Amplification

“ The difference seems to me to lie in this, that sublimity gives elevation to a subject, while amplification gives extension as well. Thus the sublime is often conveyed in a single thought, [1] but amplification can only subsist with a certain prolixity and diffusiveness.2 The most general definition of amplification would explain it to consist in the gathering together of all the constituent parts and topics of a subject, emphasising the argument by repeated insistence, herein differing from proof, that whereas the object of proof is logical demonstration, ... ”

“ In the various Armstrong circuits, the increase in strength of signals is due to amplifying effect as in the ordinary amplifier rather than the heterodyne principle. Of course, in the Armstrong circuit, these two effects are combined, but the real increase is due to amplification. ”

“ Given a chunk of cold steel of goodly mass and tune your alloy disk to pure steel, and you can get a few micro-microamperes output if the tube is pointed at the object."
"Sounds interesting. How much amplification do you need to get this reading and how do you make it tick?"
"We run the amplifier up to the limit and then sweep the tube across the object sought, and the output meter leaps skyward by just enough to make us certain of our results. Watch!" ”

“ In the same way if the rate of vibration of a wave of light is in accord with that of a molecule or atom, the amplitude or swing of the atom or molecule is increased, and the energy of the wave and therefore its amplitude is totally or partially destroyed; and as the amplitude is a function of the intensity of the light, the ray fails to be seen at all, or else is diminished in brightness. ”

“ For quantitative measurement it is necessary to have the intensity of stimulus maintained uniform, or increased or decreased in a definite manner. Instead of a tap, the stimulus of torsional vibration is more satisfactory. By maintaining the amplitude of vibration constant, or increasing or decreasing the amplitude, we can either keep the stimulus constant, or increase or decrease it in a quantitative manner. I shall first describe some of the typical results which may be obtained with the simple "straight wire form" of the apparatus. Worked with care it gives consistent and good results. ”

“ Analytical Power of the Ear.—When we listen to a compound tone, we have the power of picking out these partials from the general mass of sound. It is known that the frequencies of the partials as compared with that of the fundamental tone are simple multiples of the frequency of the fundamental, and also that physically the waves of the partials so blend with each other as to produce waves of very complicated forms. ”

“ In all this work they have taken for granted that in the spectrum thus produced in their laboratories, they have been dealing with the vibration of one unique thing, call it atom, molecule, or what you will; that one unique thing has by its vibrations produced all the lines visible, which they have persistently seen and mapped in each instance. ”

“ If we could see the particles of the air in the concert-room, and fasten our attention upon any one of them, we should see it executing a most complicated motion under the combined action of these air-wave-producing instruments. We should be fascinated by the amazing dance of molecules to and fro and from side to side, as the medley of waves of compression or rarefaction embraced them and drove them hither and thither in their resistless grasp. ”

“ I have found out that by uttering the true inner name of anything I can set in motion harmonics--harmonics, note well, half the wave length and twice the frequency!--that are delicate and swift enough to insert themselves between the whirling molecules of any reasonable object--any object, I mean, not too closely or coherently packed. By then swelling or lowering my voice I can alter the scale, size or shape of that object almost indefinitely, its parts nevertheless retaining their normal relative proportions. ”

“ When a band of music is playing, the molecule is supposed to make a complex vibration, a resultant motion of all acting influences, which the ear is supposed to analyze. It remains for the mathematician to show how a molecule influenced by twenty or more degrees of applied energy, and twenty or more required number of frequences of vibration at the same time, can establish a resultant motion which will transmit the required pitch, intensity, and timbre of each instrument. ”

“ Short waves, long waves, micro-waves, frequency-modulated waves, amplitude-modulated signals, every conceivable type of radiation signal, was beamed at the small, invisible, hurtling objects as they swung madly about the globe. ”

“ Thus we may have long waves and short waves independently of the amount of compression or rarefaction, and much or little compression or rarefaction independently of the length of the wave. We know that the difference between a high note and a low note, whether of the voice or of a musical instrument, is, that the high note we can prove to be produced by a succession of short waves—such pulses as have been described—and the low note by a succession of long waves. ”

“ An incandescent solid or liquid gives a continuous spectrum, i.e. all the different wave-lengths are represented, but the part of the spectrum which has the greatest energy is different for different substances and for different temperatures: cf. arc and gas flame in Fig. 16. This is quite in keeping with the idea already suggested that in solids and liquids there are electrons of almost every period of vibration. When they are agitated by being heated, a mixture of simple waves of all periods will be sent out giving a very irregular wave. ”

“ Now, pass a rapidly-interrupted beam of light through some substance whose absorption spectrum is to be investigated, and bands of sound and silence are observed upon exploring the spectrum, the silent positions corresponding to the absorption bands. Of course, the ear can not for one moment compete with the eye in the examination of the visible part of the spectrum; but in the invisible part beyond the red, where the eye is useless, the ear is invaluable. In working in this region of the spectrum, lampblack alone may be used in the spectrophonic receiver. ”

“ Since all sound is caused by vibration, acoustics may be defined as the science which treats of the phenomena of sound-producing vibration.
2. All sound (as stated above) is produced by vibration of some sort: strike a tuning-fork against the top of a table and see the vibrations which cause the tone, or, if the fork is a small one and the vibrations cannot be seen, hold it against the edge of a sheet of paper and hear the blows it strikes; or, watch one of the lowest strings of the piano after striking the key a sharp blow ”

“ Every one of these modes of vibration is dynamically possible by itself, and any number of them may coexist independently of each other.
By a proper adjustment of the initial amplitude and phase of each of these modes of vibration, so that their resultant shall represent the initial state of the string, we obtain a new representation of the whole motion of the string, in which it is seen to be the resultant of a series of simple harmonic vibrations whose periods are the fundamental period and its submultiples. ”

“ Imagine an unseen hand pressing the different keys in rapid succession. The ether notes will thus rise in frequency from one vibration in a second, to tens, to hundreds, to thousands, to hundreds of thousands, to millions, to millions of millions. ”

“ We are here manifestly dealing with that great principle which lies at the basis of spectrum analysis, and which has enabled scientific men to determine the substances of which the sun, the stars, and even the nebulae are composed; the principle, namely, that a body which is competent to emit any ray, whether of heat or light, is competent in the same degree to absorb that ray. The absorption depends on the synchronism existing between the vibrations of the atoms from which the rays, or more correctly the waves, issue, and those of the atoms on which they impinge. ”

“ If I have a transparent body and allow light sent out by a body giving a continuous spectrum to fall through it, I often observe that the transparent body sifts out of the light falling through it certain kind of rays. Spectra are thus produced which are called absorption spectra, because the body which is under examination does not send out any light, but absorbs some vibrations which are made to pass through it. It is an important fact that a molecule absorbs just the rays which it is capable itself of sending out. ”

“ The immense numbers of compounds of carbon, hydrogen, and oxygen,193 described in organic chemistry, are combinations of a second order, for the atoms are groups of groups. The wave of sound produced by a musical instrument may be regarded as a combination of motions; the body of sound proceeding from a large orchestra is therefore a complex aggregate of sounds, each in itself a complex combination of movements. All literature may be said to be developed out of the difference of white paper and black ink. ”

“ A spectrum interrupted by bright lines is produced when the light emanates from flames or ignited vapors and gases. 3. A spectrum interrupted by dark lines is produced, when light emanating from a source giving a continuous spectrum, is passed through gaseous or vaporous matter giving spectra of the second order.
Now, it has been found that, when various elements are volatilized in the flame of a lamp, the light gives a spectrum interrupted by bright lines—whose character and position are different for different elements. ”

“ The amount of motion communicated to the air by the thin prongs is too small to evoke at any distance the sensation of sound. But if we permit the atoms to combine chemically and form molecules, the result, in many cases, is an enormous change in the power of radiation. The amount of aethereal disturbance, produced by the combined atoms of a body, may be many thousand times that produced by the same atoms when uncombined.
The pitch of a musical note depends upon the rapidity of its vibrations, or, in other words, on the length of its waves. ”

“ For example, if the compound sound is formed of six harmonics, the removal of the source of the sonorous vibrations, from the membrane to a distance equal to 14 of a wave-length of the 1st harmonic, will remove the 2d, 3d, 4th, 5th, and 6th harmonics to distances from the membrane equal respectively to 12, 34, 1, 114, and 112 wave-lengths. ”

“ We know from those spectroscopic researches which have thrown so much light on different branches of science, that a molecule can be set into a state of internal vibration, in which it gives off to the surrounding medium light of definite refrangibility—light, that is, of definite wave-length and definite period of vibration. ”

“ We may then conveniently discard the idea of phase, and regard the amplitudes as at random positive or negative. If all the signs are the same, the intensity is n2; if, on the other hand, there are as many positive as negative, the result is zero. But, although the intensity may range from 0 to n2, the smaller values are much more probable than the greater. ”

“ Hence, if we examine a sufficient number of pieces to establish the relative frequency of the different consonances in one major and its relative minor key, and, by a much more extensive investigation, ascertain the relative frequency of occurrence of the different signatures, it is evident, that by multiplying this last series of numbers into the first, and adding those products which belong to chords terminated by the same letters, we shall have a series of numbers expressing the chance of occurrence in favour of each of the consonances of the scale, when all the keys are taken into view. ”

“ Again, the diatonic major scale is regarded by many musicians as the natural order of intervals on which the [Pg 231] compositions must be founded whenever the art of music has attained to a high degree of development, and which will therefore be universally adopted in the course of time. They form this opinion especially from the laws of Acoustics, since the intervals constituting the diatonic major scale are those which as harmonics stand in the most simple relation to the fundamental tone produced by a vibrating body. ”

“ To produce the sound in all its intensity, it is necessary and sufficient that the whole of the explosion produced by the particles of oxygen and hydrogen in a given time should be in agreement with the number of vibrations which correspond to the sound produced by the tube. ”

“ The spectrum of the light emitted by incandescent gases is not continuous, but is made up of a number of bright lines whose position in the spectrum is very definite, and which are characteristic of the elements which produce them. ”

“ In this experiment we notice that tones are high or low, according to the number of their vibrations—the higher the tone the greater the number of its vibrations per second. Again, we observe that we can make the same tone loud or soft, without making it higher or lower. We notice that loudness is obtained by striking with greater force, making the string or fork swing farther from side to side, but still swing the same number of times in a second. ”

“ Of the many possible modes only two are used in our present system of music, the major and the minor. There is only one form of the major mode, and it is the one most people recall when they think of the scale. There are three forms of the minor mode, but of these the harmonic is the most frequently used. ”

“ When light is analysed by a prism or grating into a spectrum, the course of each ray is deflected—refracted or diffracted—by an amount corresponding to its frequency of vibration or wave-length.
Motion of the medium, so long as it is steady, affects neither frequency nor wave-length, and accordingly is without influence on the result. ”

“ Instead of the numbers, which we have, say, in the most commonly used part of the musical scale, i. e., from 200 or 300 to 600 or 700 per second, we have millions and millions of vibrations per second in light waves; that is to say, 400 million million per second, instead of 400 per second. That number of vibrations is performed when we have red light produced. ”