摘要:

OBS observation of underwater explosion and natural earthquakes contributes in many respects to the ocean acoustics for understanding the nature of underwater sound propagation and acoustic properties of bottom sediments as well as subbottom structure. It was observed thatT‐phases were generated in a deep flat ocean basin by the earthquakes which occurred in the ocean crust. It is interpreted that the abyssalT‐phase is generated by the diffraction wave at the oceanic basement (layer II) which is overlying very close to the shallow earthquake origin. The arrival phases of underwater sound from explosion source to the OBS in the long range propagation in a deep ocean generally contain very small onset phases. This is regarded as the limiting ray of RSR (Refraction Surface Reflected) rays. An advantage of using OBS is to obtainS‐wave information.P‐wave toS‐wave conversion takes place very efficiently at the sea bottom as well as at the base of sediment layer.S‐wave velocity in the bottom sediment (layer I) is very low, the ratioVp/Vp ≑ 4 ∼ 3. The spectra of seismic noise upon the deep ocean floor decrease very rapidly above several Hz.

ISSN:0001-4966    

DOI:10.1121/1.2003860

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

We describe a new instrument for the collection of data on bottom loss and/or bottom reflectivity with standard hull‐mounted bathymetric equipment. The bottom returns contain substantially more information about the nature of the bottom than is currently utilized—in the form by bathymetry—yet the possible use of this information has not received enough analysis. Our preliminary analysis, and the instrument devised to collect into the shipboard computer valid statistics about the returns, comprise our report.

ISSN:0001-4966    

DOI:10.1121/1.2003864

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

When we intend the whole‐space stereophnic system, we must design this system to be simulated for original listening conditions. For this purpose, we need several equalizing networks [M. R. Schroeder and D. Gottlob, J. Acoust. Soc. Am.56, 1195–1201 (1974)]. Since these equalizers have rather complicated responses, we constructed them by digital systems. The digital equalizers described here have a form of digital filter which presents the best mean square approximation. To determine the coefficients of these filters, a direct approximation technique of log magnitude response for digital filter, proposed by I. Imai [IEEE Trans. Acoust., Speech Signal Process.25, 127–133 (1977)], was utilized. The resulting digital equalizers are recursive type and realized in a cascade connection of very simple second‐order‐type recursive digital filters (number of multipliers is two in this second‐order type filter). These equalizers have several important advantages, i.e., fewer multipliers are needed in these constructions, since we used the multipliers in time sharing fashion. And these equalizers result in easier control of the characteristics of the system.

ISSN:0001-4966    

DOI:10.1121/1.2003869

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

Musicians and nonmusicians were tested with dichotic pitch pattern triads which consisted of three tone bursts of 200 ms each with interburst intervals of 150 ms. Frequencies of the tone bursts were 630 and 1065 Hz for one set of pitch patterns and 1500 and 1935 Hz for the other set. There was an intrastimulus interval of 10 s. Subjects responded using three different response modes: (1) manual response by pressing buttons on two response boxes, (2) hummed response, and (3) verbal‐linguistic response by labeling each tone in the pattern as “high” or “low.” Musicians performed significantly better than nonmusicians on all three response mode conditions. Right and left ear performances did not shift significantly in direction of ear advantage across the three response modes for either experimental group. Percentage of correct identifications did not vary significantly across response modes. Neither musicians nor nonmusicians demonstrated statistically significant ear advantages. Stimulus set bias was present in both experimental groups in favor of the higher pitched pattern set (tone bursts of 1500 and 1935 Hz). [Work supported by NIH.]

ISSN:0001-4966    

DOI:10.1121/1.2003875

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

Distorting familiar melodies by randomly assigning notes to different octaves makes recognition difficult. This difficulty can be lessened by preserving the contour (ups and downs) of the original melody. These experiments (using complex tones) show that cuing with either the unscrambled melody itself or its title also improves performance. In experiment 1 listeners heard a “straight” version of a familiar or an unfamiliar melody, followed by a scrambled version of either the same melody or a lure. Hit rates for scrambled melodies averaged 0.80, while false alarms to lures averaged 0.40. In experiment 2, scrambled familiar melodies or lures were preceded by accurate or spurious titles, respectively. Hit rates were 0.80 and false‐alarms 0.20. These results show that listeners can use a memorized, pitch‐and‐time‐flexible, “melody template” in recognizing scrambled melodies, just as they can in recognizing an unscrambled melody temporally interleaved with other tones in the same pitch range. The template is a list of relative tone “chromas,” which can be used in the recognition of scrambled melodies just as in the transposition of the familiar melodic intervals of the NBC chimes.

ISSN:0001-4966    

DOI:10.1121/1.2003878

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

The relationship between consonant recognition under conditions of acoustic filtering and hearing loss was studied in subjects with unilateral hearing impairments. Using a procedure involving suprathreshold loudness balance between ears, a multifilter was used to match the (suprathreshold) audiometric configuration of the impaired ear. Consonant recognition data were obtained from the impaired ear and from the normal ear listening through the multifilter. To the extent that consonant recognition was similar in the two ears, the effect of the patient's hearing impairment on phoneme identification could be related to the audiometric configuration. A comparison between consonant recognition scores for the impaired ears and for the ears listening through the multifilter revealed large individual differences among subjects. These differences appeared related, in part, to the audiometric configuration. Mean consonant recognition ability, however, was almost always lower in the paired ear. In general, the more flat the audiometric configuration, the more dissimilar the consonant recognition between the two ears.

ISSN:0001-4966    

DOI:10.1121/1.2003887

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

The sound insulation of common Australian domestic roofing systems was investigated using a 103 m3room below a 203 m3transmission room. Both rooms of non‐rectangular shape satisfied recommendations of ISO/R 140. Measurements were conducted in the frequency range 100 Hz to 10 kHz. Initially, measurements of transmission loss (TL) were made using a basic ceiling with 9 mm plasterboard cladding, followed by tests when various commercially available in this were added. The enhancement of TL by infill was negligible at low frequencies. Various types of roof component, such as concrete tiles, asbestos‐cement, and galvanized steel were then studied. Due to the great number of air gaps, the TLs varied little with frequency and were low in magnitude despite large differences in cladding surface density. Finally, various combinations of roof and ceiling samples were investigated. Although inclusion of ceiling infills yielded significant increases in TL values, the enhancements at low frequencies leads to the conclusion that, for acoustic protection against traffic noise, the addition of infills is a rather fruitless exercise unless close attention is paid to proper sealing.

ISSN:0001-4966    

DOI:10.1121/1.2003892

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

The impulse response represents the transmission characteristics from the certain source point to the receiving point of the room, if we consider it to be a linear system. According to the position of the source and receiving points some differences are caused in the impulse responses, but they imply the spatial characteristics of the room. The mirror image method is often used to obtain the spatial characteristics of a room, but it is difficult to apply this method to an actual room because of the complexity of the room shape. At four slightly variant receiving points onx,y, andzaxis, we measured the impulse responses of the same source point. Then we computed the image sources to the three dimensional field. From these virtual image sources, we obtained SPL distributions, conditions of standing waves, effects of absorbing materials, mean free path, etc., in a room.

ISSN:0001-4966    

DOI:10.1121/1.2003895

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

Percussion instruments play a very important role in Oriental music. The gamelan or orchestra of Java or Bali, for example, includes several types of metallophones, gongs, cymbals and drums. We have studied the modes of vibration, timbre, and tunings of a number of these instruments, and we compare them with percussion instruments of Western origin. Although they show considerable variation in tuning, Indonesian instruments tend to follow one of two tonal systems, known as pélog and sléndro. Included in the orchestra which accompanies Chinese opera are gongs, drums, bells and cymbals. Gongs are frequently constructed so that they sound one pitch when struck, then rise or fall about a semitone, large gongs (hsiao‐lo) usually falling in pitch and small gongs (da‐lo) rising in pitch.

ISSN:0001-4966    

DOI:10.1121/1.2003905

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

Did East meet West in 1595? Equal tempered approximations 1595, Peking and Amsterdam or the riddle of the abacus and logarithms. Both Tsai‐yu and Stevin set down the mathematical figures for equal temperament. Tsai‐yu calculated the 12th root of 2 by means of the abacus, carefully computing the appropriate root for each note separately—correct to nine decimals. Stevin's calculations on the other hand, finding 11 mean‐proportional parts between 2 and 1, were based upon the 45th proposition of his French arithmetic.

ISSN:0001-4966    

DOI:10.1121/1.2003911

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP