapid fluctuation in the pressure of the atmosphere on the tympanum of the ear. If the fluctuations are irregular and non-periodic, the sound is called a noise; if they are cyclic and follow a regular and sufficiently rapid periodic law, the sound is musical. ”

“ Even among ourselves the power of hearing shrill sounds is greater in some persons than in others. Sound, as we know, is produced by [Pg 89] vibration of the air striking on the drum of the ear, and the fewer are the vibrations in a second, the deeper is the sound, which becomes shriller and shriller as the waves of sound become more rapid. ”

“ Near sounds are louder than distant ones. Now, by preserving the same pitch, quality, and duration, but with an accurately graduated reduction of loudness, a series forming a perspective of sounds may be created, which, falling in succession on the ear, will suggest to the mind a constantly increasing distance of the sound’s source. ”

“ Sound, like light, may be reflected several times in succession, and, as the reflected light under these circumstances becomes gradually feebler to the eye, so the successive echoes become gradually feebler to the ear. In mountain regions this repetition and decay of sound produce wonderful and pleasing effects. ”

“ The loudness of sound is such as is convenient for common purposes. The organs of speech can, in the present constitution of the air, produce, without fatigue, such a tone of voice as can be heard with distinctness and with comfort. That any great alteration in this element might be incommodious, we may judge from the difficulties to which persons are subject who are dull of hearing, and from the disagreeable effects of a voice much louder than usual, or so low as to be indistinct. Sounds produced by the human organs, with other kinds of air, are very different from those in our common air. ”

“ Noise affects us as an irregular succession of shocks. We are conscious while listening to it of a jolting and jarring of the auditory nerve, while a musical sound flows smoothly and without asperity or irregularity. How is this smoothness secured? By rendering the impulses received by the tympanic membrane perfectly periodic. A periodic motion is one that repeats itself. The motion of a common pendulum, for example, is periodic, but its vibrations are far too sluggish to excite sonorous waves. ”

“ Loudness of the sound depends upon the extent of the vibrations, pitch on the rapidity of the vibrations, and quality on the admixture of tones produced by vibrations of varying rates of rapidity, related to one another. ”

“ A simple noise being a sound-wave, has its wave-form or make-mark. The blending of many such would produce a tone in that likeness; hence, a musical note is a blending of like noises, and every noise is really the first wave, the key-note of a musical tone. Take the ringing of a door-bell. Here the ear hears not only a musical tone, a sound-blend, in the ring of the bell, but also the noise of the clapper's clang, clang, clang. The vibrations of the bell throw the air into musical waves, shown in Fig. 5, while a huge clang-wave will sweep
Fig. ”

“ We see, then, that the sound-waves necessary to reproduce accurately the various vowel sounds, are more complicated than those which would correspond to the fundamental tones simply in which any sound may be uttered. ”

“ The effect of every shock will be renewed before it vanishes, and the recurrent impulses will link themselves together to a continuous musical sound.84 The pulses, on the contrary, which produce noise, are of irregular strength and recurrence. The action of noise upon the ear has been well compared to that of a flickering light upon the eye, both being painful through the sudden and abrupt changes which they impose upon their respective nerves. ”

“ The Various Qualities of Sound.—Physically, sounds consist of vibrations, and these are, generally speaking, aërial waves. When the waves are non-periodic the result is a{54} noise; when periodic it is what is nowadays called a tone, or note. The loudness of a sound depends on the force of the waves. When they recur periodically a peculiar quality called pitch is the effect of their frequency. ”

“ It is certain, however, that it is one of the commonest of sound producers; if there is a boy in the home there is almost sure to be a whistle in the house. Few trouble about the scientific explanation of the sound produced by this common instrument, but experts tell us that the sound comes because condensations occur by the collision of air against the cutting edge placed in its path. ”

“ Other vocal sounds than sustained vowel notes are found to be due to still more complicated combinations of vibrations of shorter duration, and noises, as distinguished from musical sound, are formed also by the superposition of a greater or less number of systems of vibrations, the rapidities of which are wanting in harmonic relations such as we have pointed out belong to the musical scale. ”

“ How Sound is Produced. If one investigates the source of any sound, he will always find that it is due to motion of some kind. A sudden noise is traced to the fall of an object, or to an explosion, or to a collision; in fact, is due to the motion of matter. A piano gives out sound whenever a player strikes the keys and sets in motion the various wires within the piano; speech and song are caused by the motion of chest, vocal cords, and lips. ”

“ That the conditions which produce sound are all present may be demonstrated by conveying a tube from the mouth of either of the pipes to a listener's ear, when its tone will be distinctly heard. In other words, one sound destroys the other. ”

“ Sound means a succession of vibrations produced in their regular order, like music, whereas noise is a disorganized vibration. For instance, falling water, like our cataract here, is sound, but the report of George's gun was a noise."
"I can see the difference. Would a wagon going rapidly over a pavement be a noise or a sound?" ”

“ Other consonants are to be classed with the noises. Like a vowel, and like the timbre of an instrument, a noise is a blend of simple tones; but the fundamental tone in a noise-blend is not so preponderant as to give a clear pitch to the total sound, while the other tones present are often too brief or too unsteady to give a tonal effect. ”

“ Mankind are so ready to leap to conclusions without the labour necessary for a faithful elucidation of the truth, that too often a few points of resemblance are seized upon, and an inference is drawn which is calculated to mislead.
There is an idea that the phenomena of sound bear a relation to those of light,—that there exists a resemblance between the chromatic and the diatonic scales. Sound, we know, is conveyed by the beating of material particles—the air—upon the auditory membrane of the ear, which have been set in motion by some distant disturbance of the medium through which it passes. ”

“ The general terms—loudness and quality, embrace all the distinctions heard in a noise, as in the collision of two unelastic sticks. Pitch and duration can scarcely be considered as belonging to common noise. Thus we have— (1) noise whose audible distinctions are comprehended under the general terms loudness and quality; (2) common sound, whose audible distinctions are comprehended under the general terms—loudness, quality, duration, and every varying pitch; (3) musical sound, whose audible distinctions are comprehended under the general terms—loudness, quality, duration, and uniform pitch. ”

“ Concerning symphony, he shows how sounds harmonize. A quick sound is acute, a slow is grave. Therefore acute sounds move the senses the quicker; and these dying and grave sounds supervening, what arises from the contemperation of one with the other causes pleasure to the ear, which we call harmony. And by what has been said, it may easily be understood that air is the instrument of these things. For sound is the stroke upon the sense of the hearer, caused by the air; and the air strikes as it is struck by the thing moving,—if violent, acutely,—if languid, softly. ”

“ The tuning fork is musical. Here we have rapid, regular motion; vibrations follow each other at perfectly definite intervals, and the air disturbance produced by one vibration is exactly like the disturbance produced by a later vibration. The sound waves which reach the ear are regular in time and kind and strength, and we call the sensation music.
To produce noise a body must vibrate in such a way as to give short, quick shocks to the air; to produce music a body [279] must not only impart short, quick shocks to the air, but must impart these shocks with unerring regularity and strength. ”

“ Thus the air must include a vast variety of molecules of various degrees of elasticity, and capable of vibrating in as many different periods as there are tones from all kinds of sonorous bodies; and these molecules, set in motion by the musician and falling on our ear, answer to our ideas, according to each man's temperament. I myself believe that sound is identical in its nature with light. Sound is light, perceived under another form; each acts through vibrations to which man is sensitive and which he transforms, in the nervous centres, into ideas. ”

“ If there is no regular recurrence of waves, it is a noise. The rapidity of these regular beats determines the pitch of tones. That quality or timbre by which one sound is distinguished from another of the same pitch and intensity is due to the different complications of waves in the air; the ability to discriminate the various waves in the vibrating air is, therefore, the condition of our finding music in it; for every wave has its period, and what we call a noise is a complication of notes too complex for our organs or our attention to decipher. ”

“ Another action of sound causes the interference of waves. Thus the reflected waves may meet the oncoming ones and set up concentrations of sound in certain positions and a dearth of sound in others.
Summing up, it is seen that the effects of sound which may exist in a room are loudness, reverberation, echoes, resonance, and interference, and that the most common defects are reverberation and echoes. We now turn to the discussion of the methods of cure. ”

“ By various contrivances we can compel the vibrations of the air to declare themselves; we know the length and frequency of sonorous waves, and we have also obtained great mastery over the various methods by which the air is thrown into vibration. We know the phenomena and laws of vibrating rods, of organ-pipes, strings, membranes, plates, and bells. We can abolish one sound by another. We know the physical meaning of music and noise, of harmony and discord. In short, as regards sound we have a very clear notion of the external physical processes which correspond to our sensations. ”

“ The popular notion that sound rises has probably originated from the fact that in our common experience the sounds are produced near to some kind of floor, which reflects the sounds upwards, and thus adds the reflected sound to that which is directly transmitted, and thereby the general result is materially augmented. ”

“ Highest and Deepest Tones—Rapidity of Vibration Determined by the Siren—Determination of the Lengths of Sonorous Waves—Wave-Lengths of the Voice in Man and Woman—Transmission of Musical Sounds through Liquids and Solids
IN OUR last chapter we considered the propagation through air of a sound of momentary duration. We have to-day to consider continuous sounds, and to make ourselves in the first place acquainted with the physical distinction between noise and music. As far as sensation goes, everybody knows the difference between these two things. ”

“ To follow the history of the sounds in any language we must understand how sounds are produced.
Just as in a whistle or an organ sound is made by a current of air passing through certain openings, and being set in vibration by certain tongues or edges put in the way of the current, so sound is produced in the human throat and mouth by a current of air sent out from the lungs; and different kinds of sound arise from the different ways in which the current is treated as it passes through the throat and mouth. ”

“ Sufficient has already been said to make it clear to you that one essential difference between sound or noise and music, as far as regards the events taking place outside of our own organism, is that, in the first case, we have a more or less irregular motion in the air, and, in the second, a rhythmical movement, constituting a train of air waves. ”

“ Air is the usual vibrating medium. Only certain vibrations are perceptible to the human auditory organ. Those having a recurrence of below thirty or above sixteen thousand per second do not produce the sensation of sound to the average human ear. ”

“ The influence of resonance and pitch, echo and absorption of tones, i.e., the location of the sound, is of great importance. Finally, it must not be forgotten that people’s ability to hear varies with the weather. Colds reduce the power, and not a few people are influenced by temperature, atmospheric pressure, etc. These considerations show the degree in which auditory illusions can be of importance even in tests of their nature and existence. They show above all that the same object of comparison under the same circumstances must be used in every test. ”