摘要:

Since hearing aid receiver acoustical output is commonly measured by an artificial ear wherein a microphone replaces the eardrum, the measurement yields data only on nominal pressure at the eardrum. A correction factor must be applied to the artificial ear output to relate it to the free field performance of the ear (which is the norm). In other words, substituting pressure operation for free field operation of the human ear changes its frequency response, and this change must be allowed for in determining the corrective characteristics of a hearing aid. The variation is computed and is then compared with subjective test results. The sum of this correction and one for the obstacle effect of the human body wearing the hearing aid transmitter are then determined and it is concluded that such an over‐all corrections so great that it cannot be neglected in determining or comparing hearing aid characteriistics. The over‐all correction is then applied to representative instrument characteristics.

ISSN:0001-4966    

DOI:10.1121/1.1916265

出版商:Acoustical Society of America    

年代:1944

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.1916266

出版商:Acoustical Society of America    

年代:1944

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.1916267

出版商:Acoustical Society of America    

年代:1944

数据来源: AIP

摘要:

In the course of experiments involving the response of single auditory nerve‐fibers, it was found that watch ticks elicit synchronized potentials which can be recorded from a great number of fibers. An almost identical response is easily obtained from the round window. Both can be suppressed by pure tones, a frequency around 4050 c.p.s. being most effective for a particular watch. There is experimental evidence that the tick‐response, also if recorded from the fenestra rotunda, consists almost entirely of nerve potentials (aural microphonics being negligibly small in this case). Thus, it is possible to record a practically pure nerve‐response from the cochlea. This opportunity was used to determine the locus of suppression of the click‐potential by the masking pure tone. It is found that damage to the auditory nerve does not abolish the masking effect. One would therefore conclude that it takes place within the cochlea. This is in agreement with an assumption made by Galambos in his report on suppression of a single nerve‐fiber response by a second pure tone.

ISSN:0001-4966    

DOI:10.1121/1.1902382

出版商:Acoustical Society of America    

年代:1944

数据来源: AIP

摘要:

This paper gives the results of measurements of the over‐all acoustic gain shown by six commercial hearing aids. The input level was 50 db above the reference level of a General Radio sound level meter. The measurements covered the frequency range from 200 to 4096 c.p.s. A steady sound field was set up in an absorbent lined booth. A Western Electric 640A condenser transmitter was fitted into a hole at the center of a small baffle, with its diaphragm in the plane of the baffle face. The field was monitored by the sound level meter, with its microphone in a fixed position close to the edge of the baffle. The output of the condenser transmitter was fed into a measuring system consisting of an attenuator, amplifier, and indicating meter. The attenuation needed to produce a given reading on the meter was determined. The condenser transmitter was then replaced by the microphone of the hearing aid, with its diaphragm in the same position the transmitter diaphragm had occupied. The hearing aid receiver was coupled through a 2 cc closed coupler to the condenser transmitter and the attenuation required to give the same reading as before on the indicating meter was noted. The difference between the attenuations in the two cases was taken as a measure of the over‐all acoustical gain afforded by the hearing aid. All of the instruments tested, except one, showed maximum amplification in the 1000 to 2000 c.p.s. range. Among the different instruments, this maximum was between 45 and 68 db. The one exception showed a maximum gain of 42 db at 700 c.p.s. At 300 c.p.s., the spread between the different instruments was from 12 to 55 db, while at 4096 c.p.s. it was from 18 to 52 db. Only one of the instruments tested showed any significant change in frequency response with change in the “tone control setting” of the instrument. In this instrument a change of 25 db in the amplification of tones below 512 c.p.s. was possible with a change of only 4 to 8 db at the higher frequencies.

ISSN:0001-4966    

DOI:10.1121/1.1902386

出版商:Acoustical Society of America    

年代:1944

数据来源: AIP

摘要:

During the past few years a number of mathematical investigators have directed their efforts toward the solution of differential equations with variable coefficients. These analyses are useful in explaining some of the phenomena which occur in electroacoustic vibrating systems with nonlinear elements. In particular, this mathematics may be used to explain the various phenomena exhibited by a direct radiator loudspeaker with a nonlinear cone suspension system. One of the effects is a jump phenomenon in the response frequency characteristic. Another effect is the production of harmonics and subharmonics.

ISSN:0001-4966    

DOI:10.1121/1.1902368

出版商:Acoustical Society of America    

年代:1944

数据来源: AIP

摘要:

In the course of studies of violins, it became of interest to find out how much their tone analyses differed from those of certain wind instruments. Analyses were made of flute, clarinet, oboe, English horn, and French horn, rather softly blown, over their whole range. The results show no such violent variations in volume of tone as in violins, though a weak spot appears in the oboe and the clarinet. For low tones in oboe, English horn, and French horn the upper partials are strongest. These die off progressively on the way up the scale until at the top the order of prominence is the order of the partials, as in high violin tones. The order of appearance of the even‐numbered partials in the clarinet is interesting; 6, 4, and 2 are absent in the lowest tones, and they appear progressively, in that order. The second passes the third one octave below the top; the fundamental is nearly always loudest.The violin family includes theviola d'amore, in which seven or more extra wires which are not fingered are added for resonance. Some writers and many musicians believe that the extra wires increase the loudness, though wires were once supposed to kill the sound in an auditorium. To test the matter, analyses were made ofA‐440 tones from each of two violins played on theDstring, with or without allowing the openAstring to resonate. The results show no effect unless the tuning is exact, but clearly show that the resonating string weakens the output of the fundamental without appreciably affecting the upper partials. If the energy supply given to the bowed string is constant, it is clear that the roundabout process of producing sound from the violin box by way of the resonating string must involve a loss of energy. The peculiar quality of the viola d'amore, if it exists, must be due to some cause other than the presence of the extra wires.

ISSN:0001-4966    

DOI:10.1121/1.1902371

出版商:Acoustical Society of America    

年代:1944

数据来源: AIP

摘要:

The Flanders method for measurement of acoustic impedance has been adapted to the measurement of ear impedance. The results of measurement of ear impedance as seen through the caps of several types of audiometer receivers are reported. These are compared with similar measurements on a standard closed coupler used for receiver calibration. The suitability of present couplers for receiver calibration is discussed.

ISSN:0001-4966    

DOI:10.1121/1.1902376

出版商:Acoustical Society of America    

年代:1944

数据来源: AIP