ISSN:0001-4966    

DOI:10.1121/1.1916313

出版商:Acoustical Society of America    

年代:1946

数据来源: AIP

摘要:

Observations by Pottle on the change of tuning of musical wind instruments with ambient temperature are here summarized by a single coefficient representing each instrument tested. The largest effect was observed on theBB♭ sousaphone where the increase with ambient temperature occurred at the rate of 2.6 cents/°C. This is equivalent to a fractional frequency coefficient of1.6 × 10−3/°C. The cent is a logarithmic unit of frequency ratio such that 1200 cents equals one octave. A theory is developed by which the average temperature (and thus the velocity of sound) of the air within a wind instrument may be inferred from the empirically determined dependence of equilibrium tuning on ambient temperature. The theory also provides a qualitative estimate of the change in tuning which occurs while the instrument is first being warmed by the player's breath.

ISSN:0001-4966    

DOI:10.1121/1.1916314

出版商:Acoustical Society of America    

年代:1946

数据来源: AIP

摘要:

The response‐frequency and directional characteristics of gradient microphones from zero tonth order have been obtained. Higher order unidirectional microphones have also been developed. The directivity increases with the order which means corresponding discrimination against random sound. The accentuation of the low frequency response, when the distance from a small source is less than a wave‐length, increases with the order and the wave‐length. This feature may be used to obtain high discrimination against distant sounds in a close talking microphone. The amount of discrimination increases with the order of the microphone.

ISSN:0001-4966    

DOI:10.1121/1.1916315

出版商:Acoustical Society of America    

年代:1946

数据来源: AIP

摘要:

By the use of dimensionless variables and simplifying transformations Webster's plane wave horn equation is recast into a form permitting separation of the effects of horn contour and frequency. A generalized expression for the admittance also displays this separation. Further interrelations among the variables are developed which permit the formal synthesis of a horn from a given conductance or susceptance function. The conditions for realizability of the horn thus synthesized are discussed. Several applications of the results are presented, including a comparison with Freehafer's exact theory for the hyperbolic horn.

ISSN:0001-4966    

DOI:10.1121/1.1916316

出版商:Acoustical Society of America    

年代:1946

数据来源: AIP

摘要:

A new family of horns is synthesized in which the exponential forms a central member. This permits the effect of perturbations from the exponential contour to be estimated. From other members of the family unique impedance characteristics are obtained, and are discussed with possible applications in mind.

ISSN:0001-4966    

DOI:10.1121/1.1916317

出版商:Acoustical Society of America    

年代:1946

数据来源: AIP

摘要:

An approximate method for computing the theoretical supersonic acoustic field from a plane piston, recently presented by the author and L. W. Labaw, is extended to cover a larger region and is applied to concave pistons as well. The resulting equations are given for a certain range of frequencies, piston sizes, and distances from the source. The excess acoustic pressure can be evaluated from them, along the beam axis and for a narrow region around it. It is shown that the assumed nature of vibration of the piston does not matter very much unless the source is sharply curved. The locus of maximum excess pressure is not, in general, near the center of curvature. Labaw's recently published data on the acoustic fields of curved crystals are analyzed in the light of the present equations. The agreement in general is satisfactory. However, it seems that his plane crystal was faulty or else that curved crystals must produce several times the acoustic intensity of plane ones with the same applied voltage.

ISSN:0001-4966    

DOI:10.1121/1.1916318

出版商:Acoustical Society of America    

年代:1946

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.1916319

出版商:Acoustical Society of America    

年代:1946

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.1916320

出版商:Acoustical Society of America    

年代:1946

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.1916321

出版商:Acoustical Society of America    

年代:1946

数据来源: AIP

摘要:

Soundproof rooms of plaster on hollow tile are effective acoustically, but have pronounced disadvantages pertaining to their construction and demolition, and have practically no salvage value. This paper describes soundproof rooms composed of panels consisting of two sheets of steel cemented to two sheets of composition board with a rockwool blanket between. The panels are of a few standard sizes, the combination of which enables rooms of almost any size to be constructed. The rooms are supported on industrial type rubber mountings for the reduction of building vibration. For the most effective attenuation of sound a second room is constructed which completely encloses the first room except that the floor of the second room consists of the floor of the building. The construction and the demounting of the rooms involve little dirt and noise, and there is practically complete salvage value. Eighteen such rooms, comprising both kinds, have been constructed in the new building of Bell Telephone Laboratories at Murray Hill, New Jersey. Single‐frequency attenuation measurements have not been made owing to the pressure of war work, but noise meter measurements show an attenuation of 43 db for the single rooms and more than 57 db for the double rooms.

ISSN:0001-4966    

DOI:10.1121/1.1916322

出版商:Acoustical Society of America    

年代:1946

数据来源: AIP