摘要:

A strong 108 cycle fundamental and one of its harmonics were impressed on one ear in various relative phases and sound pressures. The tone quality and the loudness of the combination were found to depend on the relative phase of the two components. In a certain phase relation the loudness of the combination was 3.5 db less than the loudness of the fundamental alone; varying the phase changed the loudness of the combination by about 10 db. The above observations may be explained by assuming that the ear mechanism distorts the pure components of a complex sound pressure, producing subjective harmonics which may either constructively or destructively interfere depending on the relative phases of the components. Some evidence was found in support of an assumption that the subjective harmonics due to a single low frequency pure tone actuating the ear, are in phase as cosine functions without epoch angles.

ISSN:0001-4966    

DOI:10.1121/1.1915646

出版商:Acoustical Society of America    

年代:1934

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.1915647

出版商:Acoustical Society of America    

年代:1934

数据来源: AIP

摘要:

The theoretical studies previously made on the filtration of compressional waves in solid rods by Lindsay and White have been extended to the case of torsional waves in a rod and of compressional waves in rods having solid rods for side branches. If an infinite cylindrical rod is loaded at equal intervals of length 2lwith disks (having planes perpendicular to the rod) of massmand moment of inertiaIabout the axis of the rod, the resulting structure is found to act as a low‐pass filter for torsional waves. The transmission bands are given by the condition+1⩾cos W⩾−1, wherecos W = cos 2kl − ωI/πa4ρ0c⋅sin 2kl. Herek = ω/c = 2πν/c, where ν is the frequency of the waves. The velocity of propagationc = (μ/ρ0)12, where μ = rigidity modulus and ρ0is the mean density of the rod. The radius of the rod isa. For givenI, increase inldecreases both the cut‐off frequency of the first transmission band as well as the upper limit of the first attenuation band. For givenl, increase inIdecreases the cut‐off frequency. There is next considered the case of an infinite cylindrical rod loaded at equal intervals of length 2lwith perpendicular side rods of lengthls. The approximate assumption is made that longitudinal compressional waves in the main rod set up transverse flexural waves in the side rods. Calculation indicates that if the side rods havefreeends the structure acts as a low‐pass filter for compressional waves in the main rod. If on the other hand the side rods have rigidly clamped ends, the structure under suitable choice of dimensions (in particularl/ls≫1) can act as a high‐pass filter. Numerical illustrations are given.

ISSN:0001-4966    

DOI:10.1121/1.1915648

出版商:Acoustical Society of America    

年代:1934

数据来源: AIP

摘要:

This paper considers theoretically the propagation of compressional waves in a structure consisting of an infinite series of alternating layers of two different media which may be either fluid or solid. It is shown that such a structure acts as a low‐pass acoustic filter. A number of special cases are computed and it is found that the cut‐off frequency depends essentially on the section length and the relative acoustic impedance of the media. The problem is shown to be mathematically quite analogous to that of the propagation of acoustic waves in air through an infinite tube containing alternate constrictions and expansions. Moreover the loaded solid filter considered in a previous paper by Lindsay and White proves to be a limiting case of the non‐homogeneous medium filter of the present article.

ISSN:0001-4966    

DOI:10.1121/1.1915649

出版商:Acoustical Society of America    

年代:1934

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.1915650

出版商:Acoustical Society of America    

年代:1934

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.1915651

出版商:Acoustical Society of America    

年代:1934

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.1915652

出版商:Acoustical Society of America    

年代:1934

数据来源: AIP

摘要:

A modification of Bragg's amplitude meter is applied to a resonant diaphragm, associated with a parabolic horn, to provide a highly selective microphone. When used with an impulsive source of sound it makes possible the measurement of distances as low as 10 ft. while in the presence of sounds comparable to those in aircraft.

ISSN:0001-4966    

DOI:10.1121/1.1915654

出版商:Acoustical Society of America    

年代:1934

数据来源: AIP

摘要:

A summary of the development and use of commercial sound absorbents and some problems in their manufacture and sale.

ISSN:0001-4966    

DOI:10.1121/1.1915661

出版商:Acoustical Society of America    

年代:1934

数据来源: AIP

摘要:

By means of a beat‐frequency audio‐oscillator, amplifier and a calibrated sound reproducer capable of high acoustic output levels it was found that 27 observers with complete bilateral hearing loss, due either to congenital defect or meningitic infection, but with normal tympanic membranes, possessed average value thresholds of feeling. This finding is interpreted to signify that the threshold of feeling is not causally related to stimulation of the acoustic portion of the eighth cranial nerve. The threshold of feeling in 33 ears lacking tympanic membranes because of the radical mastoid operation or prolonged otitis media was raised 20 db or more above the average values for normal ears, which suggests that the end organs responsible for the threshold of feeling are located within the tympanic membrane and epithelium lining the combined middle ear cavity and external auditory meatus. Individuals with pronounced hearing loss and intact tympanic membranes cannot tolerate high levels of sound amplification in a headphone to enable perception of speech sounds because of the pain elicited when high amplification stimulates the threshold of feeling. Individuals with equal hearing loss but lacking tympanic membranes can use sufficiently high levels of sound amplification to enable perception of speech sounds without arousing unpleasant sensations in the ear.

ISSN:0001-4966    

DOI:10.1121/1.1915667

出版商:Acoustical Society of America    

年代:1934

数据来源: AIP