摘要:

An improved underwater earphone, insensitive to depth, has been developed. This new transducer offers good efficiency and yields speech reproduction comparable to most air acoustic earphones. The earphone design provides tympanic, rather than bone‐conduction, sensing, thereby providing directional signal information to the listener. Pairs of these devices have been used successfully in a directional communication system for underwater swimmers. Threshold levels and some man‐earphone equal‐loudness contours were obtained for this device.

ISSN:0001-4966    

DOI:10.1121/1.1912759

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

The noise criterion (NC) curves were developed both as a method for evaluating existing noise situations and as a means for specifying design goals for noise control. They have also influenced the N ratings used abroad. It has been demonstrated that if a background noise whose spectrum conforms to an NC‐curve shape is deliberately generated, it does not sound to a listener as a pleasant or neutral noise, but is both “hissy” and “rumbly.” A recent tendency in consulting practice, therefore, has been to specify noise levels that are lower than NC curves at both low and high frequencies. Also, the original NC curves were derived using Stevens's Mk. I method of calculating loudness level from noise levels measured with the old octave bands, the lowest of which was the “below 75 Hz” band. A reexamination of the noise criterion curves has been undertaken using Stevens's Mk. VI method and the new octave bands. The result is a new set of curves, called “preferred noise criterion (PNC) curves,” having levels in the bands below 125 Hz and above 1000 Hz that are lower than those of the 1957 NC curves by 2–5 dB. The new set also takes into account the engineering realities of achieving the specified noise levels with conventional air‐handling equipment. The results of a number of recent noise‐control projects in building are presented for comparison.

ISSN:0001-4966    

DOI:10.1121/1.1912760

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

The squared magnitude of the cross‐ambiguity function of two signals is shown to be given by the two‐dimensional cross correlation of the individual time‐frequency (t‐f) energy distributions of the signals. This result is used to show that a short‐time spectrum measured in the usual way is the two‐dimensional convolution of the t‐f energy distribution of the signal with a function which is simply related to the t‐f energy distribution of the window which is used.

ISSN:0001-4966    

DOI:10.1121/1.1912761

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

Behar and Menyhart, in a recent study of a variation of a technique reported earlier by us [A. C. Raes, J. Acoust. Soc. Amer.46, 831–834 (1969)], conclude that the method is not fully successful in reducing the need for a multiplicity of source positions in reverberant sound field measurements. We would point out that their study, although interesting in several respects, presents no information on effects of varying source positions, and thus sheds little direct light on the value of the new technique.

ISSN:0001-4966    

DOI:10.1121/1.1912762

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

The difficulties in solving many of the noise problems in an average household are as much social and economic as technical. With many different parties being involved in the noise problem of even a single appliance, plea is made for uniform sound ratings of equipment, for information proper application and installation, and for realistic criteria on acceptable sound levels. Recent standards for performance ratings and application information of the Air‐Conditioning and Refrigeration Institute are cited as an example of what an industry can do to further the communication of acoustical data between manufacturers, installers, and users of machinery.

ISSN:0001-4966    

DOI:10.1121/1.1912763

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

Two recent communications are compared, and one is corrected.

ISSN:0001-4966    

DOI:10.1121/1.1912764

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP