bluuebunny/crossref_metadata_2025_split huggingface dataset:
Human Factor in Piano Tone Production
Authors: White William Braid 
Published: September 2005

A special form of portable Westinghouse oscillograph, using a Western Electric double-carbon-button 387-W microphone, and one stage of radio amplification, was used to obtain a large number of sound-wave photographs representing the sounds produced at the piano by various eminent artists, particularly Rudolf Ganz, John Powell, Ernest Schelling, and Olga Samaroff. The object was to discover how variations in attack upon the piano keys, transmitted to the strings through the hammers, affect (a) the intensity, (b) the quality of the sounds produced. The following conclusions were arrived at as a result of many experiments.
(1) The number of possible variations in key speed and in the control thereof is indefinitely great, much greater than is commonly appreciated by ordinary hearers, or by ordinary players, of the piano.
(2) An indefinitely great number of variations in the velocity of the hammer during its travel to the string is likewise possible.
(3) Every velocity value of the hammer, in a manner dependent among other things upon the physical make-up of hammer and string, produces a corresponding intensity value, and a parallel color value, in the sound.
(4) Faint sounds on the piano tend to converge in color value until at the minimum of intensity all sounds from bass to treble have the same sine wave form, that is, are perfectly simple sounds. Contrariwise, as intensity increases, the number of audible harmonics increases accordingly.
(5) It may therefore be concluded that every change in loudness involves a change in color, and every change in color requires a change in loudness; that is to say, tone color control on the piano is dependent upon control of intensity, that is, upon control of hammer velocity, and that again, on control of the speed and acceleration of the key.
The paper is illustrated with numerous sound-wave photographs, the evidence of which confirms the conclusions arrived at. The interpretation of these photographs is guided by the general rule that amplitude measures loudness, and shape of vibration-pattern measures quantity.
Reverberation Time in “Dead” Rooms
Authors: Eyring Carl F. 
Published: September 2005

An analysis based on the assumption that image sources may replace the walls of a room in calculating the rate of decay of sound intensity after the sound source is cut off gives the more general reverberation time equation T = .05V−S loga(1−aa), where T is reverberation time, V the volume of the room, S the surface of the room, and aa the average coefficient of absorption of the wall surface. In the past Sabine's formula, T = .05VSaa, has been used to calculate reverberation time, but for rather large values of aa, that is, for “dead” rooms this equation gives too long a time of reverberation, or in some cases, if the time is measured, it gives a value of aa greater than unity. This we found to be the case in the Sound Stage, Sound Picture Laboratory, Bell Telephone Laboratories, Inc. Reverberation time measurements made in this room support the new formula, however. Sabine's formula turns out to be the special case of the more general equation and is to be used when aa is small, that is, for “live” rooms, but not for “dead” rooms.
The new formula is of importance in the talking picture industry for it indicates that a “dead” room may be obtained by the use of less absorbing material than that calculated by the old formula.
The “Strike Notes” from Bells
Authors: Jones Arthur Taber 
Published: September 2005

The “strike note” of a bell does not appear to be produced by vibration of the bell in any of its normal modes. The strike note is not far from an octave below the fifth partial tone of the bell, and the suggestion has been made that this fifth partial may come out with especial promptness and strength, and the attention of the ear be afterward quickly caught by lower tones, so that the tone from the fifth partial is judged to be an octave lower than it really is.
Several tests of this hypothesis have been attempted. (1) A number of musicians have given their judgment as to the pitches of the strike notes on three bells. The average is almost exactly an octave below the fifth partial. (2) The sounds from six bells have been picked up from a distance of about 300 meters. When the bells were struck so gently as to be almost inaudible at this distance, beats from suitably tuned forks showed that the fifth partial is at least as prominent as any other. (3) On the same six bells the first order difference tone from the fifth and seventh partials is close to the strike note. (4) The time during which the clapper is in contact with the bell has been found rather roughly for one bell. This time is not far from half the period of the fifth partial.
The results of other tests are not yet sufficiently definite to be of significance. The work is to be continued next summer.
The Use of Sound in Navigation
Authors: Lamson Horatio W. 
Published: September 2005

Modern methods for employing under-water sound as an aid to navigation are based upon the binaural sense.
The earliest devices, exemplified by the “C” tube, etc., mechanically placed the ears of the observer on the extremities of a beam to be rotated in a horizontal plane beneath the sea. Such cumbersome equipment was improved by employing fixed under-water receivers in conjunction with an adjustable compensator for obtaining a binaural balance.
Electrical lag lines have replaced acoustical tubes for obtaining the necessary time lag to affect compensation. The effectiveness of such a two-spot system is hampered whenever more than one sound source is present. This difficulty was subsequently overcome by obtaining a directional sensitivity by means of a multi-spot system which compensates simultaneously for a binaural and maximum focus.
Observations upon the compensators may likewise be made upon sounds traveling in a vertical plane. This enables continuous depth soundings to be taken with the vessel under way at full speed, a valuable feature.
Apparatus has also been perfected for acoustic depth soundings by timing the echo of sound reflected from the sea bottom. The use of super-audible sound waves, which can be projected in a slightly diverging beam, offer great possibilities for the location of icebergs, etc.
Absolute Amplitudes and Spectra of Certain Musical Instruments
Authors: Sivian L. J. , Dunn H. K. , White S. D. 
Published: September 2005

Systems for the reproduction of music are limited in the frequency range and in the amplitude of the sounds which they can reproduce without distortion. In order to determine what requirements such a system should meet for faithful reproduction of common forms of music, those instruments which were believed to contribute largely to low or high frequencies, or to have large amplitudes at any frequency, have been investigated. Those examined were: bass drums of three sizes, snare drum, cymbals, triangle, bass viol, bass saxophone, bass tuba, trombone, trumpet, French horn, clarinet, flute, piccolo, piano, and organ. Several measurements have also been made upon complete orchestras.
The measurements included average and peak sound pressures corresponding to the whole spectrum, and also the same quantities in thirteen bands of frequencies which together covered the complete spectrum. Several hundred peak measurements were taken in each band, each measurement representing the highest peak in one-eighth second of music. They were taken in such a way that the frequency of occurrence of the peaks in ten amplitude zones, each zone covering six decibels, was obtained. The musician in each case played a representative selection for his instrument, lasting two or more minutes.
With the complete orchestra, the highest peaks were found to lie in the region between 2,000 and 4,000 c.p.s. The greatest peaks below 64 c.p.s. were obtained when the bass drum was prominent, while the greatest peaks above 8,000 c.p.s. were very plainly due to the cymbals.
The Approximate Networks of Acoustic Filters
Authors: Mason W. P. 
Published: September 2005

The original theory of acoustic filters, given by Stewart, is based on the representation of such filters by means of lumped constants in the form of a T-network. More recently, the writer has presented a theory of acoustic filters, showing that they are equivalent to a combination of electric lines. Stewart and Lindsay have pointed out that the first theory is a first approximation of the second theory—obtained by taking the first terms of the trigonometrical expansion occurring in the latter theory.
This approximation holds well for low pass filters, at low frequencies, but does not represent very adequately the band pass filter. Accordingly a second approximation is developed in this paper. Methods are given for determining the transmission characteristics of any types of acoustic filters. These methods have been applied to analyzing all of the single band pass filters possible with one main branch and any side branch combination. There are five of these filters, and design formulae for them have been worked out. It is possible, from these formulae, to determine the dimensions of a filter necessary to have a given attenuation and impedance characteristic.
An Error in the Derivation of the Reverberation Formula
Authors: Germond Hallet H. 
Published: September 2005

Sabine's formula T = 55.3V/avs yields finite values for the period of reverberation even when the coefficient of absorption is unity. This formula is a first approximation to that developed by Norris T = −24V/vs Log10 (1−a); the latter yields T=0 for a=1. An error in the interpretation of the fundamental differential equation in the derivation of Sabine's formula is demonstrated.
Another mode of attack permits a more correct analysis of a room under certain specified distributions of absorbing material.
Some Physical Factors Affecting the Illusion in Talking Motion Pictures
Authors: Maxfield J. P. 
Published: September 2005

The advent of talking pictures has brought the physicist and engineer face to face with problems which lie not only in the field of material things but also in the field of art. This implies that many of the criteria for the judgment of excellence may be of a psychological rather than a physical nature.
The paper describes results of an empirical study of methods for controlling some of the factors available to the engineer in the field of sound recording and photography in such a manner that a pleasing illusion of reality is created in the theater. Empirical quantitative curves are given.
Means for Radiating Large Amounts of Low Frequency Sound
Authors: Kellogg E. W. 
Published: September 2005

Present electrical sound equipment has little output below about 100 cycles. An electrical device of large output in the range 30 to 200 cycles would afford new musical effects not hitherto possible.
From a review of existing literature it is concluded that an acoustic output of at least one watt should be provided. Ten watts would be desirable. The result can be attained in several ways and the amount of equipment required with various arrangements is calculated. The results should serve as a guide in the design of installations.
The Effect of Humidity Upon the Absorption of Sound in a Room
Authors: Knudsen V. O. 
Published: September 2005

P. Sabine and E. Meyer have noted that for frequencies above 2,000 d.v. the rate of absorption of sound in a room increases as the relative humidity decreases. The writer has investigated and confirmed this effect during the past year and has obtained some quantitative data which have a bearing upon problems in architectural acoustics and sound signaling. Assuming that the intensity of a plane wave in air diminishes in accordance with e—mct where c is the velocity t the time and m the absorption coefficient in the air the reverberation formula becomes (in British units) t = .049V−S loge (1 − a) + 4mV.
By making reverberation measurements, under different conditions of humidity, in two rooms having the same boundary material (painted concrete) but different mean free paths, it is possible to determine both m and a as functions of the frequency and humidity of the air. For frequencies below 512 d.v., m is negligible. It increases approximately with the square of the frequency. At 4,096 d.v., m increases from about .0015 at 70 per cent relative humdidity (21°C) to .0033 at 20 per cent relative humidity. At frequencies above 6,000 d.v., the absorption in the air in a room may be greater than the absorption by the boundaries. The absorptivity of painted concrete remains nearly constant above 512 d.v., and has a value of about .016.
Measurements with a Reverberation Meter
Authors: Chrisler V. L. , Snyder W. F. , Miller C. E. 
Published: September 2005

A description is given of apparatus with which the rate of decay of sound energy in a room may be measured. A loud speaker is used as a source of sound. When the sound has reached a steady state the loud speaker circuit is opened and at the same time a timer is started. When the sound energy has decayed to some definite value the timer is automatically stopped.
If made in a portable form this equipment may be used to study the acoustical properties of auditoriums.
Attention is called to the errors which may occur in these measurements.
Measurements are given showing absorption due to diaphragm action of materials.
The Woodwind Musical Instruments
Authors: Miller Dayton C. 
Published: September 2005

The wood-wind group of musical instruments includes four distinct types, commonly known as flutes, oboes, clarinets, and saxophones. According to peculiarities of size or method of construction these instruments have a variety of names among which are: recorder, galoubet, piccolo, flageolet, English horn, bassoon, bag-pipe, doodlesack, etc. Originally these instruments were made of wood, now many are made of metal.
A discussion is given of the tone production and of the relations of the nodes and loops of the vibrating air-column to the mouth-piece and the tone-holes in the several types of instruments. The varying qualities of tone are due to the prominence of certain overtones which are characteristic of each instrument; the general nature of these peculiarities have been determined by analysis of photographic records of the tones.
The positions of tone-holes were primitively determined by the number and length of fingers conveniently available in playing and varies according to custom. Our musical scale of the octave has been by the peculiarities of the hand! Very little of the scientific method is applicable to the design of musical instruments. Theobald Boehm, of Munich, just one hundred years ago, first made use of the principles of acoustics in the making of an orchestral instrument; this consisted simply in placing the tone-holes according to the intervals of the equally tempered scale. He followed this with a study of tone-quality which resulted, in 1847, in the present-day Boehm Flute. These studies influenced the design of all the other wood-wind instruments. A discussion is given of possible further improvements through laboratory research.
Exhibition and demonstration of primitive and modern instruments will be made with various specimens selected from the writer's historical collection of flutes, now the largest in the world.
Open Pipes, Stopped Pipes and Double Stopped Pipes
Authors: Taylor John Bellamy 
Published: September 2005

Air columns in rigid tubes reflect pulses (sound waves) at the ends. The classical sounding or vibrating air column is the organ pipe, broadly classed as either “open” or “stopped” and giving tones of different quality because lack of symmetry in stopped organ pipes suppresses the evenly numbered harmonic overtones. Pipes of both classes are usually considered to be so rigid that all of the “output” to free air occurs at two ends of open pipe or at single opening (mouth) of the stopped pipes. This rigidity assumption may not be justified.
If a pipe is stopped at both ends, symmetry is restored with opportunity for vibrations in the complete harmonic series. But with no free vent to outer air the double stopped pipes obviously may not be energized by the usual form of air stream; also confined vibrations will not be heard outside. These seemingly unworkable conditions are met by supplying energy and also withdrawing sound output at nodal points, rather than at loops (ventral segments). Such abstraction of energy at node of vibrating air column is useful in cases where the tone or vibration is to be transferred to a denser medium, e.g., to a liquid or to a solid such as a sounding board.
Further Studies on the Strike Note of Bells
Authors: Jones Arthur Taber , Alderman George W. 
Published: September 2005

(1) Difference Tones.—The pitches of the first order difference tones from the fifth and seventh partials have been obtained for 24 bells, and from the seventh and tenth partials for 13 bells. These difference tones are probably not important in the production of the strike note.
(2) Relative Intensities of the Partial Tones.—Curves from bells have been obtained with a condenser transmitter, amplifiers, and an oscillograph. Analysis of the curves from four bells do not indicate the presence of the strike note. They do show that when a bell is first struck the fifth partial is the most prominent, and that this fifth partial is rapidly damped. The relative intensities of the partials fit well with the qualitative results which had already been obtained.
(3) Duration of Contact of Clapper.—296 records of the strokes of the clappers on four bells show that the duration of the contact increases with decreasing strength of blow, and that with increasing strength of blow the duration appears to approach a definite limit. This limiting duration of contact is about half the period of one vibration of the fifth partial, a fact which doubtless explains the early prominence of the fifth partial.
A Planetary Reduction Gear System for Turntables
Authors: Bedford A. V. 
Published: September 2005

In the common synchronous gear drives for phonograph or talking picture turntables there is at least one driven gear which makes the same average revolutions as the turntable and which is driven by a higher speed gear (or worm). Commercial gears have slight but appreciable errors in both tooth spacing and shape, which necessitates a variation in the relative angular speeds of the two gears. These irregularities may introduce disturbances of frequencies corresponding to the frequency of revolution and its multiples.
The effect of the higher harmonics can be easily reduced by filtering, but to filter the lower frequencies the turntable must be prohibitively massive or the couplings must be so flexible as to put the table speed at the mercy of the irregularities of its bearings and endanger the synchronism of sound and picture.
The planetary gear system, to be described, increases the speed of the lowest-speed gear with respect to the gear meshing it, thereby increasing the frequency of the disturbance and greatly facilitating mechanical filtering.
The main turntable bearings are also run at higher speed with similar effect upon disturbances arising from frictional irregularities. Damping is also provided to dissipate transient disturbances of speed.
Mass Controlled Electrodynamic Microphones: The Ribbon Microphone
Authors: Olson Harry F. 
Published: September 2005

One of the requirements of a high quality microphone is uniform response over a wide frequency range. To attain this objective in an electro-dynamic microphone the ratio of the velocity of the mechanical system to the pressure or velocity in the acoustic system must be independent of the frequency. To maintain constant velocity in a mass controlled microphone the driving force actuating the mechanical system must be proportional to the frequency. This may be accomplished by the designing of the mechanical system so that the actuating force is derived from the pressure gradient of the sound wave. Provided the system is small compared to the wave-length of the incident sound wave the resultant pressure available for actuating the system is proportional to the frequency.
One example of this type is the ribbon microphone which consists of a light ribbon suspended in a magnetic field. The ribbon is driven from its position of equilibrium by the difference in pressure due to the difference in phase existing between the two sides. The acoustic impedance of the ribbon and air load is proportional to the frequency. The velocity of the ribbon (or the generated e.m.f.) is determined by the ratio of the resultant pressure and the acoustic impedance. In the case of the ribbon microphone this quantity is independent of the frequency.
A Theoretical Expression Relating Loudness and Intensity
Authors: Ham L. B. , Parkinson J. S. 
Published: September 2005

Three series of experiments (see also abstract 8, Journal of Acoustical Society of America, 3, p. 7, July 1931) were performed with untrained observers as follows: (A) the sound energy was reduced by definite steps, (B) the loudness was reduced to definite fractional values of original, (C) the loudness was increased by definite multiple values of original.
The reciprocals of the remaining fractions of original loudness are plotted as ordinates y against reductions of sound energy in decibels as abscissae x, while in series C the multiple increases in loudness are plotted as ordinates y against increases of sound energy as abscissae x.
An analysis of these curves shows that they may be represented by the equation: y = enx.
A discussion of the curves as related to this equation is given. For the present, n = .076 is chosen as the best value for estimating loudness reductions.
If (y) is expressed as the percentage reduction, the equation takes the form: y = 100 − 100e−.076x.
The Weber-Fechner law of loudness is a first approximation to the theoretical considerations above.
A scale for noise measurement is suggested using multiple loudness units based on the above formulae.
The Application of the Norris-Andree Method of Reverberation Measurement to Measurements of Sound Absorption
Authors: Norris R. F. , Andree C. A. 
Published: September 2005

Several methods of measuring sound absorption are in use but require rather large samples. The Norris-Andree method of reverberation measurement theoretically lends itself to sound absorption measurement, permitting relatively small samples to be used and necessitating no reference absorption material.
The paper outlines in detail the mechanical application of this method to sound absorption measurement and presents data collected over a year's time in making such measurements.
The Acoustic Design of Severance Hall
Authors: Miller Dayton C. 
Published: September 2005

Severance Hall, the permanent home of the Cleveland Symphony Orchestra, was completed in February, 1931. From the very beginning of the plans, the donor, the Management of the Orchestra, the University and the Architects, have all been united in purpose that the acoustic condition should be as nearly perfect as is possible and that nothing should be allowed to interfere with this end. Calculations were made for proposed designs and treatments, and the architects were thus enabled to adjust and adapt plans and methods without any inconvenience, and were successful in choosing dimensions, shapes and materials which in connection with the furnishings and the audience would produce the desired acoustical effect. Perhaps this adjustment has been carried out more systematically and more effectively in Severance Hall than in any other auditorium of this type.
At the conclusion of one of the sessions of the Society there will be an opportunity for the members to visit Severance Hall.