摘要:

A study of the machine recognition of the spoken digits zero through nine has been carried out by a digital computer simulation. The spoken utterances were converted to time‐frequency patterns of spectral energy. Recognition was done by cross correlating the pattern of an unknown utterance with a test pattern for each digit and selecting the digit having the highest correlation. Time normalization could be applied to all patterns, thus reducing utterances to a standard duration. Six male and one female speakers provided 38 samples of each of the 10 digits. Pauses were made between successive words for segmentation.No errors were observed recognizing a single speaker using test patterns from his own speech with time normalization. A group of five male speakers and test patterns averaged over the group produced 6% errors with time normalization and 12% without. A 25% rate occurred for the woman matched against male patterns.The study indicates both the effectiveness and limitations of this simple recognition procedure for limited vocabulary and limited number of speakers. Time normalization improves performance in all cases.

ISSN:0001-4966    

DOI:10.1121/1.1907936

出版商:Acoustical Society of America    

年代:1960

数据来源: AIP

摘要:

The thermal relaxation absorption in ethylene at temperatures between 0° and 60°C has been obtained by the Tube method for frequencies between 150 kc and 4 Mc per atm. The relaxation time, the transition probability, and the collision efficiency were determined as a function of temperature. The collision efficiency as a function of temperature seems to follow the simple exponential law :P10α exp(−c/T1/3).

ISSN:0001-4966    

DOI:10.1121/1.1907938

出版商:Acoustical Society of America    

年代:1960

数据来源: AIP

摘要:

A brief summary of existing knowledge about sonoluminescence is given. Various theories of the origin of this luminescence are discussed. The author concludes that sonoluminescence is basically thermal in origin and that it might possibly arise from microshocks with the collapsing cavities.

ISSN:0001-4966    

DOI:10.1121/1.1907940

出版商:Acoustical Society of America    

年代:1960

数据来源: AIP

摘要:

In previous work, the normal surface displacement patterns of thick barium titanate disks vibrating in various normal modes have been obtained using multiple‐beam optical interference. This technique has now been used to determine the effect of loading a disk with a liquid in contact with one plane surface. It is found that the discrete modes observed with an unloaded disk begin to merge so that the vibration patterns show a continuous transition with changing frequency as one passes from one mode to the next in the “thickness resonance” region. The radiation damping of the individual modes is appreciably less than the theoretical value, but the bandwidth covered by the group is appreciably greater than is to be expected from the simple theory of thickness resonance. In the case of a quartz disk, two modes with a frequency separation of 0.5% merge fairly completely when the disk is loaded, and the vibration patterns indicate composite motion of a more uniform character than that of either mode alone.

ISSN:0001-4966    

DOI:10.1121/1.1907942

出版商:Acoustical Society of America    

年代:1960

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.1907944

出版商:Acoustical Society of America    

年代:1960

数据来源: AIP

摘要:

A small condenser microphone inserted into the mouthpiece of a clarinet enables the vibrations of the air column to be observed. At low intensities the pressure variation in the mouthpiece is practically sinusoidal; at higher intensities harmonics increase in amplitude, but the fundamental still predominates. The sound pressure level inside the mouthpiece for loud tones reaches 166 db; this checks well with the pressure required for blowing the instrument. Simultaneous observations of mouthpiece pressure and reed displacement show that, during that part of its motion that it is not in contact with the mouthpiece, the reed follows quite faithfully the pressure variations. The reed itself is primarily stiffness controlled; however, the damping of the reed motion by the player's lip is a very important factor in the performance of the instrument. The influence of the reed on the pitch of the tone produced by the instrument will be discussed.

ISSN:0001-4966    

DOI:10.1121/1.1935149

出版商:Acoustical Society of America    

年代:1960

数据来源: AIP

摘要:

CM‐responses were recorded in cats for seven frequencies between 150 cps and 7500 cps by means of differential electrodes in the basal cochlear turn. Both air‐ and bone‐conducted signals were used. The cochlear windows were closed by means of dental cement (the round‐window membrane being protected by silicone grease). A good seal was assured by (a) careful removal of the muco‐periost under microscopic control and (b) by anchoring the cement plug against the walls of the bulla or middle‐ear, respectively. Closure of either window resulted in a drop of BC responses of approximately 10–15 db. Additional closure of the other window had no noticeable effect unless the cochlear aqueduct had also been sealed off. In that latter case, additional response losses of approximately 5–8 db were observed. In no instance was it possible to abolish the response to BC sounds to the same degree (50–60 db) as was accomplished with respect to AC sounds by closure of the oval window alone.

ISSN:0001-4966    

DOI:10.1121/1.1935155

出版商:Acoustical Society of America    

年代:1960

数据来源: AIP

摘要:

A brief résumé will be given of our method of direct measurement of acoustic impedance of the ear in experimental animals with graphs of average impedance curves for guinea pigs. The acoustical impedance of the ear of a single animal is not fixed, but quite variable, particularly in the range of best auditory acuity between 2000 cps and 7000 cps. It appears possible that these impedance variations are controlled by the animal. Experiments will be cited showing the role of the double‐chamber configuration of the middle‐ear cavity in producing impedance changes. Results of some experiments demonstrating the possible effects of tensor tympani and stapedius muscles upon the acoustical impedance of the ear will be given.

ISSN:0001-4966    

DOI:10.1121/1.1935158

出版商:Acoustical Society of America    

年代:1960

数据来源: AIP

摘要:

Three important factors in a vibration isolation problem are the characteristics of the vibrational source, the structure at the point of attachment, and the coupling element or isolator. The structure is considered a single port element and is represented by its driving point impedance. The source is considered an active single port element, and it is represented by a Thevenin or Norton equivalent circuit determined from measurements. Isolators are considered passive two ports and are represented by π orTequivalent circuits as determined from measured impedance or mobility parameters. The first step in isolating a small electric motor from a nonrigid structure was to determine the impedance representations by direct measurements at the points of connection. Then the motion of the structure was predicted and measured as a reference for isolator effectiveness. After considering the characteristics of the source and the structure, a simple isolator was designed. The effectiveness was predicted and then measured. The equivalent circuits of several other isolators, including commercial types, were determined and their effectiveness measured.

ISSN:0001-4966    

DOI:10.1121/1.1935165

出版商:Acoustical Society of America    

年代:1960

数据来源: AIP

摘要:

The Narragansett Marine Laboratory, sponsored by the Office of Naval Research, undertook a systematic seasonal study of shallow water ambient sound, commencing in October, 1958. With a general lack of information on average values and the variabilities associated with these average values, it was decided to base the experimental work on a theoretical model, which would elicit systematic seasonal differences, if they existed, as well as suggest procedures for further sampling of shallow water ambient sound. The model selected was a mixed‐model, one‐way analysis of variance experimental design, constructed to determine the existence of significant seasonal differences among months of the year, specific hours in a day, as well as to determine the contribution made to any ambient noise spectrum by variability due to weeks of the month, days of the week, and minutes within any sampling hour.

ISSN:0001-4966    

DOI:10.1121/1.1935170

出版商:Acoustical Society of America    

年代:1960

数据来源: AIP